Perspectives In Rehabilitation Ergonomics

Perspectives in Rehabilitation Ergonomics

Perspectives in Rehabilitation Ergonomics EDITED BY

SHRAWAN KUMAR Department of Physical Therapy, University of Alberta, Edmonton, Canada

UK Taylor & Francis Ltd, 1 Gunpowder Square, London EC4A 3DE USA Taylor & Francis Inc., 1900 Frost Road, Suite 101, Bristol, PA 19007 This edition published in the Taylor & Francis e-Library, 2005. “To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.” Copyright (©) Taylor & Francis Ltd 1997 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN 0-203-21261-4 Master e-book ISBN

ISBN 0-203-26988-8 (Adobe eReader Format) ISBN 0-7484-0644-1 (cased) ISBN 0-7484-0673-5 (paperback) Library of Congress Cataloging Publication Data are available Cover design by Amanda Barragry

To my wife, son and daughter, Rita, Rajesh and Sheela. With Love.

Contents

Preface

vii

List of Corresponding Authors

x

1

Aging, Disability and Ergonomics S.Kumar

1

2

Disabilities Associated with Aging in the Workplace and their Solutions M.Kumashiro

40

3

Visual Impairment: Ergonomic Considerations in Blind and Low-Vision Rehabilitation M.A.Heller and J.Brabyn

76

4

Effects of Exercise on Physical and Psychological Preparedness of Chronic Heart Disease Patients for Work: A Review G.M.Kumar and A.Mital

106

5

Integrating Ergonomics in the Management of Occupational Musculo-skeletal Pain and Disability M.Feuerstein, T.R.Zastowny and P.Hickey

140

6

Ergonomics in Vocational Rehabilitation E.A.Blumkin

164

7

Gait Analysis: A Rehabilitative Interdiscipline Z.O.Abu-Faraj, S.Hassani and G.F.Harris

189

8

Slips, Trips and Falls: Implications for Rehabilitation Ergonomics A.E.Patla

224

9

Mobility of the Disabled—Manual Wheelchair Propulsion Y.C.Vanlandewijck, A.J.Spaepen and D.Theisen

240

Wheelchair Ergonomics R.A.Cooper, R.N.Robertson, M.L.Boninger, S.D.Shimada, D.P.VanSickle, B.Lawrence and T.Singleton

281

10

vi

11

Assistive Technology M.J.Scherer and J.C.Galvin

313

12

Anthropometry for the Needs of Disabled People E.Nowak

345

13

Anthropometry of People with Disability A.Goswami

388

14

A New Approach to Clothing for Disabled Users M.Thorén

410

Index

427

Preface

Recent demographic trends in many countries indicate that society has begun experiencing rapid growth in a number of functionally subnormal people. Such a trend is projected to continue for a few decades yet. Thus, due to the changing functional composition of society more people will have functional disadvantage in activities of daily living, vocational and recreational pursuits. Such a scenario has the potential of having a significant consequence to our health, happiness and economy. Some theories of injury causation propose that over-exertion may have a significant contribution in its precipitation (Kumar, 1994). If the products, processes and facilities are designed with functional superiority as reference criteria the demand on the functionally subnormal will lead to over-exertion and hence injury. In addition, this state will also render more people handicapped. Regardless of the origin of functional deterioration or impairment, rehabilitation endeavours to restore the function to normal or as close to normal as can be expected. Ergonomics on the other hand enhances the functional capacity of people by optimizing the fit between the person and the object, process or facility. Therefore, a blend of these two disciplines will allow one to develop strategies to enhance and optimize the functional ability of a subnormal group. One may get an impression that rehabilitation and ergonomics are quite different and their merger may be somewhat far-fetched. However, Kumar (1989 and 1992) has elaborated the similarities and complementarity of these two disciplines. He has gone on to describe identical goals of and similar methodologies in these two disciplines. The scopes of rehabilitation and ergonomics are vast, as they cover every aspect of human function. These are like parallel sciences, running simultaneously in different strata of human function. Therefore, any comprehensive book on rehabilitation ergonomics can become encyclopaedic. This, however, was not the goal of this book. Here we have tried to put together chapters on an assortment of topics to keep it manageable for authors as well as readers. Furthermore, it will befair to say that rehabilitation ergonomics is in its infancy but has potential for growth. There are vast areas which remain to be explored. We hope the presentation of these few topics under one cover will trigger some additional thoughts and interests to help propel the field a bit further.

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In keeping with the theme of the book, Kumar presents a tripartite perspective on aging, disability and ergonomics. He discusses the magnitude of the problem, functional assessment, changes associated with aging and disability, and finally the role of ergonomics. He argues that ergonomics serves as an enabler. Furthermore, it optimizes the functional performance of the subnormal assisting the process of rehabilitation at the therapist-patient interface and patientenvironment interface. Kumashiro focuses on the functional deterioration which occurs with aging and consequent reduction in working capacity. He follows it up with some unique solutions which have been successfully utilized, specially in Japan. Heller and Brabyn in their chapter have focused on visual impairment and blindness with the diverse problems they present. The perceptual and cognitive problems of a congenital blind, late blind, and visually impaired are drastically different. Thus they require entirely different strategies and approaches for management. Application of ergonomics in these strategies by enlarging the sensory input through alternate channels and devices can significantly alleviate the problem. However, there are challenges which yet remain to be met. The next three chapters deal with incorporation and application of ergonomic principles in the rehabilitation of workers with cardiac, musculoskeletal and vocational problems. Kumar and Mital review the information on impairment due to cardiac problems and their management. They deviate the components of cardiac rehabilitation program, benefits of endurance training in patients with coronary heart disease, and the future trends in cardiac rehabilitation. Feuerstein, Zastowny and Hickey present the multidimensional nature of work disability and the ergonomic factors associated with increased risk of musculoskeletal disorders. Further they present approaches of integrating ergonomic principles and techniques in rehabilitation of patients with occupational musculoskeletal disorders. Although the specific contribution of ergonomics is hard to quantify from the results, yet addition of these strategies improves the outcome based on entirely medical management. Blumkin in his chapter on vocational rehabilitation has taken a broader look at disability as it may impact on occupation. With a special treatment of the subject in the context of the American Disability Act he presents physical as well as mental rehabilitation, and aspects of transportation and telecommunication. The single biggest category of disability is mobility. The disabilities may be quite varied ranging from slightly altered gait to being wheelchair bound. These conditions present very varied problems which may be treated with orthotics to restore normal gait or requiring major intervention. To understand normal gait and the methodology used to study it, Abu-Faraj, Hassani and Harris have written on gait analysis. One of the major hazards which impacts on mobility in addition to other aspects is slips, trips and falls. Patla in his chapter deals with information on this subject with implications for prevention and rehabilitation. In the next chapter Vanlandewijck, Spaepen and Theisen address biomechanical and physiological aspects of manual propulsion of wheelchairs by their

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occupants. Cooper and colleagues discuss wheelchair ergonomics for even more disabled clients dealing with consideration in proper fitting, power wheelchair access systems, overuse injuries associated with wheelchair propulsion, and wheelchair-related accidents and injuries. In the following chapter Scherer and Galvin describe and discuss the important topic of assistive technology. They highlight the value and relevance of ergonomics in designing for a better fit and selection of an appropriate device with the usability criteria in mind. Abandonment and non-use of a device will be expensive both in human and economic terms. In striking contrast to able-bodied people the anthropometry of people with disability have received little attention. However, for most ergonomic application such a database is absolutely essential. It is with this view that two different chapters on this subject are being included in this book. The chapters by Nowak describe the wider aspects of anthropometry including some methodological details before getting into anthropometry of disabled and its application. She integrates this information in rehabilitation procedures. Goswami on the other hand focuses on the sparse anthropometric data obtained on the disabled population. In the last chapter, Thorén addresses the difficult issue of clothing for disabled users. She concludes that for a meaningful solution a systematic approach is essential. Hopefully bringing all of the foregoing areas under one cover will serve as an encouragement for a systematic approach for solutions of multifarious problems facing an ever increasing group of citizens. This book is a small effort in a direction which needs and deserves extensive activity. REFERENCES KUMAR, S. (1989) Rehabilitation and ergonomics: Complimentary disciplines, Canadian Journal of Rehabilitation, 3, 99–111. KUMAR, S. (1992) Rehabilitation: An ergonomic dimension, International Journal of Industrial Ergonomics, 9, 97–108. KUMAR, S. (1994) A conceptual model of overexertion, safety and risk of injury in occupational settings, Human Factors, 36, 197–209.

SHRAWAN KUMAR

List of Corresponding Authors

SHRAWAN KUMAR Department of Physical Therapy, University of Alberta, Edmonton, Alberta MASAHARU KUMASHIRO Department of Ergonomics, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakysushu, Japan MORTON HELLER Department of Psychology, Winston-Salem State University, Winston-Salem, North Carolina, USA ANIL MITAL Ergonomics and Engineering Controls Research Laboratory, College of Engineering, University of Cincinnati, Cincinnati, Ohio, USA MICHAEL FEUERSTEIN Departments of Medical and Clinical Psychology and Preventive Medicine and Biometrics, Uniformed Services University of Health Services, Bethesda, Maryland, USA GERALD F.HARRIS Shriners Hospital for Crippled Children, Chicago, Illinois, USA EUGENE A.BLUMKIN Massachusetts Rehabilitation Commission, Boston, Massachusetts, USA AFTLAB PATLA Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada YVES C.VANLANDEWIJCK Department of Clinical Kinatropology, Faculty of Physical Education and Physiotherapy, Katholieke Universiteit Leuven, Leuven, Belgium RORY COOPER Department of Rehabilitation, School of Health and Rehabilitation, University of Pittsburgh, Pittsburgh, Pennsylvania, USA MARCIA J.SCHERER

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Rochester Institute of Technology, National Technical Institute for the Deaf, Center for Research, Teaching and Learning, Rochester, New York, USA ASIS GOSWAMI Netaji Subhas Western Centre, Sector-15, Gandhinagar-382 016 (Gujarat), India EWA NOWAK Institute of Industrial Design, Warsaw, Poland MARIANNE THOREN Chalmers University of Technology, Department of Consumer Technology, Göteborg, Sweden

CHAPTER ONE Aging, disability and ergonomics SHRAWAN KUMAR

1.1 Introduction Loss of function can result from aging, trauma or disease. Regardless of the reason for this loss, rehabilitation endeavours for restoration of function and ergonomics for its optimization. In conventional situations what rehabilitation does for people with disability, ergonomics does to people with normal functional capacity; which is enhance the functional status. A partnership between rehabilitation and ergonomics, without altering their individual focus, opens the avenue of enhancement of function of all segments of society. A mutual complementarity between these sciences was advocated by Kumar (1989 and 1992). Due to the rapidly increasing size of the older segment of our society a consideration of the aspects of aging with those of disability is desirable. Therefore, this chapter will have dual focus on aging and disability. 1.2 Aging 1.2.1 The magnitude A pronounced demographic change in the First World is noticeable from the statistics of many countries. In 1991, 16 per cent of the entire population (4.3 million people) were reported to be over the age of 60 years in Canada (Corpus Almanac and Canadian Source Book, 1995). With longer life expectancies of 74. 0 and 80.8 years for Canadian men and women respectively (Busse, 1993), it is desirable to rethink the social management policies and practices. Demographic changes which project a rapid rise of the aged group have been reported and presented for other First World countries. Czaja (1990) projected that in the decade between 1990 and 2000, the US population would increase by 7.1 per cent. In the same period she forecast a greater growth of 11.5 per cent for the

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segment aged 55 and over resulting in a gain of 6 million people. Furthermore, within this group Czaja (1990) stated that the greatest growth was expected among individuals 75 and older (26.2 per cent with a gain of approximately 4.5 million). It appears that in the past, several projections have underestimated the growth in population of this segment of population. For example, the US Census projections in 1977 for the elderly for the year 1990 was short by 1.7 million people (Manton, 1991). Based on new projections for the year 2020, the number of elderly people projected in 1977 was 7 million lower. Manton et al. (1991) have presented observed number of elderly people from 1950 to 1990, and the projected figures for this group from 1995 to 2060 (Figure 1.1). It is not the sheer increase in the number of senior citizens in North American society, rather their increase as per cent of the total population which is further revealing. This demographic shift is presented in Figure 1.2 by comparing the distribution of population between 1985 and 2000. In examining the status of the senior citizens there is considerable similarity between the US and Canada. According to the National Institute on Aging (1991), 16 per cent of the total population in Canada were 60 years, and 12 per cent were 65 years or older. Similarly in the US, 16.9 per cent of people were 60 years of age or over. This group is also growing in size as the projections show. This obviously is happening due to the increased life expectancy partially due to the reduction of risks. Such a trend in absolute numbers as well as the proportion of the total population makes it of special significance that we increase our knowledge base of the growing group (Busse, 1993). A population growth among the elderly is not unique to-North America. A similar projection is made for European countries as well. For example, in the UK it is projected that by the year 2021 the majority of the population will survive beyond middle age with a significant increase in population over 80 years of age, and reduction in the young adult population (Coleman, 1993). From the beginning of the 21st century, the proportion of over-50s in the UK is projected to reach about 48 per cent of the adult population (16+) by the year 2021 (Coleman, 1993). Sweden is very similar to UK, but a reduction in the younger age group in that country will result in a greater proportion of the population being over 50 years of age. A significant increase in proportion of people beyond the age of 80 years is quite obvious in many European countries by projections (Figure 1.3). With general increased life expectancy and increased proportion of elderly as the segment of overall population, the First World is likely to experience a shrinkage in the labor pool. The rate of economic growth and universal demand of commodities and merchandise have become part and parcel of the first world lifestyle. A shrinking labor pool will be detrimental to the economy, and is likely to affect the general productivity adversely. Furthermore, such a change in the demography of the consumer group may render many of the products currently on the market less desirable due to a lack of ergonomic fit. Thus, in order to best serve the society in general and aging population in particular, we must first

AGING, DISABILITY AND ERGONOMICS 3

Figure 1.1 The number of senior citizens (in millions) in the US.

develop a scientific knowledge base on aging and alterations associated with it in the functional characteristics and capacities. The latter will allow us to put in place the strategies which will help accomplish decreased dependency, increased productivity and personal fulfilment. 1.2.2 Aging and functional decline The work capacity in general and physical work capacity in particular declines with age (Ilmarinen, 1992 and 1995). However, any given industrial job represents a constant work demand. Thus with aging the gap between the capacity and work demand progressively declines depleting the levels of reserves (Figure 1.4). Depending on the level of the work demand, beyond a certain age the remaining reserves will not be sufficient to allow complete recovery. Ilmarinen (1992) states in context of regular industrial tasks in Finland that this threshold age is 55 years. Kumar (1990) reported that cumulative load is an important risk factor for precipitation of back injuries among physical workers. The concept of inadequate recovery failing to bring the reserves to resting level has been proclaimed to be a critical component in safety of workers (Kumar, 1994). This

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Figure 1.2 The distribution of population in the US compared between 1985 and 2000.

process of recovery becomes a little more problematic in aged workers for several reasons. First, if the work is designed based on reference values for younger workers it places the aged workers at an immediate disadvantage. Secondly, aging results in morphological and systemic changes which tend to slow down the recovery process requiring a longer rest period for older workers. Thirdly, the nutritional and recreational habits of these workers may not be able to support the required recovery enabling them to perform with an efficient system. Fourthly, aging is frequently associated with chronic diseases and some degree of disability making such workers fall below the average functional levels of healthy subjects their age. Interaction between these factors will continue to affect the working capacity of these workers as well as their health and safety (Figure 1.5). Therefore, to overcome the unfavorable consequence of such an inevitable interaction two courses of action are possible. First, to obtain an optimal relationship between these, Ilmarinen (1992) suggested a sliding adjustment in work demand to maintain a healthy difference between the work

AGING, DISABILITY AND ERGONOMICS 5

Figure 1.3 The percentage of elderly (80+) as proportion of total population for selected European countries.

demand and the functional capacity. A second approach is being advocated here. It consists of three components: (a) ergonomic, (b) administrative and (c) lifestyle. The ergonomic approach will be to systematically decrease the job demands to a level where ideally the lowest performer can handle the job. Clearly, it will not be possible in all cases. Subsequent to the ergonomic intervention an administrative approach to classification of jobs based on job demands with quantified levels of demand is developed. Also, a scheme of labour management for appropriate allocation to optimize productivity, health and safety is put in place. Finally, the workplace managers should be aware of implementation of an appropriate lifestyle (with the necessary health counselling) and encourage it for productive and healthy aging. Maximal aerobic power is known to decline by 1–2 per cent per year especially beyond the mid-20s when peak level has been reached (Astrand and Rodahl, 1977; Seliger and Bartunek, 1976; Saltin, 1990 and others). The decline is progressive and its rate is linear. However, in individual cases the magnitude is

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Figure 1.4 A comparison between the declining work capacity and constant work demand.

Figure 1.5 Interaction between work and worker factors and its consequences.

variable and can be significantly higher than the average values. In particular, inactive people may show a reduction of 20 to 25 per cent in a 4-year period (Ilmarinen et al., 1991). The varying level of personal fitness is a matter which deserves special attention in the field. The same magnitude of work, in such cases, can produce quite different level of physiological stress. Ilmarinen (1992) has reported that a workload demanding 1 litre/min of oxygen can produce a heart rate ranging between 80–120 beats per minute. Similarly, another job requiring 2 litre/min of oxygen could produce a heart rate of 120 beats per minute among fit subjects compared with 175 beats per minute among subjects of low fitness. As a practical measure, therefore, significant attention must be paid to the work-rest schedule. Unfortunately, workload itself does not have a

AGING, DISABILITY AND ERGONOMICS 7

similar training effect to aerobic physical exercise. Therefore, one does not increase physical fitness at work. For this reason physical fitness declines among workers doing physical or mental work (Ilmarinen, et al., 1991; Nygard et al., 1991). Similar to aerobic power muscle strength and endurance also decline with age among both men and women (Astrand and Rodahl, 1977). Thus, an integration of physical exercise and training in life activities (both work and recreational) is of considerable strategic significance in maintaining work ability and delaying aging. 1.2.3 Effect of exercise on maintenance of function The role of past and present physical activity has a significant impact on functional tenacity. While some studies have found little evidence that physical activity helps to maintain bone or muscle strength in the elderly (Skelton et al., 1994; Rutherford and Jones, 1992), the majority argue otherwise. A comparison of 65-year old cross country running males with 67-year old males from the general population showed no difference with regards to hair, skin or sensory aging, but it was shown that the physically active group has lower systolic blood pressure, less body fat, lower resting heart rates and superior ventilatory capacities (Larsson et al., 1984). Well-trained men also rated themselves as feeling healthier and having more energy. In their 15-month long study of 60–72year-olds, Brown and Holloszy (1993) found that low intensity training which emphasized strength, flexibility and balance did in fact produce strength, range of motion, muscular endurance and stability improvements. They also found that moderate intensity exercise not only maintained these changes, but also helped improve endurance, walking speed and other characteristics of gait. Are these gains enough to make exercise worthwhile from a functional point of view? The adoption of physical activity at any age has been said to have a ‘rejuven ating effect’ (Larsson et al., 1984) because it slows the rate of agerelated decline of some factors. Mor et al. (1989) found that 70–74-year-olds who did not exercise were 1.5 times more likely to decline functionally in a twoyear time period. Rantanen et al. (1994) elaborated even further having reported that maximal isometric strength is a valuable predictor of mobility in the 75-yearold male and female. Stronger quadriceps lead to improved independent standing and a faster walking speed (Didier et al., 1993). Hip abduction strength is invaluable for balance (Miles et al., 1993). Greater hip extension strength aids in rising from sitting and a larger strength value is crucial for the elderly female’s ability to negotiate stairs (Rantanen et al., 1994). Practising high-speed exertion exercises has also been shown to inhibit the common increase in reaction time associated with aging (Bonder and Wagner, 1994). This, coupled with increased quadricep strength and ankle range of motion, has been shown to reduce the probability of falling (Bonder and Wagner, 1994). Increasing physical activity may also have a positive effect on the elderly functionally, solely due to its

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metabolic effects. Poehlman (1992) believes that the increased energy intake that occurs in response to increased physical demand may help fight energy and protein deficiencies that often compromise the elderly’s nutritional status and functional performance. As for the question of whether exercise is protective or predictive, some argue that perhaps it is the person’s superior functional disposition to start with that predisposes them to adopt exercise (Rantanen et al., 1994). This is the old chicken or the egg question (Larsson et al., 1984) and is the basis for labelling exercise as merely predictive. The vast majority though support the belief that physical exertion is a means of prevention (Mor et al., 1989). They preach that initiation of an exercise program not only improves physical functioning, but also psychological well being and the consensus seems to be that it is never too late to start. It has also been found that activity level is a powerful predictor of contentment, sleep success, and, of perhaps the most important variable, perceived health. Numerous researchers have coined self-rated health as perhaps one of the most reliable predictors of survival (Jylha et al., 1992). An individual’s sense of health has been found to be an accurate predictor of impending decline (Mor et al., 1989). Lindgren et al. (1994) found that perceived health was affected more by mobility and sleeping impairments that by deficiencies related to hearing and eyesight. 1.2.4 Functional assessment of the aged 1.2.4.1 Activities of daily living One simple and reliable method of determining the functional status of an aging person is to determine the level and ease of performance in activities of daily living (ADL). For grading such performance three categories of ADL are identified: 1 Basic activities of daily living (BADL) which include self-care activities such as bathing, feeding and dressing. 2 Intermediate activities of daily living (IADL) which include activities necessary for personal independence in the community; able to manage shopping and cooking. 3 Advanced activities of daily living (AADL) which include activities such as exercise and employment. In general, a shift from AADL to BADL can be seen with increasing age. Social and recreational pursuits remain relatively undisturbed, while performance of

AGING, DISABILITY AND ERGONOMICS 9

occupational and physical advanced activities becomes less frequent. More time is spent on BADL and IADL and less time is spent sleeping (Ashworth et al., 1994). A look at the number of days of bed rest for different age groups allows us to see the decline in health, immunity, and general resilience with advancing age more clearly. In 12 months those 55–64 years of age spent 9.4 days in bed, those 66–74 years spent 10.7 days, those 75–84 spent 14.9 days and those 85 years of age or older spent 20.9 days in bed (US Department of Health and Human Services, 1989). Advance activities of daily living. Few studies have been done concerning AADL. It is usually assumed that if a person over 65 years of age can meet their own basic and intermediate needs then they are independent and fully functional. The topic of functioning level is rarely pursued further. In regards to working, Mor et al. (1989) found that only 15 per cent of those who did not experience functional decline over a two-year period were employed. Only 4.3 per cent of those who did decline were working. In general, males who were not working had a 1.4 times greater chance of declining functionally. Intermediate activities of daily living. The capacity of a person to carry out all home management activities, or IADL, allows that person the freedom to live independently within a community. In a 1992 study of older Americans, 21 per cent of those 65–74-year-olds and 55 per cent of those over the age of 85 had at least some difficulty with home management activities (Ashworth et al., 1994). A Danish study found that no one in their 70-year-old sample could do all of the mentioned IADL without help (Avlund and Schultz-Larsen, 1991). The most demanding IADL have been found to be heavy housework and shopping. Dependency rates for heavy housework range from 16.6 per cent (US Department of Health and Human Services, 1989) for those 65 and older to 50 per cent for females aged 70–79 to 90 per cent for the same females 10 years later (Jylha et al., 1992). Shopping dependency rates were similar at 16 per cent (Fillenbaum, 1988) for those over 60 years of age, 7.3 per cent for those over 65 years of age (US Department of Health and Human Services, 1989), and greater than 25 per cent for those 85 years or older (US Department of Health and Human Services, 1989). A study of 70–74-year-olds found that 22.3 per cent of those who could carry two bags of groceries were no longer able to do so two years later (Mor et al., 1989). Skelton et al. (1994) found that of those 65–89 years of age all were capable of lifting a typical 4 kg shopping bag from the floor to a standard table top. The Tampere Longitudinal Study on Aging observed a decrease from 82 per cent to 37 per cent over a 10-year span in the ability of 70–79-year-olds to carry a 5 kg bag for 100 m (Jylha et al., 1992). Much research has been done with regards to mobility. Seventy-two per cent of females reported difficulty in climbing stairs at the age of 75, but only 2 per cent deemed themselves unable (Rantanen et al., 1994). Ninety-six per cent of Americans over the age of 60 were reported to walk independently (Fillenbaum, 1988), but a higher percentage of 100 was reported by Danish 70-year olds (Avlund and Schultz-Larsen, 1991). A Swedish study of 75-year-olds states that

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47 per cent had mobility problems, but the degree of impairment was not specified (Lindgren et al., 1994). Vital and health statistics reported that more than 90 per cent of Americans over the age of 65 are independently mobile outside. Basic activities of daily living. Most 60–64-year-olds are generally classified as having good basic functional ability, while most 65–69-year-olds are said to have moderate basic functional ability. The same number of 60–64 and 65–69year-olds are listed as having poor basic functional ability (Jylha et al., 1992). This relatively slow decline towards dependence is reflected in the fact that only those over the age of 70 reported an increasing sense of general tiredness (Jylha et al., 1992). Since this chapter is not directed toward people whose function had deteriorated to this extent no further consideration of this group will be made. 1.2.4.2 Work ability Ilmarinen (1995) reported that in a longitudinal study where workers were followed for 10 years in the same job, the work ability significantly declined with age. He measured the work ability through ‘WorkAbility Index’ (Tuomi et al., 1991; Ilmarinen and Tuomi, 1992 and 1993). This work ability index (WAI) is based on seven categories of information obtained through the use of a questionnaire. These items are as follows: 1 Work ability compared with lifetime best. 2 Work ability in relation to work demand. 3 Number of diagnosed diseases. 4 Work impairment due to disease. 5 Absence for work due to sickness. 6 Self-prognosis of work ability after two years. 7 Psychological outlook. The responses were graded on an individual scale for each item with the total ranging from 7 to 49 (poor work ability=7–27; moderate work ability=28–43; good work ability=44–49). The work ability index has been validated against health and work ability (Eskelinen et al., 1991) and functional capacity (Nygard et al., 1991). Ilmarinen (1995) has also reported that the risk of work disability among those having a WAI score of 27 or lower was high; one-third and twothirds of workers became disabled to work within 4 and 10 years respectively. In a four-year follow-up study of 6257 aging workers in 40 different occupations, Ilmarinen (1995) has concluded that poor ergonomics was the main work-related cause of premature decline of work ability and therefore eventual disability. He also reported that given the right circumstances at work, work ability can be sustained and even improved marginally in aging workers. This group of

AGING, DISABILITY AND ERGONOMICS 11

workers took part in regular daily activities which were designed for continuous development at work sites. 1.2.5 Changes associated with aging 1.2.5.1 Morphological changes Body composition. Beginning during the third decade of life and continuing until the sixth, the percentage of body fat increases. On average, body weight increases by about 8 kg from the age of 50 to the age of 80 years (Rutherford and Jones, 1992). Bone loss. With increasing age there is an increasing bone loss. The rate of bone loss is a function of the metabolic requirements of the bone type. Distal bone, being the most metabolically demanding, begins to decrease in thickness linearly from the third to the eighth decade. Vertebral bone density peaks between 40 and 50 years of age and declines rapidly during the sixth decade. Cortical bone is maintained the longest, up until the sixth decade, due to its lesser metabolic requirements. The bone loss is usually considered to be of most importance to females due to the accelerated rate of bone loss experienced five to ten years post-menopause. A further finding that the spine is the most vulnerable of all bone to early menopausal estrogen with-drawals (Rutherford and Jones, 1992) is of great interest in chronic back ailments. Muscle mass. Between the ages of 20 and 80 contractile material within a muscle is gradually replaced with fat and connective tissue. The size and number of muscle fibers, especially fast twitch fibers, decreases (Bonder and Wagner, 1994). These changes result in decreased flexibility, strength, coordination, and increased reaction time. This change in composition results in less than half of the original number of motor units remaining (Rantanen et al., 1994) and those units which do remain experience a decrease in firing frequency capabilities (Soderberg et al., 1991). The body compensates for this by the adoption of remaining fibers into the intact motor units, thereby increasing the unit’s territory (Soderberg et al., 1991) and allowing activation of all of the fibers to occur (Rutherford and Jones, 1992). These larger motor units, when activated at their decreased frequency, can produce the same tension, up to a point, that a younger, smaller, and more highly responsive motor unit would be capable of. As tension requirements heighten the lack of muscle fibers in the older muscle results in the inability to compete. Due to the nature of the different types of muscle contraction, it is the concentric and isometric strengths which are most profoundly affected (Rutherford and Jones, 1992). Rutherford and Jones (1992) also reported a 20 per cent fall in force generating capacity of a muscle once peak age was reached. In their study of British women, Rutherford and Jones

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(1992) saw both a decrease in quadriceps cross-sectional area of 23 per cent and a decrease in quadriceps strength of 40 per cent beginning at the age of 30. An increased rate of force loss was observed during the fifth decade. Other studies such as Skelton et al. (1994) did not see this rapid decline in their healthy male and female population until 85 years of age. Skelton et al. (1994) reported that once the age of peak strength was reached the isometric knee, elbow and hand strength decreased by 1 to 2 per cent and that leg power fell by 3.5 per cent per year. Other studies have showed strength losses of approximately 1.5 per cent yearly. Skelton et al. (1994) also found that females aged 65–84 had 69 per cent of the leg extensor power of their male counterparts. Rantanen et al. (1994) corroborated their values with percentages between 66 and 73 for 75-year-olds. Further analysis of Skelton and colleague’s results showed that at 85–89 years of age women had 80 per cent the power of men. This indicates that the rate of power loss is greater for males. It was also shown that while a woman’s rates of power and strength loss is equal, a man’s power loss exceeds his strength loss (Skelton et al., 1994). It should be noted that part of the decrease in strength experienced by the elderly may be a result of disease and/or disuse in addition to the inevitable changes of aging. Interaction between morphological factors. One final area relating to ageassociated changes in body composition is the relationship between the components just discussed. It has been found that spine and cortical bone density losses correlate best with observed muscle force reductions, while the pattern of distal bone density loss resembles that of muscle size and strength decline (Rutherford and Jones, 1992). A further variable of interest is that of activity level and its role in determining morphological make-up. 1.2.5.2 Systemic changes Nervous and sensory systems. Changes to the nervous system such as increased neuronal loss, a decrease in dendritic branching, plaque formation, a decrease in conduction velocity, and less active neurotransmitters have been documented (Bonder and Wagner, 1994). The incidence of diseases such as Multiple Sclerosis and Parkinson’s also increases, with the former affecting approximately 4 per cent of those 60 years of age and older in the institutionalized, US population (Fillenbaum, 1988). Sensory changes with regards to vision and hearing have also been reported. The number of people suffering from eye diseases such as cataracts is positively correlated with advancing age (Christensen et al., 1994). A Swedish study conducted in 1994 found that in their 75-year and older sample almost one-third had vision impairments and more than one-third experienced hearing difficulties (Lindgren et al., 1994). A related study of 80–89-year-olds found that two-thirds had hearing problems (Jylha et al., 1992). They also reported that in a 10-year

AGING, DISABILITY AND ERGONOMICS 13

longitudinal follow-up the subjects had a one in three chance that their vision would worsen. Metabolic factors. Respiratory changes such as increased respiratory muscle stiffness, decreased joint range of motion of the rib cage, and increased stiffness of elastic, non-contractile tissue result in a decrease in maximum ventilation and an increased work of breathing. These changes result in the elderly having a 20 per cent higher energy cost of breathing than that of young adults (Kelly et al., 1993). Cardiovascular functions also change with age. While some components such as oxygen extraction at the tissue level are unaffected, most are subject to decline resulting in a loss of oxygen transport efficiency (Bonder and Wagner, 1994). With aging the maximum achievable heart rate falls and as a result so does the cardiac output. Homeostatic maintenance of heart rate and blood pressure is also impaired with age with a variability decrease in the former and a variability increase in the latter (Ferrari, 1992). A decrease in circulation lability, arterial distensibility, and cardiac baroreceptor sensitivity results in difficulty adjusting to changes in blood volume associated with medical treatments such as saltrestricted diets and diuretic use (Ferrari, 1992). Some cardiovascular checks such as the vascular baroreflex remain intact (Ferrari, 1992). Metabolic changes as they relate to energy consumption have also been explored. Poehlman (1992) claims that with aging one has more and more trouble balancing energy intake to energy expenditure. A falling basal metabolic rate can lead to ‘extreme fatness or thinness’ due to the lack of adjustment or over-adjustment. This can undoubtedly compromise functional independence (Poehlman, 1992). Didier et al. (1993) claim that the elderly have found ‘a compromise between performing time and energy cost’. They believe that the preservation of independence is encouraged by the body’s ability to compensate for its decreased aerobic capacity and available energy through conservation techniques. They believe that with the learning and practice that precede old age, the body has the opportunity to discover the most efficient pattern and velocity for performing a task. Some activities such as rising from the floor or bed or walking a predetermined distance were found to take the elderly longer (60 per cent longer from the floor and 33 per cent longer from the bed), but required the same energy as that demanded from the younger sample (Didier et al., 1993). Some activities like standing from, and returning to, a low seated position still took the elderly longer, but had a lower energy cost. Other activities were so economically advanced that the elderly performed them in the same time as the younger group, but with less energy demand. An example of this was rising from and returning to a standard or high chair in which it required 30 per cent and 48 per cent, respectively, more energy for the 24-year old group to perform. Other researchers such as Ashworth et al. (1994), have found that the elderly spend relatively the same amount of their time at all the different energy levels as a younger group except for sleeping.

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Diseases. While some studies claim that an 85-year-old is as healthy systemically as a 70-year-old (Christensen et al., 1994) this does not seem to represent the majority view. In the Tampere Longitudinal Study on Aging it was found that one half of those subjects who reported having no disease in 1979 had at least one by the year 1989. True, there were recoveries, but these were small in comparison to the number of new cases (Jylha et al., 1992). In general, 40 per cent of the US, non-institutionalized elderly can be classified as very or fairly healthy, 40 per cent as of average health and 20 per cent as having fairly poor or poor health (Jylha et al., 1992). 1.2.5.3 Postural changes Other age-related changes which are of great functional importance are those that affect posture. Postural changes can lead to changes in mobility and stability and therefore can have a profound effect on functional independence. The postural changes which characteristically occur with advancing age are an increased dorsal kyphosis, a decreased lumbar lordosis, an increased posterior pelvic tilt, an increased forward lean at the hips, a more anterior position of the head, an increased rounding of the shoulders, an increase in scapulae protraction, and increased elbow, hip, and knee flexion (Woodhull-McNeal, 1992; Bonder and Wagner, 1994). It should be noted that these postural changes do not necessarily occur together and that there is much postural variability in the elderly population (Woodhull-McNeal, 1992). The increased forward lean places a greater demand on the trunk and hip extensors and the increased kyphosis reduces height by approximately 5 cm in those over the age of 65 (Woodhull-McNeal, 1992). Other spinal changes such as cervical spondylosis are said to affect 80 per cent of those older than 54 (Bonder and Wagner, 1994). Inactivity has been linked to the increased forward lean and osteoporosis may produce the characteristic stoop due to the anterior wedging of the vertebrae (Woodhull-McNeal, 1992). Muscle weakness has also been suggested as a cause for the forward lean (Woodhull-McNeal, 1992), but it is also probable that the muscle weakness may in turn be a result of the overstretched position caused by the posture (Bonder and Wagner, 1994). With increasing age also comes an increase in postural sway which may be explained not only by the changing body position, but also by the degeneration of spinal mechanoreceptors (Bonder and Wagner, 1994). This increase in postural sway has been linked with increased knee flexion and decreased grip strength (Woodhull-McNeal, 1992) as well as with an increase in balance problems. Between 24 and 58 per cent of Americans over the age of 60 complain of balance difficulties. It is not surprising then that the number one health problem, cause of premature death, immobility, and nursing home placements of those over the age of 74 is falls (Bonder and Wagner, 1994). Fifty per cent of those over the age of 65 reported falling at least once during the past year (Woodhull-

AGING, DISABILITY AND ERGONOMICS 15

McNeal, 1992). None of the postural changes mentioned earlier were related to a subject’s history of falling (Woodhull-McNeal, 1992). The reduction in the number of fast-twitch muscle fibers with age may help explain the high incidence of falls due to the increased reaction time in response to equilibrium upsets (Bonder and Wagner, 1994). Increasing age can also have an effect on gait due to the postural and balance changes. Step length may decrease, walking velocity may decrease, push-off force may decrease, and double stance time may increase (Bonder and Wagner, 1994). In order to help reduce these ambulatory changes, the use of aids such as canes and walkers becomes more common with age. 12.5.3 Arthrological changes A final area where morphological changes are seen is at joints. On average 28 per cent of males and 45 per cent of females over the age of 55 report joint pain (Bagge et al., 1992; Miles et al. 1993). The areas of complaint are similar between sexes with 46 per cent complaining of back or neck, 33 per cent mentioning knees, 22 per cent stating hips, and 36 per cent naming other joints (Miles et al., 1993). Another study named the knee as the most afflicted (Bagge et al., 1992) and other studies cite lower extremity problems more than those of upper extremity. The most common diagnoses of elderly joint pain are rheumatoid arthritis and osteoarthritis. Miles et al. (1993) placed the number of those between the ages of 55–74 afflicted with arthritis as ranging from 28.4 to 55.5 per cent. The pain and decreased range of motion from arthritis has a tremendous functional impact which only grows stronger with advancing age. At age 55, 16 per cent report difficulty walking due to arthritis and 23 per cent find that arthritis makes heavy housework difficult. By the age of 85 the numbers increase to 46 and 52 per cent, respectively (Miles et al., 1993). It is interesting to note that Bagge et al. (1992) found that the time of greatest joint complaints was 70–75 years of age. The observed reduction in complaints after the age of 75 may be attributed to an increasing pain threshold, an increased psychological tolerance, and/or a decreased activity level (Bagge et al., 1992). Arthritic changes may also be responsible for postural changes that further reduce the likelihood of functional self-sufficiency (Woodhull-McNeal, 1992). The foregoing account gives a functional profile of the elderly with underlying reasons for such decline. Such an assembly of information may help us determine our strategies for courses of action, information base to develop reference criteria for design, information to predict the extent and rate of decline in functional capacity, and the biological reasons for such changes. An information base which allows ergonomists to determine ‘what’? and ‘why’? of any problem will put them on a sounder ground to determine ‘how’? An integrated approach, therefore, will permit us not only to solve or design for a specific narrow problem but also be cognizant of other interrelated problems.

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Figure 1.6 Nature and magnitude of disability in Canada in 15+ population.

1.3 Disability 1.3.1 The distribution and severity of disability In a nationwide survey of disability in Canada (Health and Activity Limitation Survey—HALS) all persons with disability either living in households in 1986 or living in institutions in March 1987 were targeted. Data were gathered using face-to-face interviews with a response rate of approximately 90 per cent. An estimated 3.3 million people were identified who suffered either physical or mental disability which interfered with their activities of daily living constituting 14.3 per cent of the total population. Six types of disabilities identified in this survey were disabilities relating to mobility, agility, hearing, seeing, speaking and mental disabilities (Figure 1.6). Nearly two-thirds of the entire disabled population were adults (15–64 years) and suffered from mobility and agility problems. Approximately 1048 000 persons had difficulty with mobility and 916 840 persons reported agility disability. Of these mobility problems, 22 per cent (230 521) were wheelchair bound and 2.3 per cent of persons with agility difficulties used aids such as an artificial hand or arm or arm brace. In addition to

AGING, DISABILITY AND ERGONOMICS 17

Figure 1.7 Proportion of persons over 15 with disabilities requiring household assistance.

disabled adults there were 214 025 disabled children between the ages of 5 to 14 years, and 1026 915 seniors with disability. Many disabled adults needed assistance in their activities of daily living, for example, meal preparation, housework and shopping (Figure 1.7). Nine per cent of disabled adults received help with preparation of meals, and almost 8 per cent needed an attendant even for short distance trips (less than 80 km). Among the seniors, 752 925 reported mobility disability of which 20 per cent used wheelchairs and 17 per cent used a walker. The prevalence of disability reported in various countries varies between a low of 0.2 per cent in Peru to a high of 20.9 per cent in Austria as extracted by DISTAT (1988) based on 63 surveys conducted in 55 countries. A lack of comparability of data from different countries and surveys becomes obvious due to variations in definitions, data collection systems and analytical methodologies used. However, percentages of disabled in a few selected countries are presented in Table 1.1.

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1.3.2 Disability due to aging In general, the rate of disability progressively increases with age. Over one-third of all disabled persons in Canada were aged 65 and older (Statistics Canada, 1990). Table 1.1 Percentage of disabled people by gender. Country

Year

Age group

Both sexes

Male

Female

Egypt Pakistan Peru Poland Turkey Australia Austria Canada China FRG Japan Philippines Spain UK

1976 1981 1981 1978 1975 1981 1976 1986 1987 1983 1980 1980 1986 1985–1986

All ages

0.3 0.5 0.2 7.1 1.5 13.2 20.9 13.2 4.9 – 2.4 4.4 15.0 14.2

0.4 0.4 – – 1.7 – 19.9 12.7 – 11.8 – 5.1 14.8 12.1

0.2 0.5 – – 1.2 – 21.8 13.8 – 9.8 – 3.7 15.7 16.1

18 yrs and over

16 yrs and over

Source: United Nations Disability Statistics Database (DISTAT, 1988)

The HALS reported that those aged 85 and over had a disability rate of 72.9 per cent and those between the ages of 15 and 24 years had a rate of 4.4 per cent (Figure 1.8). Thus the rate of disability among 85+ was five times higher than that of the national average; and the rate of the group 15 to 24 years was onethird of the national average. The number, the rate, the distribution of disability and general population is presented in Table 1.2. However, viewed differently it is obvious that approximately two-thirds of all persons with disability were under the age of 65 years. Increase in prevalence of disability with age is reported worldwide (DISTAT, 1988). The figures for some selected countries are presented in Table 1.2. The single most common cause of disability was an active disease or illness followed by a similar cause in the past. These accounted for 44.6 per cent of all physical disabilities. Approximately 20 per cent of all physical disabilities had their origin in accidents and approximately 12 per cent in the workplace.

AGING, DISABILITY AND ERGONOMICS 19

Figure 1.8 Disability rates in Canada by age group. Table 1.2 Distribution of disability by age. Country

Year

Age range

Age group percentage

0–14

15–24

25–59

60+

Bahrain

1981

Egypt

1976

Mali

1976

Pakistan

1981

Ceylon

1981

Turkey

1975

32.9 14.2 39.9 17.2 44.0 10.0 44.5 19.8 35.3 23.4 40.5 28.0

Ireland

1981

Spain

1981

Total population disabled Total population disabled Total population disabled Total population disabled Total population disabled Total population disabled Total population disabled 15+

28.0

21.9 15.5 19.3 17.5 17.6 10.4 17.1 12.8 21.0 19.1 19.3 11.7 25.1 11.7 22.2 19.5

41.4 36.7 34.5 47.1 32.1 50.9 31.5 32.7 37.1 37.1 32.7 33.6 53.7 33.6 49.2 66.2

3.7 37.7 6.2 18.1 6.2 28.6 7.0 34.7 6.6 16.6 7.3 19.3 21.2 19.3 28.6 14.3

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Country

Year

Age range

Age group percentage

0–14

15–24

25–59

60+

Canada

1983

Austria

1976

Philippines

1980

Total population disabled Total population disabled Total population disabled

21.8 11.0 22.6 3.5 40.9 22.0

35.4 14.4 20.1 6.2 22.2 13.4

23.9 21.4 36.0 37.3 31.5 43.1

18.9 53.5 20.5 53.1 5.4 23.5

Source: United Nations Disability Statistics Database (DISTAT, 1988)

1.3.3 Socioeconomic impact of disability ‘In many respects the disability rate is a socioeconomic indicator, a type of poverty index, or index of development’ (United Nations, 1990). It has also been stated by the UN (1990) that lower socioeconomic status and higher poverty levels are associated with higher disability rates. One of the important factors leading to this result is a higher unemployment rate. The low employment among persons with disability is not unique to a few countries but is a general trend among most countries. In Canada only about 40 per cent of disabled people of working age have gainful employment as opposed to 66 per cent among the general population (Statistics Canada, 1990). Furthermore, employment is unevenly distributed between the two genders. Statistics Canada (1990) also reported that almost half of the disabled men were employed but only approximately 30 per cent of disabled women had any gainful employment. Similarly, in Australia whereas 83 per cent of total males are employed only 44 per cent of those with disability have a job. Among women, the able-bodied females have an employment rate of approximately 46 per cent but those with disability have an employment rate of approximately 24 per cent. Generally, disabled people, even if employed, made far less money than their able-bodied counterparts. In Canada over 57 per cent of the persons with disability had an annual income of less than $10000 compared with 46 per cent of all Canadians. At the other end of the income scale, 6 per cent Canadians with disability made more than $35000 when about 11 per cent of all other Canadians did (Statistics Canada, 1990). 1.3.4 Disabilities In this section, attention will be focused on some of the systemic conditions which result in disability. Minimizing the negative impact of such conditions is the primary goal of rehabilitation. Restoration of function to maintain normal or

AGING, DISABILITY AND ERGONOMICS 21

close to normal activities by means of treatment, exercise or motivation are normal strategies used by rehabilitation professionals. Maximizing the outcome of their endeavor is also in the best interests of their patients and society at large. Ergonomics has an important role to play in many areas. This will be illustrated later. However, a brief description of some of the common conditions and their impact on the function of the patients follows. 1.3.4.1 Pulmonary conditions The class of the pulmonary diseases commonly seen in rehabilitation is collectively termed Chronic Obstructive Pulmonary Disease (COPD). COPDs includes asthmatic bronchitis, emphysema, chronic bronchitis, asthma, bronchiectasis, interstitial lung disease, and cystic fibrosis (Bevelaqua and Adams, 1993). Dyspnea (shortness of breath) is the symptom common to all of these conditions, but as would be expected there is huge variability in the severity of the disability suffered and the rehabilitation required. For example, during the early stages of interstitial lung disease a patient may be asymptomatic at rest, while during an acute asthma attack another patient can become totally incapacitated. The majority of the cases fall between these extremes with the patient exhibiting chronic, yet mild symptoms. Although it may take years for the condition to progress to the point where dyspnea limits activities, it is nonetheless recommended that a patient prepares for a sedentary lifestyle as soon as possible, since the rate of disease progression is highly variable. This preparation should address vocational changes that may be necessary further on in life. Table 1.3 provides an overview of the occupational consequences of pulmonary conditions (Deutsch and Sawyer, 1994). In addition to considering the patient’s blood gases and pulmonary capacity it is also recommended that a psychological assessment be included when trying to predict a patient’s functional ability as the anxiety and fear can severely inhibit pulmonary function. 1.3.4.2 Cardiovascular conditions Cardiovascular disease is the leading cause of death (Markenson, 1991) and is the most common cause of disability (Mariano, 1993). The American Heart Association (1990) reported that more than 330000 undergo coronary artery bypass annually. In the US the direct healthcare cost of coronary heart disease for the year 1990 was estimated to be $41.5 billion. Hartunian et al. (1980) had estimated that the indirect cost of the cardiovascular disease was 4.5 times that of the direct cost. Thus, cardiovascular disease is a major concern to our society in economic as well as in human terms. Since Chapter 4 by Kumar and Mital is

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devoted to this subject, only the briefest mention will be made about the scheme of classification of this disease (Table 1.4) and its vocational impact (Table 1.5). Table 1.3 Vocational impact of pulmonary disorders. Class

Impairment Vocational disabilities

I ● Avoid dust, smoke, fumes, odors and poor ventilation ● Minor problems with heavy physical exercise, repeated climbing and prolonged walking II

0%

Limitations are minimal

10–22%

● Avoid dust, smoke, fumes, odors and poor ventilation

● Avoid heavy physical exercise, repeated climbing and prolonged walking ● Avoid sudden and excessive lifting or carrying and endurance activities III

22–35%

● Avoid everything listed for class 2

● Refrain from lifting 10–20 lbs, walking more than two blocks, climbing more than one flight of stairs IV

50–70%

● Avoid everything listed for class 3

● Avoid walking more than 25 yards ● Avoid any stair climbing, lifting more than a few pounds ● Activities of daily living are affected ● Certain postural positions are affected Source: Adapted from Deutsch and Sawyer, 1994

The classification of the cardiac patients is based on a progressive disability scheme. The Class I patients show no disability or limitation in ordinary physical activities. These activities do not cause undue fatigue, palpitation, shortness of breath (dyspnea) or anginal pain. Patients in Class II have only a slight limitation in their physical work capacity. Among these the ordinary physical activities will result in fatigue, palpitation, dyspnea or anginal pain. For Class III patients, though comfortable at rest, these symptoms are evoked with less than ordinary

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physical activities. Finally, Class IV patients are unable to carry on any physical activity without discomfort. Cardiac insufficiency and anginal pain may be present even at rest and the pain increases with any physical effort. Table 1.4 Classification of cardiac patients. Functional class Permissible workloads in Cal. min−1

Maximal workloads in METs

I II III IV

6.5 4.5 3.0 1.5

4.0–6.0 3.0–4.0 2.0–3.0 1.0–2.0

Table 1.5 Vocational impact of cardiac disease. Class

Impairment

I 0–15% ● Avoid unusual or sudden physical stress ● Avoid unusual or sudden psychological stress ● Avoid heavy lifting/carrying ● Avoid repetitive climbing ● Avoid working in extremes of temperature II 20–45% ● Avoid repetitive lifting, carrying, pulling, pushing, climbing, kneeling, crouching, awkward posture ● Exercise caution in prolonged walking, working on jobs challenging for balance ● Reduce strenuous recreational activities III 50–75% ● Avoid walking 4–5 blocks ● Avoid climbing more than one flight of stairs ● Do not perform any strenuous activity ● Avoid emotional stress ● Avoid activities requiring endurance IV 80–95%

Vocational disabilities Limitations minimal, but

● Avoid prolonged physical exertion

Limitations similar to Class II only more severe

Limitations even more severe than Class III

● No physical exertion ● Curtail ADL as much as possible ● Concentration and attention affected Source: Adapted from Deutsch and Sawyer 1994

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1.3.4.3 Joint diseases Arthritic diseases are quite common in our society affecting tens of millions of people (Deutsch and Sawyer, 1994). Their vocational impact depends on the specific disease, number of joints and systems involved and the job demand. The arthritic diseases consist of rheumatoid arthritis, osteoarthritis, traumatic arthritis, ankylosis spondylitis, gout and a few others. Of these, ankylosing spondylitis and traumatic arthritis have the best functional prognoses (Deutsch and Sawyer, 1994). The most severe form of joint disease is rheumatoid arthritis (RA). RA produces swollen joints resulting in deformities, decreased range of motion and pain (Lee and Abramson, 1993). Affliction of spinal joints can lead to paralysis of muscle, weakness, slower and less coordinated motion (Lee and Abramson, 1993). Joint pain and muscle atrophy limits participation in vocational activities requiring strength and dexterity. Rothstein et al. (1991) describe four stages of rheumatoid arthritis: 1 Early—showing only roentgenological evidence of joint changes. 2 Moderate—In addition to roentgenological changes some muscle atrophy and loss of some range of motion may be present. There is no joint deformity but nodules and tenosynovitis may be present. 3 Severe—In addition to changes of stages 1 and 2 extensive muscle atrophy, joint deformity including subluxation, ulnar deviation, and hyperextension is seen. Nodules and tenosynovitis may be present. 4 Terminal—Fibrous or bony ankylosis occurs severely affecting function. RA is a chronic systemic and one of the most severe rheumatic diseases which occurs due to deranged immune system leading to synovial inflammation and erosion of articular surfaces (Markenson, 1991; Deutsch and Sawyer, 1994). It can also affect blood vessels of the skin, eyes, and nervous system resulting in decreased blood supplies to these structures. Lungs and heart may also be affected. Early symptoms include fatigue, morning stiffness, loss of appetite, and painful wrist, hand, and finger joints. Late symptoms include crepitus, ankylosis, dislocations, and muscle contractures. Osteoarthritis is a degenerative disease and is associated with age, occupational stress, sports overuse/injuries, obesity and also heredity (Deutsch and Sawyer, 1994). It is more common among older people, many of whom are asymptomatic, but others experience mild to moderate pain and stiffness which is aggravated by both excessive activity or inactivity (Deutsch and Sawyer, 1994). However, ADL is usually not significantly affected by this condition (Lee and Abramson, 1993). Anky-losing spondylitis produces inflammation of spinal cartilaginous joints most commonly among males ranging between the ages of 20–40 years (Deutsch and Sawyer, 1994). Despite a decreased range of motion in

AGING, DISABILITY AND ERGONOMICS 25

spinal joints, walking may still be functional (Lee and Abramson, 1993). Selfcare may become more difficult than before but rarely does a person become dependent due to ankylosing spondylitis. Thus, jobs not requiring spinal motion or physical labor can be carried out. Since musculoskeletal conditions are most commonly discussed in most ergonomics books they are omitted here. With respect to the impact of diseases and conditions on individuals it can be stated that the two most serious handicaps suffered are unnecessary institutionalization and unjust unemployment (Symington, 1994). It is important to determine the degree of disability because it helps determine the most effective intervention, prevention, restoration, supplementation or substitution (Badley, 1993). Only when one knows the patient’s environment can one determine their degree of handicap (Badley, 1993). The physical disability is less important than the person’s response to it (Delaney and Potter, 1993) which can be altered through the medium of ergonomics. 1.4 Ergonomics 1.4.1 Ergonomics as an enabler The field of human factors and ergonomics has largely focused on the so-called normal population ranging between the ages of 20 to 65 years. Among these there is also a predominant bias toward younger male sample in the range of 25 to 35 years. From the functional point of view, this group would constitute the most capable group. Most of the ergonomic standards appear to have been set on values obtained from this group. Thus, facilities, processes, and products are all tailored to the characteristics of the foregoing group. However, with the gray revolution in process and the projected numbers of people who will significantly deviate from this reference group, the society may be faced with a problem of large magnitude. Kelly and Kroemer (1990) reported that in the US the number of people over 65 years will reach 59 million in the year 2025 compared with 30 million in 1987. With respect to people with disability, Grall (1979) estimated a figure of 62.3 million. Though there is an overlap between the population with disability and the aging population yet the sum of the two will exceed in number any one of these groups. As reported before, with aging there is a distinct increase in disability. The overall rate of rise in disability with age can be seen by the fact that almost 70 per cent of the disabled in the UK were over the age of 60 years (Schwartz and Peterson, 1979). Coleman (1993) reported that 40 per cent of adults in the UK were over the age of 50 and predicted that by the year 2021 this figure will increase to 48 per cent. In fact, in the entire European Community,

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the rise in the number of the elderly is growing at a pace faster than other age groups. This demographic trend poses some interesting challenges for the field of human factors and ergonomics, not only from the point of revising standards but taking a pro-active approach for organizational design and management of societal human resources. This is desirable on several counts. First, enabling people with lesser capability in a traditionally shrinking labor pool will have a positive impact on global economy. Secondly, by providing means of income to people who would otherwise be sidelined will encourage self-sufficiency, independent living and a feeling of self-worth. Thirdly, such a strategy will reduce the burden on social and health programs allowing the income earners to take care of these. Finally, due to work sharing there may be a little more leisure time for most people to enhance the quality of life. The latter is particularly true because of continued consideration of a shortened work week to increase leisure time. With the perpetuation of the current situation a segment of the population will not be productive due to disabilities. However, it is suggested that the size of that group can be considerably reduced with an ergonomic intervention and a systematic decrease in the demands of the job. To achieve this goal one needs to develop extensive databases of characteristics and capabilities of the population in this group. It must be recognized that the degree of success of this approach will be dependent on the thoroughness of the database. This database must include anthropometry (physical measures), physiological profile (systemic functions), sensory and cognitive functions, pathology or structural damage, if any, and associated functional characteristics. Determination of such variables will provide the information needed to gauge the ends of the scale and numerical distribution of the population along such a scale. With the above information in hand, a thorough and determined effort could be made to evaluate occupations and their current requirements. Based on the physical and functional characteristics redesign can be undertaken. Redesign should be directed towards facilities, processes, and products. Finally, a consideration of assistive devices must be made to empower and enable those who may fall short marginally. This strategy may be one of an extremely tall order. It is unlikely that significant results could be achieved in a short duration. However, a shift in this direction is not only desirable but essential. Ignoring it will be to the detriment of society. Ergonomics can play a major role in this area. The activities geared toward achieving this goal fall under the realm of ‘Rehabilitation Ergonomics’. A more thorough account of this concept is given in Kumar (1989 and 1992).

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1.4.1.1 Strategies The most important step in achieving this goal is the development of an extensive and relevant database. For most physical activities one has to develop some force, sustain it for some time and execute motion of body parts. Therefore, the character-istics which are of most importance are strength, endurance and range of motion. It is, therefore, important to characterize the capability of people in standard activities such as pinching, gripping, lifting, pulling and pushing from the point of view of strength and also ability to sustain them. A characterization of range of motion at different body joints (upper extremities, trunk, head, neck and lower extremities) will prove very useful and important. These coupled with static and dynamic anthropometric measures will allow us to determine the upper and lower bounds in addition to the determination of the optimal range. To enhance the usefulness of the database, it is suggested that the relationship between force and motion be characterized in a dynamic motion. Whereas such measurements at various velocities may be desirable it will be essential to have such measurements performed at normal performance speed. In addition to the foregoing it will be important to have measures of balance and stability. The measurements of sensory capabilities of sight and hearing for communication, coordination, and pacing will be valuable. The foregoing measurements need to be made among normal as well as subnormal groups. Among the normal group these measurements are needed on age and gender differentiated samples. Among the subnormal group, however, the group will be divided by gender, age, and disability. The scheme is presented in Figure 1.9. Subsequent to such measurements a determination of functional equivalency/ hierarchy should be undertaken to determine the relative proficiency of different groups. The purpose of human factors/ergonomics would be to determine the functional capacity and determine the ways to enable the functional subnormal. 1.4.1.2 Implementation Implementation of enabling strategy would require assessment of individuals and their assignment to a functional group. Such an assignment would readily provide a comprehensive picture of a person’s physical capacity. A hypothetical hierarchical scale is presented in Figure 1.10. It will also be essential to develop the task requirements of jobs considered to be suitable simultaneously. Two additional considerations will need to be made. First, a through analysis of the job concerned and considerations of redesign to reduce its functional demands will be needed. Once an optimal level of redesign

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Figure 1.9 A generic classification system of disabilities.

Figure 1.10 Functional hierarchy of functional capacity.

is considered to have been reached, an exploration of ways and means (for example, assistive or augmentative devices) which may enable people deemed to be marginally subnormal should be undertaken (Figure 1.11). Examples of some augmentative devices are briefly described below. For some people with a hearing impairment, turning the volume up on an adjustable phone does not increase the clarity as the booming lower frequencies obscure the crucial high-frequency sounds. An assessment of the hearing impairment allows one to boost the relevant higher frequency on Walter Clarity Telephone to improve the hearing considerably (available from Siemens Hearing Instruments Inc., New Jersey). Motor-impaired people are often unable to use a computer due to lack of a suitable interface. Even a mouse requires too much control for these people. A joystick which acts like a mouse—MouseStick—gets around such difficulty enabling motor-deficient people to do useful things (available from Advanced Gravis Computer Technology, Bellingham, Washington). The Marvel Technologies International Inc., Calgary, Alberta have developed the Mastervoice ECU—a computer-based electronic home control.

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Figure 1.11 Functional capacity of the population in relation to current, redesigned and assisted occupational requirements.

The latter controls lights, electric beds, electric doors, appliances, TVs, radios, stereos and so on just using the human voice. Similarly, there are many assistive devices which can be useful for people with other or milder disabilities or impairments and permit them to live a productive and fulfilling life. 1.4.2 The role of ergonomics in rehabilitation Optimal functional restoration is the ultimate goal of rehabilitation. The success of rehabilitation is, therefore, measurable in terms of outcome. These outcomes are geared towards negotiating the external environment. Regardless of the source of functional impairment (trauma, sudden onset of pathology, degenerative disease, age and so on) the objective of rehabilitation remains restoration of functional normalcy. Though rehabilitation does not have one universally accepted definition, Kumar (1989) defined rehabilitation as follows: ‘Rehabilitation is a science of systematic multidimensional study of disordered human neuro-psycho-social and/ or musculoskeletal function(s) and its (their) remediation by physico-chemical and/or psycho-social means’ (p. 102). Ergonomics on the other hand has been variously defined as, ‘laws governing work’ or ‘man machine interface’. By comparison there is little similarity between rehabilitation and ergonomics. However, as presented by Kumar (1989 and 1992) rehabilitation and ergonomics have quite comparable and complementary goals philosophy and methodology even though they have different clientèle. In consideration of the field of ‘rehabilitation ergonomics’ the unique and specific objectives of these two contributing disciplines remain unaltered. However, the overall goal of enhancement and optimization of function with a variety of means become of paramount significance. Therefore,

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Figure 1.12 A theoretical model of rehabilitation and rehabilitation ergonomics.

simply stated ‘rehabilitation ergonomics is a hybrid branch of science which deals with the means of optimization of function among functionally subnormal’. The functional restoration is the final outcome of rehabilitation, the effectiveness and efficiency of the process is of ergonomic concern. In ergonomic terms, the process of rehabilitation involves two interfaces (Figure 1.12). First, the interface between the therapist and the patient which will have a bearing on the effectiveness of treatment. Secondly, the interface between the patient and the environment surrounding him. Both these interfaces will interact in determining the final outcome of the functional restoration of the patient. 1.4.2.1 Therapist-patient interface Intense therapist-patient interaction occurs at two levels: psychological and physical. The knowledge, biases and expectations of therapists may have a significant impact on the final functional outcome of the patient’s rehabilitation. These may shape the patient’s expectation, motivation and compliance. To ascertain if such biases do exist among therapists, Simmonds and Kumar (1995) tested a sample of 69 physical therapists. Each therapist viewed three videotaped assessments of patients with low back pain that differed in severity. A brief history of the patient containing his or her workers compensation status was provided with the videotape to each participating therapist. Another group of therapists was not provided any information about the patient. These therapists were required to make prognoses based on the physical assessment on the videotapes. Whereas the therapists made similar physical assessments, their prognosis of the patients were significantly different (p<0.05) across the information group. The workers compensation status was deemed to have a

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negative effect on the outcome in patients even with mild low back pain. On the other hand, the non-workers compensation status was considered positive by therapists in prognosis of recovery. Thus, such a knowledge biased the opinions and expectations of the therapists. Basmajian (1975), Peat (1981) and Har-kappa et al. (1991) have all reported that the psychosocial factors may have significant impact on the treatment outcome. Therefore, a preventive ergonomic intervention in the psychological domain at the therapist-patient interface may have a significant impact on the outcome. At the physical level, over and above the validity of the technique, the efficiency and the accuracy of treatment is of paramount importance for an effective treatment. The point will be illustrated by two examples. First, physical medicine and physical therapy are delivered through a physical medium, therefore an accurate location of a physical landmark is essential. These are invariably determined by the technique of palpation before delivering the treatment. An identification of landmark through palpation has been considered accurate and objective (Grieve, 1981; Lee, 1989). This prevalent belief has generally gone unchallenged despite the lack of objective evidence. To test this assumption Burton et al. (1990) investigated the reliability of repeated identification of palpable landmarks. He used invisible marking pen and measured the distance between consecutive marks for spinal levels S2, L4 and T12. Though the distances between the consecutive marks varied, they remained within 5 mm for S2 and L2 and 10 mm for T12 landmarks within raters. Between raters, however, for T12 this distance was 35 mm. Thus within rater these palpation results were considered repeatable and reliable for bony landmarks ‘easy-to-palpate from surface’. In a study, Simmonds and Kumar (1993) investigated the reliability of palpation of the anterior border of lateral collateral ligament at the level of the knee joint, the spinous process of L4, the posterior superior iliac spine, and the transverse process of L4. Experienced therapists were asked to mark each structure with an invisible ink and repeat the process after lapse of time. Whereas the palpation of L4 was done accurately, all others were not accurate. The level of inaccuracy increased with the depth of the tissue (p<0.02). It is conceivable that the poor reliability of many clinical tests may be due to the errors associated with palpation. Thus standardization of this procedure to enhance accuracy at this interface is of vital importance for an optimal outcome. The next stage of effective treatment will depend on the delivery of an appropriate dose of a valid treatment. One of the common treatment modalities for low-back pain is spinal mobilization. Four grades of mobilization and their needs have been advocated in the literature (McKenzie, 1987). Therapists commonly administer spinal mobilization subjectively assessing the grade of the treatment they administer. The accuracy of such an assessment needs to be established. Therefore in a study, Simmonds et al. (1995) quantified the forces exerted on and the displacements produced by the vertebral body during mobilization on a spinal model: Kumar (1995) designed and fabricated an

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Electro-Mechanical Spinal Model (US patent). On this model, 10 experienced therapists performed four grades of mobilizations at three different levels of joint stiffness—low, medium and high stiffness. The mean peak force values recorded were lowest in the least stiff condition across all grades of mobilization (57.6– 120 N). For medium and high stiffness conditions the exerted force values were similar, ranging between 82–178 N for medium stiffness and 81–162 N for high stiffness. Similarly, the peak displacement for each grade of mobilization for low, medium and high levels of stiffness ranged between 2.2–3.4 mm, 1.8–2.0 mm and 1.9–2.2 mm respectively. The results showed that there was a significant difference in force exerted due to the stiffness of the spine as well as the grade of mobilization (p<0.01). However, there was a large range of inter-therapist variability. The force exerted by different therapists varied between 7 to 380 times, whereas the displacements produced varied between 12 to 112 times. The value of any treatment depends on delivery of a valid treatment in a consistently standardized manner. The degree of variability encountered among seasoned therapists may be a reason for concern. Therefore, it is essential to standardize the treatment. The latter will be achievable through the medium of ergonomics. Enhancing this consistency will optimize the outcome of rehabilitation. 1.4.2.2 Patient-environment interface There is a considerable value in an objective and holistic assessment of a patient’s performance and a profile of the tasks to be performed. Such matching for determination of deficits as advocated by Kumar (1992) will be essential to focus the rehabilitation attempts for optimizing the rehabilitation outcome. Means. The means of successful implementation of the objectives of rehabilitation ergonomics lie in development of methodology and databases and their interpretation and integration. The methodology may be adapted for the purpose from the existing tools and methods. Using these, relevant databases need to be created to develop norms or ranges of samples of interests. These databases then need to be integrated for appropriate use, in this case design or modification. With aging, trauma or disease there may be decrement in one or more functions of the body. Most functions require motion, force application and velocity of execution. If one considers these functions in an occupational context, endurance and repetition become important. Therefore, it is essential to determine the job profile in terms of motion, force, velocity and repetition. For the information to be helpful and relevant, the data must be collected simultaneously in the occupational milieu. Therefore, the force exerting capacity through the range of motion and sustainable velocity and repetition will be essential. Thus, such multidimensional data must be collected in physical, psychological or social domains as needed (Kumar, 1992). The decision regarding a course of action (treatment, training, return to work and so on) will

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depend on the job demand. Therefore, a systematic job analysis to determine job demands would be an essential complimentary step. A quantitative overlap of the patient’s physical and psychosocial capability over the job requirement (Figure 1.13) will allow an economically trained rehabilitation professional to determine the deficiencies and select a strategy to manage the case. The hypothetical task illustrated in the figure requires a great deal of speed, precision, dexterity, perception, cognition and fast reaction time. On these criteria in this hypothetical example the identified deficiencies prohibit the worker to return to work. For this job, the patient needs further rehabilitation. However, there may be another job which this patient may be able to do. Thus, depending on the severity of deficiencies, the patient may be placed either on an alternate job, returned to rehabilitation or sent for work-hardening. Thus, in order to employ rehabilitation ergonomics one may have to consider a variety of steps and strategies as presented in Figure 1.14. Although the components of rehabilitation ergonomics are multifarious they either impact on the ‘therapist-patient’ interface or the ‘patient-environment’ interface. It will only be through a thoughtful and careful application and execution that we may be able to remove or reduce the barriers for a significant segment of our population, and make a positive contribution to the national as well as the world economy. Therefore, the model presented in Figure 1.12 represents the theoretical framework of rehabilitation ergonomics. Statistics Canada (1990) reported that a significant proportion of the population with disability requires help from family, friends, volunteers or paid care-givers. Almost one half (45.6 per cent) of all disabled people require assistance with heavy household work, and 22.4 per cent with daily housework. In terms of the cost, though the figures were not given, it is surmised that it will be significant. Many able-bodied people have to spend their time to assist. The cost of this time along with the cost of the paid healthcare worker can add up to a significant magnitude. It may be useful to point out that the largest cost for these people is not medical but maintenance, attendant care, nursing home and homecare expenses in addition to loss of productivity due to inability to work. Environment modification and assistive devices may offer disabled people a chance to decrease these costs and be a productive member of society. It is interesting to note that an emphasis on maintenance continues to be a primary strategy in managing disability. In the US 3000 times more money was spent on the maintenance category than was spent on development of methodology which will allow self-care for the disabled (McNeal, 1982). Self-care will allow selffulfilment, impart a sense of self-worth and feed back the economy. The calculation of LeBlanc and Leifer (1982) provides a strong economic justification as well. They reported that every dollar spent on assistive devices produced an elevenfold return.

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Figure 1.13 A conceptual model of holistic comparison of patients’ capability B and job requirement A.

1.5 Conclusions Given the size and significance of the population with disability (due to aging, trauma or disease), the rationale of extensive application of rehabilitation ergonomics is not only economically viable but profitable. Given the additional benefits of self-worth and actualization for people with disability, the development and application of rehabilitation ergonomics is not only desirable but becomes the strategy of choice. In planning and implementing this strategy it will be of considerable importance to develop disability-related functional databases. A theoretical basis for development of a scheme of classification based on functional needs must be established. The classification based on function will establish the grades and profiles of functional abilities/disabilities. Such information will permit ergonomists to develop many generic solutions targeted for functional groups. Routes of specific modification and design can then be picked from more established and functionally adapted facilities, processes or products as the case may be. This ergonomic approach and strategy

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Figure 1.14 Components of rehabilitation ergonomics.

will systematize our response and enhance our efficiency in dealing with this fast-growing problem. References AMERICAN HEART ASSOCIATION (1990) Heart and Stroke Facts. Dallas, TX. ASHWORTH, J.B., REUBEN, D.B. and BENTON, L.A. (1994) Functional profile of healthy older persons, Age and Aging, 23, 34–9. ASTRAND, P. and RODAHL, K. (1977) Textbook of Work Physiology. New York: McGraw-Hill. ASTRAND, P-O. and RODAHL, K. (1986) Textbook of Work Physiology. New York: McGraw-Hill.

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AVLUND, K. and SCHULTZ-LARSEN, K. (1991) What do 70-year-old men and women actually do? And what are they able to do? From the Glostrup survey in 1984, Aging, 3, 39–49. BADLEY, E.M. (1993) An introduction to the concepts and classifications of the international classification of impairments, disabilities and handicaps, Disability and Rehabilitation, 15(4), 161–78. BAGGE, E., BJELLE, A., EDEN, S. and SVANBORG, A. (1992) A longitudinal study of the occurrence of joint complaints in elderly people, Age and Aging, 21, 160–7. BASMAJIAN, J.V. (1975) Research or retrench. The rehabilitation professions challenged, Physical Therapy, 55, 606–10. BEVELAQUA, F.A. and ADAMS, F.V. (1993) Pulmonary disorders, in EISENBERG, M. G., GLUECKAUF R.L. and ZARETSKY, H.H. (Eds) Medical Aspects of Disability. A Handbook for the Rehabilitation Professional, pp. 325–41, New York: Springer. BONDER, B.R. and WAGNER, M.B. (1994) Functional Performance in Older Adults. Philadelphia: F.A.Davis Company. BROWN, M. and HOLLOSZY, J.O. (1993) Effects of walking, jogging and cycling on strength, flexibility, speed and balance in 60 to 72 years olds, Aging Clinical and Experimental Research, 5, 427–34. BURTON, K., EDWARDS, V.A. and STYKES, D.A. (1990) ‘Invisible’ skin marking for testing palpatory reliability, Journal of Manual Medicine, 5, 27–9. BUSSE, E.W. (1993) Science for healthy aging in North America, Aging Clinical and Experimental Research, 5 (2), 142–4. CHRISTENSEN, H., JORM, A.F., HENDERSON, A.S., MACKINNON, A.J., KORTEN, A. E. and SCOTT, L.R. (1994). The relationship between health and cognitive functioning in a sample of elderly people in the community. Age and Aging, 23, 204–12. COLEMAN, R. (1993) A demographic overview of the aging of the First World populations. Applied Ergonomics, 24, 5–8. CORPUS ALMANAC and CANADIAN SOURCEBOOK (1995), 3rd edn Don Mills, ON: Southam Inc. CZAJA, S.J. (1990) Human Factors Research Needs for an Aging Population. Washington, DC: National Academy Press. DELANEY, G.A. and POTTER, P.J. (1993) Disability post stroke, Physical Medicine and Rehabilitation: State of the Art Reviews, 7 (1), 27–42. DEUTSCH, P.M. and SAWYER, H.W. (1994) A Guide to Rehabilitation, Vol. 2. New York: Matthew Bender. DIDIER, J.P., MOUREY, F., BRONDEL, L., MARCER, I., MILAN, C., CASILLAS, J. M., VERGES, B. and WINSLAND, J.K.D. (1993) The energetic cost of some daily activities: A comparison in a young and old population, Age and Aging, 22, 90–6. DISTAT (1988) United Nations Disability Statistics Data Base, UN, New York. ESKELINEN, L., KOHVAKKA, A., MERISALO, T., HURRI, H. and WAGAR, G. (1991) Relationship between the self-assessment and clinical assessment of health status and work ability, Scandinavian Journal of Work, Environment and Health, 17 (Suppl 11), 40–7. FERRARI, A.U. (1992) Age-related modifications in neural cardiovascular control, Aging Clinical and Experimental Research, 4, 183–95. FILLENBAUM, G.G. (1988) Multidimensional Functional Assessment of Older Adults. Hillsdale: Lawrence Erlbaum Associates.

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GRALL, T.B. (1979) A feasibility study of product testing and reporting for handicapped consumers. Veteran Administration, NY 10550. GRIEVE, G.P. (1981) Common Vertebral Joint Problems. Edinburgh, Scotland: Churchill Livingstone. HARKAPAA, K., JARVIKOSKI, A., MELLIN, G., HURRI, H. and LUOMA, J. (1991) Health locus of control beliefs and psychological distress as predictors for treatment outcome in low back pain patients: results of a three-month follow-up of a controlled intervention study. Pain, 46, 25–41. HEALTH and ACTIVITY LIMITATION SURVEY (1986) Statistics Canada, Ottawa: Canada. ILLMARINEN, J. (1992) Job design for the aged with regard to decline in their maximal aerobic capacity. Guidelines for the practitioner, International Journal of Industrial Ergonomics, 10, 65–77. ILLMARINEN, J. (1995) A new concept for productive aging at work, in HEIKKINEN, E. (Ed.) Preparation for Aging, pp. 215–22, New York: Plenum Press. ILLMARINEN, J. and TUOMI, K. (1992) Work ability of aging workers, Scandinavian Journal of Work, Environment and Health, 18 (Suppl 2), 8–10. ILLMARINEN, J. and TUOMI, K. (1993) Work ability of aging workers, in ILLMARINEN, J. (Ed.), Aging and Work Proceedings of the International Scientific Symposium on Aging and Work, pp. 142–51, Helsinki: Institute of Occupational Health. ILLMARINEN, J., TUOMI, K., ESKELINEN, L., NYGARD, C.-H., HUUHATANEN, P. and KLOCKARS, M. (1991) Summary and recommendations of a project involving cross-sectional and follow-up studies on the aging worker in Finnish municipal occupations (1981–5), Scandinavian Journal of Work Environment and Health, 17 (Suppl 1), 135–41. JYLHA, M., JOKELA, J., TOLVANEN, E., HEIKKINEN, E., HEIKKINEN, R.L. and OSKINEN, S. (1992). The Tampere longitudinal study on aging, Scandinavian Journal of Social Medicine. (Suppl 47), 1–58. KELLY, P.L. and KROEMER, K.H.E. (1990) Anthropometry of the elderly. Status and recommendations, Human Factors, 32, 571–95. KELLY, N.G., MCCARTER, R.J.M. and BARNWELL, G.M. (1993) Respiratory muscle stiffness is age- and muscle-specific, Aging Clinical and Experimental Research, 5, 229–38. KUMAR, S. (1989) Rehabilitation and ergonomics: Complimentary Disciplines, Canadian Journal of Rehabilitation, 3, 99–111. KUMAR, S. (1990) Cumulative load as a risk factor for low-back pain, Spine, 15, 1311–6. KUMAR, S. (1992) Rehabilitation: An Ergonomic Dimension, International Journal of Industrial Ergonomics, 9, 97–108. KUMAR, S. (1994) A conceptual model of overexertion, safety and hazard, Human Factors, 36, 197–209. KUMAR, S. (1995) Therapeutic Spinal Mobilizer. US Patent. LARSSON, B., RENSTROM, P., SVARDSUDD, L., WELIN, L., GRIMBY, G., ERIKSSON, H., OHLSON, L.O., WILHELMSEN, L. and BJORNTORP, P. (1984) Health and aging characteristics of highly physically active 65-year-old men, European Heart Journal, 5 (Suppl E), 31–5.

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LEE, D. (1989) The Pelvic Girdle, pp. 15–91, Edinburgh, Scotland: Churchill Livingstone. LEE, S. and ABRAMSON, S.B. (1993) Rheumatic diseases. In EISENBERG, M.G., GUECKAUF, R.I. and ZARETSKY, H.H. (Eds). Medical Aspects of Disability. A Handbook for the Rehabilitation Professional, pp. 355–77, New York: Springer. LINDGREN, A., SVARDSUDD, K. and TIBBLIN, G. (1994) Factors related to perceived health among elderly people: The Albertina Project, Age and Aging, 23, 328–33. MANTON, K.G. (1991) The dynamics of population aging: Demography and policy analysis, The Milbank Quarterly, 69, 309–38. MANTON, K.G., STALLARD, E. and SINGOR, B.H. (1991) Future Demographic Trends in Europe and North America. What Can We Assume Today ? London: Academic Press. MARIANO, J.R. (1993) Cardiovascular Disorders, in EISENBERG, M.G., GLUECKAUF, R.L. and ZARETSKY, H.H. (Eds), Medical Aspects of Disability. A Handbook for the Rehabilitation Professional, pp. 119–46, New York: Springer. MARKENSON, J.A. (1991) Worldwide trends in the socioeconomic impact and longterm prognosis of rheumatoid arthritis, Seminars in Arthritis and Rheumatism, 21 (2 Suppl 1): 4–12. MCKENZIE, R.A. (1987) Mechanical diagnosis and therapy of low back pain toward a better understanding, in TWOMEY, L.T. and TAYLOR, J.R. (Eds), Physical Therapy of the Low Back, pp. 157–73, New York: Churchill Livingstone. MCNEAL, D.R. (1982) Applying technology to help the disabled, Engineering in Medicine and Biology, 1, 15–6. MILES, T.P., FLEGAL, K. and HARRIS, T. (1993) Musculoskeletal disorders: time trends, comorbid conditions, self-assessed health status and associated activity limitations, Vital and Health Statistics, 27, 275–88. MOR, V., MURPHY, J., MASTERSON-ALLEN, S., WILLEY, C., RAZRANPOUR, A., JACKSON, M.E., GREER, D. and KATZ, S. (1989) Risk of functional decline among well elders, Journal of Clinical Epidemiology, 42 (9), 895–904. NATIONAL INSTITUTE ON AGING (1991) Behavioral and Social Research Program: Global Aging. Comparative Indicators and Future Trends. Washington, DC: US Department of Commerce, Bureau of Census. NYGARD, C.-H., ESKELINEN, L., SUVANTO, S., TUOMI, K. and ILLMARINEN J. (1991) Associations between functional capacity and work ability among elderly municipal employees, Scandinavian Journal of Work, Environment and Health, 17 (Suppl 1), 122–7. PEAT, M. (1981) Physiotherapy; art of science? Physiotherapy Canada, 33 (3), 170–6. POEHLMAN, E.T. (1992) Metabolic deterioration with advancing age: The role of physical activity, Aging Clinical and Experimental Research, 4 (3), 260–2. RANTANEN, T., ERA, P. and HEIKKINEN, E. (1994) Maximal isometric strength and mobility among 75-year-old men and women, Age and Aging, 23, 132–7. ROTHSTEIN, J.M., ROY, S.H. and WOLF, S.L. (1991) The Rehabilitation Specialist’s Handbook. Philadelphia: F.A.Davis. RUTHERFORD, O.M. and JONES, D.A. (1992) The relationship of muscle and bone loss and activity levels with age in women, Age and Aging, 21, 286–93. SALTIN, B. (1990) Anaerobic capacity: past, present and perspective, in TAYLOR, A.W., BDLAKK, P.D., GREEN, H.J., IANUZZO, E.G., NOBLE, G., METIZIER

AGING, DISABILITY AND ERGONOMICS 39

and SUTTON, J.R. (Eds). Biochemistry of Exercise VII, pp. 387–412, Champaign, Ill: Human Kinetic. SCHWARTZ, A.N. and PETERSON, J.A. (1979) Introduction to Gerontology. New York: Holt Rinehart & Winston. SELIGER, V. and BARTUNEK, Z. (Eds). (1976) Mean values of variation indices of physical fitness in the investigation of Czechoslovak populations aged 12–55. Prague Czechoslovak Association of Physical Culture, pp. 1–117. SIMMONDS, M. and KUMAR, S. (1993) Location of body structure by palpation: reliability study. International Journal of Industrial Ergonomics, 11, 145–51. SIMMONDS, M. and KUMAR, S. (1995) Does knowledge of a patient’s workers compensation status influence clinical judgements? Journal of Occupational Rehabilitation, 6 (2), 93–107. SIMMONDS, M., KUMAR, S. and LECHELT, E. (1995) Use of a spinal model to quantify the forces and motion that occur during therapists’ tests of spinal motion, Physical Therapy, 75 (3), 212–22. SKELTON, D.A., GREIG, C.A., DAVIES, J.M. and YOUNG, A. (1994) Strength, power and related functional ability of healthy people aged 65–89 years, Age and Aging, 23, 371–7. SODERBERG, G.L., MINOR, S.D. and NELSON, R.M. (1991) A comparison of motor unit behavior in young and aged subjects, Age and Aging, 20, 8–15. STATISTICS CANADA (1990) The Health and Activity Limitation Survey. Highlights: Disabled Persons in Canada. Catalogue number, 82–602, Ottawa. SYMINGTON, D.C. (1994) Megatrends in rehabilitation: a Canadian perspective, International Journal of Rehabilitation Research, 17, 1–14. TUOMI, K., ILLMARINEN, J., ESKELINEN, L., JARVINEN, E., TOIKKANEN, J. and KLOCKARS, M. (1991) Prevalence and incidence rates of diseases and work ability in different work categories of municipal occupations, Scandinavian Journal of Work, Environment and Health, 17, (Suppl 1), 67–74. UNITED NATIONS. (1990) Disability Statistics Compendium. Series Y;4, New York: Department of International Economic and Social Affairs Statistical Office. US DEPARTMENT OF HEALTH AND HUMAN SERVICES. Physical functioning of the aged —United States. (1984) Vital and Health Statistics Series10, data from the National Health Survey No. 167, March 1989. WOODHULL-MCNEAL, A.P. (1992) Changes in posture and balance with age, Aging Clinical and Experimental Research, 4, 219–25.

CHAPTER TWO Disabilities associated with aging in the workplace and their solutions MASAHARU KUMASHIRO

2.1 Introduction This chapter will focus on the decline of physiological functions which accompany aging and loss of abilities required to execute tasks in the workplace caused by this decline. It will then turn to the development of ergonomics support in the workplace for these type of disabilities. Strictly speaking, aging begins from the moment of conception and it refers to the process from growth, maturation to old age. However, in this chapter, the term ‘aging’ will refer to those individuals from 45 to 65 years of age. When humans reach this age, they begin to exhibit a decline in those physiological functions which are required to execute their jobs ranging from muscle strength, respiration, circulation, sensory functions such as vision and hearing through to higher neural functions. Together with this deterioration, their ability to perform tasks can also decline. As a result, society views them as having a reduced ability to execute the work at hand and they are labeled as disabled workers. Specifically, they can be treated as if they fall under the classification of handicapped. Solutions must be devised to deal with those disabilities which arise from the aging process which all living things go through. These solutions are required to ensure the physical and mental well being of middle-aged and elderly workers as well as to promote a sound and vibrant society and economy. In particular, the unique solutions which have been devised by Japanese corporations to tackle these problems will be introduced in this chapter. 2.2 An overview of aging ‘Aging’ refers to the manner in which the functions, morphology and other features of living organisms change with time; the period of the process extends from birth through decline to death. It is difficult to give a definitive demarcation of the stages of aging, but to assign names to different age ranges, one may speak

M.KUMASHIRO 41

of nine stages— fetal period, infancy, childhood, puberty, youth, maturity, middle age, early old age and old age. Apart from these nine stages, the question also arises. ‘From about when does the individual begin to feel aged for the purposes of work?’ If the ‘aging worker’ is defined in terms of aging working populations, the WHO Study Group on Aging and Work Capacity (1993) defines such persons as 45 and older. Similarly, Japan’s Ministry of Labor defines persons 45 or older as middle- to older-aged workers, and persons 55 and older as older-aged workers, based on special laws to promote employment of middleto older-aged persons. Hence, when discussing aging from the standpoint of the aged workforce, it is appropriate to consider the age range from 45 to 65. Major changes in bodily functions attending aging begin to appear prominently beginning from the mid-40s, the period regarded by many as their most productive. In particular, general physiological performance, as well as functions such as capacity to recover from fatigue which affect the adjustment and maintenance of vital activities, begin to decline at an increasing rate. The extent to which these changes are felt differs from one individual to another; but people in this age group acquire through experience a common perception that it is now difficult to accommodate rapid changes in one’s living environment or recognize a decreased willingness to rise to new challenges, to learn new techniques or to take on new duties and a decline in one’s capacity to adjust to the latter. In Japan, phrases used to indicate the beginning of aging have long included the adage that ‘When one passes 40, the eyes become so weakened that daytime seems like night-time’ and ‘The aging process begins from one’s feet’. Contrasting these proverbs with physiological data, it is found about the first that accommodation, dynamic visual acuity and night-time vision are reduced, and with respect to the second that there is a decline in muscular and general bodily strength (Figure 2.1). Indeed, aging phenomena begin with a decline in sensory functions, central among which is the sense of sight. At the same time, it is taught that the decline in muscular strength starts from the legs, proceeding to the hips and then extending to the arms and hands. The vital activities of humans are maintained and controlled as the result (or output) of the harmonized actions of various mental, bodily and other functions. It is most important to recognize that the level of this output differs with each human being. Hence it is difficult to determine objectively at what point or from what time old age begins, and it is similarly difficult to set forth clear rules of a general nature regarding the onset of old age. Changes in the mental and physical functions of humans are thought to arise through comprehensive changes in multifaceted components. Japanese words used to express this include the phrase ‘the body and the mind are as one’. This phrase is used to refer to an improvement in one’s attitude toward living, in a manner of performing labor or in treatment of disease, among other situations, indicating a ‘coping’ of some kind. In the course of one’s daily routine, the phenomena of functions decline with aging, and other functions attempting to

42 DISABILITIES ASSOCIATED WITH AGING

augment the former to preserve a kind of balance, can be observed. In actuality, I have often heard the following kinds of remarks from middle- to older-aged workers at manufacturing sites and other workplaces: ‘My vision and physical strength have both dropped compared with when I was young. But, I can bring better concentration, understanding and judgment to my work’. A similar sentiment can also be found in the ancient Analects of Confucius in China: ‘At 40 we become spiritually tranquil. At 50 we begin to understand our calling in life. At 60 we finally begin to understand all the things that people tell us’. This suggests that in middle age much experience has accumulated, one’s knowledge has been organized and systematized, and as a result it is possible to perform comprehensive analyses, examinations and judgments. In this way, the aging phenomena which appear in middle age and later affect vital activities have two distinct sides: changes in physical functions which reinforce a declining tendency, and changes in mental functions which tend to be relatively stabilizing, but which on entering old age are gradually reduced. It should also be noted that there can be no rapid or sudden changes in the environmental control system within the body which relies on biochemical mechanisms within the body, such as immune reactions and nervous internal secretions. Thus, mechanisms to adjust the various functions which contribute to vital activities supplement each other to always preserve a balance, so that an aging-induced catastrophic collapse of health-giving activities is not possible. It may be concluded that the loss of one’s ability to work is also held to a minimum. Finally, there is one aspect which must not be ignored in a discussion of human aging phenomena. This is that individual differences will appear prominently in reactions to stressing agents from outside from the time that one’s prime is passed. Conversely, this can be taken to mean that if one engages in adequate health-preserving and health-reinforcing activities before the onset of old age, then mental and physical activities may be maintained sufficiently for one to enjoy ‘youth in old age’, a rejuvenation of sorts. Of course it is not too late to begin taking such measures even when one has passed one’s prime. Through the daily management of one’s health, it is possible to prevent accelerated aging. In particular, it is not an exaggeration to say that the brain is what governs human life activities. In this sense, it is important that one always strive to maintain the brain’s activities in the best possible condition. In general, when studying stress due to aging, there is sometimes a tendency to regard only overloading or overstimulation as problems; but for the human body, a state of underloading or understimulation is also a powerful stress-inducing situation (Figure 2.2). A situation of minimal stimulation occurs, for instance, in work which involves monotonous repetition. If monotonous repetition is performed continuously for a certain period of time, this state of understimulation may induce the lowering of physiological and psychological arousal levels in the cerebral cortex as a symptom of the initial stage of stress. That is, the individual falls into a kind of transitory mental saturation state in which sleeplike tendencies are pronounced, with complaints of ‘grogginess’, that one’s ‘head is fuzzy’ and one ‘can’t

Figure 2.1 Decline in muscular and body strength with aging (for the case of Japanese subjects). Arm strength, back strength and leg strength are shown as indices of general muscular strength. As an index of body strength, the maximum oxygen uptake, which is the maximum capacity for taking in oxygen in unit time, is shown. The maximum oxygen uptake determines overall physical endurance.

M.KUMASHIRO 43

44 DISABILITIES ASSOCIATED WITH AGING

Figure 2.2 Stimuli and health effects.

concentrate’. If this work is continued indefinitely, if it must be completed rapidly or if certain regulations are in force, then the stress on the individual engaged in this labor is intensified even further in both quantity and quality, leading to a chronic form of mental stress symptoms. On the other hand, an individual requires a stressor load of an appropriate quality and quantity (Figure 2.2). That is, an optimal physiological reaction and appropriate state of psychological demand play important roles in adjusting and maintaining life functions. Thus, one effective method is to provide an appropriate stressor (beneficial stimulus; stimulus which induces eustress) in daily living and work, in order to activate the brain’s functions. In any case it is clear that stressors such as external factors working to promote aging play an important role. Consequently, one must not place oneself in environments which provide either too much or too little stress. One should also try to keep a balanced, nutritious diet to properly maintain physiological activities. It is important that one understands the responses to aging and their limits and that this knowledge be used to promptly establish countermeasures. 2.3 Three rules describing aging in the workplace In order to evaluate the ability to adapt the work of middle- to old-aged workers, an objective understanding of the changes with aging in physiological functions is essential. Numerous research results on physiological functions and ability to perform tasks as they relate to work and aging may be summarized in the form of the three rules indicated in Figures 2.3 and 2.4.

M.KUMASHIRO 45

Figure 2.3 General remarks on the middle- to old-age workers; rules describing the penalties of aging.

Rules 1 and 2 shown in Figure 2.3 refer to biological aging phenomena, and indicate that such phenomena are irreversible. However, rule number 2 implies that through proper exercise based on an exercise program, the rate of the phenomena can be slowed. An example of this is given in Figure 2.5. These results were compiled for 1055 employees at a certain manufacturing company; physical strength scores are compared for groups of workers exercising for 30 to

46 DISABILITIES ASSOCIATED WITH AGING

Figure 2.4 General remarks on the middle- to old-age workers; rules describing the advantages of aging.

40 minutes daily and for workers doing no exercise at all, broken down by worker age in 5-year increments. Here the physical strength score was computed from the results of five individual tests—a side jumping test, vertical jumping test, relative grip strength test, standing trunk-flexion test, and stepping test. Here ‘exercise’ refers to 30 to 40 minutes or so of informal tennis, or jogging performed alone at dawn or at dusk, or a golf or tennis session during a day off work, or similar activities performed as recreation during lunch breaks or after work, rather than some quantified, periodic formal exercise. The results demonstrate that the physical strength or physiological age of persons who exercise is less than that of persons who do not, and that the effect of exercise is significant. Rule 3 in Figure 2.4 concerns the ability to perform job duties. It suggests that, depending on past experience or on the individual’s desire to work, this ability may actually be enhanced with aging. There are two aspects to this aging

M.KUMASHIRO 47

Figure 2.5 Changes in body strength with aging for 1055 employees at corporation X. A comparison of a group engaged in some form of exercise for 30 to 40 minutes daily and a group which does not exercise at all.

phenomenon. If the features of a job are such that ability to perform a certain type of work is the result of training, then the latter rule suggests that the level of functions contributing to this ability is higher compared with middle- to old-aged workers of the same generation. Conversely, if the characteristics of a job are such that work places an excessive burden on certain functions, then it is expected that these functions will fall far below their normal level. Hence ergonomists must immediately consider the three following problems. First, ergonomists must analyse the mental and bodily changes appearing in midlife and later from the perspective of physiological and psychological functions, to obtain a general and objective understanding of aging phenomena as one facet of the life sciences. Secondly, the task of designing methods for performing tasks and environments for living and work which are benign to the body begin with the development of tools and other artifacts for use and should be based on a correct understanding of the change in functions of middle- to oldage persons. The concept of job redesign which is today gaining in popularity is one concrete means to this end. Thirdly, various measures must be designed pertaining to the management of the psychological health conditions of middleto old-aged persons. This would include, for instance, development of a methodology for designing and managing organizations which consider human relations and factors which boost the individual’s desire to work, not to mention medical measures to improve overall mental health.

48 DISABILITIES ASSOCIATED WITH AGING

Figure 2.6 Comparison between the level of the somatic functions in aged workers and young workers (Kumashiro, 1995).

2.4 Fluctuations in the levels of physiological functions with aging Figure 2.6 compares the results of 10 physiological tests of visual functions, psychomotor functions, ability to process information, physical motor functions, hand and finger functions, and respiratory system functions for young workers and for middle-to old-aged workers. These 10 tests can each be conducted at the workplace and are each regarded as being closely related to work (Figure 2.7). That is, the results of 10 tests performed prior to work on a workday (Monday) were taken as reference values for both the young and the older workers, and the ratio (expressed in per cent) of the values for the older workers to those of the younger workers for each of the 10 tests were plotted on a radar chart. The subjects in question were 22 middle- to old-aged workers aged 47 to 58 (average age 51.7) and 22 younger workers aged 19 to 29 (average age 24.0), employed in a steel frame-machining shop and in a motorcycle part manufacturing shop in machining and assembly tasks. The average number of years of experience in their respective jobs was 16.7 years for the older workers, and 6.1 years for the younger workers. The dashed-line circle in Figure 2.6 indicates the levels of the different functions for the young workers; the solid lines similarly denote the levels of the respective functions for the older workers. Examination of the radar chart reveals that the decline in function is greatest for the case of the near-point accommodation (diopter), followed by the decline in short-term memory, which is regarded as an indication of the ability to process information. On the other hand, the ability to maintain concentration (TAF-test, developed by Takakuwa, 1962), which is thought to reflect changes in the level of activity of the cerebral cortex, as well as shifts in the center of gravity, regarded as an index of equilibrium functions, were superior among the middle- and old-aged workers.

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Figure 2.7 The items of physiological and psychophysiological functions examined (Kumashiro, 1995).

Thus, many of the physiological functions believed to be closely related to labor decline sharply with aging, but some functions are not greatly affected by the aging process. Figures 2.8 and 2.9 separately present other interesting data relating to shifts in the body’s center of gravity, for which the score of older workers was superior to that of the younger workers. The data of Figures 2.8 and 2.9 were taken for a total of 12 female workers—six older women employed as sales clerks in a certain department store in the Tokyo metropolitan area were between the ages of 49 and 56 (average age 50.7 years, average number of years of job experience 23.3 years), and six younger female clerks in the same store were aged 27 to 33 (average age 30.3, average number of years of job experience 12.2 years). Figure 2.8 compares the displacement of center of gravity with eyes closed for older and for younger workers before and after work. The figures along the vertical axis in the figure are the length (total distance of displacement of center of gravity, in mm) of the path of the center of gravity projected onto a horizontal

50 DISABILITIES ASSOCIATED WITH AGING

Figure 2.8 Comparison of shifts in the center of gravity (total distance moved) with eyes closed for middle- to old-aged and young female department store workers (Kumashiro, 1986).

plane (the X-Y plane). Using this total distance as an index in comparing the performance of older and younger workers before and after work, one sees a distinct decline in both after work compared with results taken before the start of work. However, the results before work and after work are compared for the two groups and no significant difference is discovered. Conversely, Figure 2.9 shows the displacement of the center of gravity to the left or right (X-axis direction). Significant differences are seen in the results for both groups before and after work, and the shift in center of gravity both before and after work was clearly smaller for the older workers than for their younger co-workers. On the other hand, while the forward-backward (Y-axis) displacement was reduced considerably after work compared with before work for the younger group, no such tendency was observed for the older group. Moreover, in contrast with the results in the X-axis

M.KUMASHIRO 51

Figure 2.9 Comparison of lateral component of shift in the center of gravity with eyes closed for middle- to old-aged and young female department store workers (Kumashiro, 1986).

direction, there was no significant difference in the displacements before and after work for either group. To reiterate the most noteworthy aspects of the above results, the total distance of shifts in the body’s center of gravity was notably shorter for older workers than for their younger counterparts, both before and after work. As a general rule, it has been reported that shifts in the center of gravity are larger during infancy and childhood and among older subjects age 50 and above. In interpreting these results, no doubt a variety of analyses will be proposed. Prior to examining these results, however, it is appropriate to review the features of the workplace at which the survey was conducted. First of all, there was no significant difference in the total number of steps walked by the younger and older female clerks during the course of their work, nor was any difference in workload observed during the course of the day. Secondly, because of the nature of their duties as sales clerks in a prestigious department store, by attending to customers, they are

52 DISABILITIES ASSOCIATED WITH AGING

required to maintain a rigid upright stance, with legs together and back straight as their main posture during work. Thirdly, the middle- to old-aged workers studied in this survey have worked maintaining this posture for an average of 23. 3 years. When these background factors are considered, it may be inferred that the effect of controlling one’s posture in the course of performing routine duties may act to suppress shifts in the center of gravity, and at the same time enhance such physiological functions. In other words, a posture enforced during many years of employment may serve as a kind of training, not only acting to cancel any aging-induced increases in shifts in the center of gravity, but also in enhancing equilibrium functions. Considered in this way, the decreased shift in center of gravity may be regarded as one effect of the individual’s job experience. Increases in shifts in the center of gravity bring with them the danger of inducing accidents during work. The problem is particularly serious in the construction and manufacturing industries, where equilibrium functions are essential. In fact, although the frequency of occurrence of accidents on the job varies with the type of duty, it is reported that the frequency of accidents is two to three times higher for workers age 50 or older than for workers in their 20s and 30s. Hence, the above results seem to suggest that daily training in posture control may alleviate this problem. 2.4.1 Occupational stress induced by daily work Using the above-described survey results for the 44 employees at a steel framemachining shop and a motorcycle part manufacturing shop, including 22 middleto old-aged workers and 22 young workers, the question of whether the work burden is indeed greater for older than for younger workers is now examined. 2.4.1.1 Physiological and psychological functions Analysing in detail the elements of productive activity of older and younger workers under conditions of a routine workload, no distinct differences were found between the two groups in the contents of the tasks performed, the workload, or the frequency of occurrence of different postures in the course of performing tasks. Based on the results of these observation methods, one may surmise that similar work conditions and workloads were obtained for the two groups. In light of these workload conditions, Table 2.1 lists the results of comparative studies of physiological and psychological function tests before and after work for older and younger workers. One finds, after work, a significant decline in the function for maintaining concentration (TAF-D values in TAFtests) and a significant increase in calf girth for both older and younger workers. In addition, there was a significant decrease in the near-point accommodation

M.KUMASHIRO 53

(diopter) value for younger workers. On the other hand, both groups showed a significant increase in grip strength of the left hand Table 2.1 Comparison of physiological functions of middle- to old-aged workers and young workers before and after work. The items of physiological and psychophysiological Aged workers functions (47–58 yrs) 1. (a)

(b) (c) 2. (a)

(b)

3. 4. (a)

(b)

(c)

5. (a)

Young workers (19–22 yrs)

Accommodation near-point (–) accommodation (diopter) contraction (–) (–) time (msec) relaxation time ↑ (–) (msec) The function of maintaining concentration (abbreviated as TAF-test) TAF-L values ~ (–) (–) a level of concentration TAF-D values ~ the fluctuation of a function of concentration maintenance Critical fusion frequency (CFF) ↑ Multiple choice reaction time (–) (–) the time of reaction to reach a response button placed at distances of 40 cm from the hand ~ response time (msec) 0 cm from the (–) (–) hand ~ reaction time (msec) (a)–(b) (–) (–) =movement time (msec) Short-term memory correct (–) (–) response (per cent)

54 DISABILITIES ASSOCIATED WITH AGING

The items of physiological and psychophysiological Aged workers functions (47–58 yrs) (b) 6. (a) (b)

(c) 7. 8. 9. (a) (b) 10. (a) (b)

Young workers (19–22 yrs)

revival time (–) (–) (sec) The displacement of body’s center of gravity per one minute with eye opened the lateral shift (–) (–) (mm) the (–) (–) anteroposterior shift (mm) the total shift (–) (–) (mm) Calf girth (cm) Tapping ability per 20 sec ↑ (–) Hand grip strength right hand (kg) (–) left hand (kg) Pulmonary function vital capacity (–) (–) (ml) per cent of vital (–) (–) capacity (ml)

In the table, downward arrows indicate a declining trend (p<0.10), upward arrows an increasing trend (p< 0.10). Similarly, downward arrows with a star indicate a sharply declining trend (p<0.05), and upward arrows with a star denote a sharply increasing trend (p<0.05). (–) indicates that there was no significant change. However, because calf girth showed a prominent increase (upward arrow with star), the physiological function is interpreted as a prominent decline (Kumashiro, 1994).

after work. Among older workers there was also a significant improvement in the CFF value after work, as well as a tendency toward improvement in accommodation time (relaxation time) and tapping ability. Among younger workers, there was a significant improvement in the grip strength of the right hand after work, as well as a tendency for the CFF value to be improved. Figure 2.10 compares fluctuations in heart rates during the work of older and younger workers; one sees that fluctuations in heart rate during work assume a similar pattern for both groups. At the same time, the level for older workers is lower than that for their younger co-workers. A similar tendency is also observed in the results of other function tests. This data suggests that although the level of physiological functions is lowered with aging, such phenomena do not immediately exert a strong influence on the relation between workload and perceived burden.

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Figure 2.10 Fluctuations in pulse rate during work periods for middle- to old-aged workers and for young workers (averages for 10-minute intervals) (Kumashiro, 1994).

No prominent change was observed before and after work in the results for choice reaction time, short-term memory, displacement of the center of gravity, lung capacity or ability to maintain concentration (TAF-L values in TAF-tests) for either group of workers. To summarize the above results, there was little evidence of a significant physiological burden accompanying daily work for either the middle- to old-aged workers or for the young workers used as subjects in this study. Thus it is inferred that there was little work-induced fatigue. Moreover, there was a tendency for the degree of the perceived burden to be smaller for older workers compared with younger workers. As circumstances which may have lead to this result, one may posit two different factors—the variety of jobs involved in a workplace where diverse tasks are performed, and the resulting speed of autonomous task performance. That is, compared with the paced work conditions (as for instance in mass production) which are simplified, specialized and standardized, there is relatively little occurrence of burdens on workers, and the rate of performance of work depends on individual workers; in such nonregulated modes of work, it is expected that past experience, knowledge of the workplace and levels of skill will affect the frequency of appearance of burdens on workers. In this sense, older workers are superior to their younger

56 DISABILITIES ASSOCIATED WITH AGING

counterparts, as a result of which they are able to perform tasks at an appropriate work pace and with little perceived burden. 2.4.1.2 Stress mood and feelings of fatigue Subjective symptoms of fatigue were compared between middle- to old-aged workers and young workers. Table 2.2 shows the symptoms complained of by more than 25 per cent of the workers in both groups. The rate of complaints was higher for many of the symptoms among young workers than among the older workers. Characteristic of the results was the high rate of complaints of symptoms indicating dullness and drowsiness, which were representative among younger workers. Com-plaints of tired eyes and stiff shoulders tended to be common among older workers; but as these symptoms are high regardless of age, sex and occupation, they do not seem to be characteristic symptoms of fatigue among older workers. In this way, feelings of fatigue were greater among younger than among older workers; this resembles results reported in the past on age and the feelings of fatigue. These findings thus suggest that complaints of fatigue are not necessarily correlated with an attenuation of physiological functions accompanying aging. These results on the feelings of fatigue are also supported by data on SACL (Stress and Arousal Checklist) obtained in a separately conducted questionnairebased survey study on stress moods. Mackay et al. (1978) produced a Stress Arousal Checklist (SACL) to observe emotional irregularities induced by living and working environments. The SACL is specifically designed to evaluate the feelings of stress and arousal, which are two distinct types of emotions. For this study, a ‘Questionnaire Form on Work and Health’ was prepared for the Japanese from a revised SACL and items on stressors relating to factors such as management, wages, human relations and work motivation were included. The questionnaire was intended to probe the degrees of stress and factors affecting the emergence and increase of mental stress among workers according to their ages. A total of 4758 workers were involved in this questionnaire survey, with 906 working at a factory which designs and manufactures air conditioners for a major machinery maker, and 3852 working at two petrochemical plants for a leading petrochemical company. The questionnaire forms were distributed before work and collected as early as possible after work hours on the same day or within two days. At the airconditioner plant, questionnaires were collected from 808 (709 male and 99 female) workers, a collection rate of 89.2 per cent. At the two petrochemical plants, questionnaires were collected from 3047 (2566 male and 332 female) workers at a collection rate of 79.1 per cent.

M.KUMASHIRO 57

Of the answers collected from a total of 3855 workers at the three plants, the answers from the 431 female workers and the 355 male workers who did not Table 2.2 Differences in subjective feelings of fatigue between the middle-aged and elderly workers and the young workers. Middle-aged and elderly group (n=42, 7 subjects×6 days) Before work After work

Before work

Young group (n=42, 7 subjects×6 days)

After work Experience body fatigue (26. 2%) Yawn (31. 0%)

I

Dullness and drowsiness

II

Difficulty in concentratio n Physical discomfort

III

Experience eye strain (23.8%)

Experience eye strain (76.2%)

Feel stiff in the shoulders (38.1%)

Feel stiff in the shoulders (59.5%)

Feel drowsy (47.6%) Experience eye strain (42.9%) Want to lie down (35. 7%) Feel general anxiety (26. 2%) Feel thirsty (28.6%)

Experience body fatigue (51. 2%) Feel tired in the legs (61. 0%) Feel drowsy (43.9%) Experience eye strain (78.0%) Want to lie down (34. 1%)

Feel thirsty (29.3%)

Items of subjective feelings of fatigue show complaints in more than 25 per cent of the workers in both the young and the middle-aged and elderly groups (Kumashiro, 1994).

respond to one or more question items were discarded. Thus, only the answers from the 3069 male workers with full responses were analysed. It was found that the mean stress scores and the standard deviation for the entire sample was 7.08 ±3.63. The mean stress scores for the age groups are shown in Figure 2.11 (each group was divided by 10 years). The 60–69 age group was excluded from this comparison. This group comprised only three workers. The stress score was highest at 7.83±2.92 among the youngest group consisting of 18- and 19-year-old workers, and was lowest at 6.22±3.63 among the 50–59 age group. The stress scores of these two groups were significantly different. The stress scores of the teenage (18–19) group, the 20–29 age group and the 30–39 age group exceeded

58 DISABILITIES ASSOCIATED WITH AGING

Figure 2.11 The mean stress scores for the age groups. Each group is divided into 10-year age groups (Kumashiro, 1995).

the average score. There was a general tendency for stress scores to decline with age, although the stress scores for the 20–29 age group (7.20±3.55) and the 30– 39 age group (7.22±3.64) were similar. The percentage of responses recognizing the presence of stress was obtained for 17 relevant question items, which were ranked by degree of stress. Then the rank correlation coefficient was calculated for each age group. This indicated a significant correlation (p<0.01) between age and the ranking of stress items in all age groups, except the teenage and the 50–59 age groups (r=0.551471). To observe characteristic feelings of stress by different age groups, the three stress items with the largest response rate were selected for each age group. The results indicated that one item common to all age groups was lack of a ‘feeling of contentedness’, with a response rate of 92.0 per cent for the teenage group, 83. 2 per cent for the 20–29 group, 78.2 per cent for the 30–39 group, 71.8 per cent for the 40–49 and 62.4 per cent for the 50–59 groups. The negation of a ‘feeling of pleasantness’ was found among the age groups from 18 to 39 (78.0 per cent for the teenage group, 76.4 per cent for the 20–29 group and 75.3 per cent for the 30–39 group). The lack of a ‘feeling of comfort’ was recorded in all but the teenage group (76.2 per cent for the 20–29 age group 76.1 per cent for the 30–39 group, 76.3 per cent for the 40–49 age group and 67. 6 per cent for the 50–59 age group). The negation of a ‘feeling of cheerfulness’ was observed in the 40–49 (75.7 per cent) and 50–59 (68.4 per cent) age groups. But the negation of a ‘feeling of relaxation’ was found only in the teenage group.

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An attempt was made to determine stress-inducing factors (stressors) by applying the method of quantification of qualitative statistical data (Multidimensional Qualification 1) to 18 items and responses selected from the whole range of question items concerning living conditions (outside of work), working conditions, attitudes towards the job, health conditions, and so on. The results showed five items having the largest partial correlation coefficient for each age group, and it is clear that the top five stressors for the entire sample were ‘emergence of a frustrating problem at work, physical condition, fatigue accumulation, anxiety about employment, and relations with superiors’. The ‘emergence of a frustrating problem at work’ was common to all the age groups. ‘Physical condition’ was a major stressor to all but the teenage group. Similarly ‘fatigue accumulation’ was a common stressor for all age groups older than 29. ‘Living conditions’ was an important stressor for the teenage and 20–29 groups, and ‘anxiety about employment’ and ‘relations with superiors’ were common stressors for the 20–29 and 30–39 age groups. A desire to change employers and a lack of interest in work were the two stress factors observed in the teenage group, but not in the other groups. ‘Performance evaluation by superiors’ was a strong stressor for the 40–49 age group, and scheduling of working hours and rest time was a high-ranking stressor for the 50–59 age group, although this was the weakest stressor for the teenage group. Similarly, ‘performance evaluation by superiors’ was the lowest-ranking stressor for the teenage group. A desire to change employers, which was an influential stressor for the teenage group, was the weakest stressor for the 50–59 age group. 2.5 Attempting to estimate physiological age The aptitude of aged workers for labor should be assessed by objective analysis of the changes in physiological functions with aging. It was reported (Birren, 1969) that the first study on changes in physiological functions with aging was carried out by Galton in 1877, and that studies on the concept of the functional age of industrial workers were already underway prior to World War II (McFarland, 1943). These reports suggest that scientists have held an active interest in gerontological issues for many decades. However, a considered analysis reveals that the validation of them as biomarkers of aging is difficult (Masoro. 1988). The greatest number of gerontological reports on the estimation of physiological age have been presented following the research of Benjamin (1947), Murray (1951), Robinson and Robinson (1991) and Kline and Levin (1992). The majority of these reports involved cross-sectional studies of a specific physical function by age, though a small percentage were based on different techniques. Among this minority was Robinson et al. (1975), who investigated a group of the same subjects for 31 years. Included in the crosssectional approach were Hollingsworth et al. (1965), Astrand and Rodahl (1970),

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Shock (1971), Dirken (1972) and Brokan and Norris (1980), who examined gerontological issues using many different types of physiological functions as parameters. Although numerous gerontological studies have been conducted, relatively few reports have addressed the relationships between aging and the physiological functions that are linked closely with the health conditions of industrial workers. Even fewer studies have been conducted on the influences of work burdens on the physiological functions of the middle-aged rather than the early adult worker. When one considers aging in the workplace and the diminished ability of the aged to adapt to circumstances there is a tendency to focus on physical motor performance. The same is true when aging and work adaptability are considered. In general when contemplating work adaptability, the degree of work capacity becomes essential. Many of the past research results on work capacity have employed fluctuations in the breathing and respiratory functions as indices. There are numerous such researches: examples include the reports by Bengtsson et al. (1977), Higginbotham et al. (1986), Weller et al. (1988) and Ilmarinen et al. (1991). These findings can be effectively employed when considering physical work. If, based on the numerous research results of the past, a calculated physiological age were to be substituted for a physical strength age, it would be appropriate to use as indices results for the breathing and respiratory functions. However, the rapid rate at which the industrial structure is today changing is bringing about similarly great changes in modes of labor and in resulting workloads. Under such circumstances, it seems that a new approach to the calculation of physiological age, from a fresh perspective, is called for. Many of today’s jobs make demands on sensation and sensory functions and on one’s ability to make decisions rapidly. The data described in Section 2.4 have been employed in attempts to calculate physiological age, which is now introduced. Multiple regression analysis by the stepwise method was performed using prework values from all 10 tests as (Figure 2.7) the explanation variables and using the ages of 40 subjects with a complete set of measurements as the reference variables. (The four subjects whose set of measurements were incomplete were omitted from this analysis.) The results indicate a significant correlation (multiple correlation of R=0.8890) between age and 19 measurement figures. Conversely, a significant partial correlation (p<0.01) was found only for nearpoint accommodation (pr=−0.787 625) and pulmonary function (pr=−0.631 379). By setting the correlation with near-point accommodation (diopter) as D and that with pulmonary function (vital capacity) as VC, the physiological age can be estimated by the following multiple regression equation:

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2.6 Support for middle- to old-aged workers in the workplace Since physiological functions decline in accompanying aging, there is a tendency for aged workers to be treated as a kind of handicapped person. Indeed, insofar as the previously mentioned physiological aspects are concerned, they do resemble the physically handicapped to a considerable degree. If, however, systems are provided to support functions which are affected by aging, such problems can be alleviated. It is also possible to create work conditions which aim at the effective use of our aged Table 2.3 Eight proposals for supporting middle- to old-aged workers in the workplace 1. 2. 3. 4. 5. 6.

7. 8.

Re-design of jobs to incorporate principles reflecting both the impact of the worker on the job, and the impact of the job on the worker Development of a skill diagnosis system, and development of a system for education and training based on the former Development of capacity for adaptation to labor, and of a workplace amenable to such adaptation Development of an exercise program to lower the body strength age (physiological age) Establishment of a system of pay based on type of work Understanding of stress phenomena arising as technology is introduced, and establishment of methods for evaluation and coping with stress which can be carried out by the workers themselves Development of supporting facilities, machinery, tools and other equipment taking the characteristics of middle- to old-aged workers into account Provision of an appropriate working environment (including lighting, scaffolding, etc.)

workforce. From this perspective, Table 2.3 lists representative measures for revitalizing older workers in the workplace. Among these eight proposals, numbers 1 to 6 in particular must not be limited only to older workers. Rather, they should be established on a continuing basis and from a long-term outlook as part of one’s lifelong education. There is no evidence to indicate that the will to work of aged workers is decreased. However, workers must be cultivated so that even in later years they are sound in mind and body and retain a high capacity for work. The creation of a system enabling older workers to participate satisfactorily in production activities will make possible a society in which older persons can earn their own income. This will be a means of adding a sense of fulfilment to the lives of the elderly, while at the same time providing the basis for the health of our future industry and economy.

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2.6.1 Methods for promoting practical measures to cope with aging When devising measures to support older workers in the workplace, accurate information must first be obtained. Here, an understanding of current problems is crucial. Observations throughout the workplace are essential. In making such inspections, a keen eye is needed in order to grasp the state in which workers work. When a detailed understanding of work conditions is needed, any or all of the following may be necessary. 1 Listening. For instance, group interviews and other methods to listen to workers’ views may be effective. 2 Asking. Questionnaires and other methods may be used. 3 Observing the state of work. This may include observations of posture, observations of subsidiary behavior, work analysis/motion analysis and so on, depending on circumstances. 4 Scientific measurements. For example, studies of physiological and psychological functions may also be needed. 2.7 One method for promoting practical measures to cope with aging (with emphasis on task management) As indicated in Figure 2.12, it is important that measures to cope with aging begin with job redesign. The concept of job redesign does not involve adapting humans to the environment, but rather is the task of adapting the job to the human workers. In carrying out this concept, both the impact of the human (and aging) on the job, as well as the impact of the job on the human (and his or her aging) must be studied, and ultimately a balance must be struck between the two. That is, job redesign involves the design of work conditions and a workplace environment which make it easier for humans to work and create a workplace environment which does not harm the individual’s health, while at the same time helping to raise productivity. One should focus on the following when undertaking job design. 1 Tasks involving transport/or lifting of heavy loads or objects. 2 Poor work posture. 3 Tasks which depend on sensory functions, and in particular on vision, and measures to alleviate each. Redesign is then easily accomplished.

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Figure 2.12 Basic strategy for older workers begins with job re-design.

2.7.1 Inevitable aging phenomena: simple countermeasures for the example of visual functions As the shape of labor has evolved from physical labor based on raw human strength into mechanized labor, and is now evolving further into labor centered on information processing, so it has come to depend increasingly on sensory functions, and in particular on the sense of sight, compared with the muscleintensive work of the past. Unfortunately, the decline in vision accompanying old age is more prominent than the changes in any other physiological function. The visual functions which contribute to visual acuity have already begun to decline when an individual reaches his or her late-20s. In particular, the ability of the eye to adjust to circumstances begins to decline sharply from the mid-40s, which are regarded as the prime of one’s working life. This is the undeniable onset of the failing eyesight of old age. Worsened vision with age involves the weakening of the ability of the eyes to adjust to view near objects because of the reduced elasticity of the crystalline lens. No matter how much effort is made to adjust, this condition hinders tasks involving close-up work. Reasons for this worsening of vision include hardening of the crystalline lens accompanying old age and reduced strength of the ciliary muscles. Table 2.4 lists the functions closely related to work efficiency and occurrence of accidents which decline with aging. Basic measures to cope with the decline in these functions are indicated in Table 2.5. The essence of these measures is illustrated for the example of VDT (visual display terminal) tasks, which are regarded as representative of modern tasks via a computer interface; application of these measures leads to the proposed improvements of Figure 2.13. The latter figure illustrates factors contributing to poor visual acuity which adversely affect this type of work, as well as proposed countermeasures. The introduction of computers accompanying the automation revolution has no doubt helped to lessen the burden of physical work on older workers, but the strain on visual functions has increased in its place. If the changes in visual functions attending aging are not accurately recognized when undertaking improvements of the work

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environment, then an unhappy outcome either for the older workers themselves, or for job productivity, is inevitable. Moreover, it is of the utmost importance that when these improvements are implemented they bring about a work environment that is congenial to younger workers as well. Next, two examples of improvements of work conditions actually implemented at the manufacturing work sites of two electrical equipment manufacturers are Table 2.4 Aging phenomena: First rule of the penalties of aging. Taking as an example visual functions, which are closely related to work efficiency and occurrence of accidents. Phenomenon 1. Decline of visual acuity:

Phenomenon 2. Decline in peripheral vision functions (kinetic field of vision): Phenomenon 3. Decline in focusing functions: Phenomenon 4. Decline in ocular motion capacity:

Although both static and kinetic visual acuity are in decline, the decline in kinetic vision is especially prominent; night vision also deteriorates Aging has little effect on the static field of vision Lengthened focal distances, longer time for focusing Decline in speed of ocular tracking motion, difficulty in moving focus

Table 2.5 Aging phenomena countermeasures. Taking as an example visual functions, which ar closely related to work efficiency and occurrence of accidents. Countermeasure 1 The vision of older persons under bright lighting conditions is good compared with that of younger persons, and rate of improvement of vision is also superior—adjustment of lighting conditions Countermeasure 2 Under static vision conditions, improvement is possible using corective lenses Countermeasure 3 Limit field of vision of each eye to within 120° laterally Countermeasure 4 Adjust working vision distance

introduced. The first case study involves inspection of printed circuit boards. Problems existing prior to the implementation of improvements are as indicated in the photo at the top of Figure 2.14; while a loupe was normally used in this task, only a limited area could be magnified at once and an overall view was not available, impeding the inspection process. The proposed improvement involved purchasing an easy-to handle large magnifying lens product with built-in lamp and installing it at the workplace (Figure 2.14 bottom). As a result, the following two effects were achieved. 1 Due to the improved ease of handling and ability to view a broad area at once, the task becomes easier to perform.

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Figure 2.13 Example of proposals for improvement of workstations for middle- to oldaged persons working at computer terminals (Kumashiro, 1994).

2 Mistakes due to flaws which go unnoticed are reduced, for improved work efficiency. The second example is also an instance of improvement of the task of printed circuit board inspection. However, the company in question is different from the company in the first case study. At this workplace a magnifying lens was being used to inspect the soldering of components to printed circuit boards, as in Figure 2.15, but light tended to be reflected from the top of the lens, making it difficult to see the work, and when holding the board in both hands it tended to shake, impeding comparison of the board with a diagram. Here, by using a super-compact industrial television camera to display printed circuit boards on a television monitor, it was possible to reduce after-process losses due to flaws overlooked in inspections to zero. In implementing this improvement, a camera the size of one’s thumb and capable of either slow or rapid movement along the x- and y- axes was combined with a large display which could be easily viewed by older workers. As a result, the printed circuit boards were shown magnified on the display, aiding the task of inspection by older workers and improving work efficiency. These two case studies are both instances of improvements made in the workplace by the workers themselves. Both relied on a thorough understanding

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Figure 2.14 Example of improvement of work conditions considering the decline in visual functions with aging. Replace loupe with large-size magnifying glass with built-in lamp.

of the tasks involved and of the work environment. Both improvements were suited to the respective workplaces. These two examples are excerpts from examples of workplace improvements collected by The Association of Employment Development for Senior Citizens, Japan, in 1990.

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Figure 2.15 Example of improvement of work conditions considering the decline in visual functions with aging (printed circuit board inspection). Replace large-size magnifying glass with a television monitor displaying image from super-compact industrial use video camera.

2.7.2 Decline in muscular and physical strength, and simple countermeasures for the examples of poor work posture and transport of heavy loads Regardless of the differences in age, sex and other attributes of the human subject, improvement of poor work posture must necessarily address the following six problems. 1 Reduction of the frequency of stooping postures (smaller lumbar angle). 2 Use of postures with knees extended (avoiding postures in which the knee joint is bent). 3 Avoidance of twisted or distorted postures. 4 Adjustment of working surfaces and tables at a height between the shoulders and navel of the worker. 5 Placement of work pieces within a reasonable work range (within a circular area with a radius equal to the length of the forearm). 6 Placement of work pieces within an appropriate field of vision (within a 60° lateral angle, or within 30° laterally from each eye). The examples of improvements introduced here are based on the above six problems. Before introducing the case studies themselves, a general description of the factory in question is given. The company in this example is a manufacturer of repair parts for all models of Japanese-made cars. In this sense, it is a typical example of a factory which must produce numerous types of products in small lots. The factory building itself has grown larger with each expansion of the company, resulting in a poor layout with

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Figure 2.16 For reducing workload in ball stud carrying work: (a) before improvement. Materials are loaded on a special truck for transport to the press workplace; (b) and (c) after improvement. The truck is changed to one with adjustable height (Kumashiro, 1995).

zigzags in the flow of manufacturing processes and much work involving the movement and transport of products and work pieces. Frequently identified problems included work necessitating the lifting and lowering of heavy objects, and poor working postures such as squatting and bending. The workplaces in question were the spring setting and ball-stud assembly process and the press work-marking process. Three improvements which were implemented at this factory are as follows.

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1 Ball-stud assembly. Before this improvement, ball-stud assembly involved three separate reloading operations, from insertion of the ball stud to the caulking process done by the press (Figure 2.16). In order to reduce the muscular load involved in manual lifting, a ‘level car’ with a lifting function was used and loading was reduced to one operation. 2 Example of work using a ‘marker’. Before the improvement, the height of the marker working surface from the floor was 450 mm, and the chair was also low, at 280 mm, leading to complaints of muscle strain. Also, despite the precise adjustment of the product relative to the marker, poor posture hindered fine adjustments, and there was considerable loss of time (Figure 2.17). After the improvement was implemented, the height of the working surface was set at 850 mm from the floor, allowing workers to select either a standing or sitting position from which to work. A jig was developed to eliminate the need for fine adjustments, and the task was standardized. The need for arm strength to hold the work piece down was eliminated by changing the press drive source to air, thus reducing the muscular load on the wrist. 3 Tasks involving transport of heavy objects. Here the task involved processing chips. After attempts at improvement involving the method of task performance failed, large-scale facilities had to be introduced. Hence the costs incurred in the improvement were extremely high. Before the improvement, the chips were removed using a shovel, put into a container and carried out manually. The total amount of chips produced in one day’s cutting amounted to 1700 kg, and the weight of one load of the bucket truck was 300 kg. In one day, as many as 12 trips were made. The transport distance for one trip was 150 m, taking 30 to 40 min, for a total distance during the day of 1200 m. Figure 2.18 shows schematic views of these processes. As a result of the improvement, a shooter and hopper were installed on the chip exhaust to collect the chips. The chips are carried automatically by a pipe with a built-in chain conveyor for dumping (Figure 2.19). In this case study, transport of heavy objects by workers is replaced by automated transport by machinery. It is a bold modification, and required a considerable investment in facilities. As a result of this particular improvement some workers became superfluous; but the purpose of the improvement was not to dismiss workers. The workers in question became engaged in monitoring and maintenance of the equipment, and at the same time assumed duties at the source of the chips, that is, in machining. At times, the job of cleaning up chips was assisted by many other workers engaged in machining. However, after the improvement was implemented the burden on muscles and skeletal structures accompanying the transport of heavy objects was alleviated, and simultaneously the time required to assist in cleaning of chips was reduced compared with previously, for a direct increase in productive time. Moreover, the morale and will to work of the group of workers in this workplace were improved.

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Figure 2.17 Marking work: (a) and (b) before improvement; (c) and (d) after improvement. (a) Poor work posture, table height is 45 cm and seat height is 26 cm; (b) difficult to handle. Tools and materials are requested to position with high attention, (c) Table height was set at 85 cm from the floor, allowing a worker to select either a standing or sitting position from which to work, (d) The need for arm strength to hold the product down was eliminated by changing the press drive source to air, thus reducing the muscular load on the wrist (Kumashiro, 1995).

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Figure 2.18 (opposite) The work of processing the chips. (1) Chips removed with shovel; (2) once a certain amount (10–20 kg) accumulates in the chip holder, they are moved to a large chip truck; (3) the pushing strength for starting up the chip truck is 20 kg and 10–15 kg once it is moving; (4) dumping the chips.

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Figure 2.19 The work of processing the chips (after improvement); (a) shooter for dropping the chips and hopper for catching them; (b) chip pipe with built-in chain for automatic chip disposal (Kumashiro, 1995).

2.8 One ergonomic approach to the development of support equipment for aged workers Figure 2.20 shows in flow-chart form an example of a procedure for developing equipment and other tools for supporting aged workers. This flow chart was quoted with modifications from both Kumashiro’s paper (1992) and a report to Japan’s Ministry of Labour on ‘Research and Development of Equipment and Others to Support the Elderly—Subtheme: Development of Equipment to Alleviate Workloads’ written by Kumashiro and his 11 coresearchers (1995). The flow chart shown here is intended for aged workers employed on assembly lines of mid- to large-size products, where various products are produced in small lots. This represents an ergonomic intervention conducted with the purpose of alleviating poor work postures, transport of heavy objects and similar problems occurring in the course of task performance. However, the process of

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Figure 2.20 Flowchart for an ergonomic approach to the development of support equipment for aged workers (continues on pages 65, 66 and 67) (Kumashiro 1992, 1995).

development of the equipment shown in this flow chart can also be applied to the development of other types of supporting equipment.

References ASTRAND, P. and RODAHL, K. (1970) Textbook of Work Physiology. New York: McGraw-Hill.

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BENGTSSON, C., VEDIN, J.A., GRIMBY, G. and TIBBLIN, G. (1977) Work capacity in women in relation to age as judged from a maximal work performance test, Scandinavian Journal of Social Medicine Suppl, 14, 33–9. BENJAMIN, H. (1947) Biologic versus chronologic age. Journal of Gerontology, 2, 217–27. BIRREN, J.E. (1969) The concept of functional age, theoretical background. Human Development , 12, 213–15. BROKAN, G.A. and NORRIS, A.H. (1980) Assessment of biological age using a profile of physical parameters. Journal of Gerontology, 35, 177–84. DIRKEN, J.M. (1972) Functional Age of Industrial Workers. Groningen, The Netherlands: Wolters-Noordhoff. HIGGINBOTHAM, M.B., MORRIS, K.G., WILLIAMS, R.S., COLEMAN, R.E. and COBB, F.R. (1986) Physiologic basis for the age-related decline in aerobic work capacity, American Journal of Cardiology, 57, 1374–9. HOLLINGSWORTH, J.W., HASHIZAWA, A. and JABLON, S. (1965) Correlations between tests of aging in Hiroshima subjects—an attempt to define ‘Physiologic age’. Yale Journal of Biology and Medicine, 38, 11–26. ILMARINEN, J., LOUHEVAARA, V., KORHONEN, O., NYGÅRD, C.H., HAKOLA, T. and SUVANTO, S. (1991) Changes in maximal cardiorespiratory capacity among aging municipal employee. Scandinavian Journal of Work, Environment and Health Supplementum, 1, 99–109. KLINE, J. and LEVIN, B. (1992) Trisomy and age at menopause: predicted associations given a link with rate of oocyte atresia. Paediatric and Perinatal Epidemiology, 6, 225–39. KUMASHIRO, M. (1986) Physiology and psychology of middle- to old-aged workers, in theory and practice of job redesign, The Association of Employment Development for Senior Citizens, Japan, Tokyo, pp. 13–75. KUMASHIRO, M. (1992) Toward human work: an occupational ergonomic approach to developing increased work efficiency, Proceedings of the 2nd Pan-Pacific Conference on Occupational Ergonomics, 22–31. KUMASHIRO, M. (1994) The aging effects of work abilities, A Monthly Magazine Elder, March, 10–21. KUMASHIRO, M. (1995a) How to benefit from ergonomic interventions through participation by workers, managers and the company: an example of a small- to medium-sized factory with no ergonomic knowledge, Journal of Human Ergology, 24, 123–9. KUMASHIRO, M. (1995b) Productive aging with ergonomics intervention: break down the barriers of the hiring policy for older workers. In KUMASHIRO, M. (Ed.) The Paths to Productive Aging 1–7, London: Taylor & Francis. KUMASHIRO, M. (1995) Development of Equipment to Alleviate Workloads, in A report to Japan’s Ministry of Labour on ‘Research and Development of Equipment and Others to Support the Elderly’ (unpublished). LABORATORY OF PHYSICAL EDUCATION Tokyo Metropolitan University (1989) Physical Fitness Standards of Japanese People, 4th edn, Tokyo: Fumido-shuppan, 103, 107, 111 and 237. MACKAY, C., Cox, T., BURROWS, G. and LAZZERINI, A. (1978) An inventory for the measurement of self-reported stress and arousal. British Journal Social and Clinical Psychlogy, 17, 283–4.

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MASORO, E.J. (1988) Physiological system markers of aging. Experimental Gerontology, 23, 391–7. MCFARLAND, R.A. (1943) The older worker in industry. Harvard Business Review, 21, 505–20. MURRAY, I.M. (1951) Assessment of physiological age by combination of several criteria: vision, hearing, blood pressure and muscle force. Journal of Gerontology, 6, 120–6. ROBBINSON, S., DILL, D.B., TZANKOFF, S.P., WAGNER, J.A. and ROBINSON, R. D. (1975) Longitudinal studies of aging in 37 men. Journal of Applied Physiology, 38, 263–7. ROBINSON, A.B. and ROBINSON, L.R. (1991) Quantitative measurement of human physiological age by profiling of body fluids and pattern recognition. Mechanisms of Aging and Development, 59, 47–67. SHOCK, N.W. (1971) The physiology of aging. In VEDDER, C.B. (Ed) Gerontology, Illinois. Clarles C.Thomas Publishing. TAKAKUWA, E. (1962) The function of concentration maintenance (TAF), as an evaluation of fatigue, Ergonomics, 5, 37–49. WELLER, J.J., EL GAMAL, F.M., PARKER, L., REED, J.W. and COTES, J.E. (1988) Indirect estimation of maximal oxygen uptake for study of working populations, British Journal of Industrial Medicine, 45, 532–7. WHO (1993) Aging and Work Capacity. Report of a WHO Study Group, WHO Technical Report Series 835, (World Health Organization, Geneva), 3.

CHAPTER THREE Visual impairment: ergonomic considerations in blind and low-vision rehabilitation MORTON A.HELLER AND JOHN BRABYN

3.1 Introduction This chapter is about ergonomic considerations in the development of sensory aids for visually-impaired people. It is necessary to consider relevant characteristics of individuals if one is interested in the development of useful designs. Blind people vary greatly in their educational background, and this has implications for the development and use of assisting devices. In many instances, potential problems may be averted if prior instruction prepares people for devices, since user acceptance is always an important consideration. This chapter will discuss perception in visually-impaired and blind people. The problems for the visually-impaired population include communication in written and other forms, and, most significantly for blind people, mobility. The difficulties involved in mobility are complex, and require the communication of spatial layout, signs (to help an individual identify his or her location in space), and information about heading and orientation in space. Thus, successful mobility requires understanding a spatial layout, and understanding one’s position with reference to this arrangement. In addition, people may require information about the direction in which they are walking, to avoid wandering from an appropriate path by veering off or taking a wrong turn. Thus, this chapter will discuss spatial cognition in blind people, and the devices that provide assistance to those individuals. A special emphasis will be placed on what we know about blindness and visual impairment for ergonomic considerations in the use and development of sensory aids. Devices for visually-impaired people may make use of the sense of touch as an alternative to visual information. This can create difficulties, if only because the hands are most useful for the manipulation of objects in the environment and for picking up pattern information. This dual function of the hands, as manipulanda and as a sensory apparatus, poses problems for the designer of sensory aids and the rehabilitation specialist. Similar problems exist for audition, since many mobility aids depend upon auditory sources of information. Safe and effective mobility also requires attention to auditory information from the environment,

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and this concern is relevant to the design and use of aids that are dependent upon audition. One would not want to distract a blind pedestrian from important sound cues to danger, for example, in the service of a sensory aid. The first part of the chapter is devoted to a discussion of the nature of visual impairment and blindness. Morton Heller discusses issues in blindness, spatial cognition in blind people, and tactual perception of objects and patterns in blind people. Some discussion of Braille is included, and this will be followed by a detailed treatment of tangible graphics. The problems of tangible graphics are relevant to perception and interpretation of maps and orientation aids. The discussion also focuses on tactile pictures, their identification and interpretation. Tangible pictures are important, but infrequently used devices. Little is currently known about how to effectively represent tangible three-dimensional configurations on a flat surface for touch, and work is now underway on perception of linear perspective and depth cues in tangible displays by congenitally blind people. John Brabyn discusses the use of auditory and visual displays for people with low vision. Auditory information provides important access to computers and assists daily living. Moreover, auditory information has been used to provide orientation information. Low-vision aids help people with some useful vision. One class of device involves optical manipulation and includes magnifiers and telescopes. A second class of devices electronically manipulates information to make patterns useful for people with low vision. In addition, Brabyn describes the state of knowledge about lighting conditions and devices. 3.1.1 Definition of visual impairment The term ‘visual impairment’ is broad and describes rather varied circumstances. It is not comparable to the notion of legal blindness’ (vision no better than 20/ 200 in the US), but includes both ‘blindness’ and ‘low vision’. People who are ‘blind’ have little useful vision, and are unable to rely on visual information for reading, pattern perception or mobility. Some blind people would define a ‘blind person’ as one who uses a long cane. However, there are many people making use of the long cane who have considerable useful vision, both for mobility and pattern perception. Blind people may or may not have light perception. If light perception permits localization of large forms in space, this ability may provide considerable information for mobility, especially if the individual can locate the horizon. In addition, there are many people with varying states of vision. Some individuals (with retinitis pigmentosa or diabetes) report that their visual capability varies from day to day. Some individuals have indicated that they may have ‘shadow vision’ on ‘good days’, but they are unable to see anything at other times. This chapter will describe rehabilitation and perception in blind people and people with low vision. In the research conducted by Morton Heller (1982, 1985, 1993),

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blindness was used to describe individuals who were unable to see hand movement, and were without useful pattern perception, or people without light perception. Clearly, vision of hand movements can aid pattern perception in addition to any possible benefits for mobility. 3.1.2 Age of onset Blindness may arise at birth or soon thereafter. The time of onset of visual loss has important consequences for rehabilitation and the introduction of sensory aids. Most blind people have had visual experience, and have lost sight some time after birth. These late (adventitiously) blind people vary considerably in their tactual and spatial skills. Some may have lost sight shortly after the first year of life, and will have benefited from early vision of objects while reaching or walking. Others may have lost sight at a later time, but prior to learning to read. These people are likely to have learned to read Braille, and will probably have had instruction in mobility skills. People who lose sight after attending high school or college have a lot of catching up to do, but many make successful adjustments to blindness. Blindness is often caused by diabetes in older people, and these individuals may also suffer from neuropathy. This makes for a rather difficult adjustment process. Most of us have a hard enough time learning to cope with old age, without the burden of learning to read and walk with a cane. In addition, tactile acuity may diminish with age and this presents additional problems for a late blind individual who is older when blinded (Stevens and Patterson, 1995). It is important to note that the data on the causes of blindness vary greatly as a function of geography and a variety of socioeconomic and cultural factors. However, diabetes is the most common cause of blindness among recipients of services for the blind in North Carolina. The consequences of early visual experience are discussed at length later. Early vision probably increases the quantity of one’s educational experiences, and perhaps also alters the nature of the information one is exposed to. Blind people may have minimal exposure to tangible pictures and graphics in school, and this can influence their interpretation of these sorts of configurations. Many sighted individuals have difficulty interpreting graphs and maps, but limited educational experience will magnify the problem. 3.2 Tactual pattern perception and spatial cognition in blind people Much of the thinking in this area has been influenced by preconceptions about the nature of touch, and consequent putative limitations in people who are born blind. Unfortunately, there has been too little emphasis on empirical work, and

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too much focus on often unwarranted assumptions about what people cannot do —rather than on what they can do. It may be impossible to provide clear empirical answers to some difficult theoretical issues, such as nature versus nurture (Millar, 1994). While one cannot readily find the ‘decisive’ experiment, given intractable theoretical problems, there are ways to answer important empirical questions in tactual perception, and this could be a fruitful enterprise. Revesz (1950) has been influential, and so his ideas require some discussion. Revesz thought that the sense of touch was inferior to vision for pattern perception, and this had implications for perception in blind people. Revesz argued that haptics was limited in its ability to understand perspective, and other important attributes of pictorial displays (see Heller, 1991). Moreover, Revesz asserted that the sense of touch was essentially clumsy when visual guidance was unavailable, and so one would expect poor tactual perception in people born blind. There is little doubt that sighted people benefit greatly when allowed vision of hand movements (Heller, 1982, 1983, 1985, 1987, 1993). However, blind people may have acquired increased skill from practice, and late blind individuals are not invariably better at pattern perception than congenitally blind people. This is most obvious in reading Braille, since many late blind people may not read Braille or read haltingly (Heller, 1992a, 1993). More recently, Lederman and Klatzky have argued that touch is inferior to vision in the perception of two-dimensional pattern information (for example, Lederman et al., 1990). They argue that touch is best suited for the perception of the substance-related attributes of solid forms, a position that was presented earlier by Katz (1989). Lederman et al. (1990) proposed that touch is best suited for the perception of such substance-related aspects of objects as texture, hardness and thermal properties. Furthermore, they suggest that touch requires the mediation of visual imagery when confronted by two-dimensional configurations that impose a burden on memory. There is little doubt that touch can excel in the perception of texture (Heller, 1989a). Note that congenitally blind people may be limited in their ability to process spatial information given severe time constraints (Cornoldi et al., 1991, 1993). It is very possible that time constraints may represent a special problem when people are relatively unfamiliar with a task (Heller and Kennedy, 1990), and then they function more slowly. Practice may allow one to overcome any possible limitations in imagery skills. There is ample evidence that sighted subjects rely on vision when confronted by a conflict between visual and haptic information about shapes under many circumstances (Rock and Victor, 1964). This has led some researchers to assume that vision is dominant over other sensory modalities, and is a ‘better’ sense. However, if vision is blurry, one may rely on touch (Heller, 1983), and touch may be dominant when one can see the hand in contact with a surface (Heller, 1992b). In addition, visual dominance is not obtained for texture information (Lederman and Abbott, 1981), and touch and vision may provide equivalent accuracy in judgments of coarse textures. There is even evidence that touch can outperform vision for judgments involving very fine textures (Heller, 1989a).

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Furthermore, sighted subjects often show clear preferences for touch over vision in making texture judgments in unrestricted bimodal conditions: they will avert their gaze while touching textured surfaces (Heller, 1982, 1989a). Thus, the argument that vision is a superior sense is an over-generalization, and can lead to inappropriate conclusions about the perceptual skills of blind people. Touch may operate more slowly than vision, since reading print with one’s eyes is faster than reading Braille with one’s fingers (Loomis, 1990; Foulke, 1991). However, it would be a mistake to come to negative predictions about the capability of the sense of touch derived from observation of the activities of sighted people restricted to touch. Sighted people are often less skilled and less practised at the use of touch for pattern perception, and sighted people are much slower than blind people at recognizing Braille (Heller, 1992a). They may show lower performance in pattern-matching tasks when familiarity is equated (Heller, 1989b, 1991). Reliance on vision can interfere with tactual perception in people with visual experience. Thus, sighted subjects have difficulty in tactual tasks when they are distracted by irrelevant visual information when circumstances force the use of visual imagery (Heller, 1993). This is relevant to problems of visual impairment, since reliance on visual information may be problematic for people making adjustments to recent blindness or attempting an adjustment to a progressive loss of vision. The acquisition of tactual skills may depend upon the rejection of older methods of coping, and demand increased attention to the sense of touch. A recent review of performance on spatial tasks by blind and sighted people suggests that congenitally blind, adventitiously blind and sighted persons often perform similarly. Klatzky et al. (1995) studied performance in three types of tasks, including manipulatory space, simple and complex locomotion. The data provided little evidence for the effects of visual experience on performance. It was interesting that there were large individual differences in performance, moreover, there was no evidence for mental rotation effects. These data perhaps suggest that the most relevant variable may be differential experience per se, rather than differential visual experience. 3.2.1 Braille Braille is an extremely useful form of communication for blind people. It is a system of embossed dots in a two by three matrix. As an arbitrary code, Braille patterns symbolize the alphabet of visual print forms. However, much Braille text does not involve the simple spelling out of words via substitution of Braille characters for their print equivalents. Braille exists in contracted forms, in which frequently appearing letter sequences are represented by a new Braille symbol, for example, common suffixes are contracted. This has the advantage of making the written system more compact, and will increase reading speed. However,

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learning contracted Braille can often present novel problems for later blind individuals, since Millar (1995) has reported that the utility of contractions depends upon the nature of the task one presents and the level of skill of the individual. What is picked up perceptually differs with skill level and tasks, and Millar reports large effects of context in the study of reading Braille text. Unfortunately, many blind people do not read Braille fluently, despite the advantages of written communication. If an individual loses sight very late in life, it is all too likely that the individual may not learn to read Braille. Furthermore, embossed print is not widely available, since blind people have generally rejected its use in favor of Braille. There is considerable logic to this, since Braille is far more tangible than print. Thus, Loomis (1981, 1990) reported higher recognition performance for Braille than print, when exploration is limited in time and scope. Heller has confirmed these observations (unpublished research). Blindfolded individuals may do very well (about 90 per cent correct) with large embossed print (>1.0 cm high), but this is a very cumbersome font size. If embossed print is limited to the size of normal Braille (6 mm high), Braille is far superior to embossed print. A number of researchers have wondered about laterality effects in Braille reading, especially whether the left hand might be superior. Language is localized in the left hemisphere in sighted people, and it is very possible that this may be altered in blind people as a function of experience with reading with one’s hand. However, most blind people read with both bands, but often use their left hands for keeping their place, and finding the beginning of the next line of text (Millar, 1987; Mousty and Bertelson, 1985). While there are some reports of the advantage of the left hand for reading Braille (Hermelin and O’Connor, 1971; Mommers, 1980), other researchers report no advantage for the left hand (for example, Millar, 1984). Millar reported that better Braille readers showed a right-hand advantage in character recognition. There is also one report of a lefthand advantage in the identification of digits using the vibrotactile Optacon display (Heller et al., 1990), and for patterns drawn on the skin (Heller, 1986), but laterality effects are not obtained in texture discrimination tasks (for example, Heller, 1989a). New Braille readers find great difficulty coping with tilted Braille patterns (Heller 1992a; 1993), and have problems learning the code. One general research problem is that many investigators have studied Braille learning by using blindfolded, sighted individuals. This approach has merit, but college-age, sighted subjects are influenced by a lack of visual guidance of hand movements (Heller 1992a, 1993), and depend on visualization when compensating for tilted Braille. Thus, generalization for populations of congenitally blind people is questionable. There are many devices that provide refreshable Braille output or input for computers. Some of these devices are extremely useful; however, it has been difficult to provide a full-page display. Some machines use a 40-character display and a means for rapid scanning of a page. Nonetheless, a full-page

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display facilitates access to higher order components of written text (Foulke, 1991). 3.2.2 Vibrotactile devices The Optacon is a useful mechanism for the conversion of print into an analog vibrotactile display. Some blind people use this device to read material that is not readily scanned by a computer and read aloud by synthetic speech. The Optacon translates visual input from a small hand-held camera into a vibrotactile analog display. The Optacon II display contains an array of 5 by 20 vibrating pins that can be touched with the index finger of either hand. When the camera scans a letter, the outline of that pattern is reproduced on the display in a Times Square mode, that is, a moving dynamic mode derived from movement of the camera. As the individual scans a line of text, the letters are reproduced on the tangible display, one letter at a time. Reading rates for the Optacon are normally rather slow (<50 wpm), but there are reports of some exceptional observers reading text at up to 100 wpm (Craig, 1977; Sherrick, 1991). The Optacon is useful for some people, but others may show considerable hesitation in devoting the necessary time to learning to use it. The slow reading rate is one clear impediment, as is the limited utility of the Optacon and the high cost. The earliest Optacons had a 6 by 24 pin display, and provided slightly higher resolution. However, this advantage was perhaps offset by a significant structural limitation. That is, the earlier Optacon required the use of the left index finger on the display, on the assumption that most people would want to use the right hand to control scanning with the hand-held camera. This presented a problem for left-handed individuals. The Optacon II has corrected this deficiency, and the tactile display can be felt with either index finger (Heller et al., 1990). Congenitally blind people must learn the print alphabet and a number of fonts before an Optacon will serve their needs, and this slows training. 3.3 Pictures and graphics for blind people Many blind people have had relatively little instruction in the interpretation or production of tangible pictures, despite their clear importance for education, com munication and mobility. It is possible that this lack of experience derives from multiple sources. First, useful inexpensive drawing devices are not readily available in the US (Bentzen, 1982; Gill, 1982). Second, this limited exposure may derive from preconceptions held by researchers, teachers and rehabilitation counsellors about limitations in touch and, unfortunately, from anticipated limitations in spatial cognition in blind people. Fortunately, good aids are available for people willing to go to the trouble of importing a drawing kit from other countries. A fine raised-line drawing kit is

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available from Sweden. This drawing kit can be obtained from the Swedish agency for special education (SIH, Laromedel, Tomtebodavagen 11, 171 64 Solna, Sweden). A durable raised line is produced when an ordinary ballpoint pen is drawn over the textured plastic surface. The raised lines are both tangible, visible and durable. Heller and his colleagues have used this device to examine spatial cognition and picture perception in blind people (Heller, 1989b; Heller and Joyner, 1993; Heller and Kennedy, 1990; Heller et al., 1993, 1995, 1996a, b). Some researchers have argued that tangible picture perception is poor in blind people, since congenitally blind subjects have sometimes shown low identification scores when attempting recognition of pictures for the very first time (for example, Lederman et al., 1990). However, late blind subjects may perform much better than other individuals, and it is likely that practice and education will improve performance in any task using tangible pictures (Heller, 1989b). It is important to note that any failure to identify a tangible picture does not mean that the individual does not have any idea about the shape or configuration (Kennedy, 1993; Heller et al., 1996a). The identification of pictures is a higher level cognitive function that depends upon categorical information (Heller et al., 1996a). Thus, people may know much about the configuration in a tangible display, yet not know what it is or how to name it. Failures in naming do not necessarily imply perceptual failures. Picture identification is aided when subjects are told about the category to which a picture belongs prior to feeling the picture. If one asks subjects to scan three tangible pictures with touch, and find, say, an apple, performance is very high. Performance in multiple-choice picture recognition can be as high as 90 per cent correct (Heller et al., 1996a). Moreover, tactile picture identification is also greatly improved when subjects are told the category of a picture after the picture is touched, but before it is named. Thus, categorical information aids picture identification through access to naming, and not just in any possible improvement in scanning strategies. This means that it is very likely that picture identification skills can be improved with practice, since naming is very much dependent upon higher level, top-down processes. In addition, there is evidence that when people are given bodycentered spatial reference information by aligning patterns with the body midline, there are advantages even for 2D patterns (Millar et al., 1994). The presentation of patterns in the frontal plane, as on a CRT screen, may often optimize pattern perception. This orientation will eliminate illusory effects in the horizontal-vertical illusion (Heller and Joyner, 1993). In addition, the frontal orientation can aid pattern perception for embossed letters and Braille in blindfolded sighted individuals (Heller 1992a) and for tangible pictures (Heller, unpublished research). Blind people are able to understand the point of view of another person, as demonstrated in a tactual analog of the Piagetian perspective-taking task (Heller and Kennedy, 1990). Heller and Kennedy were interested in knowing if

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congenitally blind people were able to understand how an array of objects would ‘look’ to people from different vantage points. They exposed blind people, including late blind and congenitally blind people, to a three-dimensional array that consisted of a cube, cone and sphere on a large, flat, foam-board surface (29. 5×42 cm). Subjects were required to draw the array from a bird’s eye view, and generate side views of the array as it would appear to people sitting at other positions around a table. They were not allowed to move the array, or their position, as the blind subjects attempted drawing the array of objects from their right, across from them, and from their left. In addition, the blind subjects were presented with raised-line drawings of the array of objects from all the vantage points, and had to indicate the position of the ‘viewer’ to produce the drawing. The congenitally blind subjects did as well as the sighted and late blind subjects in all versions of the task. A central problem in tangible graphics for blind people involves the representation of three-dimensional space on a flat surface (Jansson, 1992). Other problems include the lower spatial resolution of the skin, and getting an overview of a complex display (Jansson, 1992). Jansson and his colleagues (1992) have experimented with texture gradients as devices for the representation of slant in a 2D array. Tangible texture gradients may hold promise for the representation of slant. In addition, work is under way in Europe on the development of output from computers that will accomplish the same goals. Jansson is studying a virtual tactile map with the aid of a touch tablet and synthetic sound (Jansson, personal communication). The aim is to provide understandable output from computers. Heller’s work described below uses a raised-line drawing kit for the investigation of spatial representation in blind and sighted people, but there are alternative methods. Jansson (1992) and Loomis (1990) have both used ‘swell paper’ for the production of tangible displays. Swell paper actually swells when a photocopy is reproduced on the paper and the paper is heated. The lines are tangible, and this is a convenient way to generate graphic output from a computer. It would be helpful if there were some way to provide instantaneous graphic output from computers, but high resolution, refreshable devices are not yet available. Those devices that are currently used have relatively low spatial resolution. This limits their utility for the presentation of complex spatial information. 3.3.1 Linear perspective in blind people Many graphical displays use drawings that include perspective representation. There is little doubt that outline forms are comprehensible via touch, but some researchers have expressed skepticism about linear perspective. Graphics on a computer screen may include overlap, and many common graphics for vision include foreshortened representations in an attempt to depict solids and geometrical relations. We have little empirical knowledge, however, about

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whether or not blind people think in terms of visual conventions when they imagine objects and arrays. Sighted people need considerable instruction before they are able to draw in proper perspective, for example. In addition, sighted individuals vary a great deal in how well they are visually able to interpret complex two-dimensional representations, such as graphs and maps. Blind people may have minimal exposure to tangible graphics, and may require instruction in the interpretation of depictions that include foreshortening and elevated views. The general problem posed is the efficacy of representing 3D information in tangible displays. Heller et al. (1995) recently reported the results of a study of blind people making and interpreting pictures of a model house. Subjects attempted to generate raised-line drawings of a model house, and were then asked to identify the vantage point of drawings that included side views, bird’s eye top views, and some three-quarters foreshortened, elevated representations. The congenitally blind subjects had special difficulty with the views from above, but it should be noted that all subjects did poorly with tangible representations that involved foreshortening. Sighted subjects were able to benefit from prior instruction that some views could involve elevation, and showed more than one side of the house. It was proposed that blind people are also likely to benefit from prior instruction. An interesting and provocative finding emerged from the drawing task. Some blind subjects, including some congenitally blind individuals, produced side-view drawings of the roof of the house that may have represented foreshortening. It was possible that these drawings simply reflected the subjects’ knowledge that the roof included a peak and eaves. Consequently, further study was needed to see if congenitally blind people could understand other aspects of perspective. It should be noted that there may be large effects of visual experience on the nature of imagery. One blind person told the first author of this chapter (Heller), for example, that she understands that sighted people see: ‘half of a tree, but blind people imagine the whole tree’. There is evidence that Braille is size-specific, unlike visual print that can vary tremendously in size (Heller and Clyburn, 1993). Moreover, one congenitally blind person told Heller that he knows that three-quarters perspective views exist, but he could not imagine how sighted people see things that way. Supporting evidence for this skeptical idea came from a study on imagery in blind people by Arditi and his colleagues (1988), which claimed that the imagery of blind people did not include the laws of perspective, since they did not show evidence of decreasing image size with distance. Arditi et al. (1988) asked blind people to imagine familiar objects. Blind subjects tended to imagine objects within ‘arms reach’. In a further experiment, blind subjects were asked to point to the sides of objects of differing sizes at three distances. According to Arditi and his colleagues, only the sighted subjects followed the laws of perspective in their imagery, and showed a decrease in pointing span with increasing distance.

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Figure 3.1 This figure shows a side view of the apparatus. The board was mounted on a hinge and was free to rotate past the horizontal and the vertical.

Kennedy (1993), however, has reported that blind people show an understanding of perspective in their pointing behavior in a perceptual task (pp. 192–7). He asked blind subjects to point to a wall at a close distance and then a greater distance. Blind subjects showed evidence of convergence when pointing to a wall at a greater distance. Consequently, Kennedy argued that their pointing behavior reflected an intuitive understanding of an aspect of perspective, namely convergence. However, imagery and perceptual tasks may not follow the same principles as situations involving the interpretation of tangible pictures. Just because someone understands an aspect of convergence in pointing behavior does not mean that the individual will correctly interpret depictions of perspective, or show the use of the principles of perspective when drawing objects. Consequently, Heller and his colleagues (1996) conducted an experiment to determine if congenitally blind people could understand geometric perspective in tangible displays. Note that geometric perspective includes foreshortening and converging lines, and the experiments were not able to discriminate between these alternative components of perspective. Subjects were first exposed to a board on a hinge, and Figures 3.1 and 3.2 show the apparatus and the stimuli. The board (25 cm wide×17.5 cm high×1.25 cm thick) started off at the vertical, in an upright, frontal orientation. Congenitally blind, blindfolded sighted and late blind subjects were asked to draw the board using a raised-line drawing kit. Then, they were asked to draw the board at the different angles to try to: ‘Show the slant. Try to show how the board would look if I were looking at it with my eyes from where you are sitting’. The participants produced drawings at each angle, with the final drawing made of the horizontal board. The congenitally blind subjects did not spontaneously use foreshortening in their pictures. This was not surprising, since they had minimal exposure to drawing. However, it was not known if they could learn to interpret perspective drawings and this led to an additional experiment. The subjects were then told that they would touch a set of drawings of the board at the angles they had previously felt and they would feel the board at a number of positions (Figures 3.1 and 3.2). Their task was to tap the picture that corresponded to the slanted

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Figure 3.2 The second figure shows the raised-line perspective drawings used in the experiment described in this chapter.

board. They were told the pictures showed how the board looked to a sighted person. The congenitally blind subjects performed as well as the blindfolded sighted and late blind subjects. Both groups of blind subjects performed better than the sighted controls in their judgements of drawings of the vertical panel. Note that the congenitally blind subjects were able to correctly interpret the perspective drawings, and some subjects performed very well. In fact, one subject stated that he finally understood how things might look to sighted people—for the first time in his life. This subject was born without eyes. Some congenital blind subjects performed much better than sighted subjects restricted to haptics. These data suggest that congenitally blind people can rapidly learn to make sense of aspects of perspective. It is not known if the early blind participants were responding to the convergence of lines, or the reduced size cue in foreshortened representations, or both of these cues to perspective. The spontaneous comments of some of the blind subjects suggest that the relevant cue was reduced height as an indicator of slant. The important message here is that while congenitally blind people can readily learn aspects of perspective, these skills should not be taken for granted when introducing a person to graphical displays.

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3.3.2 Maps Maps are a special problem which present practical difficulties that are not apparent in other tangible graphics. They may allow a person to understand a spatial layout, and can represent a schematic diagram of a room, building or much larger space. The problem for the interpreter of a map is to first understand the spatial relations in the map itself. Then the individual must be able to imagine him- or herself in the map. Finally, it is necessary to relate the spatial relations in the map to mobility in large-scale space. This may demand an understanding of the position of one’s body with respect to the map and to the environment. Ultimately, useful maps will aid mobility. Misalignment of the map with the environment can present difficulties when one attempts orientation judgements. A misaligned map is one in which straight ahead in the map does not conform to straight ahead for the observer in his or her environment. Thus, a sighted person will have difficulty reading a map that is upside down while walking or driving. Similarly, if a map is misaligned with respect to the environment, blind or blindfolded people will show large error scores in making directional, pointing judgements (Rossano and Warren, 1989a and b). Heller recently replicated the study of Rossano and Warren (1989b), with blindfolded sighted subjects and found large gender differences. Men had much smaller mean pointing errors than women. A second study compared groups of late and early blind subjects, but failed to find any clear differences as a function of visual experience. 3.4 Auditory information displays Auditory information displays for blind persons are used in a wide variety of applications and can use either speech or other auditory codes. Many synthetic speech systems are now available for displaying the contents of computer screens and for reading printed documents scanned into a computer (Steele et al., 1989; Dixon and Mandelbaum, 1990; Cook, 1991) and digitized speech is also coming into use for navigational assistance such as talking maps and remotely readable signs (Loughborough, 1990). Mobility and spatial sensing aids for the blind commonly use a variety of auditory codes (Brabyn, 1985). These range from simple pulsed or tonal codes, indicating the presence of and distance to an obstacle, to extremely information-rich wide bandwidth displays enabling object identification as well. Other applications of auditory information displays include the many adaptations of instruments and devices needed in employment situations or in everyday life, in which information normally presented visually must be converted to auditory and/or tactile feedback. This category includes a wide variety of devices such as light detectors, meters of all kinds, measuring devices, carpentry tools, home-appliance displays, oscilloscopes, test

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instruments, liquid level indicators, power and volume-level indicators, automotive repair instrumentation, dial gauges, micrometers, computer interfacing aids and many others (Gerrey, 1984; Brabyn, 1990). In general, information can often be displayed less expensively using the auditory information channel than the tactile, though not always more effectively or even as effectively in certain applications. This section outlines some of the applications appropriate for this type of information display and some of the practical ergonomic considerations involved in designing such displays. 3.5 Auditory versus tactile information display Due to the relatively low cost of electronics, speech synthesizers and audio reproduction equipment in comparison with volatile Braille displays and machines for producing tactile drawings and maps, the use of sound as an information medium has sometimes spread beyond those areas where it is the most economically efficient display modality. A controversial historical example was the advent of the low-cost cassette tape recorder which was widely thought to reduce the necessity for Braille literacy, since students could take ‘notes’ by recording lessons, for playback after class. There is a difference, however, between the active reading process involved in Braille and passive listening to a tape, aside from the sheer difficulty of randomly accessing the desired sections of recordings. Also, the inherently spatial nature of Braille differs from the essentially serial nature of sound; some types of information are very difficult to grasp (for example, mathematical or technical texts) through a serial presentation of spoken information. This problem has been recently recognized and efforts to restore the use of Braille are being undertaken. Similarly, in the field of computer access, it is widely acknowledged by blind individuals that they would prefer volatile Braille displays over synthetic speech as a means of reading screen information; however, the large cost difference combined with different government policies on reimbursement have resulted in much less use of Braille computer-access systems in the US than in Europe. In the case of reading machines, speech is the usual mode of presentation, though a number of such systems now scan the written material into a standard personal computer for which volatile Braille display outputs are available. For certain other tasks such as map-reading and learning spatial concepts, some form of tactile display is clearly essential. However, in some cases tactile drawings and diagrams can be supplemented by auditory output as in the Nomad device, which presents tactile drawings with speech labels accessed by pressing on any given area of the drawing. Other examples of combined auditory and tactile display are given below in the field of vocational instruments. In general, although no hard and fast rules can be stated, there are clearly cases where one display modality is preferred over another, and other cases where the

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combination of the two modalities can improve the ergonomics of the resulting information system. 3.6 Ergonomic factors in speech displays For gaining access to information which is static or changes only infrequently, or for the inexpensive display of the inherently verbal information predominating in computer screen information or signage for navigation, speech is often the most suitable form of output. Recorded, digitized and synthetic speech are all important to the blind consumer; however, in some cases the needs of blind speech-users include some unique requirements. 3.6.1 Speech quality and speed trade-offs A primary and obvious ergonomic factor in speech displays designed for the general public and for communication by the speech-impaired is their perceived quality or natural-soundingness, since the listener is generally a family member, friend or naïve member of the public. Ironically, for a blind user, this is often a secondary consideration, and other ergonomic factors take precedence (Brabyn et al., 1989). This is particularly true in computer access and other common applications of synthetic speech. The situation is different for a blind user of a synthetic speech display. The audience is the user himself, who rapidly becomes a practised synthetic speech listener, able to learn the particular eccentricities of the synthesizer being used. Speed, normally associated with degraded quality, is often more important than whether or not the speech sounds natural, especially in applications such as computer access or reading where a large amount of material must be scanned rapidly. The practised user quickly adjusts to this high-speed speech, and to the low quality of many synthesizer outputs. Indeed, the blind user may wish to push the speed beyond the limits imposed by manufacturers who might feel that quality becomes unacceptable beyond a certain point. A much more important consideration is the ‘unambiguity’ of the speech—whether the pronunciation of each word and letter is distinct from all others—rather than whether the voice sounds like a real person. 3.6.2 User controls The ability to control the display rapidly and conveniently is an essential factor in speech displays for the blind. Because of the slow speed of speech compared with visual perception of computer screens, all possible steps should be taken to minimize time wasted in enunciating already-known information—such as the

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whole line when the first word may indicate that the line is of no interest or can be guessed. Some sophisticated synthesizer systems incorporate processing delays while the synthesizer calculates the best possible pronunciations and inflections for an upcoming string of speech; these delays are very undesirable to the blind user. The ability, on the other hand, to start and stop output immediately, even in midstream, and have enough control to short-circuit the system during predictable output strings is essential in order to skip to the next information of interest as rapidly as possible. In most computer screen access systems, various keystrokes and sequences must be memorized for the user to specify what information they need. This places an extra layer of strain on the blind user over and above the difficulties faced by sighted computer users. Methods for simplifying this extra layer of controls are therefore desirable, especially for beginners. For example, one solution is the use of digitizing touch tablets (as in the SKERF-Pad system we developed and the commercial Master Touch system) in which a touch-pad is used as a tactual analog of the screen. The user points to any desired location on the pad, and the screen contents at that location are enunciated. Another innovative solution was the use of x and y slider controls to specify position on the screen (as in the Frank Audiodata system). These considerations are equally important in reading machines intended to convert printed materials into synthetic speech (Brabyn, 1992a). With most current machines, output is not instantaneous and may not occur until after a delay of several seconds to a minute after material is fed in. Accordingly, the most practical use of such machines is in the reading of continuous text. For improvements in the everyday sorting and reading of mail, magazines and technical publications, or for scanning through large volumes of material and picking out the portions of interest, and so on, ergonomic enhancements will be desirable, including the ability to deal with combined text and graphics, different fonts and layouts, handwriting, poor quality print, and to scan rapidly through a document in order to ‘separate the corn from the chaff’. 3.6.3 Hybrid speech and non-speech codes In order to enhance detection of certain display features or present a rapid overview of screen contents, the use of hybrid sound codes can be helpful. For example, it is helpful to be able to use arbitrary sound codes for punctuation, and to vary pitch and/or loudness from one word or letter to the next to indicate letter case, parentheses and bold type. For rapid scanning of the screen to gain an overview of its contents, systems with slider pots or touch-pads for x-y coordinate specification can be used in conjunction with audio coding schemes which assign various sounds to text, capital letters, numbers, and so on, with silence for blanks. For numeric displays such as digital instruments, we have used a higher pitch to code the digits after the decimal point, eliminating the time

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needed to enunciate the word ‘point’. The potential for such coding systems to improve information-transfer efficiency is in its infancy. 3.7 Speech versus other auditory codes The advent of speech synthesizers has led to a common perception that speech is ‘state of the art’ and most appropriate for making almost any type of information accessible to the blind. However, speech has definite limitations. One is its slow information transfer rate compared with the auditory bandwidth used. While well adapted to expressing human thought processes, and flexible enough for adaptation to an immense variety of situations, the speed limitation of speech can be serious in more focused situations where the task at hand is not inherently verbal, but limited in scope and requires rapid information feedback. These are situations normally handled by visual information displays, which are well suited for fast parallel information transfer. For example, in measuring instruments, interactive control situations or echo ranging, the quantity being measured is often continuously varying. Reading such a signal using a synthetic speech output is much like that of reading a rapidly fluctuating voltage level using a digital multimeter. By the time the signal has been sampled and displayed (enunciated), its true value may have changed significantly. An ergonomic analogy exists between visual (digital versus analog) and auditory (speech versus continuously variable tone) displays for meters or gauges. In the visual world, analog displays are inherently faster to interpret than digital ones. A glance at an analog fuel gauge or artificial horizon tells a pilot instantly whether the tank is nearly full or nearly empty, or what the current attitude of the craft is. With digital displays time is needed for the interpretation of a displayed number of gallons in relation to total fuel capacity or horizon angle. This explains why digital displays have never caught on in the primary dynamic instrument read-outs for automobiles and aircraft. Similar considerations apply to the read-out of a number (accurate to three decimal places though it may be) in synthetic speech versus a more ‘natural’ or continuously variable auditory information display. 3.8 ‘Analog’ audio displays Many possibilities exist for non-speech auditory coding methods. A number of simple schemes, which are easy to implement electronically and have proven their practicality in a variety of applications, are described below.

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3.8.1 Variable pitch codes To display information which is varying, we have found that auditory tones with pitches corresponding to signal levels are far more satisfactory than speech outputs, and more closely simulate an analog visual display (Brabyn, 1992b). A simple example is a meter or continuity tester display which gives a rapid, approximate indication of voltage, resistance or other quantity purely through auditory pitch. Another example is the display used in the Smith-Kettlewell Light Probe, a device which gives an auditory indication of incident and reflected light. Received light intensity is coded as pitch, and rapid variations in this pitch can give complex and subtle cues as the device is aimed at a flickering light source or scanned across a visual pattern. This type of sensor and display can be used in many applications; for example, to scan a sheet of paper to locate print (such as letterhead, signature lines and so on). With practice different paper money bills can be distinguished by scanning the probe across them. This type of display has found application in many other instruments, including more complex ones such as the Smith-Kettlewell Auditory Oscilloscope. In this device, the horizontal position of a cursor superimposed on the trace is controlled by a knob with a Braille scale, while vertical trace deflection at the cursor location is coded by the pitch of a tone. By ‘scanning’ across the display with the knob, the user obtains a remarkably accurate picture of the displayed signal. Psychophysical testing has indicated that relatively subtle differences between two similar wave-forms can be discriminated. For example, the difference between sine and triangle waves can be detected, as can the small peaks caused by ringing signals on the corners of square waves. Dynamic conditions can also be dealt with, such as during the adjustment of the triggering control. Exact readings on the horizontal (time) axis can be made using the tactile scale surrounding the cursor control. If desired, a hybrid audio-tactile module of the type described below can be added for similar exact readings on the vertical axis. 3.8.2 Hybrid displays (auditory and tactile) An essential ergonomic feature of analog displays is the instant indication of the reading relative to full scale. A simple and practical hybrid tactual/auditory display which retains this feature has been found useful in measuring static or slowly varying quantities. In this hybrid approach, a pointer knob is rotated until a null is found in the amplitude of an auditory tone. This conveys an immediate impression of the signal’s amplitude relative to full scale, and an accurate Braille reading of the quantity can be taken if desired from a tactile scale surrounding the pointer knob.

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For dynamic signals, a variation on the above technique is utilized in the Smith Kettlewell Dynamic Meter Reader (Fowle, 1982), with a tonal output whose pitch varies with signal level. When the signal level reaches the equivalent of the manual dial setting, the tone is ‘chopped’ with a 50 per cent duty cycle. Thus, as the dial is rotated to the point where chopping begins, the signal level can be read from the Braille scale. Variations in the signal level are readily evident from changes in the pitch of the output tone, and the knob can be adjusted in advance for any desired ‘set point’. In addition to applications in meter-type instruments, we have recently found this type of dynamic display to be useful in such devices as auditory carpenters’ levels, designed so that the transition from steady to chopped tones occurs at the level point. Many other variations on the use of combined auditory and tactile feedback can be used. The Nomad system, using raised line graphics placed on a touchsensitive tablet connected to a talking computer, enables tactile graphics to include verbal ‘labels’ accessed by pressing down on any part of the drawing. A combination analog (audio-tactile) and digital (speech) instrument reach-out (Brabyn, 1990) allows accurate static measurements to be made with the speech output mode, while rapid, approximate measurements can be taken from the ‘analog’ display. New educational devices such as the Formboard with a Brain and the Tact Tell system (Gilden, 1993) combine hands-on object manipulation and tactile feedback with speech output reinforcement. Many other possibilities exist; these techniques are gaining more acceptance as the need is recognized to utilize all available input channels. 3.9 Information displays for orientation and mobility We have thus far mainly discussed displays for computer, reading machine and instrumentation use. Another major application of technology for this population is orientation and mobility devices, which include some auditory information displays of considerable complexity and interest. The human auditory system is capable of utilizing sophisticated coding schemes to convey complex and rapidly changing information. Perhaps the best known examples are in electronic mobility aids and spatial sensors, in which rapid, dynamic feedback is required and the use of speech is considered inefficient. In the wide band FM ultrasonic class of mobility aids and spatial sensors (including the Sonicguide and Trisensor) (Kay, 1974, 1985), the auditory display codes range as pitch, direction as interaural amplitude differences, and surface textures and target character as richly varying timbres in the audio output enabling object identification. A practised user can use such displays to make rapid decisions and subtle interpretations of object identity and motion. This type of display has also been applied in various forms in underwater and medical sonars, and demonstrates the potential for more sophisticated displays in a wide range of applications if the need arises.

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Another class of orientation and mobility devices is the technology used for navigation or orientation. The best known example is the Talking Signs system (Brabyn et al., 1993), which give the blind traveller the ability to read signs remotely, just as a sighted traveller is accustomed to do—and depends on for wayfinding in unfamiliar areas. (Braille signs do not give blind persons the same experience and ease of travel as the sighted get from print signs, because they have to be located first by the slow trial and error process of tactual exploration.) Talking Signs consist of infra-red transmitters placed at sign locations. These transmitters continuously send out the sign message on invisible light beams, to be picked up by a receiver carried by the blind traveller. The directional nature of the infra-red beam provides location information, while the sign message is converted into spoken output at the receiver. In practice, this approach has been found to make navigation drastically easier in complex environments. In this case, spoken output is the most suitable since the underlying information is verbal, while rapid scanning of the receiver by the user can quickly inform him of the presence and location of nearby Talking Signs without waiting to hear their messages. 3.9.1 Tactile scale markings It should be noted that on a wide variety of household and vocational appliances, information regarding power settings and control options can most easily be provided tactually. Often, simple raised overlays can be provided on modified knobs and dials, sometimes requiring larger diameter controls to be added to achieve sufficient tactile resolution. 3.10 Ergonomic considerations for low-vision aids As mentioned earlier, there is a tremendous range in type and degree of visual impairments among those who have less than perfect vision but retain sufficient capability to use their sight in many everyday tasks. Similarly, there is a wide range of low-vision aids and devices designed to assist this population sector in making best use of available visual characteristics (Bellecci, 1990). It should be noted here that visual acuity is not the only variable affecting task performance in this group. Other visual deficits such as field restrictions, reductions in contrast sensitivity, reduced ability to adapt to changing light levels, and other aspects of visual functioning can be equally important. Due to the diverse nature of this field, the following is only a brief summary of some of the considerations applicable to aids and devices designed to assist those with low vision.

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3.11 Optical aids and devices The most common visual aids are optical in nature, and encompass special spectacles, hand-held and stand-mounted magnifiers, and telescopes. Although the situation is gradually changing, many of these devices have not been specially designed for low-vision use but have been taken with or without adaptation from various industrial applications. Clearly, ergonomic factors are important in the design and prescription of such optical aids. The majority of these aids are, appropriately, designed with reading as the primary task in mind. In this case, it is important that a comfortable reading distance, position and field of coverage is possible for the user. With the higher powered magnifiers, whether hand-held or stand-mounted, it is difficult to achieve these goals; the higher the magnification the smaller the field of view as a general rule, and the closer the user must be (often bent forward) to the reading material. It is interesting to note here the similarities between the problem of a blind person reading a computer screen, for example, one word at a time using synthetic speech— and a low-vision person reading a screen or book one word at a time due to the restricted field of view necessitated by large magnifications. In both cases, immediate problems of scanning and obtaining an overview of the material being studied arise. This brings up another ergonomic consideration; the means by which the reading material itself is held in position or scanned behind the magnifier—or alternatively, the convenience with which the magnifier can be scanned across a page. One solution to these problems is the use of the spectacle-mounted telescope, allowing a longer reading distance to be maintained for a given magnification. In the case of telescopes, the majority are used for outdoor tasks such as reading distant signs and other mobility-related functions. These are primarily hand-held devices in the 3× to 6× range, carried in a purse or pocket (or around the neck) and used intermittently. Many such telescopes are difficult to hold, aim or focus— especially bearing in mind that many users are older persons who may have reduced physical dexterity. This problem and the sheer difficulty of holding a telescope still for a stable image (again, especially when the hand may be shaky) limits the maximum practical magnification used in such devices. One improvement in ergonomics is the use of a substantial and comfortable grip on the telescope; one such recently developed grip allows the telescope to be held and focused conveniently with one hand, leaving the other free for a stick or shopping bag (Brabyn et al., 1994). Efforts to utilize spectacle-mounted telescopes for the mobility task are apt to result in problems due to the mismatch between the visual flow field and the vestibular-ocular system, leading to feelings of nausea and difficulties in coordination. (This problem also applies to ‘minifiers’ sometimes used in an attempt to expand the visual field of persons with retinitis pigmentosa.)

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Spectacle-mounted telescopes appear to be most successful in applications where the user is stationary (such as reading or watching television) or, if the user is mobile, in configurations where the telescope is placed off-axis so the user normally sees an unmagnified field but can move their eyes up, down or to the side for intermittent ‘spotting’ of distant targets through the telescope lens. This is true, for example, in bioptic telescopes used for driving, where the telescope is usually placed in the upper part of the spectacle lens, leaving the majority of the visual field freely visible without magnification through the remainder of the lens. This avoids the flow field problems mentioned above. New developments in telescopes include the recent emergence of autofocus technologies and efforts to apply them to low-vision aids (Kuyk et al, 1990; Greene et al., 1992); these should allow improvements in the ergonomics of such devices by avoiding the need for the user to fiddle with focus controls. Naturally, one of the ergonomic factors in any spectacle-mounted device is weight; it can be expected that continuing advances in optical and electronic methods will further improve this aspect of design for all spectacle-mounted aids. 3.12 Electronic magnification and image enhancement In order to obtain larger magnifications than conveniently available optically, the use of closed-circuit television technology has been extensively applied to lowvision reading problems. Desktop systems consisting of a camera, lighting system and large monitor can achieve magnifications of ×60 or more. The reading material is normally placed on a movable table below the camera and monitor so it can be scanned under the camera. Ergonomic considerations in the use of such systems include the convenience and simplicity of the various controls for magnification, focus, image intensity and contrast. Scanning convenience is also important; automatic motorized scanning tables are available to simplify this aspect of the task. Most systems allow the contrast of the image to be reversed at the user’s will; this feature is convenient for reducing the effective glare field when reading the usual black on white documents. Contrast reversal (to a white on black image) effectively makes the majority of the screen black instead of white, reducing the potential for image degradation due to light scatter in the eye because of cataracts or other optical media opacities common in older users. Portable versions of these electronic magnification systems are now becoming commonly available, using small hand-holdable cameras and portable display systems adapted from miniature televisions. Naturally, the degree of magnification possible using a small screen is not as great as for the desktop systems, but such units offer flexibility in use due to their portable nature. Systems using hand-scanned cameras require practice in the necessary physical coordination. (The same problem arises for blind persons when they read printed text with reading machines using hand scanners.)

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A number of such systems now offer, as an option, displays adapted from the virtual reality industry, in the form of visor or goggle-mounted displays (NASA, 1989; Rubin, 1989; Massof, 1993). It is still too early to tell how well these systems will be accepted by users, but they appear to offer convenience in a number of applications. Those using solid-state displays are generally of limited contrast and image quality as yet, leading one major developer to opt for CRT type displays to achieve the high contrast considered vital for maximum effectiveness in the low-vision application (Massof, 1993). Concomitant with developments in the portability of electronic magnification systems have been studies of image enhancements which go beyond simple magnification and contrast adjustments. More sophisticated methods of manipulating contrast and other image parameters to match the user’s individual contrast sensitivity function, and even rearranging the physical layout of the image ‘remapping’ to utilize the user’s best remaining areas of vision are emerging (Peli et al., 1986; Peli and Peli, 1993; Lawton, 1989; Massof and Rubin, 1994). These and related techniques offer promise of further ergonomic improvements. 3.13 Contrast, lighting and environmental adaptations An overriding factor in the ergonomics of all low-vision aids is the importance of contrast. Many of the visually disabling conditions found in the low-vision population affect the ability of the visual system to enhance contrast, and low contrast viewing situations (driving in fog or at dusk, seeing curb edges or stair steps, seeing the ‘black on black’ controls on modern VCRs and stereo equipment, for example) are often those which create the most practical difficulty for this population. Accordingly, every effort must be made in designing and specifying rehabilitative devices and methods which maximize the available contrast. Reading materials using pastel shades for backgrounds and print colors may be attractive to the young, visually healthy viewer—but are anathema to those with any form of visual impairment. A second such overriding consideration is illumination. While there are some types of visual impairment in which the patient prefers subdued lighting, in the vast majority of cases visual performance is greatly improved by adequately illuminating the object being viewed. These improvements can be quite dramatic, even without the use of supplementary optical aids. Adequately bright and well-placed reading lamps should be specified, preferably with a balanced light spectrum. Often, the home environment of elderly persons with visual impairments are insufficiently illuminated, causing unnecessary inconvenience. Similarly, in the workplace it is important to provide sufficient light. Special lighting devices for low-vision users are still in their infancy, but one example of such a device is the Wide Angle Mobility Light (WAML) which has been used to provide battery-powdered portable illumination for night-time low-

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vision mobility. Night-viewing devices adapted from the military are also available, though their relatively high cost has so far limited their widespread acceptance. Potential also exists for special applications such as effective portable battery-powered illuminators which might be used in the workplace in situations where the user is required to move around from one place to another, as in a machine shop for example (Jampolsky et al., 1989). Similarly, experimental spectacle-mounted illuminators have been developed to address the problem of reading with high-powered spectacle adds (Jampolsky et al., 1989). These highpowered lenses have a designed viewing distance of only 1–2 inches, making it difficult to achieve bright illumination of the reading material due to blockage of ambient light by the head. Miniature, portable light sources have potential to address these and other ergonomic problems related to illumination. A related problem is the reduced ability of elderly persons with impaired vision to adapt to changing light levels. To date, few effective solutions have been developed to address this, but putting on dark glasses when going outdoors and removing them when coming in is helpful for some individuals. Related to the above ergonomic problems are the difficulties in viewing conditions created by glare. Here a distinction can be made between ‘glare recovery’ (the ability to recover visual performance after brief exposure to bright light) which is clearly related to the adaptation problems mentioned above, and ‘disability glare’ (the difficulty in seeing an object in the presence of a glare source—as in driving into the setting sun). The latter problem is exacerbated by cataracts and media opacities which increase light scatter within the eye and reduce the contrast of the retinal image. Here again, good ergonomics would dictate the use of maximum contrast where possible—and the removal or avoidance of bright light sources which would interfere with effective vision. Finally, mention should be made of general environmental factors in lowvision rehabilitation. This subject has been touched upon above, but it is important to note that the practical ergonomics of a home, outdoor or work environment for a person with low vision includes many factors which can improve the effective visibility of both work materials and environmental features—especially those relating to safety. Lighting and contrast are paramount considerations, and the latter can include such items as painting step edges to enhance their contrast and using light or colors for countertops to ease the detection of dark objects placed upon them. The visibility of signs and labels of all kinds can be improved by increasing both size and contrast. Often, placement of a workstation or computer screen to avoid glare from the window can make a practical difference. These and many other such environmental ergonomic considerations are mainly common sense, but it is surprising how often they are ignored.

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3.14 Conclusions A great variety of devices exist to aid the rehabilitation of visually impaired people. However, the effectiveness of these devices requires attention to ergonomic considerations, including user characteristics and experience. There is a great deal that remains to be learned about spatial cognition in blind people. We are just beginning to discover the influence of experience on perception and representation. Thus, congenitally blind people may be relatively unfamiliar with graphics, and this has considerable relevance to the use of computer systems. Moreover, we do not know if congenitally blind people will spontaneously understand graphics that involve the translation of 3D space onto a 2D tangible surface. However, it seems likely that all new users of tangible graphic displays will require instruction in their use. The development of useful sensory aids is hindered by the present lack of agreement on any universal icon or symbol system. While many blind people read Braille, most do not. Furthermore, while late blind subjects are obviously familiar with print letter forms, congenitally blind people may not have learned these patterns. Since most blind people lose sight much later in life, the difficulty is also exacerbated by the possible effects of aging on tactile sensitivity in blind people (Stevens et al., 1995). It should be clear that user characteristics play an important role in the development of useful techniques for the development of mobility or communication devices for blind and visually impaired people. One’s educational experience is important, and should be considered by the developers of these devices, and by rehabilitation counselors. Moreover, the educator of the blind person has the additional problem of a lack of agreement over what a ‘typical’ or ‘normal’ blind person is. Blind people are extremely heterogeneous in their background. We also do not know what normal touch is, nor do we know how to correct any possible disability in this area (see Heller and Schiff, 1991, pp. 235–8). We have good normative data for vision, and can often correct acuity problems for people with simple myopia. Unfortunately, we do not have this information for touch, and we do not have the equivalent of eyeglasses for our fingers. The ergonomics of auditory information displays for the visually impaired is complex but some patterns emerge. In general, speech output can give highprecision readings, and is often available in digital form if the observed signal is, or if the information is intrinsically verbal as in computer displays or signage information for orientation. Other forms of output such as auditory codes or hybrid audio-tactile outputs can be more user friendly when the signal is dynamic or a more ‘ANALOG’ type of display is desired. This can allow the user readily to monitor changes in the measured signal, and obtain a sense of how large the measured quantity is in relation to the full range of the measuring scale. Hybrid displays incorporating speech, other auditory cues, and various forms of tactile

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feedback and/or control may offer promising alternatives in future efforts to provide more ergonomic display of complex information. Finally, safety considerations are important in the use and development of mobility aids. Many blind people are not independent and are limited in their mobility. They fear accidents, and this fear is not without some basis. The development of devices that will assist mobility should not compromise safety, and one needs care in the use of devices that may help one group of individuals to avoid doing so at the expense of another group. For example, ramps are important aids to some people, but pose a hazard to blind pedestrians. They can be employed, but some sort of signal or warning device would be helpful. Acknowledgments Morton A.Heller received support from NIH Grant 08040 while working on this chapter. John Brabyn’s contribution was supported by grants from the National Institute on Disability and Rehabilitation Research and the SmithKettlewell Eye Research Institute. References ARDITI, A., HOLTZMAN, J.D. and KOSSLYN, S.M. (1988) Mental imagery and sensory experience in congenital blindness, Neuropsychologia, 26, 1–12. BELLECCI, C. (1990) What’s new in low vision aids. Technology Update, Sensory Aids Foundation, August, 1–4. BENTZEN, B.L. (1982) Tangible graphic displays in the education of blind persons, in SCHIFF, W. and FOULKE, E. (Eds). Tactual Perception: A Sourcebook, New York: Cambridge University Press. BRABYN, J.A. (1985) A review of mobility aids and means of assessment, in WARREN, D.H. and STRELOW, E.R. (Eds). Electronic spatial sensing for the blind, Boston: NATO ASI Series, Martinus Nijhoff. BRABYN, J. (1990) Instrument readouts for the blind. Proceedings, Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 12 (5), 2281–2. BRABYN, J. (1992a) Problems to be overcome in high technology devices for the visually impaired, Optometry and Vision Science, 69 (1), 42–5. BRABYN, J. (1992b) The design of auditory instrument and computer displays for the blind, SID 92 Digest, 663–6. BRABYN, J., COLENBRANDER, A. and WINDERL, W. (1994) Improving the ergonomics of low-vision telescope. Journal of Vision Rehabilitation, 8 (1), 12–13. BRABYN, J., CRANDALL, W. and GERREY, W. (1993) Talking signs: Remote signage solutions for the blind, visually impaired and reading disabled. Proc IEEE EMBS Conference. BRABYN, J., GERREY, W. and FOWLE, T. (1989) Speech technology for the blind. Proceedings, American Voice Input/Output Society (AVIOS) Symposium, Newport Beach, CA.

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COOK, D. (1991) A perspective on OCRs. Technology Update, Sensory Aids Foundation. CORNOLDI, C., CORTESI, A. and PRETI, D. (1991) Individual differences in the capacity limitations of visuospatial short-term memory: Research on sighted and totally congenitally blind people. Memory and Cognition, 19, 459–68. CORNOLDI, C., BERTUCCELLI, B., ROCCHI, P. and SBRANA, B. (1993) Processing capacity limitations in pictorial and spatial representations in the totally congenitally blind. Cortex, 29, 675–89. CRAIG, J.C. (1977) Vibrotactile pattern perception: Extraordinary observers. Science, 196, 450–2. DIXON, J.M. and MANDELBAUM, J.B. (1990) Reading through technology: Evolving methods and opportunities for print-handicapped individuals. Journal of Visual Impairment and Blindness, 84, 493–6. FOULKE, E. (1991) Braille, in HELLER, M.A. and SCHIFF, W. (Eds). The Psychology of Touch, Hillsdale, NJ: Lawrence Erlbaum Associates. FOWLE, T. (1982) The Fowle Gimmique. Smith-Kettlewell Technical File, Summer. FOWLE, S., FOWLE, T., ALDEN, A., GERREY, W. and WILLIAMS, J. (1987) The RAM-Talker: A Practical Speech Digitizer and Recorder. Smith-Kettlewell Technical File, Summer. GERREY, W. (1984) Custom design of aids to fit specific employment opportunities. Proceedings International Conference on Rehabilitation Engineering, Ottawa, 261–63. GERREY, W. (1989) The Addressable Nattering RAM: A Sixteen-World, FieldRecordable Speech Board, Smith-Kettlewell Technical File, Winter. GILDEN, D. (1993) Educational aids. In Annual Report of Progress, Rehabilitation Engineering Center, Smith-Kettlewell Eye Research Institute. GILL, J.M. (1982) Production of tangible graphic displays, in SCHIFF, W. and FOULKE, E. (Eds). Tactual Perception: A Sourcebook, New York: Cambridge University Press. GREENE, H., BEADLES, R. and PEKAR, J. (1992) Challenges in applying autofocus technology to low vision telescopes. Optometry and Vision Science, 69 (1), 25–31. HATWELL, Y. (1985) Piagetian Reasoning and the Blind. New York: American Foundation for the Blind. HELLER, M.A. (1982) Visual and tactual texture perception: Intersensory cooperation. Perception and Psychophysics, 31, 339–44. HELLER, M.A. (1983) Haptic dominance in form perception with blurred vision. Perception, 12, 607–13. HELLER, M.A. (1985) Tactual perception of embossed Morse code and Braille: The alliance of vision and touch. Perception, 14, 563–70. HELLER, M.A. (1986) Central and peripheral influences on tactual reading. Perception and Psychophysics, 39, 197–204. HELLER, M.A. (1987) The effect of orientation on visual and tactual Braille recognition. Perception, 16, 291–8. HELLER, M.A. (1989a) Texture perception in sighted and blind observers. Perception and Psychophysics, 45, 49–54. HELLER, M.A. (1989b) Picture and pattern perception in the sighted and blind: The advantage of the late blind. Perception, 18, 379–89.

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HELLER, M.A. (1991) Haptic perception in blind people, in HELLER, M.A. and SCHIFF, W. (Eds). The Psychology of Touch, pp. 239–61. Hillsdale, NJ: Lawrence Erlbaum Associates . HELLER, M.A. (1992a) The effect of orientation on tactual Braille recognition: Optimal ‘touching positions’. Perception and Psychophysics, 51, 549–56. HELLER, M.A. (1992b) ‘Haptic dominance’ in form perception: Vision versus proprioception. Perception, 21, 655–60. HELLER, M.A. (1993) Influence of visual guidance on Braille recognition: Low lighting also helps touch. Perception and Psychophysics, 54, 675–81. HELLER, M.A. and CLYBURN, S. (1993) Global versus local processing in haptic perception of form. Bulletin of the Psychonomic Society, 31, 574–6. HELLER, M.A. and JOYNER, T.D. (1993) Mechanisms in the tactile horizontal/vertical illusion: Evidence from sighted and blind subjects. Perception and Psychophysics, 53, 422–8. HELLER, M.A. and KENNEDY, J.M. (1990) Perspective taking, pictures and the blind. Perception and Psychophysics, 48, 459–66. HELLER, M.A. and SCHIFF, W. (1991) The Psychology of Touch, pp. 235–8. Hillsdale, NJ: Lawrence Erlbaum Associates. HELLER, M.A., JOYNER, T.D. and DAN-FODIO, H. (1993) Laterality Effects in the Haptic Horizontal/Vertical Illusion. Bulletin of the Psychonomic Society, 31, 440–3. HELLER, M.A., KENNEDY, J.M. and JOYNER, T.D. (1995) Production and interpretation of pictures of houses by blind people. Perception, 24, 1049–58. HELLER, M.A., ROGERS, G.J. and PERRY, C.L. (1990) Tactile pattern recognition with the Optacon: Superior performance with active touch and the left hand. Neuropsychologia, 28, 1003–6. HELLER, M.A., CALCATERRA, J.A., BURSON, L.L. and TYLER, L.A. (1996a). Tactual picture identification by blind and sighted people: Effects of providing categorical information. Perception and Psychophysics, 58, 310–23. HELLER, M.A., CALCATERRA, J.A., TYLER, L.A. and BURSON, L.L. (1996) Production and interpretation of perspective drawings by blind and sighted people. Perception, 25, 321–34. HERMELIN, B. and O’CONNOR, N. (1971) Functional asymmetry in the reading of Braille. Neuropsychologia, 9, 431–5. JAMPOLSKY, A., BRABYN, J., LEWIS, A. and WINDERL, M. (1989) Two experimental illumination aids. Journal of Vision Rehabilitation, 3 (3), 33–7. JANSSON, G. (1992) 3D Perception from tactile computer displays, in ZAGLER, W. (Ed.), Computers for Handicapped Persons. Wien: R.Oldenbourg. KATZ, D. (1989) The World of Touch. KRUEGER, L.E. (trans.). Hillsdale, NJ: Lawrence Erlbaum Associates. KAY, L. (1974) A sonar aid to enhance spatial perception of the blind. Radio and Electronic Engineer. KAY, L. (1985) Sensory aids to spatial perception for blind persons: their design and evaluation, in WARREN, D.H. and STRELOW, E.R. (Eds). Electronic spatial sensing for the blind, Boston: NATO ASI Series, Martinus Nijhoff. KENNEDY, J.M. (1993) Drawing and the Blind. New Haven: Yale University Press. KLATZKY, R.L., GOLLEDGE, R.G., LOOMIS, J.M., CICINELLI, J.G. and PELLEGRINO, J.W. (1995) Performance of blind and sighted persons on spatial tasks. Journal of Visual Impairment and Blindness, 70–82.

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KUYK, T., JAMES, J. and KEVERLINE, M. (Eds). (1990) A pilot study of a telescopic low vision aid with motorized focus. Journal of Vision Rehabilitation, 4 (4), 21–30. LAWTON, T.B. (1989) Improved reading performance using individualized compensation filters for observers with losses in central vision. Ophthalmology, 96, 115–26. LEDERMAN, S.J. and ABBOTT, S.G. (1981) Texture perception: Studies of intersensory organisation using a discrepancy paradigm and visual vs. tactual psychophysics. Journal of Experimental Psychology: Human Perception and Performance, 7, 902–15. LEDERMAN, S.J., KLATZKY, R.L., CHATAWAY, C. and SUMMERS, C.D. (1990) Visual mediation and the haptic recognition of two-dimensional pictures of common objects. Perception and Psychophysics, 47, 54–64. LOOMIS, J.M. (1981) On the tangibility of letters and Braille. Perception and Psychophysics, 29, 37–46. LOOMIS, J.M. (1990) A model of character recognition and legibility. Journal of Experimental Psychology: Human Perception and Performance, 16, 106–20. LOUGHBOROUGH, W. (1990) Orientation: the missing factor in O&M. Proceedings, CSUN Conference on Technology for the Disabled, 425–9. MASSOF, R. (1993) Low Vision Enhancement: Basic principles and enabling technology. CSUN Conference on technology for persons with disabilities, Los Angeles. MASSOF, R. and RUBIN, G. (1994) Face discrimination with frequency selective contrast enhanced images. Vision Science and its Applications, Technical Digest Series, 2, Optical Society of America. MILLAR, S. (1984) Is there a ‘best hand’ for Braille? Cortex, 20, 75–87. MILLAR, S. (1987) The perceptual window in two-handed Braille: Do the left and right hands process text simultaneously? Cortex, 23, 111–22. MILLAR, S. (1994) Understanding and Representing Space: Theory and Evidence from Studies with Blind and Sighted Children. New York: Oxford University Press. MILLAR, S. (1995) ‘Sound, sense, syllables and word length in prose reading by touch’. Paper presented at the meeting of the Experimental Psychology Society, Birmingham, England. MILLAR, S., BALLESTEROS, S. and REALES, J.M. (1994) ‘Influence of symmetry in haptic and visual perception’. Paper presented at the meeting of the Psychonomic Society, St Louis, Mo. MOMMERS, M.J.C. (1980) Braille reading: Effects of different hand and finger usage. Journal of Visual Impairment and Blindness, 74, 338–43. MOUSTY, P. and BERTELSON, P. (1985) A study of braille reading: 1. Reading speed as a function of hand usage and context. Quarterly Journal of Experimental Psychology, 37A, 217–33. NASA (1989) Space Age Vision Aids. NASA Technical Briefs. PELI, E. and PELI, T. (1993) Image enhancement for the visually impaired. Optical Engineering, 23, 47–51. PELI, E., AREND, L.E.Jr and TIMBERLAKE, G.T. (1986) Computerized image enhancement for visually impaired persons: New technology, new possibilities. Journal of Visual Impairment and Blindness, 80, 849–54. REVESZ, G. (1950) The Psychology and Art of the Blind. London: Longman Green.

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ROCK, I. and VICTOR, J. (1964) Vision and touch: An experimentally created conflict between the two senses. Science, 143, 594–6. ROSSANO, M.J. and WARREN, D.H. (1989a) Misaligned maps lead to predictable errors. Perception, 18, 215–29. ROSSANO, M.J. and WARREN, D.H. (1989b) The importance of alignment in blind subjects’ use of tactual maps. Perception, 18, 805–16. RUBIN, G.S. (1989) Low vision enhancement with space age technology. Research to Prevent Blindness, Science Writers Seminar, 57–8. SHERRICK, C. (1991) Vibrotactile pattern perception. In HELLER, M.A. and SCHIFF, W. (Eds). The Psychology of Touch, pp. 239–61. Hillsdale, NJ: Lawrence Erlbaum Associates. STEELE, R., GOODRICH, G., HENNIES, D. and MCKINLEY, J. (1989) Reading aid technology for blind persons: responses to a questionnaire of experienced users. Assistive Technology, 1 (2), 23–30. STEVENS, J.C. and PATTERSON, M.Q. (1995) Dimensions of spatial acuity in the touch sense: Changes over the life span. Somatosensory and Motor Research, 12, 29–47. STEVENS, J.C., PATTERSON, M.Q. and FOULKE, E. (1995) ‘Spatial acuity of touch, aging and Braille reading in blind subjects’. Paper presented at the annual meeting of the Psychonomic Society, Los Angeles.

CHAPTER FOUR Effects of exercise on physical and psychological preparedness of chronic heart disease patients for work: a review G.MAJOR KUMAR AND A.MITAL

4.0 Introduction Cardiac Rehabilitation (CR) is defined as the process by which patients with chronic heart disease (CHD) are restored to their optimal physical, mental, medical, psychological, social, emotional, sexual, vocational and economic status (Erb et al., 1979). Thus cardiac rehabilitation is multidisciplinary, involving medicine, psychology, surgery, physiology, vocational rehabilitation and engineering. The goals of a typical cardiac rehabilitation program are as follows (Parmley, 1986): 1 Return the individual suffering from CHD to optimal physiological and psychological function. 2 Reverse the adverse effects of physiological deconditioning resulting from a sedentary lifestyle which is accelerated by bed rest. 3 Prepare the individual and their family for a lifestyle that may reduce the risk of coronary heart disease and hypertensive cardiovascular disease. (This will involve activities to control smoking, blood pressure, diabetes mellitus, lip disorders and emotional stress. It will also involve discussion and classification of the disease, vocational guidance and the importance of a regular program of physical activity.) 4 Assist the individual with chronic heart disease to return to activities that were important to the quality of his or her life prior to the onset of cardiac illness. 5 Reduce the emotional disorders frequently accompanying serious health disorders. 6 Reduce the cost of healthcare through shortened treatment time and reduced use of drugs. 7 Prevent premature disability and lessen the need for the institutional care of elderly patients. The cardiac population includes those suffering from myocardial infarction, hypertension, valvular diseases, cardiomyopathy and congenital heart defect and

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the program of cardiac rehabilitation seeks to address all these groups. However, since coronary artery disease (CAD) is the most common of all these diseases and is the most common cause of interrupted employment, this chapter focuses on such patients. The chapter begins with the need for a cardiac rehabilitation program followed by the physiological and cardiovascular effects of endurance training, modes of exercise, exercise prescription and various phases of an exercise training program. It also touches upon the other interventions such as drug therapy, psychosocial counseling and diet control. The later sections of the chapter deal with the deficiencies of existing cardiac rehabilitation programs and the future trends for cardiac rehabilitation. 4.1 Need for cardiac rehabilitation Chronic heart disease is the number one killer in the USA. A large number of CHD survivors undergo cardiac rehabilitation in order to have their physical, psychological, social, economic and family status restored. The need for cardiac rehabilitation is further justified by the necessity of making CHD victims a productive part of society. In this section, the focus is on the following: 1 the prevalence of CHD survivors 2 economic factors 3 psychological and social concerns and 4 legal matters. Each of these issues is briefly discussed. 4.1.1 Prevalence of CHD survivors It is estimated that by the year 2020 at least 40 per cent of the US population will have some degree of disability caused by various physical disorders. Currently, cardiac impairment is a common and leading cause of vocational disability. Each year, roughly 500000 Americans die as a result of CHD and twice as many Americans survive a heart attack. The survivors are potential candidates for cardiac rehabilitation and re-employment. More than 5 million US citizens have symptomatic coronary artery disease. More than 800000 survive myocardial infarction, and nearly 250000 undergo coronary artery bypass graft surgery annually. Around 2 million more have symptomatic valvular heart disease. Other causes of disability due to cardiac disorders are idiopathic cardiomyopathy, congenital heart disease in adults, supraventricular and ventricular arrhythmias and pericardial disease (American Heart Association, 1990). There are approximately 4.25 million CHD survivors in the working-age range of 18–74 years. Whereas the age-adjusted death rates from CHD have declined

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over the years (226.4/100000 in 1950; 129.4/100000 in 1986), the number of CHD patients requiring productive cardiac rehabilitation has continued to grow. The number of CHD patients requiring rehabilitation is expected to increase further as the population ages and as the mortality from CHD declines due to better healthcare, the number of CHD survivors needing cardiac rehabilitation will increase (Mital et al., 1995). 4.1.2 Economic factors CHD imposes a very significant burden upon society. For example, in 1990, the direct and indirect costs of CHD were estimated to be $228 billion (Dennis, 1990). The cost of lost productivity and medical care (physician and nursing services) has been estimated to be approximately one-third of the direct cost (Hodgson, 1984). Thus, in 1990, productivity losses and healthcare costs added up to nearly $13.8 billion; a modest reduction of even 10 per cent in lost time will save at least $1.5 billion annually. In addition to productivity and healthcare costs, other costs will also be reduced if cardiac rehabilitation programs can return CHD victims to work sooner. 4.1.3 Psychological and social concerns A heart attack often has a debilitating impact on the patient’s social, physical and psychological well being. The sudden onset of heart disease followed by the patient’s admission to the clinical environment often results in increased stress, disruption of community life, separation from loved ones and pain (Ingham, 1988). Many individuals show significant alteration in behavior patterns that affect resumption of work, hobbies, social life and sexual activities. Approximately 20 per cent of those who have suffered a myocardial infarction have some type of perceived disability; a significant proportion of them drops out of the workforce within one year of infarction. Cardiac rehabilitation has been shown to help these victims cope with such psychological and social problems (Campbell, 1993). 4.1.4 Legal matters The enactment of the Americans with Disabilities Act (ADA) in July 1990 seeks to extend to the individuals with disabilities, including cardiac disabilities, civil rights protection similar to those found in other civil rights legislation related to race, sex, age and ethnicity. Regulations have been developed and enforced by the federal Equal Employment Opportunity Commission (EEOC), which also

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disseminates information to employers regarding their responsibilities under the ADA. The provisions of ADA along with those of the Rehabilitation Act of 1973 prohibit discrimination against a qualified individual with a disability in making an employment decision. A qualified individual under the Act is one who meets the definition of disabled and can perform the essential functions of the job with or without reasonable accommodation. Given these provisions of the law, employers are required to be very specific with regard to the essential tasks and functions required of a qualified applicant for any position for which they hire. Moreover, employers need to enumerate those qualifications in writing prior to advertising, interviewing or hiring. There is also a legal incentive for employers to consider job restructuring and job modifications that could both eliminate marginal tasks from the job discrimination and enable otherwise qualified individuals with specific limitations to perform the essential functions of a job (McMahon and Shrey, 1992). CHD patients, thus, need to be rehabilitated under the provisions of ADA. 4.2 Components of the cardiac rehabilitation program Although some efforts at rehabilitation of cardiac patients were begun in the 1930s, part of the usual treatment for acute myocardial infarction until the 1950s included six weeks of strict bed rest (Kellerman, 1981; Convertino et al., 1982). This corresponded to twice the assumed healing time for the damaged myocardium. This period of drastically reduced activity resulted in a substantial diminution in cardiovascular functional capacity because of both deconditioning of the myocardium and skeletal muscles and the loss of vasomotor reflexes. In 1951, early mobilization which included progressive periods of sitting upright in an armchair was found to result in a considerable decrease in morbidity and mortality in comparison with the standard treatment practices (Levine and Lown, 1951). Detailed programs of physical activity were formalized by the end of the 1950s. In the 1960s, with the proliferation of coronary-care units and continuous electrocardiographic monitoring, progressively earlier mobilization after acute myocardial infarction was practised. It was realized that the presumption of emotional and physical invalidism was an error. Cardiac rehabilitation was beginning to be dominated by aerobic exercise training. During the 1970s, the multidimensional aspects of cardiac rehabilitation were acknowledged, established methods were developed, and the team approach was promoted (Hellerstein, 1979). Cardiac rehabilitation after myocardial infarction has progressed significantly in the past 20 years. The average duration of hospitalization has been shortened from 3 weeks to 10 days or less (DeBusk et al., 1986). Exercise training in supervised gymnasium programs or at home has been demonstrated to be safe, and early exercise testing as the basis for

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prognostic assessment and the prescription of exercise training has become common practice. The primary patient population that may benefit from cardiovascular rehabilitation consists of selected patients with cardiovascular disease such as acute myocardial infarction, angina pectoris, cardiac operations (for example, bypass grafting, percutaneous coronary angioplasty, valve repair or replacement, valvuloplasty, correction of congenital abnormalities and cardiac or cardiopulmonary transplantation), cardiomyopathy, peripheral vascular disease, hypertension or angiographically demonstrated but silent disease. Most patients have the potential to benefit from the instructional aspects of rehabilitation, such as information about the acute event, medications, diet, cessation of smoking, management of stress and psychosocial adjustment. Nurse-directed group discussions are helpful for all patients as well. The exercise portion of the program is restricted to patients who have no unresolved absolute contraindication to exercise (Table 4.1). The rehabilitative process for the cardiac patient has been divided into four phases. The period of hospitalization is designated Phase 1 and lasts approximately 7 to 10 days. Phase 2 is outpatient rehabilitation and begins immediately after hospitalization and lasts 2 to 12 weeks. Phase 3 is the late recovery period and lasts at least six months beyond phase 2. Phase 4 is the maintenance phase and lasts indefinitely (Squires et al., 1990). Table 4.1 Absolute contraindications to exercise training. Unstable angina pectoris Dangerous arrhythmias Overt cardiac failure Severe obstruction of the left ventricular outflow tract Dissecting aneurysm Myocarditis or pericarditis (acute)

Serious systemic disease Thrombophlebitis Recent systemic or pulmonary embolus Severe hypertension Overt psychoneurotic disorders Uncontrolled diabetes mellitus Severe orthopedic limitations

4.2.1 Inpatient rehabilitation (phase 1) Program components of phase 1 include controlled low-level exercise, patient and family education, group and individual counselling and group discussion sessions. The objectives of phase 1 are diverse: ■ ■ ■ ■

to prevent potential deleterious effects of prolonged bed rest; to hasten adjustment to the hospital environment and the acute event; to begin risk stratification; to begin identification and modification of risk factors;

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■ to facilitate return to physical activity and thereby reduce the feeling of invalidism; ■ to provide medical surveillance—that is, to determine the appropriateness of psychologic adaption and the hemodynamic and electrocardiographic responses to exercise; and ■ to maintain neuromuscular relaxation. The physical activity program follows a step-by-step written protocol consisting of three stages (Table 4.2). Exercise guidelines are similar for all patients and are conservative in intensity and duration. Stage 1 begins when the patient is hemodynamically and electrically stable in the intensive-care unit. This stage commences with passive range-of-motion exercises and sitting at the bedside and in an armchair to maintain vasomotor reflexes that prevent orthostatic hypotension. During stage 2, the patient gradually assumes self-care activities, supervised walking and active range-of-motion exercises. An upper limit heart rate of 20 beats/minute above the rate of standing at rest is used. Stage 3 activity includes progressive slow ambulation (1 to 2 mph) for up to 10 minutes three times daily, supervised by a therapist. The hemodynamic and electrocardiographic responses to early inpatient low-level exercises have been acceptable. Heart rate responses for active range-of-motion exercises and ambulation are between 5 and 15 beats/minute above resting level. The typical systolic blood pressure response is 4 to 14 mm Hg above the resting level. A predismissal or early post-dismissal graded exercise test, with use of either a standard rehabilitation treadmill protocol or a nuclear cardiology procedure (radionuclide angiography or thallium perfusion study), is helpful in risk stratification and home activity prescription. Test end-points usually include an energy expenditure of 5 to 6 METs or signs and symptoms of ischemia or exercise intolerance. The benefits include the following: reduction in orthostatism, impaired physical work capacity, thromboembolism and hypoventilation; improved psychologic Table 4.2 In-patient cardiac rehabilitation physical activity protocol. From Squires et al. (1990) Stage

Days of program

6-day plan 9-day plan 12-day plan Activity schedule 1

1

1

1

2

2

Use bedside commode. Begin physical therapy range-ofmotion exercises to each extremity. Sit at side of bed 5– 10 min Sit in chair 5–15 min twice daily. Begin education program at bedside.

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Stage

Days of program

6-day plan 9-day plan 12-day plan Activity schedule

2

3

2

3

3

3

4

5

5

7

6

8

4

7

9

5

8

11

6

9

12

Continue physical therapy as above Sit in chair up to 30 min twice daily. Continue physical therapy as above Move to step-down area. Bathe above waist, shave and comb hair. Begin selfexercise program with physical therapy supervision. Sit in chair 60–120 min twice daily Continue self-exercise program with physical therapy supervision. Begin ambulation with physical therapist. Sit in chair 90–150 min twice daily. Begin attending education classes and discussion groups Take wheelchair shower and use bathroom ad lib. Continue physical activity as above Move to general cardiovascular ward. Dress in street clothes if desired. Be up and around room as tolerated. Begin climbing stairs with physical therapist. Take predismissal gradedexercise test. Continue physical activity as above. Take standing shower Receive final going-home instructions

status during convalescence; potential earlier return to previous activities and work; potential reduction in duration of hospital stay and increased patient sense of well-being.

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4.2.2 Outpatient rehabilitation (phase 2) Outpatient rehabilitation, or phase 2, begins at the time of hospital dismissal and usually involves close medical supervision for a period of weeks. The objectives of phase 2 are as follows. 1 To instruct patients in proper exercise procedures and to restore them to a desirable exercise capacity appropriate to their clinical status, lifestyle and occupation. 2 To provide understanding for both the patient and the family members regarding cardiovascular disease and to continue appropriate steps for modification of risk factors. 3 To meet the psychosocial needs of patients and families, restore confidence and reduce anxiety and depression. 4 To assist the primary physician in identifying medical problems and to provide surveillance concerning the recovery process and the effectiveness of the therapeutic regimen. 5 To assist in the gradual return to occupational and avocational activities (Squires et al., 1990). A typical phase 2 program is a 12-week long training program with at least three visits per week to the rehabilitation center for supervised aerobic exercises and education. Education is provided by consultations with physicians, exercise physiologists, dietitians, nurses, psychologists and other rehabilitation team members as needed. Group discussions and patient education material are generally included. Educational topics include medications, techniques for relaxation and management stress, cardiovascular disease, nutrition, physical activity, behavior-modification techniques and approaches to modification of risk factors. Home exercises are also prescribed. 4.2.2.1 Exercise testing Before the physician prescribes a particular exercise program suited to the individual patient, stress testing is done to evaluate the initial maximal oxygen uptake (VO2 max) or Maximal Aerobic Power (MAP). Exercise tests have been developed and standardized for determining MAP (Fletcher et al., 1990). There are basically two types of dynamic exercise tests, the submaximal test and the maximal test. Submaximal tests may consist of one exercise level or of several increasing or graded exercise bouts (single state versus multistage), and may be performed with or without intervening rest periods (intermittent versus continuous test protocols). The continuous multistage or graded exercise test (GXT) is the most common clinically employed exercise test.

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Figure 4.1 Principle for the indirect determination of maximal oxygen uptake. (Submaximal heart rates are determined, linear relationships between heart rate and oxygen intake or work rate established with subsequent extrapolation to the maximal heart rate.) From Lange-Anderson, 1973

The submaximal test is characterized by some predetermined arbitrary endpoint. The end-point may be defined in terms of the workload, duration of the exercise, heart rate or level of oxygen uptake. The usual end-point for clinical submaximal exercise test is a certain percentage of the age predicted maximal heart rate (PMHR); that is, 85 or 90 per cent of PMHR. Maximal heart rate may be predicted from the published tables or from the formula: PMHR=220-age (in years). The submaximal test only permits indirect determinations of MAP. It is based on the linear relationship between the steady state submaximal VO2 and HR data. MAP is estimated from the end-point of VO2 versus the HR exercise response curve which is determined by extrapolating the line out to the PMHR (Figure 4.1). Because of the linear relationship between steady state VO2 and workload, VO2 can be estimated from the standardized workload setting of the exercise testing ergometer. This is the typical clinical approach, since it eliminates the need for collecting, measuring and analysing expired air at VO2 measurement. The maximal exercise test is similar in protocol to the submaximal test, but no arbitrary fixed end-point other than the individually determined limit of maximal possible or tolerated exertion is used. In contrast to the submaximal test, MAP is determined directly from the achieved work rate. Again, VO2 may be determined through actual measurement procedures, or it may be estimated from the achieved work rate. If the submaximal or maximal test is terminated because of

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abnormal exercise response, by the subject, the test is considered to be a symptom limited test (SL max GXT) with Functional Aerobic Power (FAP) being the outcome. Selection of exercise intensity and test duration are basic considerations of GXT. The test must begin with a workload low enough to be submaximal even for subjects with poor physical fitness status. Obviously, the relative exercise intensity will determine the number of exercise bouts and the length of the test. Tests of too short duration will lack sufficient discriminating value, while tests of too long duration will submit the thermoregulatory mechanism to excessive stress which will interfere with the accurate assessment of MAP. Practical considerations suggest the use of the basal or resting metabolic energy consumption (METs) as the unit by which to gauge the energy demands of the specific workloads. The basic components of the GXT include the following. 1 Baseline. A preliminary rest period should precede the exercise test in order to collect baseline data. 2 Warm up. A 3- to 5-minute accommodation period should precede the exercise test. A low-level workload should be used (4–5 METs for normal subjects, 2–3 METs for patient groups). During the warm-up or physiological adjustment period, such measurements as HR and blood pressure can facilitate identifying the appropriate initial workload and subsequent increments in workloads from the actual test. 3 Rest. The warm-up is followed by 2 minutes of rest while physiological measurements continue. The protocol for the remainder of the test is adjusted or can-celled if any signs of exercise intolerance are observed. 4 Test. The duration of the test period depends upon the specific test protocol and the PWC of the subject. Approximately 20 minutes are recommended. The test period should consist of at least 3 to 4 stages or exercise bouts lasting 2 to 5 minutes in duration, each sufficient to achieve physiological steady state. Exercise intensity, work rate, is systematically increased so that the subject attains the intended end-point during the final exercise stage. Several testing protocols (Table 4.3) are available and vary in the rate at which speed and incline are changed at each stage. Although the Bruce protocol is more commonly used, the modified Naughton protocol is recommended for patients within 4 weeks of MI or coronary bypass surgery because it begins at a low workload of three METs and progresses at oneMET increments in each stage. 5 Recovery. Low intensity exercise should be performed for 3 to 5 minutes following the test period to facilitate recovery and cooling down. The patient should also be monitored for at least 3 minutes while comfortably resting in a chair following the cooling down exercise period (Amundsen, 1981). Once the information derived from a multistage exercise test is available, the physician prescribes exercise for the patients taking into account such factors as age, sex, clinical status, related medical problems, habitual physical activity and musculoskeletal integrity.

Table 4.3 Treadmill ETT protocols and estimated MET levels.

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4.2.2.2 Components of the exercise session Exercise training sessions should include a preliminary warm-up (10 minutes), a conditioning phase of 30–50 minutes, a cool-down (5 minutes) and ideally an optional recreation game (10–15 minutes) (Franklin et al., 1989). Warm up. Warm-up exercises facilitate the transition from rest to the conditioning phase, stretching postural muscles and increase in blood flow. More important, a gradual warm-up may reduce the potential for exercise-induced ischemic responses. The warm-up should include a musculoskeletal and cardiorespiratory component. Calisthenic exercises should precede activities that involve total body movement to increase the heart rate to within 20 beats/minute of the heart rate prescribed for endurance training. It is usually observed that the best warm-up for any aerobic activity is the prescribed activity performed at a lower intensity (Franklin et al., 1986). Conditioning phase. The conditioning phase should include aerobic endurance exercise and, for selected patients, muscular strength and endurance training (Pollock and Pels, 1984). It should, however, be prescribed in specific terms of intensity, duration, frequency and type of activity. Intensity. The prescribed exercise should be above a minimal level required to induce a training effect, but below the metabolic load that evokes abnormal clinical signs or symptoms. For most cardiac patients, the threshold intensity for exercise training probably lies between 40 and 60 per cent VO2 max. The sliding scale method, as recommended by the American College of Sports Medicine, empirically estimates a relative exercise training intensity that increases in direct proportion to the initial peak or symptom-limited aerobic capacity (Figure 4.2). The baseline intensity, set at 60 per cent VO2 max, is added to the VO2 max, expressed as METs, to obtain the percentage of VO2 max that should be used for physical conditioning (American College of Sports Medicine, 1986). To attain a desired metabolic load for exercise training, one must either measure the oxygen uptake directly or have an equivalent index of it. Since heart rate and oxygen uptake are linearly related during dynamic exercise involving large-muscle groups, a predetermined training or target heart rate (THR) has become widely adopted as an indicator of exercise intensity. One of the most commonly employed methods of establishing the THR is the maximal heart rate reserve method of Karvonen in which THR=(maximal heart rate—resting heart rate)×60 to 80 per cent plus resting heart rate (Karvonen et al., 1957). A given percentage of the maximal heart rate reserve in healthy young men has been shown to be nearly identical to the same percentage of VO2 max used during graded exercise testing (Davis and Convertino, 1975). On the other hand, it appears that this method may overestimate the desired aerobic training intensity in early cardiac rehabilitation, since it fails to correct for a non-linear heart rate oxygen uptake relationship. Another widely used method is to compute

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Figure 4.2 ‘Sliding scale’ method for estimating relative exercise-training intensity (METs) from the peak or symptom-limited aerobic capacity (METs).

the THR as 70–85 per cent of the maximum attainable heart rate during the GXT. The rating of perceived exertion (RPE) is a useful and important adjunct to heart rate as an intensity guide for exercise training. The RPE scale, first introduced by Borg (1970) consists of 15 grades from 6 to 20 (Figure 4.3). Exercise rated as 12 to 13 (somewhat hard) generally corresponds to the upper limit of prescribed training heart rates during the early stages of outpatient cardiac rehabilitation (Gutman et al., 1981). Later, for higher levels of training, ratings of 13 to 15 are appropriate and correspond to 70–85 per cent of the HRMAX. The aerobic or ventilatory threshold generally occurs within this range, with an average RPE of 13.5 and 14.2 for subjects with and without CAD, respectively. Duration. The duration of exercise required to elicit significant training effect varies inversely with the intensity; the greater the intensity, the shorter the duration of exercise necessary to achieve favorable adaptation and improvement in cardiorespiratory fitness. Conversely, low-intensity exercise may be compensated by a longer exercise duration. Exercise training for 10–15 minutes improves aerobic capacity, and 30-minute sessions are even more effective, but there is little additional benefit beyond this point. Frequency. Although deconditioned cardiac patients may improve cardiorespiratory fitness with only twice-weekly exercise, three or four evenly spaced workouts per week appear to represent the optimal training frequency. Additional benefits of five training sessions per week or more appear to be minimal, whereas the incidence of lower extremity injuries increases abruptly.

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Category RPE Scale

Category-Ratio RPE Scale

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0 0.5 1 2 3 4 5 6 7 8 9 10 •

Very, very light Very light Fairly light Somewhat hard Hard Very hard

Nothing at all Very, very weak Very weak Weak Moderate Somewhat strong Strong Very strong

Very, very strong Maximal

Very, very hard

Figure 4.3 RPE scale (6 to 20) on the left and revised scale (1 to 10) on the right.

Modes of exercise. This section discusses several modes of exercise, such as walking, walking on a treadmill, jogging, cycling and arm ergometry. It also discusses the safety and precautionary measures to be taken for each of the exercise modes. Walking. Walking is one of the most practical, safest and least expensive forms of exercise. Special attention should be given to the type of shoe worn for walking. A proper fitting shoe should accommodate the particular type of arc, width of foot and the foot’s rolling in or rolling out movements. As the patient in cardiac rehabilitation becomes better conditioned, it may be necessary to increase the walking pace to stimulate the cardiovascular system. Dramatic swinging of the arms or use of hand weights or both also helps maintain an aerobic level of exercise. For patients who have difficulty attaining the required intensity to achieve an effective stimulus, walking with a backpack weight load has also been found to be effective (Schram and Hanson, 1988). Treadmill walking. For those cardiac rehabilitation programs with limited space for walking, the treadmill is the solution. This activity is well tolerated by patients in cardiac rehabilitation because the activity is indoors and the intensity of work is variable. Unfortunately the VO2 max and, therefore, METs that are calculated from treadmill walking are frequently overestimated in patients with cardiac disease (Milesis, 1987). Monitoring THR and adjusting it accordingly appear to correct for this overestimation.

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Jogging. As the patient in cardiac rehabilitation becomes more conditioned, more intense activities may be needed to achieve an effective training level. The time at which the patient is allowed to jog is established on an individual basis. Unsupervised jogging and running should be prescribed only for certain patients with cardiac disease, because it was found that more cardiac arrests have been related to jogging (Cantwell et al., 1983). Patients who are allowed to jog include patients who have undergone complete revascularization or successful coronary angioplasty, with normal left ventricular function, exercise ECG findings and ambulatory monitoring study results; and post-infarction patients with single-vessel disease only who are symptom free, with good ventricular function and normal ECG finding and ambulatory monitoring results. Cycling. Leg ergometry is another excellent form of exercise. Since the patient in cardiac rehabilitation is usually unaccustomed to using the quadriceps, the patient commonly complains of leg fatigue before cardiovascular fatigue. Conditioning on the cycle, however, should alleviate the problem. Unlike outdoor cycling, cycle ergometry in the controlled laboratory results in similar oxygen consumption, regardless of the person’s weight. Factors to consider that can influence oxygen consumption in outdoor cycling include bike characteristics, speed, grade, wind resistance and other environmental factors. The use of an air-braked ergometer in cardiac rehabilitation is also fairly common. With the airbraked ergometer both the arms and the legs are used. The fan blades increase air flow around the exerciser, enhancing sweat evaporation and heat dissipation (Lamont et al., 1988). Arm ergometry. The arms are involved in most leisure and occupational tasks, so conditioning the arms minimizes cardiovascular stress. Arm ergometry tests are considered important for the patient who is involved in an exercise program or occupational and leisure time activities that focus primarily on arm exercises. The VO2 response is primarily related to workload rather than subject weight or gender (Balady et al., 1987). The HR response in women is usually significantly higher than in men for each workload. Rowing. Rowing machines are commonly used in cardiac rehabilitation settings. Unfortunately, few people in the general population row for exercise. This may explain why many patients in cardiac rehabilitation who row often feel uncoordinated, fatigue easily, and do not enjoy the activity. Rowing is an attractive cardiac rehabilitation exercise because of its availability, affordability and its ability to incorporate continuous rhythmic movements utilizing the large muscle group of the arms, stomach, back and legs (Petratis et al., 1988). Water exercise. From an orthopedic standpoint, water exercises are perhaps one of the most desirable forms of exercise. However, special consideration should be given in developing the swimming exercise

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prescription because the higher HR and RPE may not be accurate for water activities when compared with land activities. The type of water exercise is also of particular concern for the poor swimmer who is likely to be more stressed physiologically because of less efficient swimming strokes. Stair climbing. Stairs are commonly encountered. Thus, the cardiovascular demands of stair climbing are lessened if the patient is accustomed to them. Factors affecting the amount of work involved in stepping include the stepping rate, step height and the direction of stepping, whether up or down or both. Stepping up requires two-thirds more oxygen than stepping down. However, practical experience has shown that orthopedic problems limit stair climbing as an exercise form. In particular, knee, hip and lower back problems appear to be aggravated by this activity. Rope skipping. Because of the work and coordination required to skip rope at 60 to 80 skips per minute, rope skipping is not a likely form of exercise for the typical patient in cardiac rehabilitation. Furthermore, the HR response to rope skipping tends to be higher than for walking or running at a comparable MET level. Potential for injury from jarring action and boredom are additional problems. Rope skipping, however, is an inexpensive form of exercise. Aerobic dancing. Some patients in cardiac rehabilitation enjoy aerobic dance, but several factors should be considered. Low-impact aerobic dance where the toes never leave the floor is more desirable than high-impact dance because it seems to lower the incidence of injuries. The patient in cardiac rehabilitation should register for the proper class level (beginning, intermediate, advanced) if aerobic dance is being offered outside the cardiac rehabilitation setting. Walking through a routine without overhead hand motion is considered low-intensity dance and requires about 3.5 METs. Medium-intensity dances require approximately 5 METs, whereas high-intensity dances usually require about 9 METs of exertion. Several factors are important in determining the best modality of exercise. First, a person’s occupation or hobby may utilize certain muscle groups, and these muscles may need to be strengthened with exercise. Secondly, the physical conditions of the patient must be considered. Thirdly, the THR obtained from the SL max GXT should be accurate for the form of exercise. Finally, the exercise should be enjoyable to ensure compliance (Karam, 1989). Cool-down. Cool-down activities, such as slow walking or mild tension pedalling, permit a return of heart rate and blood pressure to near pre-exercise values. Continued movement after vigorous exercise also enhances venous return, thereby reducing the potential for hypotension and related consequences; promotes the dissipation of body heat; facilitates a more rapid removal of lactic acid than stationary recovery (Belcastro and Bonen, 1975); and ameliorates the potential deleterious effect of the post-exercise rise in plasma catecholemines.

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Omission of a cool-down immediately after vigorous exercise may result in a transient decrease in venous return, possibly reducing coronary blood flow when the heart rate and myocardial oxygen demands may still be high. Sequelae may include angina pectoris, ischemic ST-segment depression or significant ventricular dysrhythmia (Haskell, 1978). Recreational games. The inclusion of enjoyable recreational games after the conditioning phase often enhances compliance. However, game rules should be modified to decrease the energy cost and heart rate response to play. Modifications should minimize skill requirements and competition, and should maximize the potential for successful participation. Near the completion of the phase 2 program, a symptom-limited graded exercise test is usually performed. Results are used to update the exercise prescription and to determine the patient’s readiness to return to work and other activities. At this point in the program of rehabilitation, the intensity of exercise is prescribed at approximately 60–70 per cent of exercise capacity and at a level below the precipitating of signs and symptoms of ischemia. This level of exercise intensity is generally comfortable and well tolerated by most patients. The duration of exercise continues at 30 to 45 minutes, with a minimal frequency of three sessions per week. 4.2.2.3 Risk factor modification and secondary prevention Despite surgical, medical and pharmacological interventions to relieve the symptoms of CHD and training to augment the tolerance to exercise, the efficacy of these methods alone in returning cardiac patients to their premorbid position in society has been less than optimal (Hlatky et al., 1986). Clearly, there are detrimental factors other than physiological ones that contribute to the RTW outcome in patients. These risk factors for CHD have been identified as smoking, elevated total serum cholesterol and low levels of high-density lipoprotein cholesterol (HDLC), hypertension, sedentary lifestyle, lack of exercise, obesity, elevated fasting, blood glucose concentration, high level of stress and diabetes. Cardiac rehabilitation programs complemented with medical care become necessary vehicles for risk-factor reduction. As facilitators of recovery phase, physicians have identified these risk factors as predictors to future morbidity and have recommended strict compliance toward implementing lifestyle changes. Before graduating from the cardiac rehabilitation program at the end of phase 2, an occupational readiness assessment including strength and endurance testing specific to the job task is helpful for selected patients. Work-hardening activities (repetitive movements that require strength and muscular endurance similar to those of the actual job) performed during rehabilitation are beneficial for selected patients. For patients whose jobs require considerable lifting and carrying, strengthening activities during phase 2 rehabilitation are emphasized. Other

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important factors, such as environmental conditions (heat, cold, humidity and air quality), psychological stressors, duration of work periods and job retraining, should be analysed (Saeterhaug and Nygaard, 1989). 4.2.3 Phase 3 and 4 Phase 3 of the cardiac rehabilitation program involves prescribed exercise programs that can continue at home or at an exercise facility and continue for at least 6–9 months beyond phase 2. Phase 3 strives to achieve and maintain an adequate level of conditioning, the objective being a further increase in exercise capacity, return to work, recreational activities, continued education and implementation of steps for modification of risk factors. Patients may return to phase 2 if there is symptomatic deterioration, recurrence of angina, reinfarction, coronary artificial bypass grafting or coronary angioplasty. Phase 4 of a cardiac rehabilitation program is the unsupervised maintenance program consisting of efforts to modify risk factors and a routine program of physical activity that patients should continue indefinitely. Some patients have a much improved adherence rate when involved in a structured group program. These programs are held at hospital wellness centers and community facilities. Yearly evaluation, including graded exercise testing, are recommended for most patients. High-risk patients may require more frequent assessment. 4.3 Benefits of endurance training in coronary heart disease patients Endurance training may be carried out by athletes, healthy individuals who do not aspire to competitive sport and convalescents from vascular and other debilitating diseases. All of these individuals, aiming for improved fitness, will concentrate on aerobic exercise. Isometric exercises, which are useful for increasing muscular strength and muscle mass, rely on anaerobic metabolism, and will contribute to an improvement in anaerobic work capacity, or improved ability to tolerate an oxygen debt. Aerobic exercise in volves sub-maximal, dynamic exercise of longer than several minutes duration, using large muscle groups. It is the aerobic form of exercise which contributes to the improvement of all parts of the oxygen transport system, and especially to the cardiovascular system (Astrand and Rodahl, 1986). The potential benefits of dynamic, aerobic exercise over an adequate training period to the cardiovascular system are those which should promote a more efficient system better adapted to promote the health and function of individuals who have myocardial infarction. To better appreciate this it is essential to understand the physiological alterations imposed by the disease on CHD patients

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and the physiological effects of exercise training in overcoming these limitations. Some of the alterations in heart function imposed by ischemic heart disease include reductions in stroke volume, but near normal cardiac output at rest and at submaximal levels of exercise, and reductions in maximal heart rate. Maximal cardiac outputs are, therefore, limited (Forrester et al., 1977). An increase in heart rate compensates for the reduction in stroke volume at rest and at low levels of exercise. However, the decreased capacity to raise the heart rate and stroke volume causes the maximal physical work rates possible for these patients to be less than normal. The stroke volume is reduced in patients with coronary artery disease due to the diminished ability of the left ventricle to contract during systole, with a resulting reduction in the ejection fraction. Ejection fraction reduces the amount of blood ejected with each contraction. Normally, this is about 70 per cent of the blood inside the ventricle at the end of the diastolic filling period. The ejection fraction is calculated as the ratio of stroke volume to the end-diastolic volume. During upright exercise in the normal heart, the end-systolic volume decreases and the end-diastolic volume increase. In patients with coronary artery disease, there may be an increase in end-systolic volume resulting in the lowering of ejection fraction (Wallace et al., 1978). The reduction in heart rate is due to the fact that abnormal wall motion in patients who are post-myocardial infarction results in the activation of ventricular mechanoreceptors which reflexly cause bradycardia and peripheral vasodilation. Relative ischemia of the SA node will also reduce maximal heart rates. Cardiac rehabilitation programs are multidisciplinary team efforts, so a variety of different outcomes have been measured from the point of view of physical, biological, psychosocial and behavioral changes and are listed in Table 4.4. 4.3.1 Functional capacity improvement The most common assessment of patients enrolled in cardiac rehabilitation both before and immediately after treatment and the long-term outcome of follow-up is some measure of functional impairment. This usually takes the form of an exercise tolerance test (ETT). Functional capacity can be reported in METs (one MET=3.5 ml O2/body wt/min), in VO2 max, duration on a standard protocol, final stage reached on a standard protocol or rate-pressure product at anginal threshold. It is expected that the cardiac patients show improvement in all these (Michel, 1992). Cardiac patients demonstrate improvements in physical working capacity just as normal subjects do. The mechanisms of their improvements may or may not be identical to those defined for asymptomatic, apparently healthy individuals. Various studies using a variety of techniques have been employed, ranging from sophisti cated measures of cardiac output of coronary vessel size and

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Table 4.4 Benefits derived from long-term out-patient cardiac rehabilitation. From Squires et al. (1990).

collateralization during coronary angiography (Franklin, 1991) to relatively simple stress-testing procedures and indirect indices of cardiac function. Maximal oxygen consumption increases in patients after an appropriate period of endurance training at sufficient intensities and frequencies (Figure 4.4) (Mital et al., 1995; Haskell, 1979). A number of randomized and controlled studies have addressed the question of whether a supervised exercise training program improves physical capacity more than would be expected spontaneously. DeBusk et al. (1979) have reported an increase in physical capacity from 6.8 METs to 10.4 METs. Miller et al. (1984) have reported an increase from 6.5 METs to 8.5 METs. A study by Hung et al. (1984) showed an increase in work capacity from 607 kpm/min to 750 kpm/ min. The Roman et al. study (1983) concluded that aerobic capacity improved from 11 l/min to 15 1/min. The improvements in functional capacity arise from various physiological adaptations as a result of exercise. The oxygen transport system adapts favorably to exercise training in most patients, as indicated by an improvement in maximal oxygen uptake (VO2 max) measured during incremental exercise testing. An increase in the arterial-mixed venous oxygen difference as a result of an increase

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Figure 4.4 Mean maximal oxygen uptake for patients over 12 weeks of training. From Michel (1981).

in blood volume, capillary density and oxygen extraction from capillary blood by exercising skeletal muscle and in cardiac output accounts for the augmentation of VO2 max. As the patients become trained, they achieve higher maximal ventilation, at each submaximal rate and higher tidal volumes (Astrand and Rodahl, 1986). In normal individuals aerobic training has been shown to increase the number of mitochondria in muscle cells, and there is a concurrent rise in the activity of the enzymes involved in muscle metabolism (Holloszy, 1967). In addition, the proportion volume of red muscle fibres, which are capable of storing oxygen in the form of myoglobin, increase, while white fibres, which are adapted to anaerobic metabolism, are pro-portionately less (Kiessling et al., 1971). These muscular and metabolic adaptations to training account for a measurable increase in the arteriovenous oxygen difference at the capillary exchange step in the ladder. Thus, there is a greater unloading of oxygen by hemoglobin because of a higher capacity to use oxygen by the muscle cell, and the difference in oxygen content of the venous side to the arterial side of the capillary bed is greater. 4.3.2 Improvement in cardiac performance In addition to the overall improvement in the general physiological system of the cardiac patients, there are substantial specific improvements in the cardiovascular system. Endurance training lowers the heart rate significantly at each submaximal workload and it does not usually improve the cardiac output in

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Figure 4.5 Effect of training on heart rate response of cardiac patients. From Michel (1981).

coronary artery disease. This means the stroke volume is greater after training than before (Nakai et al., 1987). The maximal heart rate usually increases slightly (Figure 4.5) (Haskell, 1979). Also, the endurance training in the cardiac patient lowers the resting blood pressure. In many patients, the systolic blood pressure is consistently lower at each submaximal workload as well (Hedback et al., 1990). Since the product of the heart rate and the systolic blood pressure is useful in the estimation of myocardial function, it is often used as an important non-invasive measure of improvement. The rate-pressure product (RPP) is significant because it has a high correlation with myocardial oxygen consumption (Kiamura et al., 1972). A high RPP at any level of work indicates an inefficient cardiovascular system which is causing the heart to make greater effort at more oxygen cost to meet the demand of the workload. This inefficient system cannot increase the cardiac output very much in spite of large increases in systolic blood pressure. Large increases in systolic blood pressure with small increases in cardiac output reflect an inability of the poorly conditioned cardiovascular system to adequately decrease the total peripheral resistance. Since conditioning the patient does reduce RPP, there is an improvement in myocardial efficiency, and in the ability to decrease total peripheral resistance. At maxima effort, which after training reaches a new higher work rate, conditioning often results in an increase in maxima RPP, indicating an increased power output of the heart, and an increase in myocardial oxygen consumption (Figure 4.6). In cardiac patients who are symptomatic, this finding is very significant. The heart can now tolerate more work before symptoms of angina or ischemia changes on the ECG appear. Some of the mechanisms believed to be responsible for such an increase in the myocardial oxygen supply are:

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Figure 4.6 Effect of training on mean rate-pressure product (HR×SBP) responses of cardiac patients. From Michel (1981).

1 Retrogression or delay of progression of coronary atherosclerosis 2 Increase in lumen diameter of major coronary vessels 3 Coronary collateral vascularization 4 Redistribution of regional blood flow 5 Increase in volume of blood flowing to an ischemic area. An improvement in exercise stroke volume after one year of exercise training has been demonstrated in some cardiac patients (Hagberg et al., 1983). An increase in the maximal heart rate was also observed. Increasing the muscular strength of the upper extremities results in the use of a lower percentage of the maximal contractile force during routine tasks and enables patients to accomplish activities at a lower heart rate and blood pressure and thus at a lower myocardial oxygen demand. For a specific exercise intensity, the myocardial oxygen requirement, as measured by the rate-pressure product, is reduced. 4.3.3 Psychological effects The occurrence of CHD often leads to a collapse in the patient’s self-esteem, prolonged anxiety, depression and neurotic symptoms. The emotional upheaval arising as a result of it may be more debilitating than even the physiological effects. Psychosocial benefits of participation in cardiac rehabilitation have been noted anecdotally by most researchers describing improved attitudes in cardiac patients following their participation in a cardiac rehabilitation program (Erdman and Duivenvoorden, 1983). Cardiac patients who exercise regularly have an improved psychologic profile characterized by less anxiety and depression, more confidence, and more self-

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esteem than non-exercising patients (Roviaro et al., 1984; Taylor et al. 1986). Also certain patient-perceived barriers to complete rehabilitation, such as fear of activity, fatigue, feeling of illness, emotional disturbance, angina pectoris and a defeatist attitude, may be removed by exercise training (Sanne, 1986). Patients who participated in a multidimensional cardiac rehabilitation program were found to show better psychosocial adjustment and lower anxiety and depression (Dracup et al., 1991; Stern and Cleary, 1981). Tools, such as Quality of Life index and Sickness Impact profile, have been used to measure life satisfaction and psychosocial functioning respectively (Daumer and Miller, 1992). Cardiac rehabilitation patients were found to show significant improvement in their state of anxiety in a study using a health-related quality of life questionnaire (Oldridge et al., 1991). Studies using standard measures of psychological distress such as Beck Depression Inventory (BDI) and the Profile of Mood States (POMS) have shown significant improvement in the psychosocial functioning of cardiac rehabilitation patients (Newton et al., 1991). A study by Conn et al. (1992) shows that participation in a rehabilitation program enhances the health state, quality of life, self-esteem and performances of exercise, diet and medication self-care. 4.3.4 Symptomatic subjective changes A reduction in the symptoms of angina pectoris, exercise-related dyspnea, fatigue and claudication is an important outcome of cardiac rehabilitation (Thomson, 1988). Angina pectoris in the stable angina patient has as its onset a stable degree of myocardial oxygen demand that, due to the presence of coronary disease, cannot be met. Myocardial ischemia may produce chest pain, and usually does produce ECG changes or ST segment depression, which are read as positive of ischemia. Patients who experience symptoms of their disease use them as a warning system, and reduce their physical demands, or degree of emotional involvement, in an effort to reduce pain by restoring the balance of oxygen demand to oxygen supply in the myocardium. Cardiac rehabilitation, through exercise conditioning and methods of stress reduction, attempts to reduce the frequency with which symptoms appear. This goal supposes an outcome measure of symptomatic threshold, symptom frequency and severity of pain intensity or discomfort. The symptomatic threshold for angina is related to the rate pressure product and many patients who are experiencing angina when they begin the program end up with a new, higher RPP for their anginal threshold (Michel, 1992).

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4.3.5 Epidemiological changes Many randomized trials have shown a trend toward reduced mortality in patients in rehabilitation after myocardial infarction compared with usual care controls. Differences in mortality, however, have been small and no definitive evidence exists that cardiac rehabilitation saves or prolongs lives after myocardial infarction. However, some studies have reported positive outcome evidenced by reduced mortality. The end-points were all-cause death, cardiovascular mortality and non-fatal reinfarction. The results showed that there was a significant reduction of 24 per cent in the cardiac rehabilitation patient group for all-cause death. A significant reduction of 25 per cent was similarly found for cardiac rehabilitation subjects for cardiovascular mortality. There was no significant reduction in non-fatal reinfarction in the cardiac rehabilitation group (Oldridge et al., 1988). Another study found a 20 per cent greater reduction in total mortality and cardiovascular mortality than among the post-MI control subjects. This difference persisted for three years after the intervention (O’Connor et al., 1989). 4.3.6 Healthcare cost reduction The medical cost associated with hospitalization is also found to be less for those participating in the training program compared with those who do not. A study by Ades and associates (1992) found that the per capita hospitalization charges for participants in cardiac rehabilitation were $739 lower than the charges for non-participants. This was due to both a lower incidence of hospitalizations and lower charges per hospitalization. Another study (Levine et al., 1991) found that the rehabilitation program did not increase the healthcare costs of post-MI care, as the increase in cost due to participation in the program was balanced by the decreases in readmission for cardiovascular diseases. It concluded that the comprehensive cardiac rehabilitation program is a major strategy that leads to both lowered costs and positive health effects. 4.3.7 Risk-factor reduction The three most virulent risk factors for CHD are recognized as hypertension, high blood cholesterol and smoking. In addition, a sedentary lifestyle, obesity, diabetes mellitus and stress are among the modifiable factors that contribute to patients’ risk-factor profiles for CAD. Cardiac rehabilitation programs are multifaceted, including exercise, quitting smoking, stress reduction, diet modification and education about contributory behaviors. The success of cardiac rehabilitation is often measured by the achievement of behavioral goals that result in objective positive end-points. Blood cholesterol, fractioned into high-

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density, low-density, and very low-density lipoprotein is monitored and treated by dietary alterations and drugs to achieve low-risk ratios. Weight reduction is emphasized by the combination of dieting and an increase in exercise and is monitored by weigh-ins. Cessation of smoking is reinforced by group programs, and success is measured by self-reporting, which can be verified by measuring the levels of carbon monoxide in blood and levels of thiocyanate in saliva. Blood pressure is monitored weekly and treated vigorously with drugs and exercise. Stress-reducing behavioral programs are often incorporated into cardiac rehabilitation. The efficacy of the modification of risk factors in reducing the progression of coronary artery disease and future morbidity and mortality has been established. The Coronary Artery Surgery Study registry enabled investigators to assess the effects of either continuing or discontinuing the smoking habit. The five-year mortality was substantially reduced for those who quit smoking (15 per cent) compared with those who continued to smoke (22 per cent), with a relative risk of 1:55. End-points of both myocardial infarction and sudden cardiac death were more favorable for the ex-smokers than for those who continued the habit (Vlietstra et al., 1986). Dietary and medical intervention play an important role in lipid management. An LDL level of 2.6 mmol/L (100 mg/dl) or lower and HDL level of 1.0 mmol/L or greater should be the goal in CHD patients. Various studies have shown a reduction in total cholesterol level and reduction in mortality due to drug therapy. Another study (Coronary Drug Project Research Group, 1978) showed a reduction of 10 per cent in the cholesterol level and a 27 per cent reduction in non-fatal myocardial infarction after five years. The follow-up after 15 years showed a reduction in mortality from all causes was 11 per cent lower among patients treated medically which suggests a potential long-term benefit from a relatively brief course of therapy directed as LDL-C and HDL-C. Epidemiologic data have demonstrated improved survival among patients who have anginal pectoris or who have had myocardial infarction and have adequately controlled hypertension, in comparison with patients who have uncontrolled or inadequately controlled arterial blood pressure (Connolly et al., 1983). Correction of obesity by reduction of excess body fat decreases the symptoms of angina and fatigue and improves established risk factors such as blood lipids, hypertension, elevated blood glucose concentration and left ventricular hypertrophy (Lavie et al., 1988). 4.3.8 Risks of exercise training Exercise training in patients with coronary artery disease is not without risk. Contraindications to exercise testing and training must be strictly followed (Table 4.1). Cardiac patients may have a limited coronary reserve, so the increase in myocardial oxygen demand during exercise may result in ischemia

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and may potentially precipitate a lethal arrhythmia or myocardial infarction. Cardiac arrest may occur long after the clinical event. With proper patient screening and care in prescribing exercise, exercise training can be safely performed by most cardiac patients. However, the complication rates for cardiac exercise sessions are usually low. It is reported that the rate of occurrence of cardiac arrest is 1 in 111996 hours of patient exercise and the corresponding rates for myocardial infarction and sudden cardiac death are 1 in 293 990 and 1 in 783 972 hours of exercise respectively (Van Camp and Peterson, 1986). All personnel involved in exercise programs and family members of cardiac patients, when appropriate, should undergo training in cardiopulmonary resuscitation in order to minimize the risk of an untoward event. Musculoskeletal injuries are common in persons who participate in exercise programs. In general, higher intensity activities that involve weight bearing, such as jogging, traditional aerobic dancing, racket sports and basketball, are more likely to result in an injury than low intensity activity. An assessment of previous injuries and orthopedic limitations by a physical therapist is an important consideration. Risks of injury can be minimized by using low-intensity activities such as walking or non-weight-bearing exercise such as stationary cycling, swimming or other water activities. 4.4 Future trends in cardiac rehabilitation In spite of the various benefits arising out of participation in a cardiac rehabilitation program as detailed above, the timing or re-employment after myocardial infarction has not improved much. The conventional programs which enhance the aerobic capacity of the patients have thus failed to reduce the period of work disruption after myocardial infarction. A reduction in lost time from work has not been achieved since 1970. The majority of cardiac patients, on average, take six months to return to work. Sedentary patients take approximately 60–80 days to return to work. Victims engaged in physical work return to employment after approximately 90 to 110 days. Thus, there is an immediate need to improve the vocational status of the patients by incorporating new approaches in the current cardiac rehabilitation program. A three-year field study entitled ‘Development and Evaluation of a Job-Simulated Cardiac Rehabilitation Program’ initiated by University of Cincinnati in 1993 reflects progress in this direction. At present, traditional cardiac rehabilitation programs do not include the active participation of the employer in developing return-towork options. The project provides transitional work programming for an experimental group of cardiac rehabilitation patients. It uses a protocol for rehabilitating CHD patients, using a physical training program based on actual job requirements and using a patient’s transferable work skills for placement in jobs within their physical and psychological capabilities. Also, the new model is expected to be highly cost effective.

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Acknowledgment This work was supported by the National Institute on Disability and Rehabilitation Research of the United States Department of Education through its Field Initiated Research Grant No. H133G30010. References ADES, P.A., HUANG, D., WEAVER, S.O. and BURLINGTON, V. (1992) Cardiac rehabilitation participation predicts lower rehospitalization costs, American Heart Journal, 4, 916–21. AMERICAN COLLEGE OF SPORTS MEDICINE (1986) Guidelines for Graded Exercise Testing and Exercise Prescription, p. 1, Philadelphia. AMERICAN HEART ASSOCIATION (1990) Heart Facts, New York. AMUNDSEN, L.R. (1981) Cardiac Rehabilitation, p. 18–20, New York: Churchill Livingstone. ASTRAND, P.O. and RODAHL, K. (1986) Textbook of Work Physiology, Third Edition, New York: McGraw Hill. BALADY, G.J., MANGONE, C.L. and WEINER, D.A. (1987) Standardization of an arm ergometry exercise testing protocol; physiologic responses in normal subjects, Journal of Cardiopulmonary Rehabilitation, 7, 501. BELCASTRO, A.N. and BONEN, A. (1975) Lactic acid removal rates during controlled and uncontrolled recovery exercise, Journal of Applied Physiology, 39, 932–6. BORG, G. (1970) Perceived exertion as an indicator of somatic stress, Scandinavian Journal of Rehabilitation Medicine, 2, 92–8. CAMPBELL, J. (1993) How necessary is cardiac rehabilitation? Professional Nurse, 2, 279. CANTWELL, J.D. (1983) Cardiac rehabilitation in the mid-1980s, Physician Sportsmedicine, 14, 89–96. CONN, S.C., TAYLER, S.G. and CASEY, B. (1992) Cardiac rehabilitation program participation outcomes after myocardial infarction, Rehabilitation Nursing, 17 (2), 58–62. CONOLLY, D.C., ELVEBACK, L.R. and OXMAN, H.A. (1983) Coronary heart disease: effects of hypertension and its treatment on the survival of patients, Mayo Clinical Proceedings, 58, 249. CONVERTING, V., HUNG, J., GOLDWATER, D. and DEBUSK, R.F. (1982) Cardiovascular responses to exercise in middle-aged men after 10 days of bedrest, Circulation, 65, 134. CORONARY DRUG PROJECT RESEARCH GROUP. (1978) Natural history of myocardial infarction in the Coronary Drug Project: long-term prognostic importance of serum lip levels, American Journal of Cardiology, 42, 489–98. DAUMER, R. and MILLER, S.P. (1992) Effects of cardiac rehabilitation on psychosocial functioning and life satisfaction of coronary artery disease clients, Rehabilitation Nursing, 7 (2), 69–74. DAVIS, J.A. and CONVERTING, V.A. (1975) A comparison of heart rate methods for predicting endurance training intensity, Medicine and Science in Sports, 7, 295–8.

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DEBUSK, R.F., HOUSTON, N., HASKELL, W., FRY, G. and PARKER, M. (1979) Exercise training soon after myocardial infarction, American Journal of Cardiology, 44, 1223–9. DEBUSK, R.F., BLOMQUIST, C.G., KOUCHOUKOS, N.T., LUEPKER, R.V., MILLER, H.S., Moss, A.J., POLLOCK, M.L., REEVES, T.J., SELVESTER, R.H. and STATSON, W.R. (1986) Identification and treatment of low-risk patients after acute myocardial infarction and coronary-artery bypass graft surgery, New England Journal of Medicine, 314, 161–6. DENNIS, C. (1990) Vocational capacity with cardiac impairment. In: Medical Perspectives in Vocational Assessment of Impaired Workers, Rockville, MD: Aspen. DRACUP, K., MOSER, D.K., MARSDEN, C., TAYLOR, S.E. andGULY, P.M. (1991) Effects of multidimensional cardiopulmonary rehabilitation program on psychosocial function, American Journal of Cardiology, 68, 31–4. ERB, B.D., FLETCHER, G.F. and SHEFFIELD, T.L. (1979) Standards for cardiovascular exercise treatment programs, Circulation, 59, 1084 A. ERDMAN, R.A. and DUIVENVOORDEN, H.J. (1983) Psychologic evaluation of a cardiac rehabilitation program: A randomized trial in patients with myocardial infarction, Journal of Cardiac Rehabilitation, 3, 696–704. FLETCHER, G.F., FROELICHER, V.F., HARTLEY, L.H., HASKELL, W.L. and POLLOCK, M.L. (1980) Exercise standards: a statement for health professionals from the American Heart Association, Circulation, 82 (6), 2286. FLETCHER, B.J., GRIFFIN, P.A., LLOYD, A., BENNETT, J.M. and ALEXANDER, J. W. (1990) Cardiac rehabilitation in the workplace: current concepts and methodology. AAOHN Journal, 38 (9), 440–7. FORRESTER, J.S., DIAMOND, G.A. and SWAN, H.J.C. (1977) Correlation classification of clinical and hemodynamic function after acute myocardial infarction. American Journal of Cardiology, 39, 137–45. FRANKLIN, B.A. (1991) Exercise training and coronary collateral circulation, Medicine and Science in Sports Exercise, 23 (6). FRANKLIN, B.A., GORDON, S. and TIMMIS, G.C. (1989) Exercise in Modern Medicine, Baltimore: Williams & Wilkins. FRANKLIN, B.A., HELLERSTEIN, H.K., GORDON, S. and TIMMIS, G.C. (1986) Exercise prescriptions for the myocardial infarction patient, Journal of Cardiopulmonary Rehabilitation, 6, 62–79. GREENLAND, P. and CHU, J.S. (1988) Efficacy of cardiac rehabilitation services, Annals of Internal Medicine, 109, 650–63. GUTMAN, M.C., SQUIRES, R.W., POLLOCK, M.L., FOSTER, C. and ANHELM, J. (1981) Perceived exertion-heart rate relationship during exercise testing and training cardiac patients, Journal of Cardiac Rehabilitation, 1, 52–9. HAGBERG, J.M., EHASANI, A.A. and HOLLOSZY, J.O. (1983) Effect of 12 months of intense exercise training on stroke volume in patients with coronary artery disease, Circulation, 67, 1194–9. HASKELL, W.L. (1978) Cardiovascular complications during exercise training of cardiovascular patients, Circulation, 57, 920–4. HASKELL, W.L. (1979) Mechanisms by which physical activity may enhance the clinical status of cardiac patients, Heart Disease and Rehabilitation, 276–96.

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HEDBACK, B.E.L., PERK, J., ENGWALL, J. and ARESKOG, N.H. (1990) Cardiac rehabilitation after coronary artery bypass grafting: Effects on exercise performance and risk factors. Arch. Phys. Med. Rehabilitation, 71, 1069–74. HELLERSTEIN, H.K. (1979). Cardiac Rehabilitation: A Retrospective View. In M.L.Pollock and D.H.Schmidt, Eds, Heart Disease and Rehabilitation, 1st edn 1979, 2nd edn 1986, New York: John Wiley & Sons. HLATKY, M.A. HANEY, T. and BAREFOOT, J.C. (1986) Medical, psychological and social correlates of work disability among men with CHD, American Journal of Cardiology, 58, 911. HODGSON, T.A. (1984) Health care expenditures for major diseases in 1980, Health Care Financing Review, 5 (4). HOLLOSZY, J.O. (1967) Biochemical adaptations in muscle. Effects of exercise on mitochondrial oxygen uptake and respiratory enzyme activity in skeletal muscle, Journal of Biological Chemistry, 242, 2278. HOSKINS, T.A. and HABASEVICH, R.A. (1978) Cardiac rehabilitation: an overview, physical therapy, 58, 1183–90. HUNG, J., GORDON, E.P., HOUSTON, N., HASKELL, W.L., GORIS, M.L. and DEBUSK, R.F. (1984) Change in rest and exercise myocardial perfusion and left ventricular function 3 to 26 weeks after clinically uncomplicated acute myocardial infarction: Effects of exercise training, American Journal of Cardiology, 54, 943–50. INGHAM, A. (1988) The psychological response of patients to admission to coronary care for heart disease, and its effects on rehabilitation, Intensive Care Nursing, 4, 24. KARAM, C. (1989) A Practical Guide to Cardiac Rehabilitation, Maryland: Aspen Publications. KARVONEN, M., KENTALA, K. and MUSTALA, O. (1957) The effects of training on heart rate: A longitudinal study. Annals Medicinae Experimentalsis et Biologiae Fenniea, 35, 307–15. KELLERMAN, J.J. (1981) Cardiac rehabilitation: Reminiscences, international variations, experiences, Journal of Cardiac Rehabilitation, 1, 43. KIESSLING, K.H., PIEHL, K. and LUNDQUIST, C.G. (1971) Number and size of skeletal muscle mitochondria in trained sedentary men. In O.A.Larsen and R.O.Malmborg, Eds, Coronary Heart Disease and Physical Fitness, Baltimore, MD: University Park Press. KIAMURA, K., JORGENSSEN, C.R., GOBEL, F.L., TAYLOR, H.L. and WANG, Y. (1972) Hemodynamic correlates of myocardial oxygen consumption during upright exercise, Journal of Applied Physiology, 32, 516–22. LAMONT, L.S., SANTORELLI, C.G., FINKELHOR, R.S. and BAHLER, R.C. (1988) Cardiorespiratory responses to an air-braked ergometry protocol, Journal of Cardiopulmonary Rehabilitation, 8, 207–12. LAVIE, C.J., GAU, G.T. and SQUIRES, R.W. (1988) Management of lipids in primary and secondary prevention of cardiovascular diseases, Mayo Clinical Proceedings, 63, 605. LEVINE, L.A., PERK, J. and HEDBACK, B. (1991) Cardiac rehabilitation—a cost analysis, Journal of Internal Medicine, 230, 427–34. LEVINE, S.A. and LOWN, B. (1951) The ‘chair’ treatment of acute coronary thrombosis, Transactions of Association of American Physicians, 64, 316. MCMAHON, B. and SHREY, D. (1992) The Americans with Disabilities Act, disability management and the injured worker, Journal of Workers Compensation, 1, 9.

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MICHEL, T.H. (1992) Outcome assessment in cardiac rehabilitation, International Journal of Technology Assessment in Health Care, 8 (1), 76–84. MILESIS, C. (1987) Prediction of treadmill performance from clinical characteristics in healthy persons, Journal of Cardiopulmonary Rehabilitation, 7, 365–73. MILLER, N.H., HASKELL, W.L. and BERRA, K. (1984) Home versus group training for increasing functional capacity after myocardial infarction, Circulation, 70, 645–9. MITAL, A., SHREY, D., BRODERICK, T.M., MAJOR-KUMAR, G., BROWN, K.C. and GUSTIN, B.W. (1995) Cardiac rehabilitation: current status and future trends, Critical Reviews in Physical and Rehabilitation Medicine, 7 (1), 33–49. NAKAI, Y., HIASA, Y. and MAEDA, T. (1987) Effects of physical exercise training on cardiac function and graft patency after coronary artery bypass grafting, Journal of Tho-rasic Cardiovascular Surgery, 93, 65–72. NAUGHTON, J., BRUHN, J.G. and LATEGOLA, M.T. (1968) Effects of physical training on physiologic and behavioral characteristics of cardiac patients, Archives of Physical Medicine and Rehabilitation, 49, 131. NEWTON, M., MUTRIE, N. and MCARTHUR, J.D. (1991) The effects of exercise in a coronary rehabilitation program, Scottish Medical Journal, 36, 38–41. O’CONNOR, G.T., BURING, J.E., YUSUF, S., GOLDHABER, S.Z., OLMSTEAD, E. M., PAFFENBARGER, R.S.Jr and HENNEKENS, C.H. (1989) An overview of randomized trials of rehabilitation with exercise after myocardial infarction, Circulation, 80, 234–44. OLDRIDGE, N., GUYATT, J.E., FISCHER, M. and RIMM, A.A. (1988) Cardiac rehabilitation after myocardial infarction, Journal of American Medical Association, 260, 945–50. OLDRIDGE, N., GUYATT, G., JONES, N., CROWE, J., SINGER, J., FEERY, D., MCKELVIE, R., RUNIONS, J., STEINER, D. and TORRANCE, G. (1991) Effects on quality of life with comprehensive rehabilitation after acute myocardial infarction, The American Journal of Cardiology, 67, 1084–9. PARMLEY, W.W. (1986) President’s page: Position report of cardiac rehabilitation, Journal of American College of Cardiology, 7 (2), 451–3. PETRATIS, M.M., WILLIAMS, M.A., RYSCHON, K.L., FOGLAND, T.L., ANGELLILO, V.A. and ESTERBROOKS, D.J. (1988) Cardiovascular responses to rowing ergometry versus treadmill exercise in men with coronary heart disease, Journal of Cardiopulmonary Rehabilitation, 8, 232–7. PICARD, M.H., DENNIS, C. and SCHWARTZ, R.G. (1989) Cost-benefit of early return to work after uncomplicated myocardial infarction, American Journal of Cardiology, 63, 1308. POLLOCK, M.L. and PELS, A.E. (1984) Exercise prescription for the cardiac patient: An update. Cardiac Rehabilitation (Clinics in Sport Medicine): Philadelphia. ROMAN, O., GUTIERREZ, M., LUKSIC, I., CHAVEZ, F., CAMUZZI, A.L., VILLALON, E., KLENNER, C. and CUMSILLE, F. (1983) Cardiac rehabilitation after acute myocardial infarction. 9-year old controlled follow-up study, Cardiology, 70, 223–31. ROVIARO, S., HOLMES, D.S. and HOLMSTEN, R.D. (1984) Influence of a cardiac rehabilitation program on the cardiovascular, psychological and social functioning of cardiac patients, Journal of Behavioural Medicine, 7, 61–81.

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SAETERHAUG, A. and NYGAARD, P. (1989) Early discharge and early rehabilitation and return to work after acute myocardial infarction, Journal of Cardiopulmonary Rehabilitation, 9, 268–72. SANNE, H. (1986) Rehabilitation after a myocardial infarction, Acta Med. Scand (Suppl, 712) 72–8. SCHRAM, V. and HANSON, P. (1988) Cardiovascular and metabolic responses to weightloaded walking in cardiac rehabilitation patients, Journal of Cardiopulmonary Rehabilitation, 8, 28–32. SQUIRES, R.W., GAU, G.T., MILLER, T.D., ALLISON, T.G. and LAVIE, C.J. (1990) Cardiovascular rehabilitation: Status. Mayo Clinic Proceedings, 65, 731–55. STERN, M.J. and CLEARY, P. (1981) Psychosocial changes observed during a low-level exercise program, Archives of Internal Medicine, 141, 1463–7. TAYLOR, C.B., HOUSTON-MILLER, N., AHN, D.K., HAKSELL, W. and DEBUSK, R. F. (1986) The effects of exercise training programs on psychosocial improvements in uncomplicated postmyocardial infarction patients, Journal of Psychosomatic Research, 30, 581–7. THOMSON, P.D. (1988) The benefits and risks of exercise training in patients with coronary artery disease. JAMA, 259, 1537–40. VAN CAMP, S.P. and PETERSON, R.A. (1986) Cardiovascular complications of outpatient cardiac rehabilitation programs, JAMA, 256, 1160–3. VLIETSTRA, R.E., KRONMAL, R.A., OBERMAN, A., FRYE, R.L. and KILLIP, T. (1986) Effect of cigarette smoking on survival of patients with angiographically documented coronary artery disease: A report from the CASS registry , JAMA, 255, 1023–7. WALLACE, A.G., RERYCH, S.K., JONES, R.H. and GOODRICH, J.K. (1978) Effects of exercise training on ventricular function in coronary disease, Circulation, 58, (Suppl II), 197. WENGER, N.K., HELLERSTEIN, H.K. and BLACKBURN, H. (1982) Physician practice in the management of patients with uncomplicated myocardial infarction; changes in the past decade, Circulation, 65, 421–7. WORLD HEALTH ORGANIZATION (1964) Technical Report Service. Rehabilitation of patients with cardiovascular disease: report of WHO expert committee, 270.

Appendix A4.1 Glossary of medical terms The following glossary contains a selection of words and terms used in this chapter. Angina (also termed angina pectoris). Chest pain or discomfort due to inadequate supply of blood and oxygen to the heart muscle, resulting from the narrowing of one or more coronary arteries. Angiography. A diagnostic technique that involves the injection of X-ray dye (contrast) into the heart chambers or blood vessels, thus providing a detailed picture of the inside of these structures. The record of pictures is called an angiogram. Angioplasty. A technique used to dilate arteries at the point where they have become narrowed by a plaque. Arrhythmia. Any deviation from the normal rhythm of the heartbeat.

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Arteriosclerosis. A general term referring to the hardening and loss of elasticity of the arterial walls associated with the aging process. Atherosclerosis. A form of arteriosclerosis in which, in addition to the hardening and loss of elasticity of the arteries, a fatty substance (plaque) forms on the inner walls of the arteries, causing obstruction to the flow of blood. Beta blockers. Drugs that block the action of the beta receptors, the nerve endings that affect the heart rate and the force of contraction. They are used for the treatment and control of angina, high blood pressure and certain cardiac arrhythmias. Bradycardia. An abnormally slow heart rate. Generally, anything below 60 beats per minute is considered bradycardia. Calcium channel blockers. Drugs that block the calcium transport mechanism in blood vessels and heart muscle cells. They relax the walls of the coronary arteries, and thus prevent coronary spasm. They are used mainly for the treatment and prevention of angina. Cardiomyopathy. A general term for diseases that involve primarily the heart muscle (myocardium). Collateral circulation. Circulation of the blood through nearby smaller vessels when a main vessel has been blocked. Congestive heart failure. A condition in which the weakened heart is unable to pump enough blood to maintain normal circulation. It leads to congestion of the lungs and retention of water. Diastole. In each heartbeat, the period during which the pumping chambers relax and fill with blood. The diastolic reading obtained in blood-pressure measurement is the lower number. Dyspnea. Difficulty in breathing. Echocardiography. A diagnostic technique that utilizes ultrasound waves to visualize and examine the heart structures. The record of pictures is called echocardiogram. Electrocardiography. A diagnostic technique in which small metal discs (electrodes) are placed on the patient’s chest, arms and legs, for the purpose of recording the electrical activity of the heart. The resulting tracing is called electrocardiogram (ECG or EKG). Embolism. The blocking of blood vessels by a clot (embolus) carried in the blood-stream. Hypercholesterolemia. An excess of cholesterol in the blood. Hypertension. High blood pressure. A condition characterized by an excessive amount of pressure within the arteries. Hypertrophy. Increases the size and thickening of a muscle, thereby adding to the number of muscle units able to contract, and strengthening the force of contraction. It generally occurs in response to an increased workload. Ischemia. A local, usually temporary, deficiency in oxygen supply to some part of the body, due to obstruction or constriction of the blood vessel supplying that part. Lipoprotein. A complex consisting of lipid (fat) and protein molecules bound together. Since lipids do not dissolve in the blood, they must circulate in the form of lipoprotein.

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Myocardial infarction. (Heart attack). An irreversible damage to an area of the heart muscle, caused by a total blockage of a coronary artery. Obesity. Excessive weight. Generally defined as a 20 per cent excess over ideal body weight (based on one’s age, height and bone structure). Stroke. An interruption of the blood flow to the brain, causing damage to the brain. Depending on the severity and location of the stroke, it may result in partial or total paralysis, loss of speech, or death. Systole. In each heartbeat, the period during which the pumping chambers (ventricles) contract and eject their blood content. The systolic reading obtained in blood pressure measurement is the higher number. Tachycardia. An abnormally fast heart rate. Generally, anything over 100 beats per minute is considered to be tachycardia.

CHAPTER FIVE Integrating ergonomics in the management of occupational musculo-skeletal pain and disability MICHAEL FEUERSTEIN,* THOMAS R.ZASTOWNY AND PAUL HICKEY

5.1 Introduction Occupational musculoskeletal disorders (OMDs) of the spine and upper extremities and associated work disabilities represent a major public health problem (Chaffin and Fine, 1992) and represents the major source of work disability in the US (Bureau of Labor Statistics, 1994). This situation has stimulated much research, debate and exploration of new approaches to prevention, assessment and rehabilitation. One in particular, occupational rehabilitation involves the integration of principles and techniques of pain treatment, sports medicine, ergonomics, rehabilitation and occupational medicine, orthopedics, vocational rehabilitation and behavioral medicine. This approach has been applied to the evaluation and rehabilitation of chronic work disability secondary to occupational musculoskeletal disorders (OMDs) and typically involves a multidisciplinary team of providers. It has been referred to as occupational rehabilitation because of its emphasis on return to work in patients with occupationally related disorders. This chapter will address integrating ergonomics into the practice of occupational rehabilitation. The occupational rehabilitation approach described here places significant emphasis on the workplace and specific interventions directed at workplace factors (for example, ergonomic and psychosocial) assumed to inhibit return to work (for example, Feuerstein and Hickey, 1992; Feuerstein et al., 1993). In this model, the treatment efforts are tailored to a diverse set of presenting problems and include, when appropriate, medical management, physical conditioning, work conditioning, pain and stress management, workplace psychosocial and ergonomic consultation and intervention and vocational counseling and placement. The approach is structurally similar to the functional restoration approach developed by Mayer and colleagues (Mayer and Gatchel, 1988; Mayer et al., 1987) with a greater emphasis on the workplace. This chapter first provides a brief overview of the multidimensional nature of work disability as the conceptual basis for a multidisciplinary approach to

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rehabilitation of work disability associated with the OMDs. In this approach, particular emphasis is placed on the role of ergonomic and psychosocial factors in OMDs and work disability and methods for ‘fitting the task’ to the worker. A brief review and discussion of treatment approaches in occupational rehabilitation with special emphasis on ergonomics is provided, followed by clinical case examples to illustrate the integration of ergonomics in occupational rehabilitation efforts. This chapter offers perspectives taken from clinic-based treatment directed at facilitating a safe return to the workplace. The occupational rehabilitation approach is only briefly outlined in this chapter. For a more detailed consideration of this approach the reader should refer to Feuerstein and Zastowny (in press). The comprehensive and intensive approach described in this chapter was developed primarily for the complex chronic patient who has received multiple attempts at medical management, physical therapy and other impairment-based interventions yet remains workdisabled. While variations have been applied to those individuals with less chronic levels of disability, the outcome of such efforts remain to be determined. 5.2 The multidimensional nature of work disability Evidence from a number of domains continues to provide support for a multidimensional understanding of work disability including: the recognition of the limitations of traditional medical management of OMDs, and related shortfalls of classic models of disease in explaining the common discrepancies between perceived disability and documented pathology (Waddell and Main, 1984; Waddell et al., 1980; Waddell et al., 1992); the increasing recognition that OMDs and work disability, particularly in more chronic situations, are likely to be the consequence of a complex interaction among such factors as medical status; physical capabilities in relation to work demands (biomechanical, metabolic and psychological) and psychological and behavioral resources (worker traits, psychological readiness for work, symptom management) of the injured worker (Feuerstein, 1991); the use and effectiveness of multidisciplinary teams in the treatment of these disorders (Feuerstein et al., 1994); and continued research on the psychosocial dimensions of these disorders, suggesting that effective management often involves engagement of the patient’s motivation, sense of self-efficacy and ability to manage pain and distress. 5.3 Ergonomic factors associated with musculoskeletal pain and discomfort There are several work-related factors that can initiate, maintain or exacerbate musculoskeletal pain, discomfort and injury. Clinicians involved in the assessment of workers with various occupational musculoskeletal disorders

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should consider the potential role these ergonomic stressors can have on the likelihood of a safe, more comfortable and productive return to work. The factors include, but are not limited to: ■ ■ ■ ■ ■ ■ ■

awkward working postures forceful exertions, both static and dynamic repetitive motions or prolonged activities localized contact stresses whole-body or segmental vibration temperature extremes organizational and psychosocial work factors (Putz-Anderson, 1988; Keyserling, et al., 1991; Kuorinka and Forcier, 1995).

Sociodemographic factors such as age, race, gender and anthropometric characteristics (such as body size) also play important roles. Ergonomic risk factors have been observed in a variety of jobs both in the service and manufacturing industries. For the most part, all jobs contain these factors to some degree depending upon the physical tasks involved in the job, the characteristics of the workers and the individual’s personal work style (Feuerstein, 1996). However, the risk of musculoskeletal pain and injury typically increases as the worker’s exposure to the ergonomic factor increase in frequency, intensity and duration. Additionally, it is important to note that these risk factors do not exist independent of each other. The ergonomic risk factors are interrelated and often interact dynamically in the workplace. 5.3.1 Awkward working postures Two areas of ergonomic research related to posture include anthropometry (worker’s physical characteristics) and biomechanics (mechanical forces on body parts associated with work). Research and clinical experience indicate that there are some postures that workers attain that have been identified as awkward or stressful and can lead to musculoskeletal discomfort. Poor working and static postures generate biomechanical stress on the body. For example, exposure to awkward postures repeatedly or for prolonged periods can lead to a variety of potentially disabling injuries and disorders of the musculoskeletal tissue and/or peripheral nerves (Keyserling et al., 1991). Awkward postures of the upper extremities that have been identified include elevated elbows, reaching behind the torso, extreme elbow flexion, extreme forearm rotation, wrist deviation, wrist flexion, wrist hyperextension and pinching (Armstrong, 1989). Awkward postures of the low back that have been identified include mild to severe trunk forward flexion, extension, lateral bending and twisting (Chaffin and Andersson, 1991). Trunk lateral velocity, trunk twisting velocity and trunk sagittal angle

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have recently been specifically associated with increased risk of days lost or restricted due to low back pain (Marras et al., 1995). Another critical factor in determining required work postures and risk is workplace design. Several workplace factors including workstation layout, equipment design and the shape and orientation of handles of some hand tools can all affect the postures necessary to complete a set of job tasks (Keyserling et al., 1987). Easy-to-use assessment tools have been developed to quickly identify postural stresses in the workplace for the upper extremities (McAtamney and Corlett, 1993; Keyserling et al., 1993) and for the lower back (Keyserling et al., 1992). 5.3.2 Forceful exertions Lifting, lowering, pushing, pulling and carrying are among the activities that are considered to be forceful whole-body exertions and represent work tasks associated with pain and injury. Proper techniques in this area have the potential to maximize mechanical advantage and minimize physical demands. In order to move an object or load, a certain amount of muscle force is required to move the body with no load. Since the object being manipulated or lifted is typically in contact with the hands, the object may be some distance from the working muscles of the lower back, placing the low back at a biomechanical disadvantage. This biomechanical disadvantage can leave the structures of the back vulnerable to injury. The handling of heavy weights has been identified as a risk factor for developing low back pain (NIOSH, 1981; Bigos et al., 1986). The muscle force required to overcome the load also results in compressive forces on the structures of the lower back, in particular the intervertebral discs. The size and shape of the load, the weight of the load, as well as the position of the load relative to the spine or intervertebral discs, can affect the compressive forces on the spine (Chaffin and Anderson, 1991). The National Institute of Occupational Safety and Health (Waters et al., 1993) has developed a method to predict the compressive forces on the lumbar spine during occasional and repetitive lifting. This research reports that the compression forces on the disc above 650 kg are associated with an eight times greater relative risk of back disorders. The NIOSH methods can assist in the decision-making process to modify a job to reduce the risk of lower back pain. In addition to back symptoms/disorders, upper extremity problems are also common. The upper extremities are at risk of injury due to forceful exertion while using the hands. Jobs that require the use of hand tools and other objects are assumed to increase the risk of certain cumulative trauma disorders (PutzAnderson, 1988; Kuorinka and Forcier, 1995). Hand tools that require pinch grip are heavy to hold or are slippery or slick as well as tools that vibrate, and knives or scissors that have become dull can increase the amount of force required to use the particular tool. Additionally, if the job requires the use of gloves due to a

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cold environment, there is an increase risk of overexertion. The use of gloves increases the need for a forceful grip of the tool or object (Eastman Kodak Company, 1986). The type of glove and the material the glove is made of can also affect the amount of force needed to grip an object. 5.3.3 Repetitive motions or prolonged activities Repetitiveness has been cited by several researchers as an ergonomic risk factor, particularly in upper extremity disorders (Kuorinka and Forcier, 1995). Repeating the same movement or series of movements throughout the working day places increased mechanical stress on the tendons, ligaments and muscles involved in the movements. However, it is difficult to quantify repetition impact across various jobs and to assess the contribution to various levels of risk. For example, 20000 repetitions per day may be substantial for a person on an assembly line but may not be viewed as high repetition for work in a processing position. In a study of tenosynovitis of the upper extremity, Kurppa et al. (1979) found that high repetitive work rates of 7600 to 12000 cycles per shift were a significant risk factor. Similarly, Armstrong et al. (1987) reported that a combination of high repetition and high muscle force was associated with a 12-times greater risk of work-related musculoskeletal symptoms in the hands and wrists. Repetitiveness is also a potential risk factor for lower back problems as well as for the upper extremities. Andersson (1979) reports that repetitive bending of the trunk has been associated with low back pain. However, it is typical that a combination of risk factors such as awkward joint posture (bending forward or twisting of the trunk), high muscle force exertion (lifting a heavy load) and repetition (lifting the load several times per hour throughout the work shift) increases the overall risk for symptoms. Any time repetition is considered an ergonomic risk it is useful to quantify the job demands. For example, information regarding the repetition or cycles per shift can be obtained from analysis of the work standards and work methods for the particular job in question. Prolonged or sustained effort or exertion also represents a potential workrelated risk. Sustained or static postures can lead to localized muscle fatigue. The amount of muscle effort relative to the maximal muscle contraction required to maintain a specific posture is related to the length of time the effort can be sustained (Rohmert, 1973). Typically, a 100 per cent or maximal voluntary contraction (MVC) of a muscle group can be maintained for only about 6 seconds (Rohmert, 1973). Grandjean (1988) states that as a muscle contraction reaches approximately 60 per cent of maximum, blood flow becomes almost completely interrupted. As percentage blood flow decreases to the working muscle, time to fatigue increases. Grandjean further noted that efforts greater than 8 per cent of MVC sustained for the entire work shift can contribute to premature muscular fatigue. Fatigue during sustained muscular contraction can produce discomfort and, on occasion, pain (Astrand and Rodahl, 1986). With

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work breaks, sufficient to allow for recovery, intermittent maximal contraction can be generated indefinitely. If more specific data are required, muscle activity can be estimated through the use of electromyography or by using workers’ perception of the amount of muscle exertion required to perform a task (Rodgers, 1988). Jobs that require constant or sustained sitting or standing can increase the risk of musculoskeletal discomfort, in particular low back pain (Magora, 1972). Also, Andersson (1987) studied muscle activity in the muscles of the low back in seated individuals. The findings suggest that the position of the individual is important in the resultant muscle activity and degree of fatigue. The use of arm supports, lumbar supports and an increase in back-rest inclination appear to decrease the amount of muscle activity in the back. Workers whose jobs require them to remain in one position for prolonged periods of time may also experience localized muscle fatigue in the supporting muscle groups. As muscle fatigue increases, pain and potential for injury may increase as well. 5.3.4 Localized contact stresses Localized contact and mechanical stresses can be defined as those forces caused by physical contact between the body tissue and an object or tool in the workplace (Keyserling et al., 1991). Examples of these contact stresses include resting the arms on the edge of a desk or table that may be sharp and unpadded, using the hand or fist as a ‘hammer’ and using a tool that may be poorly designed for a given individ ual (right-hand-dominant scissors used by a left-handdominant person). It has been suggested that these contact stresses may increase the risk of upper extremity work-related musculoskeletal disorders such as carpal tunnel syndrome and other problems of the nerves as well as circulatory and/or tendon problems. Localized contact stresses are not limited to upper extremity problems as in the case of a poorly fit chair, which may affect the blood flow to the legs. Typically, mechanical stresses are less severe when the contact is with a fleshy part of the body as opposed to areas where nerves and tendons are near the surface. 5.3.5 Vibration Vibration or mechanical oscillations, produced by either regular or irregular periodic movements of a body about its resting state (Grandjean, 1988), represent another potential ergonomic workplace risk. Both whole-body or localized vibration exposure are related to the development of musculoskeletal disorders. A good example is the use of power tools. Power tools expose the user to hand-arm vibration and can develop hand-arm vibration syndrome. Gripping a vibrating hand tool causes an increase in the available muscle effort in an

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attempt to manipulate and control the tool while it vibrates. This increase in muscle force may further contribute to musculoskeletal disorders (Lundstrom and Johansson, 1986). 5.3.6 Temperature extremes (cold in particular) Working in cold temperatures has been identified as a risk factor for musculoskeletal disorders (Clark, 1961; Neilson, 1986). Cold temperatures cause a decrease in strength and coordination and can also induce pain. In addition, working in cold temperatures may require the use of gloves. As noted earlier, glove use requires increased muscle force when gripping, pinching and using hand tools in an attempt to provide that same amount of force ungloved (Eastman Kodak Company, 1986). This increase in force can increase the risk of discomfort. Cold temperatures can be the result of ambient room temperatures and/or the result of exposure to cold air blowing over the hands and arms, possibly delivered from the exhaust of a power tool. 5.3.7 Organizational and psychosocial work factors The impact of the physical work environment on behavioral and psychophysiological responses of the worker is also an area of significant concern for those involved in identifying ergonomic risk (Gamberale et al., 1990). The psychosocial aspects of work (for example, work design and organizational problems, workload control, pacing, social support, rest-work periods, management of change) have been reported to play an important role in affecting health status at the workplace (World Health Organization, 1989). In addition, lack of control over the aspects of the job, whether real or perceived, can exacerbate work-related musculoskeletal symptoms (Bongers et al., 1993). Perceived control over stress is an important mediating variable in reducing the impact of stressors in a variety of contexts (Feuerstein et al., 1986). 5.3.8 Summary This general review illustrates the potential role of a set of ergonomic factors present in a variety of jobs. These ergonomic factors, depending upon intensity, frequency and duration of exposure can set the stage for heightened discomfort, fatigue, pain and injury. They also can exacerbate an existing pain problem and reduce the likelihood of a positive return-to-work outcome. Comprehensive rehabilitation efforts require an evaluation of the presence of these factors in a given patient’s work environment with the intent of determining whether exposure to such factors exceeds the physical and psychological capabilities of

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the patient. Exposure to these factors should be modified so that the worker can effectively complete required job tasks without increasing the likelihood of an exacerbation of symptoms (that is, ergonomic evaluation) or risking reinjury. Additionally, such an evaluation may suggest the need for a more comprehensive occupational rehabilitation program to reduce the impact of such factors through physical conditioning, work conditioning and training in work practices (Feuerstein and Hickey, 1992). 5.4 Treatment approaches in occupational rehabilitation Before presenting some specific examples of the integration of ergonomic principles into management of OMDs and associated work disability, a summary of occupational rehabilitative interventions is provided. Typically such programs are multidisciplinary and emphasize some combination of medical management, physical conditioning, pain and stress management, ergonomic evaluation and consultation, vocational counseling/placement and education regarding personal safety and health in the workplace. Within these broad ares, occupational rehabilitation programs often specifically include the following components. ■ Medical. Further diagnostic evaluation, medication management, physician education of the patient, case management/follow-up. ■ Physical. Therapeutic exercise/physical conditioning, work conditioning/ simulation, physical therapy modalities. ■ Psychoeducational/psychosocial. Cognitive-behavioral therapy, stress management, pain management, back school, operant conditioning. ■ Ergonomic. Worksite ergonomic job analysis, redesign of workstation/work method to reduce risk, assist with reasonable accommodations. ■ Vocational. Counseling, placement, retraining. In such programs, the combined rehabilitation efforts are focused on: (1) Providing clinical evaluations; (2) identifying barriers to work re-entry; (3) developing targeted interventions to reduce the impact of these barriers, and (4) providing rehabilitation services. Return to work is viewed as complex function of multiple factors (medical status, physical capabilities, ergonomic characteristics and psychological and behavioral resources). Detailed psychosocial assessment using this approach also includes pre-injury worker traits, personal work style, psychological readiness to return to work, ability to manage pain and distress and identification of psychiatric symptoms if present. The role of problem-solving skills regarding symptom management and the ability to manage musculoskeletal health and safety at work are also considered. A successful return to work is seen as a

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cumulative outcome achieved through multidisciplinary treatment. Other outcomes of interest are increased physical capacity in relation to work demands, improved symptom management and the ability to more efficiently self-manage personal workplace health and safety issues. The primary focus in occupational rehabilitation is not on factors affecting pain but rather functional improvement and work re-entry. Common areas of assessment useful in the evaluation of occupational musculoskeletal disorders include symptoms/pain, function, workplace, family and secondary psychiatric features. All these factors are assumed to influence work disability. These areas of injury are typically integrated into a multidisciplinary ‘Functional Capacity Evaluation’ (FCE) that assesses each of the dimensions including medical status, physical capabilities in relation to work demands (biomechanical, metabolic, psychological) and the individual patient’s psychological and behavioral resources including workers traits, psychological readiness for work (for example, supervisor support, family support, personal expectation) and ability to manage pain and other symptoms. Following the comprehensive FCE, a detailed treatment plan is developed that generally includes some combination of physical conditioning, work conditioning, pain and stress management and ergonomic intervention. The ergonomic intervention may include ergonomic job analyses, teaching and training in personal body mechanics, the redesign of workplace and workstation features, suggestions for optimal work cycles and work-style, and organizational consultations for prevention, early stage interventions and rapid response systems. 5.5 Integration of ergonomics in occupational rehabilitation Ergonomic job analysis followed by strategic interventions is one pathway for integrating ergonomic principles and techniques into occupational rehabilitation. In this context, the ergonomic job analysis (EJA), developed as part of the management of an individual with recurrent or chronic work disability associated with an occupational musculoskeletal disorder, relates to the need to identify factors that may present barriers to return to work or work retention following the report of persistent symptoms, injury and pain. These barriers are based on the conceptual model of work disability presented earlier. The EJA is especially valuable for use in those cases where the job demands are particularly unclear, jobs in which ergonomic risk factors are suspected, or in cases where the physical capabilities or extent of pathology is such that information regarding work demands is essential to generate a conclusion regarding the likelihood of returning to a specific job. Information collected during the EJA falls into two main areas: documenting, in detail, the current physical demands of the job and documenting the risk-relevant tasks of the job. This is accomplished through a combination of on-site observation, videotaping

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when feasible, and an interview with the patient, supervisor and co-workers. Measurement of the major work demands characteristic of the work tasks the patient is expected to return to or new work assignments that the patient may have to move into depending upon the outcome of the rehabilitation is critical. Information regarding each area is used in the context of rehabilitation to facilitate a reduction of any physical-capability/work-demand discrepancies that may exist. Interventions may include the enhancement of physical capabilities and modification of ergonomic risk factors in an effort to reduce the probability of symptom reoccurrence, exacerbation or maintenance upon return to work. A summary of the steps in conducting a clinical EJA is provided in Table 5.1 (Feuerstein and Hickey, 1992). The clinician completes the EJA, paying particular attention to workplace factors that might be modified to reduce the impact of ergonomic stressors on pain, fatigue and work re-entry. 5.5.1 Case studies The following three case studies illustrate the application of ergonomic principles and techniques within occupational rehabilitation. 5.5.2 Case study 1 5.5.2.1 Brief history A 43-year-old, right-handed female with a history of neck, right shoulder and arm pain was referred for a Functional Capacity Evaluation (FCE) and potential work rehabilitation program. The patient had worked for 23 years as a dental hygienist. She had been treated conservatively with rest and non-steroidal antiinflammatory medications by her family physician and a neurologist. However, the level of pain had caused her to reduce her workload from full-time (five 8hour days per week) to part-time (three 8-hour days per week: Monday, Wednesday and Friday). She had been out of work completely for two continuous months within the last year. This pattern precipitated referral for evaluation and rehabilitation for symptom management and functional restoration including return to work. On evaluation, she reported a significant decrease in her symptoms and levels of pain associated with the two-month work absence. Symptoms appeared to be exacerbated by her work, a conclusion consistent with recent epidemiological investigations of work-related musculoskeletal disorders in dental hygienists (Atwood and Michalak, 1992).

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Based on the FCE, the treatment goals were to increase strength and range of motion of the neck, right arm and shoulder, improve pain-coping skills, improve stress-management skills and improve the use of proper body mechanics. In addi Table 5.1 Steps in conducting a clinical ergonomic job analysis. 1.

2.

3.

4.

5. 6. 7. 8.

Identify purpose Estimate whether an individual can return to a specified job or set of jobs Identify ergonomic stressors/risks to target in ergonomic consultation to reduce workplace risks and facilitate safe work re-entry Establish physical and work-conditioning goals for rehabilitation program (i.e., based on physical capabilities/work demands discrepancies) Assist in determining certain pain and stress-management goals (e.g., need to modify work style) Specify scope Former job Potential new job (if known) Determine job elements to analyse Generate list of potential ergonomic stressors/problematic job tasks Develop rationale for choice of stressors/tasks in a given case (e.g., pattern of symptoms) Identify measurement options and estimate time required Direct observation Videotape Supervisor interview Co-worker interview Physical measurement devices (e.g., force gauges) Psychological measurement devices (self-report, visual analog scales) Quantification and data analyses Generate brief report Discuss findings and recommendations with worker, supervisor, clinical staff and others involved. Use problem-solving approach Follow-up after patient returns to work Workplace walk-through Interview with worker/supervisor

tion to these goals, an Ergonomic Job Analysis (EJA) was planned to evaluate her work situation to suggest accommodations and consider modifications to decrease the risk of exacerbating and/or maintaining her level of pain. 5.5.2.2 Ergonomic job analysis An ergonomic job analysis (EJA) was conducted for the position of dental hygienist. The purpose of the EJA was to document the demands of working as a

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dental hygienist and to offer suggestions to accommodate the position to allow the patient to work more comfortably. Data collection for the position of dental hygienist was obtained from three sources: patient interview, Dictionary of Occupational Titles (DOT) US Department of Labor (1991) job description and videotape at the dental office where the patient is employed. The videotape was then analysed for the presence of ergonomic risk factors of the upper extremities. Job Description: Dental Hygienist (DOT). Performs dental prophylaxis. Removes calcareous deposits, accretions and stains from teeth by scaling accumulation of tartar from teeth and beneath margins of gums, using rotating brush, rubber cup and cleaning compound. Applies medicaments to aid in arresting dental decay. Charts conditions of decay and disease for diagnosis and treatment by dentist. May expose and develop X-ray film. May make impressions for study casts. May remove sutures and dressings. May administer local anesthetic agents. May place and remove rubber dams, matrices and temporary restorations. May place, carve and finish amalgam restorations. May remove excess cement from coronal surfaces of teeth. May specialize in providing clinical services and health education in program designed to improve and maintain oral health. Table 5.2 lists the risk factors that were observed during the EJA in sufficient frequency, intensity and/or duration. These risk factors have a realistic potential, in part, to increase and/or maintain the patient’s discomfort and fatigue during the work day, particularly given her documented physical capacities. 5.5.2.3 Ergonomic recommendations 1 Posture. In an effort to correct her posture while she is working, several changes should be considered. Adjust the dental hygienist’s chair so that she can sit with her feet flat on the floor, knees at a 90° angle. Raise the patient’s chair, flatten out the patient in the chair to a supine position, slide the dental hygienist’s chair in and under the patient’s head, work closer to the patient’s head, move the chair around the patient’s head (from the patient’s ear around toward the top of the patient’s head) as often as needed. 2 Prolonged activities. Since she spends several minutes at a time in awkward postures, she should be encouraged to take more frequent breaks. This could be accomplished by encouraging her to have her patients rinse their mouths more often during the cleaning, which will allow her to take a short break. 3 Work organization. She may wish to work with the staff who schedule appointments for her to identify patients who would require greater physical exertion for her (that is, first-time patients, patients who have not had their teeth cleaned on a regular basis and so on). Perhaps if she identified these patients, they could be scheduled to vary her workload (easy patient, difficult patient, easy patient, rather than two difficult patients in a row).

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The changes in posture and position that we have suggested may take time for her to become comfortable with since she has been working for approximately 23 years. The new postures represent a significant change in her viewing angle on the patient but, as this new position is practiced, she should become as proficient as she appears to be now. 5.5.2.4 Follow-up The patient was contacted one year after post-treatment. At that time she was continuing to work three days per week (Monday, Wednesday and Friday). Her pain intensity was reported to be diminished to a ‘tolerable level’. She has monthly appointments with a chiropractor for an ‘adjustment’. She attends a low-level aerobic dance class three days per week (Tuesday, Thursday and Saturday) for approximately 50 minutes per session and does upper extremity and cervical flexibility exercises at home on a daily basis. Table 5.2 Case study 1 Dental hygienist. Suspected ergonomic stressors identified in the EJA. Awkward posture Sitting while leaning over the patient, head forward looking down at the patient; arms up and extended forward, elbows sometimes above shoulder height. Wrist bent (palm in toward forearms), extreme deviation from neutral at times. Prolonged or repetitive activities Patient maintained awkward postures (see awkward posture) for several minutes at a time (observed up to seven minutes, repeated over the 40 minutes that she was observed). She reports that she sees eight patients per day over 8 hours and maintains the awkward posture, for several minutes at a time, repeated during each scheduled appointment. Forceful exertions Scaling, polishing, brushing and using dental floss are some examples requiring force exerted on the fingers, hand and arms. Localized contact stresses The dental tools used may cause some contact stress on the fingers and hands. Also, there may be some contact stress on the back of the legs from the front edge of the chair. This does not appear to be a problem at this time. Whole body or segmental vibration There appears to be some vibration exposure to the hand and fingers while using the motorized polishing tool. This does not appear to be a problem at this time. Environmental conditions Air conditioned/heated comfortably, room and task-lighting appear to be adequate. Patient adjusts the task-lighting as needed. This does not appear to be a problem at this time. Work organization

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Patient appears to organize herself well for each case. Tools and supplies are ready and within comfortable reach when she needs them. Patients are scheduled by the staff at the front desk. Set up to see eight patients per day. Each patient is slotted for one hour. Takes a one-hour lunch break in the middle of the day. Currently works on Mondays, Wednesdays and Fridays. Work pressure Patient did not report undue pressure to complete her work faster than she is currently working or to see more patients than one per hour. She appears to have some selfimposed pressure to do a good job. Work satisfaction Patient appears to have a high level of job satisfaction. She is, however, concerned about the pain that she experiences related to her work.

She reports a significant increase in her awareness of ergonomic issues such as working posture, duration of work activities, effort levels and rest and recovery breaks throughout the work day. She states that flattening the dental patient’s chair and working up around the top of the patient’s head has improved her comfort level. More frequent rest breaks and micro-rest breaks has also improved her comfort level. She reports that she is more comfortable at work and following work she has less neck and arm pain than she has experienced in the past. She also reports increased energy levels during the work week. Other hygienists in the office have begun to utilize some of the recommendations which is an added benefit from her increased knowledge and application of ergonomic issues related to her work. 5.5.3 Case study 2 5.5.3.1 Brief history A 28-year old female with a two-and-a-half year history of low back pain was referred for an FCE with the vocational goal of returning to work as a bank-teller. The patient originally injured her lower back lifting a patient while employed as a nurse’s aide. The patient was initially treated conservatively with bed rest, nonsteroidal anti-inflammatory medications and passive physical therapy, with limited success. Approximately 10 months after the initial episode of low back pain the patient underwent a lumbar laminectomy. Following surgery, she made improvements in her physical status including lower extremity and trunk strength, sensation and range of motion to within normal limits. However, she continued to experience persistent central lumbar pain with occasional radiation into the left lower extremity extending to the heel, and down the right lower

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extremity to the knee. Her low back pain increased with sitting longer than two hours and standing more than one hour, bending and decreased with walking. The patient was advised by her surgeon to seek alternative employment in a light effort position other than returning to work as a nurses’ aide. She was advised against lifting objects weighing more than 9.1 kg (20 pounds) and to avoid prolonged sitting, standing or repetitive bending. With the help of a vocational counselor, the patient sought employment as a bank teller. An FCE was scheduled to determine whether the patient could return to work as a bank teller and the indication for occupational rehabilitation. An EJA was also scheduled to determine the need for ergonomics modifications to the workstation to allow for a successful return to work. Based on the FCE, the treatment goals were to improve muscular strength and endurance of the trunk, improve work tolerance, lessen fear of reinjury, provide education on safe body mechanics associated with prospective job target (bank teller). 5.5.3.2 Ergonomic job analysis An EJA was conducted for the position of the bank teller. The purpose of the EJA was to document the demands of working as a bank teller and to offer suggestions to accommodate the position to allow the patient to work comfortably for up to 40 hours per week. Data collection for the position were obtained from four sources: patient interview, Dictionary of Occupational Titles (job description), bank supervisor interview and systematic analysis of the workplace. Job description: Bank teller (DOT). Receives and pays out money, and keeps records of money and negotiable instruments involved in various banking and other financial transactions, performing any combination of the following tasks: receives checks and cash for deposit, verifies amounts, and examines checks for endorsements. Enters deposits into depositors’ accounts and issues receipts. Cashes checks and pays out money upon verification of signatures and customers’ balances. Places holds on accounts for uncollected funds. Orders supply of cash to meet daily needs, counts incoming cash, and prepares cash for shipment. May compute services charges, file checks, and accept utility payments. May photograph records using microfilming equipment. May operate various office machines. May sell domestic exchange, travelers’ checks, and savings bonds. May open new accounts and compute interest and discounts. Table 5.3 lists risk factors that were observed during the EJA in sufficient frequency, intensity and/or duration. These risk factors have a potential to increase and/or maintain the patient’s discomfort and fatigue during the workday, particularly given her documented limited physical capacities.

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5.5.3.3 Ergonomic recommendations 1 Posture. Remove the shelf/organizer located directly under the work surface in an attempt to provide the patient with sufficient clearance for her legs while in a Table 5.3 Case study 2 Bank teller. Suspected ergonomic stressors identified in the EJA. Prolonged activities The workstation work surface height is 104 cm (41 inches) from the floor. The work surface height appears to be a good match for the patient when she is in a standing position. She appears to be able to stand at the workstation and work without awkward body postures. However, she reports that she experiences an increase in lower back pain, usually when standing for more than one hour at a time. Awkward posture (a) The height of the workstation can be used either for standing or sitting. There are adjustable stools attached to each of the workstations. Additionally, there is a foot rest attached to most of the workstations. However, the adjustable height of the stool does not allow for a neutral posture when sitting. The stool is too low and this contributes to awkward postures of the trunk and upper extremities while sitting on the stool and attempting to work. (b) The printer assigned to her workstation appears to be outside her comfortable reach capability. This requires repeated reaching with full extension of the arm and bending at the waist with each transaction, increasing the risk of premature fatigue in the muscles used to perform the maneuver. (c) It is difficult for the patient to sit on the stool attached to the workstation because of the limited leg clearance under the workstation due to a shelf/ organizer directly under the work surface. This causes her to sit back and away from the workstation, increasing her forward bending and reach distances in order to perform work. This forward-bent position increases compression forces on the lumbar discs and may ultimately lead to increased pain. Forceful exertions The existing stool does not provide any lower back support and requires the patient to use her own trunk muscles to support herself while using the stool to sit. Localized contact stress The foot rest attached to the workstation is located at an awkward height to offer any support for the patient’s legs while sitting. This will force her legs to dangle from the front edge of the chair and place direct mechanical pressure against the back of her legs. Environmental conditions Air conditioned/heated comfortably, room and task-lighting appear to be adequate.

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sitting position. This will allow her to sit with her legs under the work surface, decrease the reach distance to her work and reduce the amount of bending and use of the lower back muscles. Relocate the printer to within a comfortable reach for the patient. Reducing the reach distance would reduce the risk of premature fatigue as well as the possibility of increasing her level of pain. 2 Force exertion/prolonged activities. Substitute the stool with a tall, height adjustable office chair. Preferably the chair would provide her with lower back support and be height adjustable from 61–81 cm (25 to 32 inches) from the floor up to the seatpan. The chair should be adjusted so that the patient’s resting elbow height is equal to the work surface height 104 cm (41 inches). 3 Localized contact stress. Provide an angled foot rest under the workstation in an effort to keep her legs in a neutral position (90° angles at the hips, knees and ankles), approximately 10 inches high. 4 Work organization. Encourage the patient to change her working posture from sitting to standing and standing to sitting approximately every 20–30 minutes throughout the working day. 5.5.3.4 Follow-up The patient was contacted one year following intervention. She continues to work full-time as a bank teller. She continues to utilize the ergonomic modifications that were recommended. She reports her pain level as ‘manageable’. Her supervisors have incorporated the ergonomic interventions of her workstation into the other workstations along the teller line. 5.5.4 Case study 3 A 32-year-old, right-hand dominant, female was referred for an FCE with a chief complaint of bilateral upper extremity pain. She had undergone a carpal tunnel release on the right hand approximately six months prior to the FCE. Results of the FCE revealed diminished pinch, grip and arm strength, bilaterally, as compared to normative data. Upper extremity gross motor coordination was within normal limits. She reported pain levels of 8 out of 10 (Visual Analog Scale) at its worst. She reported some pain-free days, however, there were more painful days than pain-free days. Tinel’s sign produced tingling in the right palm. Phalen’s sign was found to be positive on the left hand and negative on the right side. At the time of the FCE the patient was working full-time as a legal secretary. However, there were many tasks that she avoided during the work day because they tended to increase her symptoms. The majority of her work day was spent sitting at her desk using a computer, telephone, dictaphone, typewriter, manual hole-punch and manual stapler. The most common task during the work day was

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word processing using the computer keyboard and mouse. She transcribes audiotapes using a dictaphone with a headset and a foot pedal. The next most common task during the work day was using the telephone. She reports the use of the manual stapler and hole punch numerous times per day. These activities, in particular, produce an increase in her symptoms. On occasion a secretary was hired on a temporary basis from an employment agency to help out in the office. This helped the patient to get caught up in her daily tasks and accomplish some tasks that were beyond her current capabilities. Based on the results of the FCE, the treatment goals were determined to be: improve upper extremity muscle strength and endurance, improve posture and teach pacing skills. The patient initiated physical therapy sessions with limited success. She reported a decrease in her symptoms immediately following physical therapy; however, her symptoms were quickly exacerbated at work. 5.5.4.1 Ergonomic job analysis An EJA was conducted for the position of legal secretary. The purpose of the EJA was to document the risk-relevant tasks of the job and to offer suggestions to modify the tasks to reduce the risk and improve patient comfort. Data collection for the position of legal secretary were obtained from three sources: patient interview, Dictionary of Occupational Titles (job description), and systematic analysis of the work place. Job description: Legal secretary (DOT). Prepares legal papers and correspondence of legal nature, such as summonses, complaints, motions and subpoenas. May review law journals and other legal publications to identify court decisions pertinent to pending cases and submit articles to company officials. Table 5.4 lists the risk factors that were observed during the EJA with a frequency, intensity and/or duration that could exacerbate symptoms. These risk factors have a potential, in part, to increase and/or maintain the patient’s discomfort and fatigue during the work day, particularly given her documented physical capabilities and symptom pattern. Table 5.4 Case study 3 Legal secretary. Suspected ergonomic stressors identified in the EJA. Awkward joint posture There appears to be a discrepancy 8.9 cm (3.5 inches) between where the patient naturally rests her elbows and the height of her keyboard on the work surface. This causes her to utilize her shoulder and upper arm muscles to raise her arms to a level where she can reach the keyboard. Sustaining this position can lead to fatigue and discomfort in the muscles of her shoulders and upper arms. In order to reduce this discrepancy, the natural solution would be to raise the office chair approximately 8.9 cm (3.5 inches). However, she cannot raise her chair because she has limited clearance under the desk to allow her to do so. Additionally, she uses the dictaphone foot pedal

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and if she were able to raise her chair then she would no longer be able to reach the foot pedal. At the time of the evaluation there appeared to be a discrepancy 5.1 cm (2 inches) between the patient’s resting eye height and the height of her computer monitor. This causes her to look up and tilt her head back in an attempt to properly view the screen. This awkward posture can result in fatigue of the neck and shoulder muscles and place pressure on the structures in the neck that lead into the arms. Constrained posture The patient’s desk has drawers on both sides. The clearance under the desk is not very wide. She has approximate 3.8 cm (1.5 inches) of clearance on either side of her legs. This does not allow her to move her legs freely and because of this she tends to sit in a fairly constrained posture while at her desk. This constrained posture can lead to increases in her level of discomfort. The patient has a typewriter stand and a filing cabinet just the right of her chair. When she moves her chair back she often hits the chair on the cabinet as evidenced by the numerous scrapes on the cabinet and the tears in the fabric of the chair. Due to the closeness of these pieces of office furniture she tends to sit in an awkward and constrained posture to avoid hitting the cabinet with the chair. This posture, if prolonged, can increase the risk of muscular fatigue and discomfort. Localized contact stress The patient’s desk is made of wood and has a glass covering over the work surface. The front edge of the desk, where the glass ends, is squared-off and presents a fairly sharp surface. The patient rests her forearms on this sharp angle while using the computer keyboard. Additionally, the chair in use is rather narrow and small relative to the patient’s upper leg length and hip width cause in pressure against the back of the legs and the buttocks. Prolonged activities The patient reports that she rarely takes work breaks throughout the work day and on some days she works through her lunch break. Additionally, she reports 5–10 hours of overtime per week. Forceful exertions The patient uses the telephone quite often and for prolonged periods of time during the workday. She states that she cradles the telephone handset between the ear and shoulder while writing notes. This awkward posture can result in fatigue of the neck and shoulder muscles and place pressure on the structures in the neck that lead into the arms. The patient is required to staple and punch holes in documents to be filed. She uses a manual stapler and a manual hole-punch. She is required to staple and punch up to 100 times per day on an average work day. She reports increased amounts of fatigue in the hands and forearms. Other factors that may affect patient safety and comfort The chair that the patient uses appears to be an older chair which lacks some of the fundamental adjustments such as easy height adjustment. Additionally, the seat pan on

M.FEUERSTEIN, T.R.ZASTOWNY AND P.HICKEY 159

the older chair is rather narrow and the lumbar support also appears inadequate. Both lack of adjustability and proper support can contribute to discomfort during the working day. The chair has a 4-point base. Such chairs can tip over more easily than chairs with 5-prong bases.

5.5.4.2 Ergonomic recommendations 1 Constrained postures/localized contact stress. Replace the existing desk with a desk that provides more clearance under the desk and has rounded edges on its front. This will reduce the risk of constrained postures of the legs and reduce the risk of contact stresses on the structures of the forearms. Arrange the office furniture to reduce the risk of constrained postures to increase ease-of-use and productivity. Replace the existing chair with a chair that has a five-point base to prevent tipping. Additionally, the seat pan of the chair should be wide enough to accommodate the patient’s upper leg length and hip width. 2 Awkward postures. Consider the use of an articulating keyboard arm wide enough to accommodate a keyboard and a computer mouse. This will allow her to rest her arms naturally at her sides, with her elbows bent at 90 degrees, and still be able to reach the keyboard and mouse. 3 Forceful exertions. Consider the use of a telephone headset to be used for prolonged or repeated phone calls to reduce the risk of awkward and forceful postures of the neck. Provide an electric stapler and an electric holepunch to reduce the repetitive muscle effort required when using manual equipment. 4 Prolonged activities. Allow the patient to take a break at regular intervals during the work day. At this time work breaks should allow 30 minutes of continuous keyboarding. Additionally she should avoid prolonged periods of overtime work. 5.5.4.3 Follow-Up The patient was contacted approximately six months after treatment. She continues to work full-time as a legal secretary. The ergonomic recommendations took approximately 3 months to be implemented. The patient had been working in the accommodated workplace for approximately 3 months. She reported a significant improvement in her symptoms. Although she continues to experience pain, her reports of pain were 3 out of 10 at its worst and there were more painfree days than painful days.

160 INTEGRATING ERGONOMICS

5.6 Conclusions Integrating ergonomics into occupational rehabilitation efforts of all kinds holds significant promise for improving outcomes. This chapter was written primarily from a descriptive clinical perspective to illustrate the application of ergonomic principles and techniques into the rehabilitation of injured workers with an OMD. The approaches presented are not based upon a large amount of outcome research. Currently, the authors are not aware of well-controlled outcome research on the specific effects of clinical ergonomic interventions on measures of pain, fatigue, performance at work, return-to-work rates and long-term retention. The case studies that are available suggest that such controlled outcome research is justified. Indeed, it would be very useful to know whether the clinical effects of medical management could be enhanced with systematic low cost ergonomic interventions. At this point there is some evidence that an integration of ergonomic interventions into a multi-component rehabilitation program for complex chronic cases with either upper extremity (Feuerstein et al., 1993) or low back pain (Feuerstein, 1991) is associated with improved outcomes beyond that of usual care. However, the specific contribution of the ergonomic component remains unclear. Also, it is not evident at present whether intervening from an ergonomic perspective early in the history of the work-related musculoskeletal disorder will improve outcomes beyond medical management and/or physical therapy alone. These are questions with important clinical implications, given the ever present need to improve the outcome of these highly prevalent multiply determined disorders. *Note

The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the United States Department of Defense or the Uniformed Services University of the Health Sciences. References ANDERSSON, G.B.J. (1979) Low back pain in industry: Epidemiological aspects, Scandinavian Journal of Rehabilitation Medicine, 11, 163–8. ANDERSSON, G.B.J. (1987) Biomechanical aspects of sitting: an application to VDT terminals, Behavior and Information Technology, 6, 257–69. ARMSTRONG, T.J. (1989) Ergonomics and cumulative trauma disorders of the hand and wrist, In Hunter-Schneider-Mackin-Callahan (Eds). Rehabilitation of the Hand: Surgery and Therapy, 3rd edn, pp. 175–91, St. Louis: The M.V.Mosby Company.

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ARMSTRONG, T.J., FINE, L.J., GOLDSTEIN, S.A., LIFSHITZ, Y.R. and SILVERSTEIN, B.A. (1987) Ergonomic consideration of the hand and wrist tendinitis, Journal of Hand Surgery, 12A (Pt. 2), 830–7. ASTRAND, P.O. and RODAHL, K. (1986) Textbook of Work Physiology: Psychological Bases of Exercise, New York: McGraw Hill. ATWOOD, M.J. and MICHALAK, C. (1992) The occurrence of cumulative trauma in dental hygienists, Work, 2, 17–31. BIGOS, S.J., SPENGLER, D.M., MARTIN, N.A., ZEH, J., FISHER, L. and NACHEMSON, A. (1986) Back injuries in industry: A retrospective study, Spine, 11, 252–6. BONGERS, P.M., DE WINTER, C.R., KOMPIER, M.A.J. and HILDEBRANDT, V.H. (1993) Psychosocial factors at work and musculoskeletal disease, Scandinavian Journal of Work Environment and Health, 19, 297–312. BUREAU OF LABOR STATISTICS. (1994) Work Injuries and Ilnesses by Selected Characteristics, 1992. US Department of Labor, Technical Release USDL-94–213, Washington, DC. CHAFFIN, D.B. and ANDERSSON, G.B. (1991) Occupational Biomechanics, 2nd edn., New York: John Wiley. CHAFFIN, D.B. and FINE, L.J. (1992) A National Strategy for Occupational Musculoskeletal Injuries—Implementation Issues and Research Needs, US Department of Health and Human Services (DHHS)NIOSH Pub. 93–101. CLARK, R.G. (1961) The limiting hand skin temperature for unaffected manual performance in the cold, Journal of Applied Psychology, 45, 193–4. EASTMAN KODAK COMPANY (1986) Ergonomic Design for People at Work, Vol. 2, New York: Van Nostrand Reinhold. FEUERSTEIN, M. (1991a) A multidisciplinary approach to the prevention, evaluation and management of work disability, Journal of Occupational Rehabilitation, 1, 5–12. FEUERSTEIN, M. (1991b) ‘Managing the complex low back pain patient: A costeffective approach to work re-entry’. Paper presented at the 12th Annual Scientific Meeting of the Society of Behavioral Medicine. Washington, DC. FEUERSTEIN, M. (1996) Workstyle: Definition, empirical support and implication for prevention, evaluation and rehabilitation of occupational upper extremity disorders, in MOON, S. and SAUTER, S. (Eds) Beyond Biomechanics: Psychosocial Influences on Cumulative Trauma Disorders in Office Workers, pp. 177–206, London: Taylor & Francis. FEUERSTEIN, M. and HICKEY, P.F. (1992) Ergonomic Approaches in the Clinical Assessment of Occupational Musculoskeletal Disorders, in: TURK, D.C. and MELZACK, R. (Eds), Handbook of Pain Assessment, pp. 71–99, New York: Guilford Press. FEUERSTEIN, M. and ZASTOWNY, T.R. (in press) Occupational Musculoskeletal Disorders and Work Disability: A Multidisciplinary Approach, New York: Plenum Press. FEUERSTEIN, M., CALLEN-HARRIS, S., HICKEY, P., DYER, D., ARMBRUSTER, W. and CAROSELLA, A.M. (1993) Multidisciplinary rehabilitation of chronic workrelated upper extremity disorders: Long-term effects, Journal of Occupational Medicine, 35, 396– 403.

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FEUERSTEIN, M., LABBE, E.E. and KUCZMIERCZYK, A.R. (1986) Health Psychology: A Psychobiological Perspective, New York: Plenum Press. FEUERSTEIN, M., MENZ, L., ZASTOWNY, T.R. and BARRON, B.A. (1994) Chronic back pain and work disability: Vocational outcomes following multidisciplinary rehabilitation, Journal of Occupational Rehabilitation, 4, 229–51. GAMBERALE, R.M., KJELLBERG, A., AKERSTEDT, T. and JOHANSSON, G. (1990) Behavioral and psychophysiological effects of the physical work environment, Scandinavian Journal of Work, Environment and Health, 16, 5–16. GRANDJEAN, E. (1988) Fitting the Task to the Man: A Textbook of Occupational Ergonomics, Philadelphia: Taylor & Francis. HYMOVICH, L. and LINDHOLM, M. (1966) Hand, wrist and forearm injuries, the results of repetitive motions, Journal of Occupational Medicine, 8, 573–7. KEYSERLING, W.M., ARMSTRONG, T.J. and PUNNETT, L. (1991) Ergonomic job analysis: A structured approach for identifying risk factors associated with overexertion injuries and disorders, Applied Occupational Environmental Hygiene, 6, 353–63. KEYSERLING, W.M., FINE, L.J. and PUNNETT, L. (1987) Postural stress of the trunk and shoulders: Identification and control of occupational risk factors, in: American Conference of Government Hygienists (Ed.) Ergonomic Interventions to Prevent Musculoskeletal Injuries in Industry, pp. 11–26, Chelsea, MI: Lewis Publishers. KEYSERLING, W.M., STETSON, D.S., SILVERSTEIN, B.A. and BROUWER, M.L. (1993) A checklist for evaluating ergonomic risk factors associated with upper extremity cumulative trauma disorders, Ergonomics, 36, 807–31. KEYSERLING, W.M., BROUWER, M.L. and SILVERSTEIN, B.A. (1992) A checklist for evaluating ergonomic risk factors resulting from awkward postures of the legs, trunk and neck, International Journal of Industrial Ergonomics, 9, 283–301. KINNEY, R.K., GATCHEL, R.J., POLATIN, P.B. and MAYER, T.G. (1991) The functional restoration approach for chronic spinal disability, Journal of Occupational Rehabilitation, 1, 235–44. KUORINKA, I. and FORCIER, L. (1995) Work Related Musculoskeletal Disorders (WMSDs): A Reference Book for Prevention, Washington, DC: Taylor and Francis. KURPPA, K., WARRIS, P. and KOKKANEN, P. (1979) Tennis elbow, Scandinavian Journal of Work, Environment and Health, 5, 15–8. LUNDSTROM, R. and JOHANSSON, R.S. (1986) Acute impingement of the sensitivity of the skin mechanoreceptive units caused by vibration exposure of the hand, Ergonomics, 29, 687–98. MAGORA, A. (1972) Investigation of the relationship between low back pain and occupation: III Physical requirements: Sitting, standing and weight lifting, Industrial Medicine and Surgery, 4, 5–9. MARRAS, W.S., LANVENDER, S.A., LEURGANS, E., FATHALLAH, F.A., FERGERSON, S.A., ALLREAD, W.G. and SUDHAKAR, L.R. (1995) Biomechanical risk factors for occupationally related low back disorders, Ergonomics, 38, 377–410. MAYER, T.G. and GATCHEL, R.J. (1988) Functional Restoration for Spinal Disorders: The Sports Medicine Approach, Philadelphia, PA: Lea and Febiger. MAYER, T.G., GATCHEL, R.J., MAYER, H., KISHINO, N.B., KEELY, J. and MEENEY, V. (1987) A prospective two-year study of functional restoration in

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industrial low back injury, Journal of the American Medical Association, 258, 1763–7. MCATAMNEY, L. and CORLETT, E.N. (1993) RULA: A survey method for the investigation of work related upper limb disorders, Applied Ergonomics, 24 (2), 91–9. NIELSON, R. (1986) Clothing and thermal environments: field studies on industrial work in cool conditions, Applied Ergonomics, 17 (1), 47–57. NIOSH. (1981) Work Practices Guide for Manual Lifting. Cincinnati, OH.: US Department of Health and Human Services. (Technical Report No. 81–122). PUTZ-ANDERSON, V. (Ed) (1988) Cumulative Trauma Disorder—A Manual for Musculoskeletal Diseases of the Upper Extremity. Philadelphia: Taylor and Francis. RODGERS, S.H. (1988) Job evaluation in worker fitness determination, State of the Art Reviews: Occupational Medicine, 3, 219–39. ROHMERT, W. (1973) Problems determining rest allowances: Part 1. Use of modern methods to evaluate stress and strain in static muscular work, Applied Ergonomics, 4, 91. U.S. DEPARTMENT OF LABOR (1991) Dictionary of Occupational Titles (5th Ed.) Washington, D.C.: U.S. Department of Labor. WADDELL, G. and MAIN, C.J. (1984) Assessment of severity in low back pain disorders, Spine, 9, 204–8. WADDELL, G., MCCOLLOCH, J.A., KUMMEL, E.G. and VENNER, R.M. (1980) Nonorganic physical signs in low back pain, Spine, 5, 117–25. WADDELL, G., SOMERVILLE, D., HENDERSON, I. and NEWTON, M. (1992) Objective clinical evaluation of physical impairment in chronic low back pain, Spine, 17, 617–28. WATERS, T.R., PUTZ-ANDERSON, V., GARG, A. and FINE, L.J. (1993) Revised NIOSH equation for the design and evaluation of manual handling tasks , Ergonomics, 36, 749–76. WORLD HEALTH ORGANIZATION (1989) Work with visual display terminals: psychosocial aspects and health, Journal of Occupational Medicine, 31, 957–68.

CHAPTER SIX Ergonomics in vocational rehabilitation EUGENE A.BLUMKIN

6.1 Disability and disability population The Americans with Disabilities Act of 1990 defines a disability as health condition(s) that significantly impair a major life activity (ADA, 1990). Under this very broad definition, nearly every fifth person in the USA has some sort of a disability (Fulbright and Jaworski, 1990). See Figure 6.1. 6.1.1 Definition of work disability However, all the people classified as disabled do not necessarily have a work disability. The definition of work disability differs significantly from the general disability definition. Work disability (previously called ‘handicap’) describes condition(s) that prevents a person from working or limits the kind or amount of work he or she can do for periods of more than 6 months. More specifically, this

Figure 6.1 Disability population in the USA.

definition is applied to non-institutionalized people between 16 and 64 years of age (Smith and Leslie, 1990). The age range (16 to 64) as well as the period of

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disability (6 months) are arbitrary parameters. They may change depending on accepted definitions of working age and general disability. However, for the purposes of this chapter, only people satisfying this definition will be studied. 6.1.2 Demography of work disability population in the USA According to three major studies (Bureau of Census, 1988; NHIS, 1983–5; Bureau of Census, 1986), the population of people with work disability is estimated to be about 10 per cent of the working age population (Kraus and Stoddard, 1991). See Figure 6.2. It should be noted that there is a small decrease with no statistically significant difference in rates of work disability as reported by censuses and the Social Security Administration (SSA) over time. However, both censuses and the SSA reported some increase in severe disabilities (that is, disabilities preventing people from Table 6.1 Selected medical conditions and work disability. Condition

Prevalence of medical conditions (Number of people)

Conditions causing work disability(ies) (%)

Mental retardation Absence of leg(s) Lung or bronchial cancer Blind in both eyes Multiple sclerosis Cerebral palsy Partial paralysis in extremity Absence of arm(s)/hand(s) Complete paralysis in extremity Cancer of digestive sites Paralysis of non-extremity sites Intervertebral disk disorders Rheumatoid arthritis Heart disease/disorders Orthopedic impairments (except extr., back) Emphysema Epilepsy Pneumoconiosis/asbestosis

392000 151000 72000 129000 91000 91000 185000

75.3 72.9 72.7 71.9 58.9 58.2 55.0

33000 214000

51.6 50.8

67000 82000

46.8 42.0

1472000 389000 1117000 98000

40.7 40.1 39.9 39.5

541 000 282000 90000

38.7 37.0 35.9

166 E.A.BLUMKIN

Condition

Prevalence of medical conditions (Number of people)

Conditions causing work disability(ies) (%)

Cerebrovascular disease Ischemic heart disease Cancer of genitourinary sites Diabetes Cancer of the female breast Orthopedic impairment of the back

434000 1391000 69000

32.5 31.6 29.3

1213000 68000 1854000

29.0 22.1 21.3

Source: La Plante, 1989.

Figure 6.2 Work disability statistics.

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gainful employment against disabilities limiting work-related activities) (Smith and Leslie, 1990). There are several problems with demographic studies that attempt to describe the work disability population, two of which are directly related to the ‘human factors’ characteristics of the living and working environments of people with disabilities. Thus, all studies do not collect or take into consideration data on physical and social environments with which people with disabilities deal. Analysis of human factors or ergonomic parameters of the environments is routinely avoided. In the absence of this data, the studies may incorrectly estimate work disability populations, especially those with severe work disabilities. For example, a person suffering from severe mobility impairment may or may not be severely work disabled. It will depend on several nonmedical factors, including occupation, living and transportation arrangements and most importantly, his or her work environment. Another problem exists with the lack of data on discrimination against people who are disabled or perceived to be disabled. In working environments, if discrimination against people with disabilities exists, even people with minor work disabilities would consider themselves severely work disabled. Therefore, in the presence of environmental and discrimination data, analysis of demographic surveys may yield different results. Table 6.2 Distribution of employees with and without disabilities among major occupational groups. Occupational group

With a work disability Without a work disability

Males

Females

Males

Females

Total employed population

100% 2052000 18.2 374000 17.5 361000 12.5 257000 4.6 95000 19.6 403000 27.4 563000

100% 1582000 16.0 254000 39.5 626000 27.3 433000 1.4 22000 2.2 35000 13.3 212000

100% 57584000 26.3 15192000 19.9 11468000 9.2 5311000 3.7 2144000 19.8 11420000 20.9 12049000

Managerial and professional speciality Technical, sales and administrative support Service Farm, forestry and fishing Precision, production, craft and repair Operators, fabricators and laborers

100% 48 141 000 25.6 12361000 45.3 21850000 17.0 8219000 0.8 424000 2.2 1092000 8.7 4194000

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6.1.3 Types of work disabilities Current work disability classification is based on the type of impairment. There are several major categories of work disabilities. 1 Sensory impairments (visual, hearing or other sensory impairments). 2 Mobility impairments (mobility, strength, manipulation or other mobility impairments). 3 Intellectual or psychiatric/psychological impairments (brain damage, genetic intellectual impairments, psychiatric diseases, psychological problems and learning and behavior disabilities). Most people with work disabilities have a combination of two or more types of impairments. It is obvious that people reporting more than one type of impairment will have a greater level of severity of disabling conditions. Thus, among people who reported a combination of visual, hearing and orthopedic impairments, 85 per cent reported severe work disability compared with 54 per cent for people having orthopedic and hearing impairments and 66 per cent for people having visual and orthopedic impairments, respectively (Smith and Leslie, 1990). Table 6.1 (adapted from LaPlante and Mitchell, 1989) presents information about the prevalence of 24 selected medical conditions causing the highest rates of work disability. Unfortunately, existing classifications have a major disadvantage: they do not address specific human characteristics and parameters as they are relevant to work environments. For example, it is obvious that differently classified impairments could lead to similar work limitations. Thus, both advanced multiple sclerosis and traumatic vision loss, for example, will lead to serious vision-related work limitations. In many ways, ergonomic adaptations that need to be made in the workTable 6.3 Distribution of employees with and without disabilities among major occupational groups. (Adapted from Kraus and Stoddard, 1991.) Industry group Males

With a work disability Without a work disability Females

Males

Females

Total employed population 3.9 82000 0.2 4000

100% 2052000 1.9 30000 0.1 3000

100% 1582000 3.3 1939000 0.1 89000

Industry group

Agriculture Forestry and fishing

100% 57584000 1.1 565000 32000

100% 48 141 000

ERGONOMICS IN VOCATIONAL REHABILITATION 169

Industry group

With a work disability Without a work disability

Males

Females

Males

Females

Mining

1.1 24000 12.6 259000 21.0 431000 9.2 190000

1000 1.1 17000 12.2 193000 3.8 60000

0.9 563000 10.2 5915000 23.5 13581000 9.3 5412000

0.3 145000 1.1 567000 13.7 6636000 4.2 2070000

5.2 108000 11.4 235000 4.5 94000

1.8 19000 19.3 307000 7.2 115000

5.3 3056000 14.7 8482000 4.7 2751000

2.4 1195000 18.9 9106000 9.5 4589000

25.7 528000 4.7 97000

47.3 750000 4.8 76000

22.4 12911000 5.0 2885000

43.7 21043000 4.5 2195000

Construction Manufacturing Transportation, communications and other public utilities Wholesale trade Retail trade Finance, insurance and real estate Services Public administration

place and the work procedures of both categories of people will be similar. From an ergonomic prospective, along with information on specific impairments, it would be even more important to collect data on specific work-related functional limitations, such as reach, grasp and lift. Often, even more detailed data are necessary, for example, specific movements, exact sound frequency limitations and dimensions of parts of the body. As will be seen later, it is possible to obtain this data for each vocational rehabilitation client. On the macro-level, however, this information is not collected. For the purpose of this chapter, it will be beneficial to examine the occupational distribution of the employed work disability population. Table 6.2 represents the distribution of employees (males and females) with disabilities among major occupational groups compared with that for the non-disabled population (Adapted from Kraus and Stoddard, 1991). There are two important conclusions that can be drawn from this data. First, it is clear that people with disabilities, both males and females, hold significantly fewer managerial and professional specialty jobs. Secondly, people with disabilities tend to occupy less skilled positions (for example, operators, fabricators and laborers) significantly more often than people without disabilities. Also interesting is the elevated prevalence of females with disabilities in service occupations.

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Table 6.3 shows the distribution of employees with work disabilities by industry. It is clear that people with disabilities are mostly employed in the service, manufacturing and retail/wholesale trade industries. It is interesting to note, however, that there is no statistically significant difference in employment distribution by industry between people with and without work disability. 6.2 Vocational rehabilitation system in the USA 6.2.1 History and legal basis of vocational rehabilitation The history of vocational rehabilitation reflects human struggle to establish the rights of people with disabilities to participate in all aspects of life. Early elements of vocational rehabilitation in the USA could be found as a part of the medical or social activity of some charitable organizations. Organizations such as the Red Cross, the Carnegie and Rockefeller Foundations, the National Tuberculosis Association, Goodwill Industries and the Easter Seal Society incorporated some elements of vocational rehabilitation in their work. At the federal level, the first compulsory insurance law covering sickness for seamen was passed by Congress in 1798 after Alexander Hamilton argued for the necessity of attracting recruits and protecting them from ‘want and misery’ (Esco Oberman, 1965). However, only when the Workmen’s Compensation statutes were passed in some states, did the subject of workmen’s rehabilitation begin to receive real national attention. Even though the first workmen’s compensation statutes did not survive judicial review (Maryland, 1902), the Federal Government (1908) established its own provisions that were referred to as ‘workmen’s compensation’. These provisions covered federal employees only and were limited to certain occupations. By 1911, ten states had adopted their own compulsory workmen’s compensation laws. By 1921, the number had increased to 45 states. In the early days, vocational rehabilitation was looked at as the last one of three steps in the comprehensive workmen’s compensation system. The first two steps, accident prevention and injury compensation, were considered to be much more important. Development of the vocational rehabilitation system was positively influenced by veteran’s rehabilitation legislation following World War I and the civilian Rehabilitation Act of 1920 (Smith-Fess Act). The law specifically required cooperation between federally funded veteran’s rehabilitation programs and workmen’s compensation programs.

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It should be noted, however, that even though the original rehabilitation laws did qualify a wide range of disabilities, the emphasis was on physical disabilities and those related to industrial accidents and military service. The first federal law containing some elements of vocational rehabilitation of the general disabled population was the Smith-Huges Act of 1917 (Esco Oberman, 1965). The Act established federal grants to the states to organize and support the vocational education system. It established a format for vocational rehabilitation as a public activity. This format was later incorporated in the Smith-Fess Act of 1920 (Public Law No. 236) that authorized the vocational rehabilitation (VR) program to be administered at state level by the state boards of vocational education and at federal level by the Federal Board of Vocational Education (Policy Directive, RSA-PD-96–02, 1995). This first comprehensive federal law established vocational rehabilitation with emphasis on the rehabilitation of workers injured in industry. The Act specifically stated that it was enacted ‘in order to provide for the promotion of vocational rehabilitation of persons disabled in industry or in any legitimate occupation’. However, it was a document of great importance for vocational rehabilitation. The Act defined disability as ‘…a physical defect or infirmity, whether congenital or acquired by accident, injury or disease…’ (Public Law 236). It is considered to be a starting point for the federally supported public vocational rehabilitation system in the USA. During the next 50 years, the Smith-Fess Act underwent several rounds of amendments and renewals that did not significantly change the scope and primary provisions of the law. However, the Social Security Act of 1935 incorporated specific provisions for the vocational rehabilitation of disabled adults. Compared with the Rehabilitation Act of 1920 (Smith-Fess Act), the Social Security Act of 1935 was a permanent law not requiring reauthorization every few years. Not until 1973, as a result of the human rights movement of 1960s, was a new Rehabilitation Act passed by Congress. It replaced the original law of 1920, creating a public vocational rehabilitation program. The Act also significantly widened the definition of disability and the scope of services available to eligible individuals with disabilities. It also introduced some anti-discrimination provisions related to the employment of people with disabilities (Rehabilitation Act 1973). For the purpose of this chapter, it is important to mention the provisions for the rehabilitation technology services established by the Act. As will be subsequently discussed, all ergonomics applications in vocational rehabilitation are usually provided under the umbrella of ‘rehabilitation technology services’. The Americans with Disabilities Act of 1990 (ADA) was the first civil rights law aimed at protecting people with disabilities against discrimination in the most important areas of life. The ADA introduced the notion of ‘reasonable accommodations’. According to the law, the ‘reasonable accommodations’ have to be provided for people with disabilities in order for them to access or retain

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employment. Because ‘reasonable accommodations’ are usually described as modifications of the work environment or work procedures to permit an individual with a disability to perform a job, it is clear that one of the most essential ways to do that is to use ergonomic science and techniques. 6.2.2 Scope and structure of vocational rehabilitation services According to the National Tabular Report for the Federal Fiscal Year 1993, the Vocational Rehabilitation System served nearly 1.1 million people with disabilities, with almost 70 per cent of the people served having disabilities classified as severe. Of all the people served, 18.51 per cent (or almost 200000 people) were successfully rehabilitated. This demonstrates how important the role of the public vocational rehabilitation is in modern society. Title 1 of the Rehabilitation Act of 1973, as amended in 1992, describes a wide range of services that could be provided within the scope of the state public VR system. The following services are most relevant. 6.2.2.1 Eligibility determination services Eligibility determination is the process used at the beginning of vocational rehabilitation in order to determine the eligibility of an individual who applied for services and to assess his or her vocational rehabilitation needs. The eligibility determination process is used to estimate the probability of achieving employment outcomes, ‘entering or retaining full-time or, if appropriate, part-time competitive employment in the integrated labor market (Rehabilitation Act 1973, 1992)’. The determination process may include gathering the individual-specific data on employment-related physical and mental capacities, employment history, jobrelated education and occupational skills, the appraisal of work-related behavior and assessment of the adequacy of the individual relative to performance in different prospective work environments. Eligibility determination is performed by skilled vocational rehabilitation professionals and is based on the information submitted by the applicant. If, in the process of eligibility determination, some additional information needs to be obtained in order to make a decision regarding a client’s eligibility for future vocational rehabilitation services or regarding the scope of those services, a referral to an appropriate specialist should be made. In reality, mostly medical specialists receive referrals at this stage. Occasionally, work evaluators are consulted. Other work environment professionals do not get involved at the eligibility determination stage. Even though the eligibility determination provisions specifically include the procurement of rehabilitation technology services in order to assess and develop

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specific work environment-related capacities, rehabilitation technology professionals are not routinely contacted at this stage. As will be seen later, the exclusion of non-medical specialists from the eligibility determination process creates many problems that could have been avoided earlier in the process. 6.2.2.2 Counseling, guidance and placement services Counseling, guidance and work-related placement services include job search assistance, placement assistance, job retention assistance, help in placement and specific services related to maintain, regain or advance in employment. These services are not time-specific and could be provided to eligible vocational rehabilitation services recipients at any time as pre- or postemployment services. Counseling, guidance and work-related placement services are exclusively provided by vocational rehabilitation professionals (vocational rehabilitation counselors). 6.2.2.3 Training services Training services could include college and university level educational courses (degree and non-degree), professional and vocational courses and related services and expenses if training services, in the opinion of the vocational rehabilitation counselor, will lead to obtaining, retaining or advancement in employment. 6.2.2.4 Physical and mental restoration services This group of services could include necessary corrective surgery or therapeutic treatment applied to correct or modify any physical or mental condition that is considered to be a barrier to employment. Necessary hospitalization could be a part of the services. Prosthetic and orthotic services and devices constitute a large part of the physical restoration services provided mostly for vocational rehabilitation clients with mobility impairments. For some time, prosthetic and orthotic services were the only vocational rehabilitation services that directly employed the latest technology advancements for improving the vocational capacities of vocational rehabilitation clients. It should be noted that some early rehabilitation technology services (discussed later in this chapter) were placed in the category of prosthetic and orthotic services within the Veterans Administration system.

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6.2.2.5 Transportation services Transportation services could be procured in connection with the rendering of any vocational rehabilitation services. Transportation services could include, for example, providing payment for public transit transportation, transportation in specially modified vehicles and private taxicab services. An example of transportation service is providing reimbursement for using a wheelchair lift-equipped public transit bus or van to a client in a wheelchair attending physical rehabilitation procedures in a medical facility that is located outside the reach of the client’s own wheelchair ride. Transportation services do not include modifying private vehicles for vocational rehabilitation clients in order for them to drive or be transported in the vehicle. 6.2.2.6 Telecommunication services and devices Telecommunication services and devices are provided in connection with other vocational rehabilitation services in order to increase the client’s abilities to communicate for the purposes of increasing the impact of vocational rehabilitation services, and obtaining, retaining or advancement in employment. An example of a communication service is an interpreter helping a deaf person to participate in an employment-related meeting. Computer software and hardware that translates text into speech is an example of a telecommunication device. 6.2.2.7 Rehabilitation technology services According to the Rehabilitation Act, ‘the term rehabilitation technology means the systematic application of technologies, engineering methodologies or scientific principles to meet the needs of and address the barriers confronted by individuals with disabilities in areas which include education, rehabilitation, employment, transportation, independent living and recreation’ (Rehabilitation Act 1973, 1992). Rehabilitation technology services include rehabilitation engineering, assistive technology devices and assistive technology services. An example of a rehabilitation engineering service is the design, testing, manufacture and installation of specialized driving equipment for a private vehicle that is used by an individual with a disability to access the employment site or rehabilitation facility. Any technical device that is used by a person with a disability to improve employment outcomes is an assistive device. Thus, an electric stapler operated by a person with arthritis is an assistive device. An example of an assistive technology service is the ergonomic evaluation of a prospective worksite of an individual with a disability.

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Figure 6.3 Structure of the vocational rehabilitation process.

6.2.3 Vocational rehabilitation process The flowchart in Figure 6.3 depicts the common process used by the Vocational Rehabilitation Agencies for public vocational rehabilitation. A system of milestones known as status is used to track the client’s standing within the system and measure the outcomes. The process begins with a referral

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(usually a self-referral) to a local office of the agency. A person who wants to receive services completes an application and submits the necessary medical and other information to a vocational rehabilitation counselor. The counselor may request additional data, including, for example, a medical specialist’s evaluation and a psychological evaluation. Based on information obtained, the counselor makes a decision regarding the person’s eligibility for vocational rehabilitation services. A person who is not eligible for vocational rehabilitation services because of the extreme severity of his or her disability could be eligible for other services under the Rehabilitation Act, notably supportive employment or independent living. Some clients require extended evaluation in order to assess their eligibility for receiving vocational rehabilitation services. For persons who are found to be eligible, the next step is the preparation of the Individual Written Rehabilitation Plan (IWRP), which outlines the services that will be provided and the specific outcomes that are expected at different stages of the IWRP fulfilment. The plan is created by the vocational rehabilitation counselor with the client’s input and participation. Different rehabilitation professionals may be contacted at this stage to estimate the scope of their future involvement and different time and cost requirements. For example, an orthopedic physician may be contacted if some orthopedic rehabilitation treatment is anticipated. Next the vocational rehabilitation process is initiated according to the IWRP. The counselor is responsible for providing and coordinating the proposed services. The client’s responsibility is to actively and wilfully participate in services with the ultimate goal being full rehabilitation, that is, gainful long-term full- or part-time employment in the competitive work environment. The vocational rehabilitation process could be interrupted by significant changes in the client’s health, sudden and total non-rehabilitatable disability, a client finding a job, a client’s refusal to continue in the program, or the death of the client. Initial successful completion of the program is described as Status 26. Achieving this status means that employment is secured. The client leaves the vocational rehabilitation system as successfully rehabilitated. However, some subsequent vocational rehabilitation services are still available, even if the client is already employed. These services are called ‘post-employment’ services and are described by Status 32.

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6.3 Role and perspectives of rehabilitation ergonomics in vocational rehabilitation 6.3.1 Vocational rehabilitation ergonomics Ergonomics involves ‘designing for human use and optimizing working and living conditions’ of people (Sanders and McCormick, 1985). A more concise definition given by Chapanis (1985) and modified by Sanders and McCormick (1985) defines ergonomics as the field of science that ‘discovers and applies information about human behavior, abilities, limitations and other characteristics to the design of tools, machines, systems, tasks, jobs and environments for productive, safe, comfortable and effective human use’. Rehabilitation ergonomics (RE) is that part of ergonomic science that deals with individuals and populations of people who possess or are perceived to possess at least one medical or psychological condition that significantly impairs their normal life activities. Vocational rehabilitation ergonomics (VRE) is the area of rehabilitation ergonomics that deals with ergonomic issues in the vocational rehabilitation (VR) of people with disabilities. Even though the elements of vocational rehabilitation ergonomics have been employed by vocational rehabilitation professionals for years, the area of VRE has not been well defined. It could be attributed to the problems of defining ergonomic science itself or to an absence of any systematic ergonomic application within vocational rehabilitation. Several professional organizations, for example, the Rehabilitation Engineering Society of North America (RESNA), the Society of Automotive Engineers (SAE), the Institute of Electrical and Electronics Engineers (IEEE) and the Human Factors and Ergonomics Society (HFES) have been involved in some aspects of vocational rehabilitation ergonomics for almost 20 years. RESNA, for example, has established a special interest group on job accommodation for people with disabilities. Similarly, the SAE’s Adaptive Devices Standards Committee and Task Groups deals with many problems that people with disabilities encounter trying to use their private vehicles. Elements of ergonomics have always existed within public vocational rehabilitation. Under the umbrella of rehabilitation technology and rehabilitation engineering, different rehabilitation technology specialists (for example, rehabilitation engineers, occupational therapists and rehabilitation technology suppliers) have been involved in attempting to solve a wide range of problems related to vocational rehabilitation ergonomics. There were two main directions. The first direction was mostly represented by continuous efforts to extend medical rehabilitation into the area of vocational rehabilitation. Thus, adjustment of technology devices (for example, wheelchairs, prosthetic and orthotic devices) for use in a vocational setting was conducted as a part or extension of medically

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necessary treatment. Similarly, ergonomic evaluations of the jobs and abilities of clients to perform their jobs were conducted to measure the outcome of medical rehabilitation. This direction was not concerned with adapting the environments but rather with attempting to adapt clients to the unchanged working conditions designed for an able-bodied workforce. Not surprisingly, this area was almost exclusively addressed by medical practitioners: for example, occupational and physical therapists, kinesiologists and medical technologists. This had a most positive impact on the process of vocational rehabilitation by bringing medical rehabilitation as far as possible. However, not having the technical background and skills, and not working as a team with technical and vocational specialists, medical practitioners often could not adequately address the problems of adapting the work environments, tools and procedures to meet the needs of people who could not be rehabilitated completely using medical techniques only. The second direction was represented by the rehabilitation technology professionals working in the area of vocational rehabilitation. A limited number of such professionals, mostly engineers, was employed by the public vocational rehabilitation agencies. Originally, very few had any exposure to the life sciences and human services. Engineering (mechanical, electrical and biomedical) was the area of their expertise. They brought engineering skills and methods into the human services area. Their training in ergonomics was limited. However, the human factors/ergonomic approach was similar to the general engineering approach. By gaining additional, often informal, education in ergonomics/human factors and in the life sciences, and teaming up with medical professionals, they were able to provide rehabilitation technology services that included specific tasks attributed to professional ergonomists. Even though some note of the importance of ergonomic applications in vocational rehabilitation was made on the early stages of development of the public vocational rehabilitation, the first position statements on this subject did not appear in the USA until several years ago. In 1993 McQuistion discussed ergonomics and rehabilitation engineering. She noted that rehabilitation engineering should be considered a specialty within ergonomic science. She based her conclusion on the analysis of tasks performed by rehabilitation engineers working in the area of vocational rehabilitation. More specifically, McQuistion used the notion of ‘reasonable accommodations’ introduced by the Americans with Disabilities Act of 1993 to support this conclusion (McQuistion, 1993). The area of rehabilitation engineering, however, is much wider. It is a part of engineering science, and each particular application is based on specific engineering knowledge and principles. Each task performed by a rehabilitation engineer may or may not include ergonomic considerations as primary elements. With highly diverse and sophisticated technology used for vocational rehabilitation purposes, the primary area of expertise of a rehabilitation engineer is usually described by his or her underlying engineering background. Thus, a rehabilitation engineer dealing with mostly mechanical systems (for example,

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manual wheelchairs, and driving aids) would probably have a mechanical engineering background. In comparison, a rehabilitation engineer who deals with computer software or hardware for people with disabilities would normally be an electrical or electronics engineer. Even engineers with a specialized degree in rehabilitation engineering (there are several graduate rehabilitation engineering programs in the country) will concentrate in more specialist areas. It should be noted, however, that McQuistion limited the scope of rehabilitation engineering to aspects of designing for people with disabilities. Her paper properly addresses a very important issue of ergonomic considerations in the process of design for people with disabilities. Thus, rather than concentrating on studying disability and limitations per se, the rehabilitation engineering professional, as the first requirement, should concentrate on evaluating a person’s abilities that are not affected or minimally affected by the health problems causing the disability. The second requirement should involve assessing the limitations caused by the disability and considering those limitations in the design process. Lastly, the design should not negatively influence the existing disability, nor should it lead to the development of a new disability. The paper also appropriately stressed the necessity of the involvement of ergonomic professionals in rehabilitation engineering. It should be noted that actual design represents only one part of rehabilitation technology applications. Different opinion regarding the place of ergonomics in vocational rehabilitation was expressed by Blumkin (1994, 1995). According to his position, vocation rehabilitation ergonomics is part of general ergonomic science. Vocational rehabilitation ergonomics studies the work environments of people with disabilities within the vocational rehabilitation process. The author stressed the fact that vocational rehabilitation ergonomics should assist in the vocational rehabilitation process in its continuity, starting from the time an individual applies for vocational rehabilitation services and ending with longterm job placement. 6.3.2 Pre-employment vocational rehabilitation Vocational rehabilitation ergonomics applications in pre-employment vocational rehabilitation may be divided into two major groups: applications related to eligibility determination decisions and applications related to the vocational rehabilitation process itself. The eligibility determination decision is made based on the determination of disability and an assessment of the client’s ability to obtain and retain employment after utilization of all available vocational rehabilitation services. The eligibility determination process cannot involve any paid services or procurements that are not essential for making the eligibility decision alone. Therefore, only evaluations (including rehabilitation technology and ergonomic evaluations) that are important for making that decision can be used at the

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eligibility determination level. Services such as ergonomic evaluation of a specific workstation, ergonomic furniture procurement and procurement of vehicle modification services should be deferred. A full ergonomic evaluation could be used, along with medical, psychological and vocational evaluations, to determine the client’s eligibility for services and his or her fitness to the particular set of occupations or work environment. A comprehensive initial vocational assessment is not complete without the assessment of the work environment. This type of ergonomic assessment, if neglected, could completely alter the eligibility decision and/or the proposed vocational rehabilitation goals. Some of the assessments could be achieved by using several ergonomic techniques and applying them (starting from the eligibility determination stage) to the client and his or her possible work environments. Thus, the musculoskeletal stress analysis methods originally developed for safety reasons in order to prevent musculoskeletal injuries and illnesses in the general workforce could be adapted for specific disabilities as a tool for work environment fitness assessment. Thus, one method (Bloswick and Dumas, 1994) proposes a set of adaptations to the musculoskeletal stress analysis techniques (notably, the NIOSH Work Practices Guide (WPG) for Manual Lifting and Biomechanical Analysis) and the metabolic stress analysis techniques in order to use them for disabled/rehabilitated workers. In the NIOSH WPG manual lifting formula, the authors propose to reduce the 26 kg (51 lb) load constant in order to correct for the reduced physical strength of the disabled/rehabilitated worker. Similarly, in applying the biomechanical analysis techniques they propose to decrease the lowest acceptable back compressive forces in analyses of work environments for workers with disabilities. Similar solutions are proposed for the metabolic stress analysis techniques. The authors assert that using the reduced values representing the worker’s metabolic capacity will better predict the worker’s fitness for a particular job. The proposed techniques, unfortunately, can only be applied to a relatively small group of the vocational rehabilitation clients or applicants. Mostly cases with a single physical disability and manual material handling job environments could benefit from that approach. Even then, however, extensive epidemiological data are needed to justify applied quantitative values. A slightly different approach is used when the eligibility decision has been made. The vocational rehabilitation counselor develops an individual written rehabilitation plan (IWRP) and planning for the future job begins. In the process of IWRP development and while providing the full range of vocational rehabilitation services, the counselor is required to utilize all the available types of rehabilitation technology services, some of which are directly related to vocational rehabilitation ergonomics applications. The rehabilitation technology specialists are usually contacted early at the IWRP development stage, even if they were not originally involved in the eligibility decision. The following are

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some of the services that could be provided and which could involve the utilization of modern ergonomic techniques: ■ ■ ■ ■ ■ ■ ■ ■

ergonomic assessments of houses and worksites ergonomic evaluation, adaptation and design of workstations ergonomic evaluation and redesign of work procedures ergonomic evaluation, adaptation and design of tools ergonomic evaluation and adaptation of computer hardware and software ergonomic assessment of communication needs ergonomic assessment of transportation issues, and human factors assessment of psychosocial environments.

All these techniques carry a two-fold purpose. The ultimate goal is not only to satisfy specific ergonomic requirements of the person with disabilities, but also to provide general ergonomic recommendations that are sound and could be used, if possible, by co-workers. Currently, not all these listed techniques are used equally in the vocational rehabilitation process. The following is a discussion concerning the applications that are most frequently used by the rehabilitation technology professionals working in the area of vocational rehabilitation. 6.3.2.1 Workstations for people with mobility impairments As it was noted previously, people with disabilities tend to work in less skilled occupations such as fabricators and assemblers. For people with mobility impairments, as well as for the large population of people with disabilities working in service areas, it is common to have a permanent workstation. The jobs will presumably utilize only the upper part of the body. Common characteristics for almost all workstations for people with mobility impairments are seating posture and a desk-type work surface. Some type of video data terminal (VDT) and computer hardware is a common part of this work environment. It is important for a client to have a rehabilitation technology professional to provide ergonomic recommendations for the workstation configuration. Often, it could be done at a stage when a specific job site is not yet determined, but when a general decision about available occupations and industries is made. Having data about the person’s abilities and limitations, the rehabilitation technology professional could employ several different techniques for the preliminary design of the workstation. One of the most promising methods uses computer-generated human images and elements of computer-aided design (CAD) to simulate environments for people with disabilities (Johansson et al., 1992; Eriksson et al., 1993). (See Figure 6.4.)

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Even though this technique is used to plan existing occupational environments, it could be very helpful in generating ergonomic recommendations in cases where the worksite is not determined. It would be particularly beneficial if used by a vocational rehabilitation counselor to demonstrate the client’s abilities to perform the job to a prospective employer as a part of placement efforts. There are several difficult areas in computer simulations of work environments of people with disabilities, one of which is related to the absence of reliable anthropometric data for different groups of people with disabilities, most notably those with mobility impairments. Some scientists and professionals even question the usefulness of such data because their experience shows how significant the difference is between the individuals within the group. Obtaining the anthropometric data for each client and transferring it into the codes understood by the appropriate CAD software is another problem. There also could be significant differences in the rehabilitation devices and equipment used by clients. Appropriate simulation of the rehabilitation aids should also be included. Developing the computer workstations for people with mobility impairments represents another major part of the present and future tasks of ergonomists in vocational rehabilitation. Currently, the existing standards (ANSI VDT Standard and similar) and guidelines are used in designing work environments. However, dealing with the special needs and limitations of people with mobility impairments requires some variations from long-accepted principles. For example, it is widely accepted that in a computer workstation the terminal screen should be directly in front of the operator. This position will provide a neutral posture and will reduce stress in the neck, back and eye muscles. However, this posture may not be the appropriate one if the muscles on one side are injured or there are deformities in the upper body. In that case an asymmetrical VDT positioning may be warranted. Similar situations with seating, special keyboards and other parts of the workstation are common in the practice of the rehabilitation technology professionals. Obviously, with the general computerization of work environments, the need for ergonomic assessments of computer workstations will increase in both the general population and in the population of people with disabilities. 6.3.2.2 Ergonomic issues in the private transportation of people with disabilities Compared with the public transportation of people with disabilities, which was traditionally dealt with at the federal and state levels distinct from general transportation programs, private transportation was left out of the picture. For a long time, because of the relatively small size of the market and its diversity, automotive manufacturers did not pay attention to the needs of people with

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Figure 6.4 (a) Testing the ability to reach the monitor; (b) Testing accessibility for the wheelchair. (Reprinted with permission from Eriksson et al., 1993).

disabilities. Nevertheless, a private vehicle continued to be major means of transportation for many disabled people, especially those with mobility impairments. Having a vehicle suitable for use by a disabled person was a major help in successfully obtaining and keeping the job. However, dealing with those issues was left completely to the vocational rehabilitation agencies. The vehicle modification programs originally initiated by the Veteran’s Administration was followed by the State Vocational Rehabilitation agencies. In creating the programs, the vocational rehabilitation agencies realized that by

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providing specialized vehicle modifications to eligible clients (mostly people with mobility impairments), their chances of obtaining gainful employment would be significantly enhanced. These programs became a test site for the utilization of rehabilitation technology in general and vocational rehabilitation ergonomics in particular in vocational rehabilitation. There are two types of vehicle modifications provided by vocational rehabilitation agencies: structural and non-structural. Structural modifications involve significant changes in the vehicle systems, additions and adaptations that alter most important vehicle systems: for example, body structure, braking, steering, transmission and entry-exit systems. Structural modifications are usually provided to full-size vans or mini-vans. Non-structural modifications do not involve any significant changes and are often limited to simple additions: for example, hand controls and outside wheelchair carriers. This chapter discusses structural modifications only. The scope of ergonomic problems arising from structural vehicle modifications will depend greatly on the severity of the client’s disability. Depending on the client’s ability to drive, two different sets of structural modifications could be provided. The first set of modifications, known as passenger modifications, or ‘transporters’, will make the client a passenger in the vehicle. Modifications will usually include some type of entry-exit device (for example, wheelchair lift or ramp), wheelchair tie-down, lowered floor or raised roof. If it was determined by a qualified specialist that the person could drive, in addition to passenger modifications (to transport the person if somebody else is driving), the set of ‘driver’ modifications could be provided. Driver modifications are more technically sophisticated and could include, for example, magnet-operated entry-exit systems, reduced effort braking and steering mechanisms, electric tie-down, joy-stick driving devices, head-rest mounted secondary controls, elbow-operated switches and special power seats. Figure 6.5 shows how sophisticated modern automotive adaptive equipment can be. The vehicle depicted is used for evaluation purposes and combines various types of driving equipment that should be matched exactly with the client’s abilities. Many additional considerations should be taken into account: for example, the stability of the client’s present condition, psychological factors and temperature balance. It was demonstrated, for example, that a mechanical system consisting of a person in a wheelchair has vibration characteristics which are different from those of an able-bodied person in a regular automotive seat (Blumkin, 1991). Automotive suspensions are not designed for wheelchair passengers or drivers so the comfort of the ride and sometimes even the safety of a disabled person could be significantly compromised. From Figure 6.5 it is evident that ‘driver’ modifications precipitate many questions that could be answered only by a qualified ergonomist or human factors professional. Another example of such a question could involve the wheelchair-lifts design for drivers with disabilities (Figure 6.6).

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Figure 6.5 Interior of the adapted van (courtesy of As-Tech Inc.).

The lift is controlled by the person in the wheelchair. Ergonomic analysis of the wheelchair-lift operations should take into consideration the user’s severe physical limitations. The ergonomics-based design of the lift and its control systems should include several interlocks or ‘foolproof’ features to prevent the user from the most dangerous outcome—falling off the platform. Special positioning of the switches, well-structured operation of the lift and its parts, doors and interlocking electrical circuits should be developed and installed with the disabled user requirements in mind. 6.3.2.3 Ergonomics of job placement The implementation of the Rehabilitation Act and the ADA have greatly improved the chances of people with disabilities to obtain and retain gainful and competitive employment. However, not all employers comply with the nondiscrimination and reasonable accommodation provisions of the law. According to the data from the Equal Employment Opportunity Commission (EEOC) there are more than 45000 ADA actions pending. Some 50.7 per cent of all ADA cases claimed wrongful discharge, while nearly 25 per cent of claims asserted failure to provide reasonable accommodations by the employer. Employers have already paid more than $50 million to settle ADA claims. This makes job placement both easier and more difficult. Employers are concerned about the consequences of not hiring a qualified individual with a disability, but at the same time they fear that providing reasonable accommodations will be very costly. It is here that the ergonomist’s role

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Figure 6.6 Wheelchair lift (courtesy of RICON Corporation).

becomes evident. The ergonomist working in vocational rehabilitation should be able to recommend accommodations for an applicant or employee with a disability, estimate the cost of the accommodations and assert their reasonableness. In fact, the majority of reasonable accommodations do not cost anything. Simple adjustments of the work schedule to provide for extra rest periods, and lowering or lifting up the work surface are good examples of such accommodations. In addition, reasonable accommodations could often be viewed as generally sound ergonomic or safety measures that could be successfully applied by non-disabled employees. The employer could also use a specialist in vocational rehabilitation ergonomics to help to determine the essential tasks of the job and to quantify the job requirements (Bloswick and Dumas, 1994b). For clients of vocational rehabilitation and vocational rehabilitation professionals, it is an important part of the placement process. It helps not to waste time and effort for placements that will not result in long-term rehabilitation. 6.4 Conclusions The purpose of this chapter was to introduce vocational rehabilitation ergonomics as a part of rehabilitation ergonomics science, to discuss its place in

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the vocational rehabilitation of people with disabilities, and to analyse its future applications. With the general population growth and the aging of the workforce, the population of people with work disabilities will increase. At the same time, the advancement of technology (and rehabilitation technology in particular) will make a return to work possible for more and more people with disabilities. The applications of ergonomics science should and will play a significant role in that process. Acknowledgments The author would like to acknowledge the help and support received from the Massachusetts Rehabilitation Commission and Department of Work Environment, University of Massachusetts, Lowell. Please note that the views and opinions expressed in this chapter do not necessarily represent the views and opinions of the organizations mentioned. References AMERICANS WITH DISABILITIES ACT (1990) 42 USC-12111. AMERICANS WITH DISABILITIES ACT (1990) Special report, Fulbright and Jaworski, 1991. BLOSWICK, D.S. and DUMAS, M.A. (1994a) Ergonomics and disabled/rehabilitated worker: using analytical tools to assess risk, Proceedings of the 12th Triennial Congress of the International Ergonomics association, 3, pp. 228–331, Toronto. BLOSWICK, D.S. and DUMAS, M.A. (1994b) Ergonomic implications of the Americans with Disabilities Act. Proceedings of the 12th Triennial Congress of the International Ergonomics Association, 3, pp. 293–295, Toronto. BLUMKIN, E.A. (1991) Application of the finite element method for design of seats and seating systems, Rehabilitation R&D Progress Reports, p. 461, Washington DC: Department of Veterans Affairs. BLUMKIN, E.A. (1994) Applications of occupational ergonomics in vocational rehabilitation, Proceedings of the 12th Triennial Congress of the International Ergonomics Association, 3, p. 220, Toronto. BLUMKIN, E.A. (1995) ‘Ergonomic issues in vocational rehabilitation’. RESNA Regional Conference, Mansfield, Massachusetts. BUREAU OF THE CENSUS (1989) Labour Force Status and Other Characteristics of Persons with a Work Disability, 1981–1988, Current Population Reports, Series P-23, No. 160, July, Special Studies, Washington, DC: US Department of Commerce. ERIKSSON, J. and BJERKEN, J. et al., (1993) Simulation of Physical Disabilities in Computer Design Environments, Proceedings of ECART 2, Stockholm, Sweden. ESCO OBERMAN, A. (1965) A History of Vocational Rehabilitation in America, Minneapolis: T.S. Denison & Company, Inc. HENDRICKS, D.J. and HIRSH, A.E. (1990) The job accommodation network: A vital resource for the 90s, Rehabilitation Education, 5, 261–4.

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JOHANSSON, G.I. and ERIKSSON, J et al., (1992) Computer-aided planning of working and living environments for disabled people in MATTILA, M. and KARWOWSKY, W. (Eds) Computer Applications in Ergonomics, Occupational Safety and Health, Elsevier Publishers. KRAUS, L.E. and STODDARD, S. (1991) Chartbook on Work Disability in the United States, An InfoUse Report, Washington, DC: National Institute on Disability and Rehabilitation Research. LAPLANTE, M.P. (1989) Disability risks of chronic illnesses and impairments, Disability Statistics Report No. 2, San Francisco: National Institute on Disability and Rehabilitation Research. LESLIE, J.C. (1995) Worksite accommodations—adaptation from a pragmatic perspective. Technology and Disability, 4 (2), 131–5. MATERIALS OF SENATE FLOOR DEBATES on S. 143 (1995) Workforce Development Act, October. MCQUISTION, L. (1992). Rehabilitation technology: Engineering new careers in rehabilitation, American Rehabilitation, Summer, pp. 8–35. MCQUISTION, L. (1993) Ergonomics for One, in Ergonomics and Design, The Magazine of Human Factors Applications, pp. 9–10, January. REHABILITATION ACT (1973) (as reauthorized in 1992). Public Law 102–569. REHABILITATION SERVICES ADMINISTRATION (1995) Policy Directive, RSAPD-96–02, November. SANDERS M.S. and MCCORMICK, E.J. (1987) Human Factors in Engineering and Design, McGraw-Hill, USA. SMITH, R.V. and LESLIE, J.H. Jr (1990) Rehabilitation Engineering, CRC Press, USA. SSI/DI/VR DATA REPORT, FY93/92

CHAPTER SEVEN Gait analysis: a rehabilitative interdiscipline ZIAD O.ABU-FARAJ, SAHAR HASSANI AND GERALD F.HARRIS

7.1 Introduction Human locomotion is an acquired yet complex activity requiring little thought during routine activities. Our understanding of the genesis and development of gait activity remains enigmatic despite significant advances in science and technology. Throughout history, locomotion has evoked curiosity. Analyses have been reported with tools ranging from simple visual observation to video recordings and even more sophisticated computer-based photogrammetric methods. Modern advances in the field began near the end of the nineteenth century with the development of photographic techniques. Perhaps the greatest contributions during that period came from Etienne Jules Marey, a physiologist from Paris, and Eadweard Muybridge, a photographer from the USA. (Marey, 1873, 1885; Marey and Demeny, 1987; Muybridge, 1955). In 1885, Marey utilized a photographic gun to capture displacements of the trunk and limbs during human walking. He also employed a chronophotographic apparatus to obtain a stick diagram of a runner (Winter, 1990a). Muybridge later conducted a series of experiments to monitor locomotor patterns in humans and animals. In one of his experiments, he recorded the patterns of a running individual by employing a chain of 24 stationary cameras positioned side-by-side and mechanically triggered in sequence (Winter, 1990a; Shepherd, 1988a). Today, the multiple still cameras of Marey have been replaced with video cameras. We are now also able to quantitatively evaluate human motion in three dimensions with significant accuracy. Modern technology allows the analysis of joint angles, angular velocities and angular accelerations (kinematic analysis); ground reaction forces, joint forces, moments and powers (kinetic analysis), and electromyographic activity. Energy consumption is also monitored during ambulatory testing in some laboratories. Gait analysis has demonstrated the efficacy for pre-treatment evaluation, surgical decision making, post-operative follow-up and the management of both adult and pediatric patients. For instance, surgical treatment for children with cerebral palsy has advanced from the days of isolated procedures to the present

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more comprehensive multilevel approach (DeLuca, 1991). Gait analysis has also proved useful in understanding neuromuscular disorders (Sutherland, 1990; Olney et al., 1991; Wagenaar and Beek, 1992), assessing prosthetic joint replacement (Collopy et al., 1977; Rittman et al., 1981; Murray et al., 1983; Olsson, 1986; Berman et al., 1987, 1991; Wykman and Olsson, 1992) and studying sports injuries (Andriacchi and Mikosz, 1991; Jacobs and Schernu, 1992), amputation (Waters et al., 1976; Skinner and Effeney, 1985; Gitter et al., 1991; Colborne et al., 1992), orthotics (Lehmann et al., 1986, 1987; Brodke et al., 1989) and assistive devices (Logan et al., 1990). This chapter describes the temporal and dynamic characteristics of the human gait cycle. The physiological and electromyographical principles responsible for appropriate gait activity are also addressed. Finally, techniques used to determine these characteristics are presented. 7.2 The gait cycle The gait cycle is often defined as the period between the initial contact of the foot and subsequent foot contact, Figure 7.1. The gait cycle is divided into stance and swing phases. Stance phase is that portion of the cycle when the foot is in contact with the ground. Typically, stance represents about 60 per cent of the total normal adult walking gait cycle (Vaughan et al., 1992a; Perry, 1992b; Gage, 1991a). Swing phase, on the other hand, is that portion of the gait cycle when the foot is not in contact with the ground and the leg is ‘swinging through in preparation for the next foot strike’ (Vaughan et al., 1992a). The swing phase typically occupies about 40 per cent of the gait cycle. The gait cycle is also characterized by eight events (Figure 7.1). Stance begins at initial contact (IC) when the foot touches the ground. When this initial contact is made with the heel, the event is referred to as heel strike or heel contact (in individuals with pathology, heel contact may not occur). During initial contact, the body center of mass (COM) is at its lowest position and the leg is positioned to begin stance with the first foot rocker (heel rocker) (Gage, 1991a; Perry, 1992c). Loading response (LR) is the period of initial double support defined from IC (0 per cent) to 10 per cent of the gait cycle (Perry, 1992b; Gage, 1991a). During loading response, the limb acts as a shock absorber with resulting knee flexion coincident with load acceptance and deceleration. Weight acceptance is defined as the period from IC through LR. It is during weight acceptance that the leg provides shock absorption, weight-bearing stability and control of forward progression (Perry, 1992b; Gage, 1991a; Õunpuu, 1994). Single-limb support is defined as the period from mid-stance (MST) through terminal stance (TST). During this period the contralateral limb is in swing phase. Mid-stance is the period immediately following the loading response. It covers the first half of single-limb support from 10 to 30 per cent of the overall gait cycle (Perry, 1992b; Gage, 1991a; Õunpuu, 1994). Mid-stance is defined

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Figure 7.1 The gait cycle and eight events: initial contact (IC); load response (LR); midstance (MST), terminal stance (TST); pre-swing (PS); initial swing (ISW); mid-swing (MSW); terminal swing (TSW).

from the time the contralateral foot clears the ground (initiation of opposite limb swing phase) to the instant when the body COM is decelerating as it passes over the stance limb forefoot. Mid-stance corresponds to the second foot rocker (ankle rocker) as the ankle dorsiflexes (Gage, 1991a; Perry, 1992c). Terminal stance constitutes the second half of the single limb support phase, which occupies 30 to 50 per cent of the overall gait cycle (Perry, 1992b; Gage, 1991a; Õunpuu, 1994). This event corresponds to the third rocker (forefoot rocker) (Gage, 1991a; Perry, 1992c). Terminal stance is initiated at the time of heel rise and continues until the contralateral limb contacts the ground. During this event the body COM leads the forefoot and accelerates as it is falling forward towards the unsupported limb. The three rockers (heel, ankle and forefoot) serve to control the forward fall of the body during normal ambulation. The last event of stance is known as pre-swing (PS) which is a prelude to limb advancement. Pre-swing is the final period of double-limb support, occurring from about 50 to 60 per cent of the gait cycle (Perry, 1992b). This period is initiated by initial contact of the contralateral limb and ends at terminal contact of the ipsilateral (stance) limb (Perry, 1992b; Gage, 1991a; Õunpuu, 1994). Terminal contact (TC) occurs just as the stance foot clears the ground. This period concludes the stance phase and initiates the swing phase. Usually, the great toe (hallux) is the last foot segment to clear the ground prior to swing. This final stance phase event is also termed ‘toe off. Swing phase, also known as limb advancement (Perry, 1992c), constitutes the last phase of the gait cycle. During this phase, the swinging limb acts as a ‘compound pendulum’, the period of which is governed by the mass moment of inertia (Gage, 1991; Hicks et al., 1985; Tashman et al., 1985). Variations in gait cadence are highly dependent on one’s ability to alter the period of this pendulum. In fact, three events have been identified as responsible for controlling the pendulum swing period: initial swing (ISW), mid-swing (MSW)

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Figure 7.2 The gait cycle and subcomponents.

and terminal swing (TSW). Initial swing is a period of acceleration or deceleration occurring at 60 to 73 per cent of the overall gait cycle and usually occupying one-third of swing phase (Perry, 1992b; Õunpuu, 1994). This event begins from toe-off and continues to a position where the swinging limb is aligned with the contralateral limb. Mid-swing is a transitional period covering the middle third of the swing phase from 73 to 87 per cent of the overall gait cycle (Perry, 1992b; Õunpuu, 1994). This event is initiated when the swinging limb is aligned with the contralateral limb and is terminated when the swinging limb is forward of the stance limb and the tibial shaft is vertical. Terminal swing constitutes the last third of the swing phase. It occurs from 87 to 100 per cent of the overall gait cycle, and is initiated with vertical tibial alignment continuing until IC (Perry, 1992b; Gage, 1991a; Õunpuu, 1994). Figure 7.2 illustrates the gait cycle and its subcomponents. Normal stance phase is also characterized by three foot rockers: heel, ankle and forefoot (Figure 7.3). The first foot rocker (heel rocker) is produced as the heel contacts the floor and the foot plantarflexes into full ground contact. During IC, the heel rocker acts as an unstable lever system, since foot-to-ground contact is made at a single point causing the foot to rotate forward. The heel rocker also acts as a shock absorber which tends to decelerate the foot at IC (Gage, 1991a; Perry, 1992c). The second foot rocker (ankle rocker) is initiated during foot flat. During this period with full foot-to-ground contact, momentum forces the tibia to rotate forward, causing ankle dorsiflexion (Gage, 1991a; Perry, 1992c). The third rocker (forefoot rocker) occurs at the end of MST and early TST as the body center of pressure (COP) approaches the metatarsal heads and the heel begins to elevate. During this period, the joints of the metatarsal heads simulate a pivoted hinge which functions as a rocker for the forward fall (Gage, 1991a; Perry, 1992a). This forward fall is caused as the body COM leads the COP. The forefoot

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Figure 7.3 The three foot rockers: heel (first) rocker, ankle (second) rocker and forefoot (third) rocker.

rocker (third rocker) serves as an acceleration rocker to prepare for limb advancement in PS. 7.3 Temporal gait parameters The gait cycle is also described by the temporal parameters: step length, step period, stride length, speed, cadence, natural cadence and stance-to-swing ratio. Step length, expressed in meters, is the distance from IC to contralateral IC. Step period, expressed in seconds, is the elapsed time associated with the step length. Stride length, expressed in meters, is the distance between IC and subsequent ipsilateral IC. In symmetrical gait, stride length is equal to twice the step length. Speed, commonly expressed in meters per second, is the rate of change of linear displacement along the predefined direction of progression per unit time. Cadence, expressed in steps per minute, is defined as the rate at which an individual ambulates. Natural cadence, also expressed in steps per minute, is defined as the rate at which an individual ambulates at a self-selected comfortable speed. Stance-to-swing ratio is the stance interval divided by the swing interval (Õunpuu, 1994; Sutherland et al., 1988a; Perry, 1992; Gage, 1991b). These parameters are the most common temporal measures used during gait analysis, and are often helpful when diagnosing pathological conditions (Gage, 1991b). Temporal gait parameters alone, however, rarely provide sufficient insight into the origin of gait abnormalities. Under these circumstances, more quantitative measures are required.

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7.4 Anatomic terminology In motion analysis studies, it is often necessary to describe body position in directional and functional terms. This section reviews the descriptive terminology regarding standard anatomic terminology, directional terms and motion analysis parameters (Vaughan et al., 1992a; Õunpuu, 1994; Thompson, 1977; Hay and Reid, 1982; Inman et al., 1981; Harris and Wertsch, 1994). In the standard anatomical position, the subject is standing erect with the head facing forward, the arms held by the side, the heels joined together and the feet forward so that the great toes make contact. Human locomotion occurs in all three anatomical planes, the sagittal, coronal and transverse. These planes are typically referenced to the human body in the standard anatomical position (Figure 7.4). The positions of the body or body segments in these planes are often described in terms of directional expressions. Anterior (ventral) is the direction pointing towards the front of the body or body segment. Posterior (dorsal) is the direction pointing towards the back of the body or body segment. Superior (cephalic) is the direction pointing towards the head, it also refers to the upper part of a structure. Inferior (caudal) is the direction pointing towards the toes (away from the head), it also refers to the bottom part of a structure. Medial is the direction pointing towards the mid-sagittal plane of the body or midline of a structure. Lateral is the direction that points away from the mid-sagittal plane of the body or midline of a structure. Proximal is the direction closer to the attachment of an extremity or limb. Distal is the direction farther away from the attachment of an extremity or limb. The sagittal plane is the plane that divides the body or body part into right and left segments. The mid-sagittal plane, also termed the median plane, is a vertical plane that divides the human body exactly into left and right halves. The coronal (frontal) plane is any vertical plane orthogonal to the sagittal plane. The coronal plane is also defined as the plane that divides the body or body part into anterior (ventral) and posterior (dorsal) segments. The transverse plane is any plane orthogonal to both the sagittal and coronal planes. The transverse plane divides the body into superior and inferior segments. Motion analysis requires that the movements of the body or body segments in the three anatomical planes be accurately described. Abduction is defined as the action of moving a body segment away from the midline, or long axis, of the body in the coronal plane. Adduction is described as the gesture of bringing the body segment back towards the midline of the body. Flexion is described as the action which decreases the angle formed between two articulating bones, while extension is described as the action which increases that angle. Usually, flexionextension motions occur in the sagittal plane. Plantarflexion is described as the excursion of the foot in the sagittal plane away from the anterior tibia. Dorsiflexion is the excursion of the foot in the sagittal plane towards the anterior tibia. Inversion of the foot refers to the sole of the foot turning towards the mid-

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Figure 7.4 The standard anatomic position and the three anatomical planes: sagittal, coronal and transverse.

sagittal plane of the body, while eversion of the foot is the opposite motion. Varus is defined as the medial angulation posture of the distal segment of a joint, while valgus is defined as the lateral angulation posture of the distal segment of a joint. 7.5 Kinematics Kinematics is the branch of engineering mechanics in which the motion of bodies is described without regard for the underlying forces (Gage, 1991a; Woltring et al., 1985). A major focus of kinematics is the study of the relative movement between body segments, frequently depicted as rigid links. Kinematic parameters include measures of diarthrodial joint angles, displacements, velocities and accelerations. In most clinical gait analysis laboratories, kinematic data are commonly represented in the sagittal, coronal and transverse planes at the pelvis, hip, knee and ankle joints. The patient data and normal control data are usually presented together allowing analysis of the temporal and stride events

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Figure 7.5 Example of kinematic pattern data. The solid curves represent the patient’s motion and the dashed curves represent the mean motion of the laboratory normal sample group. The vertical lines separate stance phase from swing phase; initial contact occurs at 0 per cent of the gait cycle.

(foot contact, foot off, swing, stride length, stride time, cadence and walking speed) and the kinematic patterns (Figure 7.5). Each anatomical plane generally depicts several distinct kinematic measures. In the sagittal plane, joint angular motions include pelvic tilt, hip flexion/ extension, knee flexion/extension and ankle plantar/dorsiflexion. In the coronal plane, joint angular motions consist of pelvic obliquity, hip abduction/adduction and knee valgus/varus. Transverse plane joint angular motions include pelvic rotation, hip rotation, tibial rotation, foot rotation and foot progression. However, joint angle depictions may vary with different systems and are highly dependent on the marker arrangement and the biomechanical models utilized (Õunpuu, 1994). In general, markers are placed over predefined anatomical landmarks, such as joint centers, segment centers and bony prominences. Figure 7.6 illustrates joint motion in the Figure 7.6 (Continued) three anatomical planes. Kinematic data have been used extensively in the analysis of gait disorders, and while extremely useful, it should be noted that there are additional parametric measures also available. Kinematic data do not include information on

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Figure 7.6 Types of motion in the three anatomical planes: (a) sagittal plane motion: hip flexion/extension, knee flexion/extension and ankle plantar/dorsiflexion; (b) coronal plane motion: pelvic obliquity, hip abduction/adduction, knee valgus/varus and hindfoot valgus/ varus and (c) transverse plane motions viewed from superior to inferior: pelvic internal/ external rotation, knee internal/external rotation, foot internal/external progression angle and foot internal/external rotation. (For parts (b) and (c) see pages 174 and 175.)

biomechanical efficiency (oxygen consumption and oxygen cost), ground reaction forces, joint moments or joint powers. This is of concern because an ambulatory individual can present stable kinematic patterns, yet reveal considerable variability in kinetic patterns (Winter, 1984). According to Gage, kinematic gait analysis of an individual with cerebral palsy may not uncover compensatory coping responses (Gage, 1991a).

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7.6 Ground reaction forces Ground reaction forces (GRFs) are traditionally measured with force plate dynamometers. Alternatively, GRFs can be measured with pressure sensitive insole systems, such as the Electrodynogram (EDG, Langer Biomechanics Group, New York, NY), the EMED system (Novel Electronics Incorporated, Minneapolis, MN) and the F-Scan system (Tekscan, Boston, MA). Force platform studies normally Figure 7.6 (Continued) illustrate barefoot, isolated steps, while insole systems allow investigation of ongoing step-to-step alterations. Force plate dynamometers typically employ strain gauge or piezoelectric transducers, such as the AMTI force plate (Advanced Mechanical Technology Incorporated, Newton, MA) and the Kistler force plate (Kistler Instrument Corporation, Amherst, NY). Processing of force platform output can provide GRF vector components including vertical load, anterior-posterior and

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medial-lateral shear loads, moments about the vertical axis and location of the body center of pressure (COP). The vertical load pattern in normal individuals walking at their natural cadence follows an ‘M’ shaped curve with peaks typically reaching 110 per cent of body weight (Winter, 1990b; Sutherland et al., 1988b). Sutherland et al. reported that children demonstrate somewhat lower average vertical and shear peak forces as compared with adults (Sutherland et al., 1988). The vertical load curve is highly sensitive to any action or reaction which perturbs the ground reaction vector, for example, the gesture of arm lifting which can diminish the peak component to less than body weight (Charnley and Pusso, 1968). Additionally, both shear and COP measurements are influenced by the position and movement of all body segments, including the head, arms, trunk, pelvis and legs. It has also been reported that disturbances such as pain, weakness and unilateral hip pathology alter the vertical force pattern (Charnley and Pusso, 1968). Variations in cadence influence the magnitude and duration of

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the vertical load curve and have a direct effect on the gradient of the ‘M’ curve, which indicates the rate of limb loading (Crowinshield et al., 1978; Mann and Hagy, 1980; Skinner, 1981; Soames and Richardson, 1978). 7.7 Kinetics Kinetics is the branch of engineering mechanics in which motion is studied with regard for the underlying forces responsible. These forces include external and internal forces. The study of human motion analysis is governed by the application of Newton’s three laws. The first of these is the law of inertia. Every body persists in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed on it. (Resnik and Halliday, 1966) The second law states that the change in velocity is proportional to the force: F=ma (Resnik and Halliday, 1966). The third law states that: to every action there is always opposed an equal reaction; in other words, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts. (Resnik and Halliday, 1966) In application if the motion of the body segments are determined from a kinematic analysis and force data are collected from a force platform, then the joint reaction forces and moments responsible can be determined. At each joint a state of equilibrium exists such that the internal joint reaction forces and moments balance the externally applied forces (Seireg and Arvikar, 1975). Moments are usually normal-ized to body weight and leg length, and are expressed as a per cent of body weight times leg length (Andriacchi and Mikosz, 1991). Joint power can also be computed once the moment, joint angles and angular velocities are determined (Winter, 1990c). Thus, in addition to the kinematic data, gait analysis can provide kinetic information including hip, knee and ankle joint moments and powers, see Figure 7.7. This additional information may be useful in examining specific pathologic conditions and surgical procedures designed to restore normal mechanics. Moment analysis has proved useful in providing insight into subtle functional adaptations such as the increased flexion moment observed at the hip and knee in the anterior cruciate ligament-deficient patient (Andriacchi et al., 1985). Preoperative knee adductor moments have been recommended as predictors of post-operative clinical results from high tibial osteotomy (Prodomos et al., 1985). Joint moments can also be useful for clinical decision making in cerebral palsy (Lai et al., 1988). It is also important to realize the sources of error in kinetic gait models. These include any kinematic errors, any errors in GRF measurement and errors in

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Figure 7.7 Example of kinetic data. The four rows represent: sagittal plane internal joint moments; coronal plane internal joint moments; transverse plane internal joint moments and total joint power. The three columns represent: hip, knee and ankle joint data. The solid curves represent the patient’s results and the dashed curves represent the mean results of the laboratory normal sample group. The vertical lines separate stance phase from swing phase. Initial contact occurs at 0 per cent of the gait cycle.

estimates of anthropometric characteristics (segment length, segment mass, center of mass, joint centers and mass moments of inertia). The anthropometric data are usually based upon the height, weight and sometimes gender of the individual (Hinrichs, 1985). Mathematical techniques used in the biomechanical gait models may also vary somewhat between facilities.

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7.8 Physiology and human gait 7.8.1 Neural control—central and peripheral Human walking is a complex behavior regulated by the nervous system which is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and the spinal cord, while the PNS is comprised of nerves projecting from the brain and spinal cord to peripheral organs such as muscles, skin and visceral organs (Vander et al., 1990a). The central and peripheral nervous systems interact in an efficient manner to coordinate muscle movement. The human nervous system is comprised of one trillion (1012) neurons, without consideration of the glial cell population, which outnumbers neurons by approximately 10:1 to 50:1 (Ganong, 1993). Neurons are segregated into three types: afferent neurons, efferent neurons and interneurons (Ganong, 1993). The afferent neurons are primarily responsible for transmitting information from the PNS to the CNS. In the PNS, sensory stimulation, such as an increase in muscle tension, is detected by receptors located at the end of the afferent neuron. Information is relayed from the afferent neurons to the brain and spinal cord for integration, fine-tuning and feedback responses. The function of the efferent neurons is to transmit commands from the CNS to the PNS. For muscle contractions to occur, efferent motor neurons (alpha motor neurons) relay commands from the brain and spinal cord to targeted muscles. The interneurons, located within the CNS, are responsible for transferring information between the afferent and efferent neurons, and to neighboring interneurons. Under the command of higher brain centers (motor cortex, basal ganglia, thalamus, cerebellum), interneurons can turn movements on or off (Vander et al., 1990a; Ganong, 1993; Shepherd, 1986). The neural pathways underlying the functional basis of human movement are depicted in Figure 7.8 Although the size and structure of a neuron is correlated with its function, a neuron is generally composed of the following: a cell body (soma) containing the nucleus, a single or multiple dendritic arborization, an axon and axonal terminals (Figure 7.9). Dendrites and somas receive and integrate one or more signals from neighboring neurons and are present in efferent neurons and interneurons. The axon is a process, which emanates from the soma and transfers information from the dendrites and soma towards other neurons and effector cells, such as muscle fibers. The axonal terminal is formed by the collateral branching of the axon. Chemical messengers, known as neurotransmitters, are stored in vesicles embedded in the axonal terminal and are released during excitation. The neurotransmitters are released into the gap, termed synaptic gap or cleft, formed by neighboring neurons (Ganong, 1993; Guyton, 1984; Angevine, 1986). Information in the nervous system is coded by changes in the electrical activity of the neuron. The resting membrane potential of a neuron is the

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Figure 7.8 The neural pathways critical to human movement.

potential difference across the cell (plasma) membrane, such that the inside is more electro-negative than the outside. The resting membrane potential ranges from −40 to −75 mV (Vander et al., 1990a). In response to a neurotransmitter or a stimulus, ion permeability in the plasma membrane is altered, thereby causing the generation of an electrical current across the plasma membrane. If a net excess of positive ions enter the membrane, the membrane becomes depolarized. On the other hand, if an influx of negative ions causes the membrane potential to become more negative than the resting level, the membrane becomes hyperpolarized. In order for nerves and muscles to communicate with each other, an action potential (AP) must be initiated. The AP is an all-or-nothing phenomenon produced by the depolarizing cell reaching its threshold potential— typically the membrane must be depolarized by at least 15 mV from the resting membrane potential (Vander et al., 1990a). Once an AP is generated, adjacent

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Figure 7.9 Motor neuron anatomy.

areas of the cell membrane also become stimulated, allowing the AP to propagate down the axon and into the axon terminals. Upon reaching the axonal terminal, the AP causes the release of neurotransmitters into the synaptic cleft, which bind to receptors on the neighboring membrane (post-synaptic cell). Depending on the type of receptor and neurotransmitter, this effect may be excitatory (depolarization) or inhibitory (hyperpolarization) (Vander et al., 1990a; Johnson, 1992a; Rab, 1994; Wolfe, 1993). Activation and inhibition of neurons allows the nervous system to control muscle activity during walking. For example, activation of the hip flexors (iliacus, rectus femoris, sartorius) and inhibition of the hip extensors (gluteus maximus, semitendinosus, semimembranosus) of a limb, allows the same leg to step forward. Voluntary motor movement is controlled by a hierarchy within the CNS with the cerebral cortex at the highest level and the spinal cord at the lowest level

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(Figure 7.10). The cerebral cortex receives and integrates information from the basal ganglia, thalamus, cerebellum, striatum and amygdala (Johnson, 1992b). The motor cortex executes its commands for motor activity to lower levels of motor control through the routes created by both pyramidal/corticospinal and extrapyramidal tracts. The pyramidal tract is composed of nerves that transmit commands from the motor cortex to the spinal cord in order to generate discrete movements of skeletal muscle activity. The extrapyramidal nerve tracts consist of nerves originating in the basal ganglia, reticular formation, cerebellum and mid-brain to control posture and fine-tune neuromuscular activity. Nerves that originate in the cerebellum form the vestibulospinal tract. The cerebellum evaluates, integrates and compares input data from diverse areas such as the cortex, muscles, tendons, skin and end organs (auditory, visual and vestibular). It then projects its commands to the vestibulospinal tract to maintain balance and posture. The basal ganglia receive input from the cortex and provide coordination of movement at both the conscious and subconscious levels. This process is achieved by the descending pathways to other regions of the brain and spinal cord. The reticulospinal tract originates in the reticular formation and is responsible for conveying information to the spinal cord for control of muscle activity. These extrapyramidal nerves provide interconnections between the spinal cord, cerebral cortex, basal ganglia and cerebellum, forming a complex feedback system that regulates muscle movement (McArdle et al., 1991a; Gage, 1991c; Shepherd, 1988c). The spinal cord represents the lowest level of motor control. Peripheral nerves enter on the dorsal side of the spinal cord while efferent neurons exit the cord on the ventral side. The spinal cord consists of both the gray matter and white matter. The gray matter is composed of interneurons, cell bodies and dendrites of efferent neurons and the in-coming afferent neurons fibers. The white matter is composed of myelinated axons of the interneurons (Vander et al., 1990a). Within the spinal cord, groups of neurons alternate between excitation and inhibition to generate stereo-typed movements—these neurons are known as central pattern generators. Local pattern generators control muscle movement for different areas of the body and produce programmed movements such as rhythmical motions of the limb (Gage, 1991c; Vander et al., 1990b). The spinal central pattern generator relies on afferent input from the higher brain levels as well as from sensory organs to provide optimal control of locomotion. 7.8.2 Skeletal muscle and the motor neuron To fully comprehend the nervous system’s ability to control locomotion, a basic understanding of the structure of skeletal muscle and the mechanism for muscle contraction is needed. Skeletal muscle consists of thousands of multinucleated muscle fibers, which run parallel to one another. The muscle fibers are comprised of substructures called myofibrils ranging from a few hundred to

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Figure 7.10 Hierarchy of motor control within the central nervous system.

several thousand. Each myofibril is composed of a series of joined sarcomeres (organized actin and myosin filaments), which serve as the functioning unit for muscle contraction (Rab, 1994; Guyton and Hall, 1996a). Each fiber is separated by a layer of connective tissue called endomysium. As many as 150 fibers are grouped together by another connective tissue called the perimysium. The entire skeletal muscle is enclosed by a fibrous connective tissue called epimysium. The tendon constitutes the final element of this organization, and is comprised of strong connective tissues which link the skeletal muscle to the bone (McArdle et al., 1991b). The structural organization of skeletal muscle is depicted in Figure 7.11. A single motor neuron and the muscle fibers it innervates is termed a motor unit. A motor unit may contain as many as 2000 to 3000 muscle fibers, but each

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Figure 7.11 The structural organization of skeletal muscle.

muscle fiber is controlled by one motor neuron (McArdle et al., 1991a). The axon of the motor neuron sprouts into multiple branches constituting the axonal terminal. These terminals spread out into grooves on the surface of the muscle fiber. Excitation of the motor neuron results in the release of chemical messengers (acetylcholine, ACh) from the axon terminal into the neuromuscular junction (the space between the axonal terminal and muscle fiber plasma membrane). The binding of acetylcholine to its receptor site on the fiber plasma membrane (motor end plate) results in the generation of an AP along the muscle fiber. Excitation of this fiber results in the release of calcium from the sarcoplasmic reticulum. This allows myosin to bind to the actin and slide the actin towards the center of the sarcomere, causing the muscle fiber to shorten (Vander et al., 1990c). Once the calcium ions are pumped back into the

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sarcoplasmic reticulum, actin is released from myosin, causing the muscle to relax. Coordination of movement is dependent on information from muscles, tendons and skin. Muscle length and the rate at which muscle length is changed are detected by muscle spindle stretch receptors. These receptors are located at the end of the afferent nerve fiber of the muscle spindle and are positioned within the muscle. When an external force is applied, the muscle stretches and pulls on the spindle fibers, thus activating the stretch receptors. The strength of the stretch is proportional to the rate at which the receptors fire. The stimulation of stretch receptors provides feedback to the brain and spinal cord, resulting in the contraction of the same skeletal muscle (Guyton and Hall, 1996b). Muscle tension is monitored by the Golgi tendon organs, located in the tendon at the point of muscle insertion. Contraction of the muscle stimulates the Golgi tendon, resulting in inhibition of the agonist muscle to promote activity of the antagonistic muscle. There are several types of skin receptors which respond to various stimuli such as pressure, temperature and pain. These are specialized receptors responsible for transmitting information to the CNS about alterations in the surrounding environment. For instance, a painful stimulus can evoke a limb withdrawal. The information gathered from the sensory receptors is integrated, processed and executed by the CNS (Gage, 1991c; Vander et al., 1990b). There are four different pathways in the CNS that process information from the sensory organs (muscle, tendons, skin). The first pathway is known as the monosynaptic reflex and provides a direct link between the afferent and efferent motor neurons in the spinal cord, eliciting a muscle contraction. For example, the knee-jerk response caused by a tendon tap stimulates the stretch receptors in the thigh. As a result the afferent nerve fibers transmit information to the motor neurons in the thigh muscles. When this information is received, the motor units are in turn excited and cause the thigh muscle to contract producing a jerk reaction (Johnson, 1992b; Gage, 1991c). A second pathway, responsible for reciprocal inhibition, is innervated by the afferent nerve fibers to initially activate the interneurons, which in turn inhibit the motor neurons in the antagonistic muscles. A third route is also formed by the afferent nerve fibers, and tends to activate the interneurons of synergistic muscles, thus assisting the intended motion. In the final path, the communication between the afferent neurons and the cerebral cortex is established through the path created by the interneurons. Optimal control of human locomotion is dependent on the integrative role of these four neural pathways and signal processing by the CNS (Vander et al., 1990a). Often pathological conditions involving the neuromuscular system present deviations from normal muscular activities. These deviations can frequently be assessed through techniques which employ electromyographic principles.

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7.9 Electromyography Dynamic or kinesiologic electromyography provides details about the timing of muscle activity and the relative intensity of the muscle activity. Both surface electrodes and fine wire electrodes have been utilized for gait electromyography (EMG) analysis. Surface electrode data are more repeatable than fine wire data (Kadaba et al., 1985), although surface electrodes detect fewer discrete phases of muscle action (Lyons et al., 1993; Yang and Winter, 1985). Surface electrodes detect group muscle actions; whereas, wire electrodes are used when the identification of the activity of specific and deep muscles is required (Perry et al., 1981; DeLuca and Merletti, 1988). Signals picked up from neighboring muscles (muscle cross-talk) can be observed with both surface and wire electrodes. However, the spectral content of the signal recorded with the fine wire electrode allows the filtering of some of the lower frequency volume conducted signals and thus allows reduction of muscle cross-talk. Koh and Grabiner (1992) described a double differential technique to reduce crosstalk in surface EMGs. Current commercial electromyographic systems are available in either cable or telemetry designs or a combination of both. Cable systems are reliable and less expensive than telemetry; however, they can encumber the subject with multiple tethers. Radio telemetry is vulnerable to electromagnetic interference and can require more frequent technical service. New combined cable telemetry that sends multiple signals on a single cable is available and offers the advantages of both systems. The information being analysed is the interference pattern with the EMG being considered to be ‘on’ when at least 5 per cent of the maximal recording obtained during a manual muscle test is recorded (Perry, 1992a). Other normalization schemes may use amplitude criteria based on the maximum or mean level of the EMG signal obtained during gait, or with a known force level. Automated methods for determining the onset and cessation of gait EMG have been reported (Bogey et al., 1992). The raw EMG signal can be analysed or processed. A higher sampling rate is required to accurately acquire raw EMG signals. The most common methods of EMG signal processing are full wave rectification, linear envelope or moving average and integration of the full wave rectified EMG (Figure 7.12). The linear envelope is created by filtering a full-wave rectified signal with a low pass filter. The linear envelope is useful to assess on/off activity but clonus bursts of muscle activity may not be seen (Gage, 1992a). Use of the term ‘integrated EMG’ for the linear envelope is discouraged to avoid confusion with mathematical integration of the signal (Winter, 1990a). Many variables influence the recorded EMG signal such as magnitude of tension, velocity of shortening, velocity of lengthening, rate of tension build-up, fatigue and reflex activity (Winter, 1990a). The relationship between the EMG signal and the force generated has been studied extensively (Inman et al., 1952; Bigland and Lippold, 1954; Close et al., 1960; Bouisset, 1972; Milner-Brown

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and Stein, 1975; Weir et al., 1992) but needs to be interpreted with caution in gait. It should be appreciated that although gait EMG can give information on when a muscle is active and can show a relative increase in activity, dynamic EMG does not tell us about the strength of the muscle, whether the muscle is under voluntary control or whether the contraction is isometric, concentric or eccentric (Gage, 1992). There can be constant change throughout the gait cycle in multiple factors known to affect the relationship between the EMG signal and the force generated, such as the joint angle, muscle fiber length and type of contraction (isometric, eccentric, concentric). Symmetry of gait EMG should not be assumed (Õunpuu and Winter, 1989). There are also reported shifts in the spectral content of EMG signals with fatigue (Lindstrom et al., 1970; BiglandRitchie, 1981; Bigland-Ritchie et al., 1983; Moritani et al., 1985). It is important to realize that spectral shift may affect the EMG signal amplitude. DeLuca (1979) has shown that fatigue has been noted to decrease the amplitude of the EMG signal obtained with wire electrodes but increase the amplitude of the EMG signal obtained with surface electrodes. Seven types of muscle-timing errors in gait have been defined: premature, prolonged, continuous, curtailed, delayed, absent or out of phase (Perry, 1992a; Bekey et al., 1977). The premature or prolonged timing abnormalities may represent the pathokinesiology of the muscle or may reflect an adaptive firing needed because of kinematic abnormality. Curtailed, delayed or absent and out of phase are all timing errors that may represent adaptive patterns. Continuous muscle activity is always abnormal. In cerebral palsy the dynamic EMG is useful in the preoperative evaluation of equinus and hip deformities (Perry et al., 1960, 1976, 1977) and in the analysis of rhizotomy results (Cahan et al., 1990; Vaughan et al., 1991). Dynamic EMG in conjunction with kinematic analysis plays an important role in evaluating gait in cerebral palsy individuals. The dynamic EMG signal is analysed to identify whether the rectus femoris is firing continuously during swing phase. Posterior transfer of the distal rectus femoris has been found useful to augment knee flexion during swing in some individuals (Gage et al., 1987). Overall indications for rectus femoris transfer include a positive Duncan-Ely test, dynamic EMG evidence of prolonged swing phase rectus femoris activity and the reduction of swing phase knee motion by at least 20 per cent (Gage, 1991a, 1992b). Analysis of dynamic EMG timing is also important in evaluating ankle valgus/varus deformities, although there is controversy regarding the role of dynamic EMG in posterior tibialis surgical procedures in cerebral palsy (Milner-Brown and Stein, 1975; Perry et al., 1977; Barnes and Herring, 1991).

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Figure 7.12 Dynamic electromyographic data. The first row represents a typical raw EMG data recorded with bipolar electrodes. The second row represents a full-wave rectification (absolute value) of the raw EMG signal. The third and fourth rows represent the result of linear envelope (moving average) and integrated processing of the rectified EMG signal, respectively. (Reproduced with permission, Archives of Physical Medicine and Rehabilitation, 75, 216–25, 1994.)

7.10 Gait analysis system methodology 7.10.1 Cine with manual digitization In the early days, gait analysis systems utilized motion picture or cine technology to film real-time events for analysis. Markers, such as wooden wands, affixed to pelvic and tibial belts, were utilized to simplify identification of body-segment motion. With markers mounted over anatomical landmarks, manual digitization of marker locations on a frame-to-frame basis allowed quantitative identification of marker positions in two dimensions (2D) with respect to the focal plane of the camera. Identification of marker positions in three dimensions (3D) is possible, but requires the use of two or more cameras. Nevertheless, the major drawback of cine analysis and manual digitization is the overwhelming processing time required for data digitization and the need for extensive operator training (Sutherland, 1984).

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7.10.2 Electrogoniometers An electrogoniometer is an apparatus consisting of two rigid links coupled by a potentiometer that measures the interposed angle. Electrogoniometers can be employed in either 2D or 3D joint motion measurement (Lamoreux, 1971; Chao, 1980). In application, the rigid links are strapped to a proximal and distal limb segment while the electrical output of the potentiometer is used for joint angle monitoring. Design refinements have enabled the use of electrogoniometers with a parallelogram structure in extremely difficult applications. Such applications include knee joint motion, where the instant center of rotation is continuously changing and cannot be accurately modelled as a simple hinge. Additionally, modifications to the basic electrogoniometer design have allowed its clinical use with orthotics and prosthetics (Zuniga et al., 1972; Hannah and Morrison, 1984). In spite of the simple operation and direct data measurement, electrogoniometric systems are difficult to apply, measure only relative joint angles and can encumber a small subject (Gage and Õunpuu, 1989). 7.10.3 Video technology Currently, in a typical clinical setting, the use of a relatively inexpensive single video camera can provide refinement to observational gait analysis. Features such as slow-motion replay and freeze frame are available on many video cassette recorders (VCRs). These features allow significant improvement over unaided visual observation. Further, sagittal and coronal plane motion can be observed concurrently with the use of a screen splitter and several cameras. Computerized systems utilizing multicamera video information are needed to provide 3D motion analysis: Expert Vision (Motion Analysis Corporation, Santa Rosa, CA), Optotrak (Northern Digital Incorporated, Waterloo, Ontario, Canada), Peak Performance (Peak Performance Technologies Incorporated, Englewood, CO), Selspot (Selective Electronics Incorporated, Southfield, MI), Vicon (Oxford Metrics Limited, Oxford, England), Watsmart (Northern Digital Incorporated, Waterloo, Ontario, Canada) and others. 7.10.4 Automated motion tracking systems Automated tracking (photogrammetric) systems offer the most sophisticated method for human motion analysis. With these systems, either passive (retro) reflective or actively illuminated (optoelectric) markers are tracked by an automated multicamera system. Active marker systems provide higher sampling rates (200–300 Hz), an increased number of markers and frequency-coded data sorting. However, active markers require that the subject carry a power pack or

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tether. In these systems light emitting diodes (LEDs) are pulsed at a predetermined frequency. Passive markers, on the other hand, do not require power packs, but they do require a source of illumination. Systems employing infra-red strobes, usually at or near each camera, are preferable to minimize subject distraction. Although standard video technology allows sampling at 50 or 60 Hz, some systems offer higher sampling rates (200 to 2000 Hz) for highspeed analysis. To reduce potential sources of error, accurate method of camera and system calibration is essential. The use of markers located at known positions in the laboratory allows quantitative characterization of system accuracy. This accuracy is often described in terms of a percentage of the known separation distance. Another important attribute in reducing potential errors is system resolution. This describes the ability to discriminate position in terms of a linear measure and should be defined with reference to the volume within which the data are captured. In most gait laboratory facilities, system calibration is routinely conducted on a daily basis and is used to correct for variations due to camera placement, temperature fluctuations and sensor and electronics drift. 7.10.5 Marker systems In both active and passive marker systems, the overall accuracy of the system relies on the optimal positioning of the markers with respect to anatomic landmarks. A major focus in marker set design is to maximize the distance between markers and reduce image overlap and sorting difficulties. Nonetheless, a resulting drawback is that small body segments such as children’s feet cannot always be completely identified or kinematically modelled. Currently available commercial passive marker systems include Ariel (Ariel Life Systems Incorporated, La Jolla, CA), Vicon (Oxford Metrics Limited, Oxford, England), Peak Performance (Peak Performance Technologies Incorporated, Englewood, CO), United Technologies (United Technologies Research Center, East Hartford, CT), Expert Vision (Motion Analysis Corporation, Santa Rosa, CA), Elite (Elite Motion Analyser, Milano, Italy), and others, whereas commercially available active marker (optoelectric) systems include Selspot, Watsmart and Optotrak. Each provides a unique marker system, software package and hardware characteristics. The specific analysis capabilities of each system rely on both the vendor-supplied hardware and software. Several of these systems offer optional features such as marker data filtering, generation of stick figures, analysis of joint velocities, determination of joint moments and powers, and graphical, clinical presentation of the resulting data. Additionally, many of these systems provide user access to data files. Although the 3D coordinates of a marker, whether active or passive, can be determined when viewed by two cameras, the realities of gait analysis necessitates that four or five cameras be utilized. The objective of such a strategy

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is to obtain complete marker coverage at all times, preventing the obstruction of one or more markers in situations such as arm swing and the use of assistive devices. If a marker is not viewed by at least two cameras concurrently, then its position must be estimated. A predictor corrector method is frequently used for marker position estimates. Marker dropout can significantly obscure joint motion data and, when manually supplemented, represents at best an educated estimate of the actual marker position. Such estimates can be deceptive, especially in the analysis of gait patterns (Kadaba et al., 1989, 1990). The use of multiple cameras increases the overlap and reduces marker drop-out. Systems that acquire bilateral data commonly utilize six cameras. Guidelines for marker placement vary widely among systems. Marker placement depends on the biomechanical limb segment model and the procedure for determining joint centers utilized by the system. Common sources of error include inaccurate placement with respect to anatomical landmarks, skin and soft tissue movement, marker drop-out from limb swing or assistive device, trunk rotation and marker vibration (Kadaba et al., 1989; Davis 1992; Vaughan and Sussman, 1993). The estimated joint center locations and segment anthropometric data that are based upon markers can be utilized for a preanalysis ‘snapshot’, thus increasing the accuracy of characterizing the limb segment geometry with respect to the known marker locations. 7.10.6 Biomechanical modeling of gait data In gait analysis the marker system is coupled to a biomechanical or mathematical model (Winter, 1990a, b; Andriacchi and Mikosz, 1991; Vaughan et al., 1992b). The marker and model combination allows calculation of angular and linear position, velocity and acceleration of the body segments with respect to either a fixed laboratory coordinate system or with reference to another body segment. Velocities (angular and linear) are determined by computing the change in position that occurs during a unit of time (typically one camera frame). The motion is then described with respect to the fixed laboratory or another moving body segment. In most laboratories the motion description convention is: foot with respect to tibia, tibia with respect to thigh, thigh with respect to pelvis and pelvis with respect to fixed laboratory coordinate system. Once the markers are identified in 3D space, their collective position is used to describe the body segment motion characteristics. A rigid body in space must be represented by at least three markers (Antonsson, 1982; Ramakrishnan and Kadaba, 1991; Meirovich, 1970). Determinations of body joint position are then made on the basis of the relative position of the proximal and distal body segments about the joint of interest. The most proximal body segment (typically the pelvis) is referenced to a cartesian coordinate system whose origin is located at a physical point in the laboratory. The more distal segments are referenced relative to their nearest proximal segments.

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Characterization of joint motion in terms of clinical planes requires that motion be expressed in terms of orientation about three orthogonal axes. Classically, Euler angles are used to provide 3D representation (Chao, 1980; Ramakrishnan and Kadaba, 1991; Grood and Suntay, 1983). This is a technique of describing the orien tation of one coordinate system relative to another. Three angles are described, each associated in order with a rotation of the moving coordinate system (distal body segment) with respect to a reference coordinate system (proximal body segment of the laboratory). Pelvic motion and foot progression angle are described with respect to the fixed laboratory coordinate system. The Euler method requires that the order of rotation be specified. In gait analysis the usual order is first rotation about sagittal, then coronal and last the transverse axis of rotation. Other methods for describing 3D motion include direction cosines (Shames, 1967), helical axes (Woltring et al., 1985; Shiavi et al. 1987), and the method of Grood and Suntay (1983). Helical parameters have been used by Shiavi to describe knee joint motion (Shiavi et al., 1987) and by Seigler to describe ankle joint motion (Seigler et al., 1988). The Euler system is the most commonly used method clinically for describing 3D motion. The helical axes system has also been used but is more difficult to interpret clinically and may be less useful for describing joint kinematics during gait (Ramakrishnan and Kadaba, 1991). The fidelity of the biomechanical link segment model used in the analysis represents a source of error. The model is coupled to the marker set and is subject to certain underlying assumptions. For example, it is assumed that the greater trochanteric markers are at a fixed distance from the center of hip joint rotation. With femoral deformity or hip anteversion this assumption is not accurate so the kinematic and kinetic data need to be interpreted carefully. This highlights the need for an accurate and thorough clinical assessment with any gait analysis. 7.11 Conclusion Current and future directions in gait analysis will include more sophisticated tools for the analysis and interpretation of data such as pattern analysis, neural networks and artificial intelligence. There is potential for much greater clinical application of moment and power data. Future biomechanical modeling of gait data will more routinely include upper body segments and allow analysis of the flow of energy and power between body segments. More sophisticated models will also allow more accurate analysis of the biomechanical effects of orthotics, prosthetics and assistive devices. Because of competition and technological advances, it is expected that gait analysis systems will become less expensive and more accessible for routine clinical applications. Data banks with pretreatment and post-treatment results will need to be established through multicenter clinical studies. Continued mathematical synthesis of gait, anthropometric and physiologic data will improve musculoskeletal computer

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modeling which in turn may improve pre-treatment assessment, surgical planning and post-operative follow-up. Acknowledgment Special thanks is expressed to Steven M.Kidder for his technical support of the EMG section about signal processing methods. References ANDRIACCHI, T.P. and MIKOSZ, R.P. (1991) Musculoskeletal dynamics, locomotion and clinical applications, in MOW, V.C. and HAYES, W.C. (Eds.) Basic Orthopaedic Biomechanics, pp. 51–92, New York: Raven Press. ANDRIACCHI, T.P., KRAMER, G.M. and LANDON, G.C. (1985) The biomechanics of running and knee injuries, in FINERMAN, G. (Ed.) American Academy of Orthopaedic Surgeons, Symposium on Sport Medicine, The Knee, pp. 23–32, St Louis, MO: Mosby. ANGEVINE, J.B. (1986) The nervous tissue, in FAWCETT, D.W. A Textbook of Histology, Eleventh Edition, pp. 311–66, Philadelphia: W.B. Saunders. ANTONSSON, E.J. (1982) A Three Dimensional Kinematic Acquisition and Intersegment Dynamic Analysis System for Human Motion. Doctoral Dissertation, Boston, Massachusetts: Massachusetts Institute of Technology. BARNES, M.J. and HERRING, J.H. (1991) Combined split anterior tibial-tendon transfer and instramuscular lengthening of the posterior tibial tendon. Journal of Bone and Joint Surgery, 73A, 734–8. BEKEY, G.A., CHANG, C., PERRY, J. and HOFFER, M.M. (1977) Pattern recognition of multiple EMG signals applied to the description of human gait. Proceedings of the IEEE, 65 (5), pp. 674–91. BERMAN, A.T., ZARRO, V.J., BOSACCO, S.J. and ISRAELITE, C. (1987) Quantitative gait analysis after unilateral or bilateral total knee replacement. Journal of Bone and Joint Surgery, 69, 1340–5. BERMAN, A.T., ZARRO, V.J., BOSACCO, S.J. and ISRAELITE, C. (1991) Quantitative gait analysis after unilateral or bilateral total hip replacement. Archives of Physical Medicine and Rehabilitation, 72, 190–4. BIGLAND, B. and LIPPOLD, O.C.J. (1954) The relation between force, velocity and integrated electrical activity in human muscles. Journal of Physiology, 123B, 214–24. BIGLAND-RITCHIE, B. (1981) EMG force relations and fatigue of human voluntary contractions. Exercise and Sports Sciences Reviews, 9, 75–117. BIGLAND-RITCHIE, B., JOHANSSON, R., LIPPOLD, O.C.J. and WOODS, J.J. (1983) Contractile speed and EMG changes during fatigue of sustained maximal voluntary contractions. Journal of Neurophysiology, 50, 313–24. BOGEY, R.A., BARNES, L.A. and PERRY, J. (1992) Computer algorithms to characterize individual subject EMG profiles during gait. Archives of Physical Medicine and Rehabilitation, 73, 835–41.

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BOUISSET, S. (1972) EMG and muscle force in normal motor activities, in DESMEDT, J.E. (Ed.) New Developments in Electromyography and Clinical Neurophysiology, pp. 547–83, Basal, Switzerland: Karger. BRODKE, D.S., SKINNER, S.R., LAMOREUX, L.W., JOHANSON, M.E., ST HELEN, R., MORAN, S.A. and ASHLEY, R.K. (1989) Effects of ankle-foot orthoses on the gait of children. Journal of Pediatric Orthopaedics, 9, 702–8. CAHAN, L.D., ADAMS, J.M., PERRY, J. and BEELER, L.M. (1990) Instrumented gait analysis after selective dorsal rhizotomy. Developmental Medicine and Child Neurology, 32, 1037–3. CHAO, E.Y.S. (1980) Justification of triaxial goniometer for the measurement of joint rotation. Journal of Biomechanics, 13, 989–1006. CHARNLEY, J. and Pusso, R. (1968) The recording and the analysis of gait in relation to the surgery of the hip joint. Clinical Orthopaedic and Related Research, 58, 153–64. CLOSE, J.R., NICKEL, E.D. and TODD, F.N. (1960) Motor-unit action-potential counts: Their significance in isometric and isotonic contractions. Journal of Bone and Joint Surgery, 42A, 1207–22. COLBORNE, G.R., NEUMANN, S., LONGMUIR, P.E. and BERBRAYER, D. (1992) Analysis of mechanical and metabolic factors in the gait of congenital below knee amputees: A comparison of SACH and Seattle Feet. American Journal of Physical Medicine and Rehabilitation, 71, 272–8. COLLOPY, M.C., MURRAY, M.P., GARDNER, G.M., DI, ULIO, R.A. and GORE, D. R. (1977) Kinesiologic measurements of functional performance before and after geometric total knee replacement. Clinical Orthopaedic and Related Research, 126, 196. CROWINSHIELD, R.D., BRAND, R.A. and JOHNSTON, R.C. (1978) The effects of walking velocity and age on hip kinematics and kinetics. Clinical Orthopaedic and Related Research, 132, 140–4. DAVIS, R. (1992) Sources of error in clinical gait analysis, in Clinical Decision Making in Gait Analysis, pp. 177–9. St Paul, Minnesota: Gillette Children’s Hospital (Course Syllabus). DELUCA, C.J. (1979) Physiology and mathematics of myoelectric signals. IEEE Transactions on Biomedical Engineering, 26, 313–25. DELUCA, C.J. and MERLETTI, R. (1988) Surface myoelectric signal cross-talk among muscles of the leg. Electroencephalography and Clinical Neurophysiology, 69, 568–75. DELUCA, P.A. (1991) Gait analysis in the treatment of the ambulatory child with cerebral palsy. Clinical Orthopaedics, 264, 65–75. GAGE, J.R. (1991a) Normal gait, in Gait Analysis in Cerebral Palsy, pp. 61–100, London: Mac Keith Press. GAGE, J.R. (1991b) Basic measurement techniques, in Gait Analysis in Cerebral Palsy, pp. 12–36, London: Mac Keith Press. GAGE, J.R. (1991c) The neurological control system for normal gait, in Gait Analysis in Cerebral Palsy, pp. 37–60, London: Mac Keith Press. GAGE, J.R. (1991d) Knee dysfunction in cerebral palsy, in Clinical Gait Analysis Symposium, pp. 37–42, Newington, Connecticut: Newington Children’s Hospital (Course Syllabus).

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GAGE, J.R. (1992a) EMG fundamentals and interpretation, in Clinical Decision Making in Gait Analysis, pp. 45–50, St Paul, Minnesota: Gillette Children’s Hospital (Course Syllabus). GAGE, J.R. (1992b) Distal hamstring lengthening/release and rectus femoris transfer, in SUSSMAN, M.D. (Ed.) The Diplegic Child, pp. 317–39, Rosemont, Illinois: American Academy of Orthopaedic Surgeons. GAGE, J.R. and ÕUNPUU, S. (1989) Gait analysis in clinical practice. Seminars in Orthopaedics, 4 (2), 72–87. GAGE, J.R., PERRY, J., HICKS, R.R., KOOP, S. and WERNTZ, J.R. (1987) Rectus femoris transfer to improve knee function of children with cerebral palsy. Development Medicine and Child Neurology, 29, 159–66. GANONG, W.F. (1993) Excitable tissue: Nerve, in Review of Medical Physiology, Sixteenth Edition, pp. 43–55, Norwalk, Connecticut: Appleton & Lange. GITTER, A., CZERNIECKI, J.M. and DEGROOT, D.M. (1991) Biomechanical analysis of the influence of prosthetic feet on below-knee amputee walking, American Journal of Physical Medicine and Rehabilitation, 70, 142–8. GROOD, E.S. and SUNTAY, W.J. (1983) A joint coordinate system for the clinical description of three-dimensional motions: Applications to the knee, Journal of Biomechanical Engineering, 105, 136–44. GUYTON, A.C. (1984) Fluid environment of the cell and transport through the cell membrane; in Physiology of the Human Body, Sixth Edition, pp. 58–95, Philadelphia: Saunders College Publishing. GUYTON, A.C. and HALL, J.E. (1996a) Contraction of skeletal muscle, in Textbook of Medical Physiology, pp. 73–85, Ninth Edition, Philadelphia: W.B. Saunders. GUYTON, A.C. and HALL, J.E. (1996b) Motor functions of the spinal cord: The cord reflexes, in Textbook of Medical Physiology, Ninth Edition, pp. 685–97, Philadelphia: W.B. Saunders. HANNAH, R.E. and MORRISON, J.B. (1984) Prosthetic alignment: Effect on gait of persons with below-knee amputations. Archives of Physical Medicine and Rehabilitation, 65, 159–62. HARRIS, G.F. and WERTSCH, J.J. (1994) Procedures for gait analysis. Archives of Physical Medicine & Rehabilitation, 75, 216–25. HAY, J.G. and REID, J.G. (1982) Introduction, in The Anatomical and Mechanical Bases of Human Motion, pp. 5–15, New Jersey: Prentice-Hall Inc. HICKS, R., TASHMAN, S., GARY, J.M., ALTMAN, R.F. and GAGE, J.R. (1985) Swing phase control with knee friction in juvenile amputees. Journal of Orthopaedic Research, 3, 198–201. HINRICHS, R.N. (1985) Regression equations to predict segmental moment of inertia from anthropometric measurements: An extension of the data of Chandler. Journal of Biomechanics, 18, 621–4. INMAN, V.T., RALSTON, H.J. and TODD, F. (1981) Kinematics, in Human Walking, pp. 22–61, Baltimore: Williams & Wilkins. INMAN, V.T., RALSTON, H.G., SAUNDERS, J.B., FEINSTEIN, R.B. and WRIGHT, E. W. (1952) Relation of human electromyogram to muscular tension. Electroencephalography and Clinical Neurophysioly, 4, 187. JACOBS, R. and SCHENAU, G. (1992) Intermuscular coordination in a sprint push-off, Journal of Biomechanics, 25 (9), 953–65.

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JOHNSON, L. (1992a) Propagation of an action potential, in Essential Medical Physiology, pp. 61–8, New York: Raven Press. JOHNSON, L. (1992b) Automatic nervous system, in Essential Medical Physiology, pp. 113– 21, New York: Raven Press. KADABA, M.P., RAMAKRISHNAN, H.K. and WOOTTEN, M.E. (1990) Measurement of lower extremity kinematics during level walking. Journal of Orthopaedic Research, 8, 383–92. KADABA, M.P., WOOTTEN, M.E., GAINEY, J. and COCHRAN, G.V.B. (1985) Repeatability of phasic muscle activity. Performance of surface and intramuscular wire electrodes in gait analysis. Journal of Orthopaedic Research, 3, 350–9. KADABA, M.P., RAMAKRISHNAN, H.K., WOOTTEN, M.E., GAINEY, J. GORTON, G. and COCHRAN, G.V.B. (1989) Repeatability of kinematic, kinetic and electromyographic data in normal adult gait. Journal of Orthopaedic Research, 7, 849–60. KOH, T.J. and GRABINER, M.D. (1992) Cross talk in surface electromyograms of human hamstring muscles. Journal of Orthopaedic Research, 10, 701–9. LAI, K., KUO, K.N. and ANDRIACCHI, T.P. (1988) Relationship between dynamic deformities and joint moments in cerebral palsy. Journal of Pediatric Orthopaedics, 8, 690–5. LAMOREUX, L.A. (1971) Kinematic measurements in the study of human walking. Bulletin of Prosthetic Research, 3, 10–15. LEHMANN, J.F. CONDON, S.M., DE LATEUR, B.J. and PRICE, R. (1986) Gait abnormalities in peroneal nerve paralysis and their correction by orthoses: A biomechanical study. Archives of Physical Medicine and Rehabilitation, 67, 380–6. LEHMANN, J.F., CONDON, S.M., PRICE, R. and DE LATEUR, B.J. (1987) Gait abnormalities in hemiplegia: Their correction by an ankle-foot orthosis. Archives of Physical Medicine and Rehabilitation, 68, 763–71. LINDSTROM, L., MAGNUSSON, R. and PETERSEN, L. (1970) Muscular fatigue and action potential conduction velocity changes studied with frequency analysis of EMG signals. Electromyography, 10 (4), 341–56. LOGAN, L., BYERS-HINKLEY, K. and CICCONE, C.D. (1990) Anterior versus posterior walkers: A gait analysis study. Developmental Medicine and Child Neurology, 32, 1044–8. LYONS, K., PERRY, J., GRONLEY, J.K., BARNES, L. and ANTONELLI, D. (1993) Timing and relative intensity of hip extensor and abductor muscle action during level and stair ambulation: An EMG study. Physical Therapy, 63, 1597–605. MANN, R. and HAGY, J. (1980) Biomechanics of walking, running and sprinting. American Journal of Sports Medicine, 8 (5), 345–50. MAREY, E.J. (1873) De la Locomotion Terrestre chez les Bipedes et les Quadrupedes. Journal d’Anatomie et de Physiologie, 9, 42. MAREY, E.J. (1885) Development de la Methode Graphique par l’Emploi de la Photographie, Paris: G. Masson. MAREY, E.J. and DEMENY, G. (1887) Etude Experimentale de la Locomotion Humaine. Comptes Rendus Hebdomadoires des Seances de l’Academie des Sciences, 105, 544. MCARDLE, W.D., KATCH, F.I. and KATCH, V. (1991a) Neural control of human movement, in Exercise Physiology: Energy, Nutrition and Human Performance, pp. 367–83, Philadelphia: Lea & Febieger.

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MCARDLE, W.D., KATCH, F.I. and KATCH, V. (1991b) Skeletal muscle: Structure and function, in Exercise Physiology: Energy, Nutrition and Human Performance, pp. 348–65, Philadelphia: Lea & Febieger. MEIROVICH, L. (1970) Methods of Analytical Dynamics, pp. 123–4, New York: McGraw-Hill. MILNER-BROWN, H.S. and STEIN, R.B. (1975) The relation between surface electromyogram and muscular force. Journal of Physiology, 246, 549–69. MORITANI, T., MURO, M., KIJIMA, A., GAFFNEY, A. and PARSONS, D. (1985) Electro-mechanical changes during electrically induced and maximal voluntary contractions: Surface and intramuscular EMG responses during sustained maximal voluntary contraction. Experimental Neurology, 88, 484–99. MURRAY, M.P., GORE, D.R., LANEY, W.H., GARDNER, G.M. and MOLLINGER, L.A. (1983) Kinesiologic measurements of functional performance before and after double compartment marmor knee arthroplasty. Clinical Orthopaedic and Related Research, 173, 191–9. MUYBRIDGE, E. (1955) The Human Figure in Motion, New York: Dover Publications Inc. OLNEY, S.J., GRIFFIN, M.P. MONGA, T.N. and MCBRIDE, I.D. (1991) Work and power in gait of stroke patients. Archives of Physical Medicine and Rehabilitation, 72, 309–14. OLSSON, E. (1986) Gait analysis in hip and knee surgery. Scandinavian Journal of Rehabilitation Medicine, 15S, 5–53. ÕUNPUU, S. (1994) Terminology for Clinical Gait Analysis, American Academy for Cerebral Palsy and Developmental Medicine Gait Lab Committee, Draft No. 2, pp. 1–20. ÕUNPUU, S. and WINTER, D.A. (1989) Bilateral electromyographical analysis of the lower limbs during walking in normal adults. Electroencephalography and Clinical Neurophysiology, 72, 429–38. PERRY, J. (1992a) Dynamic electromyography, in Gait Analysis: Normal and Pathological Function, pp. 381–411, Thorofare, New Jersey: SLACK Inc. PERRY, J. (1992b) Phases of gait, in Gait Analysis: Normal and Pathological Function, pp. 9–16, Thorofare, New Jersey: SLACK Inc. PERRY, J. (1992c) Basic functions, in Gait Analysis: Normal and Pathological Function, pp. 19–47, Thorofare, New Jersey: SLACK Inc. PERRY, J. (1992d) Glossary, in Gait Analysis: Normal and Pathological Function, pp. 495– 502, Thorofare, New Jersey: SLACK Inc. PERRY, J., HOFFER, M.M., GIOVAN, P., ANTONELLI, D.and GREENBERG, R. (1960) Gait analysis of the triceps surae in cerebral palsy. Journal of Bone and Joint Surgery, 56A (3), 511–20. PERRY, J., EASTERDAY, C.S. and ANTONELLI, D.J. (1981) Surface versus intramuscular electrodes for electromyography of superficial and deep muscles. Physical Therapy, 61 (1), 7–15. PERRY, J., HOFFER, M.M., ANTONELLI, D., PLUT, J., LEWIS, G. and GREENBERG, R. (1976) Electromyography before and after surgery for hip deformity in children with cerebral palsy. Journal of Bone and Joint Surgery, 58A (2), 201–8. PERRY, J., HOFFER, M.M., ANTONELLI, D., PLUT, J., LEWIS, G. and GREENBERG, R. (1977) Preoperative and postoperative dynamic electromyography

Z.O.ABU-FARAJ, S.HASSANI AND G.F.HARRIS 221

as an aid in planning tendon transfers in children with cerebral palsy. Journal of Bone and Joint Surgery, 59A, 531–7. PRODROMOS, C.C., ANDRIACCHI, T.P. and GALANTE, J.O. (1985) A relationship between gait and clinical changes following high tibial osteotomy. Journal of Bone and Joint Surgery, 67A, 1188–94. RAB, G.T. (1994) Muscle, in ROSE, J. and GAMBLE, J.G. (Eds). Human Walking, Second Edition, pp. 101–21, Baltimore: Williams & Wilkins. RAMAKRISHNAN, H.K. and KADABA, M.P. (1991) On the estimation of joint kinematics during gait. Journal of Biomechanics, 24 (10), 969–77. RESNIK, R. and HALLIDAY, D. (1966) Particle dynamics, in Physics, pp. 79–108. New York: John Wiley & Sons Inc. RITTMAN, N., KETTELKAMP, D.B., PRYOR, P., SCHWARTZKOPF, G.L. and HILLBERRY, B. (1981) Analysis of patterns of knee motion walking for four types of total knee implants. Clinical Orthopaedic and Related Research, 155, 111–7. SEIGLER, S., CHEN, J. and SCHENCK, C.D. (1988) The three-dimensional kinematics and flexibility characteristics of the human ankle and subtalar joints—Part I: Kinematics, Journal of Biomechanical Engineering, 110, 364–73. SEIREG, A. and ARVIKAR, R.J. (1975) The prediction of muscular load sharing and joint forces in the lower extremities during walking. Journal of Biomechanics, 3, 51–61. SHAMES, I.H. (1967) Engineering Mechanics, Second Edition, p. 21, Englewood Cliffs, New Jersey : Prentice-Hall. SHEPHERD, G.M. (1988a) Locomotion, in Neurobiology, Second Edition, pp. 412–27, Oxford: Oxford University Press. SHEPHERD, G.M. (1988b) in Neurobiology, Second Edition, pp. 39–64, Oxford: Oxford University Press. SHEPHERD, G.M. (1988c) Motor hierarchies, in Neurobiology, Second Edition, pp. 428–49, Oxford: Oxford University Press. SHIAVI, R., LIMBIRD, T., FRAZER, M., STIVERS, K., STRAUSS, A. and ABRAMOVITZ, J. (1987) Helical motion of the knee: Kinematics of uninjured and injured knees during walking and pivoting, Journal of Biomechanics, 20, 653–65. SKINNER, H.B. and EFFENEY, D.J. (1985) Gait analysis in amputees. American Journal of Physical Medicine, 64, 82–9. SKINNER, S.R. (1981) The correlation between gait velocity and rate of lower extremity loading and unloading. Bulletin of Prosthetics Research, 18, 303–4. SOAMES, R.W. and RICHARDSON, R.P.S. (1978) Stride length and cadence: Their influence on ground reaction forces during gait, in WINTER, D.A., NORMAN, R.W., WELLS, R.P. and HAYES, K.C. (Eds) Biomechanics IX-A. pp. 406–10, Champaign, Illinois: Human Kinetics. SUTHERLAND, D.H. (1984) Gait Disorders in Childhood and Adolescence, pp. 1–13, Baltimore: Williams & Wilkins. SUTHERLAND, D.H. (1990) Gait analysis in neuromuscular disease. San Diego Children’s Hospital Instructional Course, pp. 333–41, unpublished. SUTHERLAND, D.H., OLSHEN, R.A., BIDEN, E.N. and WYATT, M.P. (1988a) Methods, in The Development of Mature Walking, pp. 3–23, London: Mac Keith Press.

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SUTHERLAND, D.H., OLSHEN, R.A., BIDEN, E.N. and WYATT, M.P. (1988b) Forceplate values by age, in The Development of Mature Walking, pp. 163–77. London: Mac Keith Press. TASHMAN, S. HICKS, R. and JENDREJCZYK, D. (1985) Evaluation of a prosthetic shank with variable inertial properties. Clinical Prosthetics and Orthotics, 9, 23–5. THOMPSON, J.S. (1977) An introduction to gross anatomy, in Core Textbook of Anatomy, pp. 1–13, Philadelphia: J.B. Lippincott. VANDER, A.J., SHERMAN, J.H. and LUCIANO, D.S. (1990a) Neural control mecha nisms, in Human Physiology: The Mechanisms of Body Function, Fifth Edition, 167–217, New York: McGraw-Hill Publishing Company. VANDER, A.J., SHERMAN, J.H. and LUCIANO, D.S. (1990b) Control of body movement, in Human Physiology: The Mechanisms of Body Function, Fifth Edition, pp. 325– 45, New York: McGraw-Hill Publishing Company. VANDER, A.J., SHERMAN, J.H. and LUCIANO, D.S. (1990c) Muscle, in Human Physiology: The Mechanisms of Body Function, Fifth Edition, New York: pp. 283–324, McGraw-Hill Publishing Company. VAUGHAN, C.L. and SUSSMAN, M.D. (1993) Human gait: From clinical interpretation to computer simulation , in GRABINER, M, D. (Ed.) Current Issues in Biomechanics, pp. 53–68, Champaign, Illinois: Human Kinetics. VAUGHAN, C.L., BERMAN, B. and PEACOCK, W.J. (1991) Cerebral palsy and rhizotomy. Journal of Neurosurgery, 74, 178–84. VAUGHAN, C.L. DAVIS, B.L. and O’CONNOR, J.C. (1992a) The three-dimensional and cyclic nature of gait, in Dynamics of Human Gait, pp. 7–14, Champaign, Illinois: Human Kinetics Publishers. VAUGHAN, C.L., NASHMAN, J.H. and MURR, M.S. (1992b) What is the normal function of tibialis posterior in human gait, in SUSSMAN, M.D. (Ed.) The Diplegic Child, pp. 397–409, Rosemont, Illinois: American Academy of Orthopaedic Surgeons. WAGENAAR, R.C. and BEEK, W.J. (1992) Hemiplegic gait: A kinematic analysis using walking speed as a basis. Journal of Biomechanics. 25, 1007–15. WATERS, R.L., PERRY, J., ANTONELLI, D. and HISLOP, H. (1976) Energy cost of walking of amputees: The influence of level of amputation. Journal of Bone and Joint Surgery , 58A, 42–6. WEIR, J.P., WAGNE, L.L., HOUSCH, T.J. (1992) Linearity and reliability of the EMG v. torque relationship for the forearm flexors and leg extensors. American Journal of Physical Medicine and Rehabilitation, 71, 283–7. WINTER, D.A. (1984) Kinematic and kinetic patterns in human gait: variability and compensating facts. Human Movement Science, 3, 51–76. WINTER, D.A. (1990a) Kinematics, in Biomechanics and Motor Control of Human Movement, Second Edition, pp. 11–50, New York: John Wiley and Sons. WINTER, D.A. (1990b) Kinetics: Forces and moments of force, in Biomechanics and Motor Control of Human Movement, Second Edition, pp. 75–102, New York: John Wiley and Sons, Inc. WINTER, D.A. (1990c) Mechanical work, energy and power, in Biomechanics and Motor Control of Human Movement, Second Edition, pp. 103–39, New York: John Wiley and Sons, Inc. WINTER, D.A. (1990d) Kinesiological electromyography, in Biomechanics and Motor Control of Human Movement, Second Editioni, pp. 191–212, New York: John Wiley and Sons, Inc.

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WOLFE, S. (1993) The functions of membranes in ionic and molecular transport, in Molecular and Cellular Biology, pp. 189–227, Belmont, CA: Wadsworth Publishing Co. WOLTRING, H.J., HUISKES, R. and DELANGE, A. (1985) Finite centroid and helical axis estimation from noisy landmark measurement in the study of human joint kinematics. Journal of Biomechanics, 18, 379–89. WYKMAN, A. and OLSSON, E. (1992) Walking ability after total hip replacement. Journal of Bone and Joint Surgery, 74B, 53–6. YANG, J.E., WINTER, D.A. (1985) Surface EMG profiles during different walking cadences in humans. Electroencephalography and Clinical Neurophysiology, 60, 485–91. ZUNIGA, E.N. LEAVITT, L.A., CALVERT, J.C., CANAZONERI, J. and PETERSON, C. R. (1972) Gait patterns in above-knee amputees. Archives of Physical Medicine and Rehabilitation, 53, 373–82.

CHAPTER EIGHT Slips, trips and falls: implications for rehabilitation and ergonomics AFTAB E.PATLA

8.1 Introduction The focus of this chapter is to explore the threats to dynamic stability during locomotion from slips and trips, strategies available to recover from these unexpected events, implications for preventing injuries in the workplace and rehabilitation strategies should an injury occur. Human locomotion is by its very nature an unstable act. The roots of the word cadence used to describe this activity is ‘cadere’ meaning ‘to fall’. Each step we take involves a fall followed by a recovery. During 80 per cent of a stride, we are in single support with the body center of mass outside the base of support: thus by definition of static stability we are falling (Winter, 1991). Clearly what prevents a fall from occurring is the next support created by the swing limb. This cycle of falling and recovery is nicely captured by the analogy of an egg rolling end over end which has been used to describe walking. A useful place to start would be to define what we mean by the various terms in the title. Slip is an unwanted displacement of the foot with respect to support surface. While in ice skating the displacement of the foot over the ice is intended, during normal locomotion such an occurrence is clearly undesirable. The two critical phases during locomotion when a slip may occur are at initial foot contact and at push-off during the late stance phase. Since during the pushoff phase the body center of mass is moving in the opposite direction of the slip, and moving towards the supporting limb, the consequences are not as severe. In contrast, during initial foot contact the body center of mass is moving away from the supporting limb in the direction of the slip, resulting in a potential hazardous consequence. During normal locomotion, the chances of a slip are minimized by the active reduction of foot contact velocity (~0.4 m/s) through late stance activity of the hamstring muscles. Under normal friction conditions, a slip is avoided: should ground conditions change, of course the results would be different. A trip is the unexpected obstruction of the movement of the limb during the swing phase of locomotion. Consider forward locomotion, the preferred choice.

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During the swing phase the limb is moving at considerable speed (~4.5 m/s) with minimal ground clearance (<1 cm, thus minimizing the energy cost involved in limb elevation) to generate the next base of support. If this moving limb were to come into contact unexpectedly with an obstacle in its travel path, the transfer of linear momentum to angular momentum can result in a stumble and/or a fall. A trip during the early swing phase is less dangerous since the body center of mass is moving towards the supporting limb: during late swing phase a trip is considerably more dangerous since the body center of mass is moving away from the supporting limb. A fall is an uncorrected displacement of the body center of mass outside the base of support. Fall on the same level accounts for a large part of the injuries even among the elderly (Malmivaara et al., 1993). A trip or a slip may result in a fall should the recovery strategies not work. Slips and trips account for the majority of the falls during locomotion (Manning et al., 1988). The consequences of a fall range from minor bruising and loss of face to sprains and fractures (Cummings et al., 1988). The resulting loss in productivity, and the physical and social costs, are considerable. Among the elderly, not only is the incidence of falls due to trips and slips higher (Baker and Harvey, 1985), but the associated injuries and consequences to lifestyles are far more damaging (Tinetti and Powell, 1991). Since many of the falls in the younger population occur in the workplace, we need to develop preventative strategies for reducing the incidence of trips and slips. While prevention is clearly the desirable alternative, we have to be prepared to deal with failures as they occur through appropriate rehabilitation programs. To develop strategies for rehabilitation and prevention of falls, we need to better understand the strategies for maintaining dynamic equilibrium during locomotion. These are discussed next. 8.2 Strategies for dynamic equilibrium during locomotion Evolution has provided us with both reactive and proactive control of dynamic stability during locomotion. This is achieved by unique sensory systems that can detect actual and potential perturbations to balance, a complex nervous system that can evaluate, process and transform these sensory signals into appropriate motor commands and the musculoskeletal apparatus that not only carries out the commands from the nervous system, but also simplifies the control through its unique properties. 8.2.1 Reactive control of dynamic stability Contributions of musculoskeletal apparatus. The first and often overlooked line of defence is the properties of the musculoskeletal apparatus. Young et al. (1992) have shown how the joint angle-dependent moment arms of muscles provide an

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intrinsic mechanism for stabilizing posture. Well-known force/length and force/ velocity of the muscles provide visco-elastic restorative forces (potentially both active and passive) when muscle length and velocity are perturbed by an external force. As well as muscles other passive tissues also provide joint stability because of their elastic and viscous properties. What is particularly attractive about these restorative mechanisms is that there are no delays involved and they are operational all the time: they do not have to be internally or sensorially triggered. The limitation is that the magnitude and range of perturbations that can be handled are low under normal operating range of the joints. Sensory triggered reflex and voluntary responses.The next level of reactive control relies on the detection of perturbations to balance primarily by the kinesthetic and vestibular sensory systems. The kinesthetic system provides information about the relative orientation and movement of body parts; muscle tension; orientation of the support surface and orientation of the body with reference to the support surface. Afferent receptors in the muscles, tendons, joints and skin provide the necessary sensory input which is processed at all levels in the nervous system. The vestibular system provides angular acceleration and deceleration, angular velocity, linear acceleration and deceleration of the head, and orientation of the head with reference to gravity. Afferent receptors in the semicircular canals and otolith organs provide the necessary sensory input which is also processed at various levels within the nervous system. Information from both sensory systems results in fast-acting corrective responses that occur in less than a simple reaction time. The fastest responses are the monosynaptic reflexes. The term reflex was coined to reflect the hard-wired rigid connection between sensory input and motor output (literally ‘flexing back of the sensory input into motor output’). A large body of neurophysiological studies have shown that the reflexes are far from being this hard-wired input/output circuitry; rather, under higher level control these are a powerful arsenal that can provide functionally appropriate responses. Consider the monosynaptic stretch reflex response in the soleus muscle in humans, which will provide a restorative force when the muscle is stretched. Stein and his colleagues (1991) have clearly shown that the gain of the soleus H-reflex (electrical analogue of the mechanical stretch reflex) is modulated during locomotion: it is very low during the swing phase and high during the push-off phase. This modulation of the gain of the reflex makes functional sense. For example during the swing phase when the foot is being actively dorsiflexed to clear the ground or an obstacle, high-reflex gain of the stretched soleus muscle would be counterproductive and result in a trip. Therefore, the nervous system primes the spinal circuitry in advance to ensure the appropriate phase and task-specific gain of the reflex. This is necessary since the same sensorimotor apparatus has to be used for a variety of movements which have their own specific requirements. Polysynaptic reflexes are also similarly modulated to provide functionally appropriate responses. Consider the protective flexor reflex which serves to

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withdraw the limb from an undesirable stimuli detected by the skin mechanoreceptors. Yang and Stein (1990) have studied the response in the tibialis anterior muscle in response to the same cutaneous input applied during various phases of the step cycle. Typically the response involves a complex early, middle and late latency response to cutaneous input. They have shown that during the late stance phase, the response is negligible: this makes functional sense since normal response during the push-off phase would be destabilizing. The gain of the reflex is high during the early swing phase to ensure adequate recovery from a trip. While these studies on reflexes mediated by specific receptors provide unique insights into fast-acting reactive responses, it is important to keep in mind that in case of a trip many different receptors are activated. Recently we have characterized responses to a realistic trip during locomotion (Eng et al., 1994). This study has shown that latency of the responses to trip are in the range of 60– 140 msec: thus monosynaptic reflex response were not elicited. Responses were observed in a large number of muscles in both the stance and swing limb (Figure 8.1), and included enhancement and reduction in specific muscle activity. This suggests a more complex organization of response that does not neatly fall into a receptor specific reflex response, and is similar to triggered responses observed during postural control studies. Researchers have argued that the complex context-dependent response required during locomotion makes the relatively simple and localized monosynaptic responses inappropriate (Dietz, 1992). For example, the gain of the soleus H-reflex during standing is considerably higher than during locomotion (Stein, 1991). Can we extend this logic and ask why would the nervous system rely at all on fast-acting reflex responses? Why not wait to process the sensory information at a higher level and proceed with an appropriate voluntary response? The answer can be found in a recent study carried out in my lab on stability margin during obstacle avoidance (Liu et al., 1996). We have shown that the nervous system has less than 200 msec to implement a recovery response in case of a trip; this is the time it would take for the body center of mass to travel outside the forward edge of the base of support as defined by the line connecting the stance and swing limb toe (Figure 8.2). Thus, reliance on voluntary response only to recover from a trip would be disastrous, since simple reaction time is ~200 msec. Eng et al. (1994) have also shown that the functional outcome of the responses to a trip were phase dependent: a trip during the early swing phase resulted in elevation of the limb while a trip during the late swing phase caused a lowering of the limb (Figure 8.1). While the recovery from an early trip was nearly complete within one step, recovery from the late trip persisted during the next step. This clearly suggests that although fast-acting responses (reflexes or triggered responses) are the necessary and important first line of active defense against perturbations, additional voluntary responses are required to complete the recovery process.

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Figure 8.1 Sequencing of response to an unexpected trip during early swing (a) and (b) late swing. St-Stance limb muscle; SW—swing limb muscle; GIM—gluteus medius; MGa —medial gastrocnemius; PL—peroneus longus; BF—biceps femoris; TA—tibialis anterior; RF—rectus femoris and VL—vastus lateralis. (From Eng et al., 1994.)

8.2.2 Proactive control of dynamic stability It is clear that total reliance on reactive control to maintain stability is not desirable. Besides what it would do to your mental state if you are always working in a

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Figure 8.2 Birds-eye view of the support foot (solid line figure) and the swing foot (dotted line figure) while the swing toe is over the obstacle. Center of mass position (solid circle) and velocity vector direction (dashed line) are shown for six trials. The solid line connecting the support toe (solid square) and swing toe (open square) define the forward edge of the support base. ART— available response time. (From Liu et al., 1996.)

crisis mode constantly reacting to events, it is also harmful to the tissues. Consider what repeated trips would do to your foot, for example. Reactive control is as it should be, a back-up system when the proactive system fails. There are three modes of proactive control and they are discussed next. Predictive control. Predictive control is employed when perturbations to balance cannot be avoided. These perturbations are present any time we move a body segment and are manifestations of Newton’s Third Law. Every movement, even the normal locomotor movements, perturb the body by displacement of body center of mass and reactive moments (Eng et al., 1992). Thus, this balance control strategy is not triggered by sensory input, but rather internally generated and is continuously operating in the background. The nervous system predicts the consequences of these perturbations and plans the appropriate corrective responses either prior to or concurrently with the perturbations. The pitching motion of the trunk with acceleration and decceleration in each step cycle is controlled primarily by the moments about the hip joint. The tipping of the upper body towards the unsupported side is primarily regulated by the hip abductors: the magnitude of destabilization is controlled by the foot placement with respect to body center of mass. Collapse in the vertical direction is prevented by controlling the moments about the knee joint which have been shown by Winter (1991) to covary with the hip joint moments. By using the hamstrings to deccelerate the limb extension during the swing phase, gentle foot contact (horizontal velocity ~0.4 m/s) is achieved and the chances of slipping are minimized. During normal level locomotion as simulations have shown, tripping

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Figure 8.3 Spatial trajectories (vertical (y) versus horizontal (x) displacement profiles) of the right hip and right toe marker from toe-off to foot contact as a subject goes over obstacles of different heights (0.5 cm to 3.8 cm) from Patla, (1995); Behavioral and Brain Sciences).

is avoided primarily through active dorsiflexion (Mena et al., 1981). Studies examining postural responses to additional movement-generated perturbations applied during locomotion are relatively few (Nashner and Forssberg, 1986; Patla, 1986; Hirschfeld and Forssberg, 1991). These studies have shown that proactive responses to perturbations initiated by arm movements are functional, ensuring stability and forward progression. This mode of proactive control of balance suggests the presence of a movement and body schema within the nervous system. Avoidance control. The most powerful means of ensuring stability is to actively avoid the perturbation altogether. The identification and avoidance of potential threats to stability are made possible by the visual system. Whereas sensory modalities such as the kinesthetic system need physical contact with the external world to transduce and supply relevant information, vision can provide us with information from a distance. This allows us to interpret and take appropriate action before reaching the site of potential perturbation. These actions are classified as avoidance strategies (Patla, 1991) and include the following: (a) selection of alternate foot placement by modulating step length and width; (b) increased ground or head clearance to avoid hitting an obstacle on or above ground respectively; (c) changing the direction of locomotion (steering) when the obstacles cannot be cleared; and (d) stopping. Clearly, avoidance strategies

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represent locomotor adaptations that are primarily implemented to ensure the dynamic equilibrium of the moving body. The work done in my lab has provided unique insights into the basis for the selection of alternate foot placement (Patla et al., 1992), minimum time (expressed in terms of the step cycle metric) required for implementing these avoidance strategies (Patla et al., 1989; 1991; 1992), and the characteristics of locomotor pattern changes (Patla et al., 1989; 1991; 1992; 1996; Patla and Rietdyk, 1993; Patla, 1991). The major findings from our studies on avoidance strategies are as follows. 1 Most avoidance strategies can be successfully implemented within a step cycle; only steering has to be planned one step cycle ahead. 2 Selection of alternate foot placement is guided by simple rules. Minimum foot displacement from its normal landing spot is a critical determinant of alternate foot-placement position. When two or more choices meet the above criteria, modifications in the plane of progression are preferred. Given a choice between shortening or lengthening step length, subjects chose increased step length. Inside foot placement is preferred over stepping to the outside provided the foot does not cross the midline of the body. As discussed by Patla et al. (1992), these rules for alternate foot-placement selection ensure that avoidance strategies are implemented with minimal changes while maintaining the dynamic equilibrium and allowing the person to travel forwards safely. 3 The modifications made to the locomotor pattern to implement avoidance strategies are complex and task specific. They are not simple amplitude scaling of the normal locomotor patterns: rather both ipsi and intralimb muscle activation patterns show phase (of the step cycle) and muscle specific modulations (Patla, 1991; Patla and Rietdyk, 1993). 4 Both visually observable and visually inferred properties of the environment influence the avoidance strategy selection and implementation (Patla, 1991). We have shown, for example, that the perceived fragility of the obstacle modulates limb elevation (Patla et al., 1992). When obstacle avoidance response has to be initiated quickly, subjects show a two-stage modulation of limb trajectory; initial large change is in response to an obstacle followed by adjustments related to the height of the obstacle (Patla et al., 1991). Since tripping is one of the focii of this chapter it is useful to discuss the changes in locomotor patterns further. Limb elevation over the obstacle is achieved not simply by flexing the joints of the swing limb, but also by hip hiking (Figure 8.3) (Patla and Rietdyk, 1993). The control of limb elevation over the obstacle is not very precise even though psychophysical studies show that subjects are accurately able to perceive obstacle height. The relatively larger toe clearance over the obstacle (~10 cm) compared with normal ground clearance (~1 cm) allows the subject to be more variable. What is particularly interesting is that toe

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Figure 8.4 Toe clearance variability as a function of obstacle height and for leading and trailing limb. (From Patla et al., (1995) Journal of Motor Behavior.)

clearance variability increases as a function of obstacle height and whether the subjects can see their limbs (in their peripheral vision) as they are going over the obstacle (Figure 8.4) (Patla et al., 1995). Also, when the obstacles are of low contrast, toe clearance is affected (Patla et al., 1995). These observations have very important implications for the incidence of tripping in the workplace and are discussed later. Accommodation control. Different terrains have to be accommodated as we travel from one place to another. These terrains may have different geometric characteristics such as sloped surfaces or stairs, and/or may have different surface properties such as compliance (a soggy field), and frictional characteristics (icy surface) that can influence the body-ground interaction (Patla, 1991). Unlike avoidance strategies which normally would influence one or two steps, accommodation strategies would usually involve modifications sustained over several steps. The types of changes made to the normal locomotor rhythm may include those discussed under avoidance strategies. For example, while walking on a icy surface step length is often reduced. Other changes include a change in locus of propulsive power as found in stair climbing (propulsive power from the muscles around the hip and knee joint) compared with level walking (major propulsive power from muscles around the ankle joint) (Winter, 1991). The initial planning of gait adjustments during a transition from a normal level surface to a different surface has to be visually mediated. Knowledge acquired through experience, though, plays an important role in the visual regulation of locomotor patterns. An icy surface poses a far greater hazard to a person from the tropical climes than to a native of northern countries. In a recent study (Patla et al., 1993), we showed how subjects did alter their foot placement (and body posture) and velocity based on the visually perceived surface compliance

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characteristics. Once the foot contact has been made with the altered surface, other sensory modalities, in particular the kinesthetic system, can play an important role in the modulation of gait patterns. Since we are interested in dynamic stability we will focus our attention on those surfaces that will adversely affect balance. Surfaces with low frictional characteristics increase the probability of slipping. We have recently investigated strategies used by the subjects to step on and off a slippery surface (Patla and Halverson, 1996). A special apparatus allowed us to alter the frictional characteristics either in the medio-lateral or the anterior-posterior plane. Our results show that subjects were not, as expected, manipulating the foot-contact velocity or foot-contact area. Rather primary modification included shorter step length, and changes in muscle activity of the stance limb and not the swing limb. Increase in reaction time clearly indicated that subjects took longer to plan for the step on a low friction surface compared to a normal surface. Major increases in muscle activity were observed during the single support phase on the low friction surface, clearly reflecting the overriding challenge of balance control (Figure 8.5). 8.3 Implications for rehabilitation We have discussed the various strategies available to maintain dynamic stability during locomotion. It is clear that for these strategies to work, integrity of the sensory systems, central nervous system and the musculoskeletal apparatus are essential. What works in our favour is that there is redundancy in the balance control system at all levels. Consider the sensory systems and the information they provide for regulating balance. Information about body orientation and movement is provided by all three sensory modalities, vision, kinesthetic and vestibular systems. This overlap of information protects the locomotor control system from failure when one of the system deteriorates; under normal operating conditions the multiple sources of similar information provides for checks and balances. Postural control studies have clearly shown that control of upright posture is preserved even when two of the sensory modalities are affected (Horak et al., 1989). Patients who have lost their eyesight or suffer from peripheral neuropathy which affects the kinesthetic system are able to maintain reasonably normal mobility. Similarly, we have multiple sources of muscle power that can be used for locomotion and balance. For example, walking can be achieved either by active push-off using the ankle plantarflexors or through active pull-off using hip flexors. This ability to shift the locus of propulsive power allows great flexibility but comes at some cost (step length is generally lower when using hip flexors to achieve forward propulsion) and added bonus (hip pull-off is less destabilizing). Elderly subjects prefer to use hip pull-off instead of push-off which can be potentially destabilizing (Winter et al., 1990). When we travel over an icy

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Figure 8.5 EMG activity during single support phase on surface with normal friction (rollers locked) and low friction (rollers unlocked). For the medial gastrocs muscle the response in this phase is not significant so it is not shown. (From Patla and Halverson, 1996, in preparation.)

surface, by necessity we shift to using the hip pull-off strategy. This reorganization of propulsive synergy can occur rapidly (Dickey and Winter, 1992). The various neural substrates within the nervous system are involved in maintaining balance. Damage to these substrates can have severe consequences. For example, damage to the basal ganglia adversely affects the predictive control of balance (Horak and Frank, 1994). Cerebellar damage results in poor scaling of the reactive postural responses (Horak et al., 1990). Cortical lesions can have wide-ranging effects depending on the locus and extent of the lesions. For

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example, damage to the parietal cortex can affect the use of vision in controlling movement (Milner and Goodale, 1993). Successful rehabilitative strategies should exploit the redundancy and plasticity of the system. The challenge is to identify and treat the primary neurophysiological or musculoskeletal deficits and not the adaptive changes to the primary deficits. We need to facilitate the recovery process through a variety of means. The study by Haines (1974) suggests that maintenance of muscle strength alone does not guarantee preservation of balance control. Exercise of balance control in one context (standing) does not transfer to another context (walking) (Winstein, 1989). This suggests that we need to exercise a balance control system in various contexts. Recently we have developed exercises that work on the balance control system, and have shown that this improves balance even in the relatively healthy elderly (Frank et al., 1994). The balance exercise program includes the following: specific muscle strengthening (hip muscles which are critical for balance during walking); walking exercises that force the subjects to travel over cluttered terrains (modifying their walking patterns online), and involve exaggerated movements (that provide self-generated perturbations); exercises that provide sensory conflicts (primarily providing moving environments); and exercises that stress the postural control system responsible for maintaining upright posture. This experience suggests that it is possible to develop intervention programs for improving dynamic equilibrium. 8.4 Implications for preventing slips and trips in the workplace Under normal circumstances, the balance control systems works: it has several fail-safe mechanisms as discussed before. If the work environment challenges these mechanisms to the extreme, there are bound to be problems. Consider the incidence of slipping in the workplace. Numerous studies have shown that slipping accidents account for a large portion of work-related injuries (~60 per cent) (Manning et al., 1988). Contaminated floors with small patches of lubricants or loose gravel, and inappropriate footwear soles can increase the chances of slipping. Since subjects use prior knowledge and vision to modify their step on a low friction surface, conditions that compromise vision (poor lighting) or lull them into a false sense of security will increase the incidence of slipping. Although tripping accounts for a smaller proportion of workplace-related injuries (approximately 17 per cent) (Manning et al., 1988) the workplace environment challenges proactive obstacle-avoidance strategies. For example, carrying loads while stepping over obstacles is challenging from several perspectives. First, load carrying displaces the body center of mass anteriorly, placing it closer to the forward edge of the supporting base. This will reduce the available response time in case of a trip even further. Secondly, carrying a load eliminates important visual exproprioceptive input about the limb as it is going

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Figure 8.6 Percent of contact with obstacle in two experiments, illustrating the role of attention in obstacle avoidance. In the first experiment, the probability of high obstacle was 40 per cent and low obstacle was 10 per cent, while in the second obstacle the probability of the occurrence of low obstacle was 50 per cent.

over the obstacle; we have shown that this increases the variability in toe clearance and the probability of an accidental trip (Figure 8.3) (Patla et al., 1995). Thirdly, carrying a load eliminates the use of arms in the recovery process. Arms provide a way to cushion a fall, and are a common protective response. Finally, contact of the body with the falling load and other objects around the workplace can increase the severity of injuries. There are other factors in the workplace that predispose an individual to the chances of tripping. For example, poor lighting and other distractors such as noise can increase the likelihood of accidental contact. Studies have shown that biasing the attention of subjects can increase the probability of tripping (Zohar, 1978; Patla, unpublished observations) (Figure 8.6). Since recovery from a trip can persist in subsequent steps (Eng et al., 1994) and workplace layout may not afford unimpeded execution of multiple steps following a trip, a fall outcome becomes more probable. In summary, several factors compromise the ability of individuals to successfully implement proactive avoidance and accommodation strategies. This places a huge and undue burden on the reactive balance control system to maintain dynamic equilibrium: it is no surprise that failures occur. Through careful management we need to restore balance, so to speak, and ensure that the control system has the ability to use all available resources to maintain dynamic equilibrium.

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Acknowledgment The work described was supported by a grant from NSERC Canada. References BAKER, P.S. and HARVEY, H. (1985) Fall injuries in the elderly, in RADEBOUGH, T.S., HADLEY, E. and SUZMAN, R. (Eds) Clinics in Geriatric Medicine, Philadelphia: W.B. Saunders. CUMMINGS, S.R., NEVITT, M.C. and KIDD, S. (1988). Forgetting falls: The limited accuracy of recall of falls in the elderly. Journal of American Geriatric Society, 36, 613. DICKEY, J.P. and WINTER, D.A. (1992) Adaptations in gait: Resulting from unilateral ischaemic block of the leg. Clinical Biomechanics, 7, 215–25. DIETZ, V. (1992) Human neuronal control of automatic functional movements: Interaction between central programs and afferent input. Physiological Reviews, 72 (1), 33–69. ENG, J., WINTER, D.A. and PATLA, A.E. (1994) Lower limb muscle coordination during the recovery to an unexpected tripping perturbation. Experimental Brain Research, 102, 339–49. ENG, J.J., WINTER, D.A., MACKINNON, C.D. and PATLA, A.E. (1992) Interaction of the reactive moments and center of mass displacement for postural control during voluntary arm movements, Neuroscience Research Communications, 11 (2), 73–80. FRANK, J., PATLA, A.E., WINTER, D.A., BRAWLEY, L., SHARRATT, M. and PRENTICE, S. (1994) An activity program to improve balance control in older adults, in TAGUCHI, K., IGARASHI, M. and MORI, S. (Eds) Vestibular and Neural Front. pp 231–34, Elsevier Science Publishers. HAINES, R.P. (1974) Effect of bed rest and exercise on body balance. Journal of Applied Physiology, 36, 323. HIRSCHFELD, H. and FORSSBERG, H. (1991) Phase-dependent modulations of anticipatory postural activity during human locomotion, Journal ofNeurophysiology, 66 (1), 12–19. HORAK, F.B. (1990) Comparison of Cerebellar and Vestibular Loss on Scaling of Postural Responses, in BRANDT, T., PAULUS, W., BLES, W., DIETERICH, M., KRAFCZYK, S. and STRAUBE, A. (Eds) Disorders of Posture and Gait, pp 370–3, Stuttgart: Georg Thieme Verlag. HORAK, F. and FRANK, J. (in press) Three Separate Postural Systems Affected in Parkinsonism, in STUART, D.G., GURFINKEL, V.S. and WIESENDANGER, M. (Eds) Motor Control VIII, Tucson; Motor Control Press. HORAK, F.B., SHUPERT, C.L. and MIRKA, A. (1989) Components of postural dyscontrol in the elderly: A review. Neurobiology of Aging, 10, 727–39. LIU, S.H., PATLA, A.E., SPARROW, W.A., CHARLTON, J. and ADKIN, A.L. (1996) Determining dynamic stability during obstacle avoidance, Gait and Posture, 4, 197–8. MALMIVAARA, D.P., HELIOVAARA, M., KNEKT, P., REUNANEN, A. and AROMAA, A. (1993) Risk factors for injurious falls leading to hospitalization or

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death in a cohort study of 19 500 adults, American Journal of Epidemiology, 138, 384–94. MANNING, D.P., AYERS, I., JONES, C., BRUCE, M. and COHEN, K. (1988) The incidence of underfoot accidents during 1985 in a working population of 10000 Merseyside people. Journal of Occupational Accidents 10, 121–30. MENA, D., MANSOUR, J.M. and SIMON, S.R. (1981) Analysis and synthesis of human swing leg motion during gait and its clinical applications. Journal of Biomechanics, 14 (12), 823–32. MILNER, A.D. and GOODALE, M.A. (1993) Visual pathways to perception and action. Progress in Brain Research, 95, 317–37. NASHNER, L.M. and FORSSBERG, H. (1986) Phase-dependent organization of postural adjustments associated with arm movements while walking. Journal of Neurophysiology, 55, 1382–94. PATLA, A.E. (1986) Adaptation of postural responses to voluntary arm raises during locomotion in humans. Neuroscience Letters, 68, 334–8. PATLA, A.E. (1991) Visual control of human locomotion, in PATLA, A.E. (Ed) Adapt ability of Human Gait: Implications for the Control of Locomotion, pp 55–97, Elsevier Publishers. PATLA, A.E. (1995) The γ model: Can it walk? Behavioral and Brain Sciences, 18 (4), 775–6. PATLA, A.E. and RIEDTYK, S. (1993) Visual control of limb trajectory over obstacles: effect of obstacle height and width. Gait and Posture, 1, 45–60. PATLA, A.E., ARMSTRONG, C.J. and SILVEIRA, J.M. (1989) Adaptation of the muscle activation patterns to transitory increase in stride length during treadmill locomotion in humans. Human Movement Science, 8, 45–66. PATLA, A.E., BEUTER, A. and PRENTICE, S. (1991a) A two-stage correction of limb trajectory to avoid obstacles during stepping. Neuroscience Research Communication, 8 (13), 153–9. PATLA, A.E., PRENTICE, S. and UNGER-PETERS, G. (1993) Accommodating different compliant surfaces in the travel path during locomotions, Proceedings of the Fourteenth International Society for Biomechanics Conference, 11, 1010–11. PATLA, A.E., MARTIN, C., HOLDEN, R. and PRENTICE, S. (1992b) The effects of terrain difficulty on characteristics of voluntary visual sampling of the environment during locomotion. Society for Neuroscience Abstracts, San Diego. PATLA, A.E., PRENTICE, S.D., MARTIN, C. and RIETDYK, S. (1992c) The bases of selection of alternate foot placement during locomotion in humans, in WOOLLACOTT, M. and HORAK, F. (Eds) Posture and Gait: Control Mechanisms, pp. 226–9, University of Oregon Press. PATLA, A.E., PRENTICE, S., ROBINSON, C. and NEUFELD, J. (1991b) Visual control of locomotion: Strategies for changing direction and for going over obstacles, Journal of Experimental Psychology: Human Perception of Performance, 17 (3), 603–34. PATLA, A.E., RIETDYK, S., MARTIN, C. and PRENTICE, S. (1996). Locomotor patterns of the leading and trailing limb as solid and fragile obstacles are stepped over: Some insights into the role of vision during locomotion. Journal of Motor Behavior, 28 (1), 35–47. PATLA, A.E., ROBINSON, C., SAMWAYS, M., and ARMSTRONG, C.J. (1989) Visual control of step length during overground locomotion: Task-specific

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modulation of the locomotion synergy. Journal of Experimental Psychology: Human Perception and Performance, 25 (3), 603–17. PATLA, A.E., ELLIOTT, D.B., FLANAGAN, J., RIETDYK, K.S. and SPAULDING, S. (1995) Effects of age-related maculopathy on strategies for going over obstacles of different heights and contrast. Gait and Posture, 3 (2), 106. STEIN, R.B. (1991) Reflex modulation during locomotion, in PATLA A.E. (Ed.) (Adaptability of Human Gait: Implications for the Control of Locomotion, pp. 21–36, Elsevier Publishers. TINETTI, M.E. and POWELL, L. (1991) ‘Fear of falling and low self-efficacy: A cause of dependence in elderly persons’. Paper presented at the American Society for Gerontology Meeting. WINSTEIN, C.J. (1989) Balance retraining: does it transfer? in DUNCAN, P. (Ed.) Balance, American Physical Therapy Association. WINTER, D.A. (1991) The Biomechanics and Motor Control of Human Gait: Normal, Elderly and Pathological. Waterloo, Ontario: University of Waterloo Press. WINTER, D.A., PATLA, A.E. and FRANK, J.S., et al. (1990) Biomechanical walking pattern changes in the fit and healthy elderly. Physical Therapy, 70 (6), 340. YANG, J.F. and STEIN, R.B. (1990) Phase dependent reflex reversal in human leg muscles during walking. Journal of Neurophysiology, 63, 1109–17. YOUNG, R.P., SCOTT. S.H. and LOEB, G.E. (1992) An intrinsic mechanism to stabilise posture: joint-angle-dependent moment arms of the feline ankle muscles. Neurosci Lett, 145, 137–40. ZOHAR, D. (1978) Why do we bump into things while walking? Human Factors, 20, 671–9.

CHAPTER NINE Mobility of the disabled—manual wheelchair propulsion YVES C.VANLANDEWIJCK, ARTHUR J.SPAEPEN AND DANIEL THEISEN

9.1 Relevance of ergonomics Because of the fast evolution of new materials and new production techniques, the use of wheelchairs by people with a disability has become increasingly important. Starting with an overview of ergonomic factors that play a role in different issues related to the production, adaptation, selection and use of manually propelled wheelchairs (Sections 9.1 to 9.3), this chapter aims to introduce the reader to the physiological and biomechanical aspects of manual wheelchair propulsion (Section 9.4). 9.1.1 What is ergonomics? The main objective of research in the field of ergonomics is to understand the type and interrelation of factors influencing the quality of a task performed by a person in a given environment. The list of requirements imposed on the performer by the task usually becomes longer and less flexible with increasing restrictions of the environment, or circumstances under which it is to be executed. The person performing the task possesses a variety of skills and abilities that normally allow them to fulfil their intentions. In most cases, some kind of interaction between the person and the environment is necessary. For example, the person may want to have a discussion with someone, while at the same time recovering from the exertion of a walk just finished. For that reason, he or she may prefer a bench or easy chair, rather than a couch or bed, as a more suitable compromise for both tasks. We have learned to make use of our abilities, live with our limitations and adapt our environment to our needs in the best way we can, often unconsciously taking the related costs and expected benefits into account. Ergonomics is the field of study aimed at analysing and structuring the different factors and combinations of factors influencing the interface or interaction between a person and his or her environment. One of the most

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challenging aspects of this type of study is its multidisciplinary scope, which is both simultaneously its strength and its weakness; its strength because it relates multiple factors which belong to different scientific disciplines that are not always combined, its weakness because of the typical pitfalls for interdisciplinary work and lack of data, knowledge and experience, and the difficulties associated with the understanding of scientific language used by researchers and field workers with different educational backgrounds. 9.1.2. Ergonomics applied to assistive devices In many cases, designers of consumer goods or workplaces normally take the abilities of the majority of consumers or workers into account. Tables with anthropometric data provide ‘normal’ data for the size of body segments, the range of motion, the strength of the joints and so on. This data is then used in the design of new products that are meant to answer the requirements of ‘most’ users. Rather than manufacturing a series of chairs with different heights, a manufacturer might prefer to produce only one type of chair with the sitting height at 42 cm. This chair will allow more than 95 per cent of the clients to rest with their feet on the ground while seated, but is not necessarily the most comfortable one for long-legged persons. However, because of economies of scale and for situations in which many different persons will use the same chair, the proposed solution might be the optimal compromise for everyone’s comfort. A portion of the population which can no longer be neglected, currently estimated at approximately 10 per cent, is in some way excluded by the rules that apply to the ‘normal’ consumer, despite the effort towards ‘design for all’ which has gained significant attention more recently. These exceptions often follow from a disability, which in turn leads to functional restrictions, which vary from the ‘normal’ ones. Disabilities are extremely different in nature and level, and therefore need special attention when appropriate interfaces are to be developed. Although the general principles used in ergonomics also apply in this situation, two major differences are noticeable. First, interfaces, tools and so on, are tailored more specifically to the special needs of a smaller user group. Secondly, knowledge in the field of pathology is a crucial component of the knowledge base of the designer, not only to understand the disability, but more importantly to comprehend the functional remaining abilities in order to exploit these to their maximum potential. The tools, appliances and gadgets developed for this interfacing purpose are often called assistive devices. They are built to bridge the ‘extra’ gap between the requirements imposed by the environment and the abilities available to the person with a disability. A critical parameter in bridging this gap is the amount of compensation offered by the specific device or solution, that brings the user closer to the generally accepted standard performance.

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9.1.3 The case of manually propelled wheelchairs The design, manufacturing and use of wheelchairs fits perfectly in this framework. Further discussion in this chapter is limited to the series of manually propelled wheelchairs. Many different reasons exist why a person prefers or needs to use a wheelchair. Lack of motor control of the lower limbs, reduced muscle force, deformities of one or more body segments, the user being overweight, reduced postural control and so on, may cause difficulties in either the transportation from one place to another or in the static support of the body in an upright position, or in both. Depending on the level of the functional limitations and on the places between which transportation is needed (inside, outside, public or private) the choice of the wheelchair type might be completely different. As illustrated here, no direct relationship exists between the pathology underlying the reduced abilities, and a specific type of wheelchair. Furthermore, the diversity in both the type and level of handicap, the different type of transportation and support tasks required, and the variety of situations in which the tasks are executed have led to an extensive product demand and supply. Needless to say, manufacturing, selecting, using and maintaining such a vast range of products, most of which are only needed in relatively small quantities, creates a series of problems, which are almost non-existent in normal consumergoods markets. 9.2 Influence of ergonomics in important wheelchair issues Principles in ergonomics play an important role in several issues related to the correct use of the appropriate wheelchair in the proper situation. Since one of the main concerns in systems ergonomics is to take factors relating to different knowledge areas into account, it is not surprising that these principles also apply to quality control and manufacturing as well as financing issues. 9.2.1 Quality control Most often, the quality of a wheelchair is expressed in technical terms such as safety, reliability and strength and therefore can be expressed as technical quality. A second type of quality, which is at least as important as the technical quality, is the comfort with which the wheelchair can be used under different circumstances —for example, transportation, handling while lifting in and out of a car, effort needed, seating comfort, transfer to bed and toilet—which is called the functional quality.

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9.2.1.1 Selection process Before entering into the discussion of both types of quality characteristics, we would prefer to add a third component, which has proved to be directly related to the previous two. As explained above, a large range of manually driven wheelchairs has resulted from the diversity of demand for assistance in transportation and body support. It is not too difficult these days to find names, brands, technical specifications and so on for at least a few thousand manually propelled wheelchairs. Several national and international databases can assist in finding this information. Whereas previously, a potential user went to the closest shop or service to decide their purchase, they are now aware of a much larger list of possible solutions. This situation makes the necessity for professional and independent advice or assistance inevitable and essential. Professionals delivering this type of service should always have the expertise in a systems ergonomics analysis and approach. One of the main requirements is to have a global understanding of the problem, not only based on the specific request for a wheelchair, because this may sometimes be only partially complete, with much essential information necessary to the selection missing. The service provider should make an active search to discover the interrelation of tasks and requirements resulting from the transportation/support problem, in the complete set of situations that arise during the day. A practical way of analysing the set of requirements is by listing all activities from morning to evening on normal (for example, working) days and on special holidays and checking on the specific problem tasks. The service provider should also be aware of the selection of modules and options in wheelchairs and of the possibility or necessity of individual adaptations (for example, seating shells). With each of the proposed solutions or alternatives the service provider should then clearly indicate the level at which the user can expect to be able to solve their problem: the list of requirements as prepared during the analysis should be compared with the possibilities offered by each of the alternatives. In this way, the user will know more precisely what the functional consequences are for the different choices, allowing them to have a significant contribution in the selection process. Finally, service providers in assistive technology should also check the quality of the solutions proposed some time after the delivery of and training with the device. Although this kind of follow-up work is time consuming, it is extremely valuable both for the individual consumer as well as for the future quality of the service. A solution that may have appeared to be efficient in a ‘shop environment’ is often found to be ineffective in the real user environment, because the user’s and service provider’s interpretations of the requirements are not always the same, or perhaps because the user has overlooked some crucial issue.

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9.2.1.2 Technical quality It is not the purpose of this chapter to review the different parameters which are tested to assess the technical quality of a wheelchair. We merely emphasize the importance of an ergonomics approach in the selection of criteria that should include issues directly relevant to the user, such as resistance to propulsion, friction and wear of moving components. Because of the extremely high cost involved at the moment in the reliable testing of many wheelchairs there is an inevitable need for an international exchange and recognition of test data. Every possible effort should be made to increase the speed of standardization processes in this area. 9.2.1.3 Usability, user comfort From the above, it is clear that quality control of technical parameters is an extensive task. Assessment of usability issues is even more demanding. This follows from the fact that users with different functional abilities might use the same device or wheelchair. For this reason, user involvement is essential in the evaluation of the interface between the user and their environment. The complexity of this problem necessitates an approach that is different from the one used in testing technical quality. Rather than arriving at specific results for technical items in the testing of a specific device, functional assessment should concentrate on criteria, protocols and methods which clearly indicate the quality of the device in use. Furthermore, this knowledge should be merged with user experience. It is important, particularly in the field of rehabilitation, to develop systems that allow the structuring of usability issues in assistive technology. These developments cannot be seen independently from recent progress in international communication channels such as the Internet and others. 9.2.2 Manufacturing Manufacturers in assistive technology are facing extremely difficult problems. On the one hand they need to produce the highest possible volume of products to reduce manufacturing costs. On the other, these products should suit the client’s individual capabilities and limitations. As a consequence, economies of scale, as exist for general consumer products, do not apply to assistive devices. In some cases, considering the ‘design for all’ principle from the very beginning of the design of a new product may solve the problem for a larger user group, without a significant increase in cost or discomfort for other users; the design that takes the requirements of people with some limitations into account often suits most of the users better.

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Modular design, increasingly used in wheelchair manufacture, is currently seen as a major solution to conflicting requirements. The combination of a number of variants of each of the components of a wheelchair enables the assembly of an enormous range of products that are better suited to individual needs, without completely destroying the possibility of manufacturing acceptable numbers of each of the components separately. This technique also has another interesting influence: the responsibility for and the importance of the selection process is strongly shifted towards the user and the service provider (such as the higher need for information and training). The increase in quality will therefore coincide with an increase in the cost for service provision. 9.2.3 Financing issues Finally, ergonomic principles can also influence the financing of assistive devices in general or, more specifically, wheelchairs. Generally speaking, if a person’s functional abilities are reduced because of disability, illness or an accident, they are in an economically weaker situation than people without these limitations. In many countries this situation has led to the decision to provide financial support for the use of assistive devices. Often, product lists based on the pathology or handicap of a user have been developed to regulate the reimbursement of specific groups of devices. In some cases, users are not completely satisfied and criticize the ineffectiveness of such lists. One reason for this criticism has already been explained and can be derived from the observation that the handicap or pathology is hardly one of the three key factors influencing the choice of the device. A more appropriate approach should be based on functional abilities (rather than disabilities) and the task requirements in the specific user environment. Even if such a system were used, it would be necessary to combine the outcome of the proper selection procedure with its benefits and costs. The benefits should follow from the selection procedure, since the service provider is able to indicate the functional recovery created by the device in the different tasks and circumstances. With the right choice and adequate indication of the benefits, the value of the proposed solution for both the user and the community should still be made explicit. Rules, regulations or laws should indicate the priorities of the community (for example, basic personal communication, basic mobility, independent life, educational and vocational opportunities, social contact and leisure) and measure these against the proposed solutions (with the amount of task regain). The involvement and responsibility of the user in this matter is a prerequisite, but at the same time has a counter side. A higher contribution from the community (higher level of reimbursement) should imply a higher level of commitment, also financially, from the user, to ensure a proper balancing of community effort and value for the user.

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Finally, the cost of the purchase of the device, and service provision (assistance in selection, training and so on) should be included, also in a structured way. For wheelchairs, a cost for the appropriate service provision in the order of one-third of the cost of the device should be expected, and may be regarded as an added value in terms of the proper selection of the apparatus. 9.3 Required knowledge What knowledge is needed to adequately assess the selection of a wheelchair, its technical and functional qualities and requirements, the user’s abilities and the advantages gained from the efficient use of the correct device? 9.3.1 Human functioning It is clear that a good understanding of the user’s abilities is a solid starting base not only in the process of the selection of a device, but also in the development, design and manufacturing as well as in more generic questions, such as the assessment of the added value of a device, or the organization of reimbursement schemes. It is also clear that a sound insight into the functional consequences of a disability will increase the knowledge of human functioning and limitations. With respect to this approach we often seem to underestimate the abilities of a person, and certainly children, to learn new techniques, to adapt to new situations and to train for higher performance. More specifically, acknowledging redundancy in certain tasks (for example, in language or in bilateral movements which can also be executed unilaterally) is sometimes a decisive issue in the solution to assistive devices. 9.3.2 Systems ergonomics—the global approach Users intend to contribute as much as possible towards finding the solution to their problem. They may ask for assistance in the selection of a wheelchair even before it has been made clear that a wheelchair is the right type of choice. Service providers should have a reflex, based on a systems ergonomics approach, to retrieve the basic functional need behind the request for the purchase of a wheelchair. Furthermore, they should find out in what kind of circumstances and for what kind of tasks a solution is needed. The expertise needed to understand all the different types of environment is unlikely to be found within one individual. Finding solutions in a home environment can be completely different from solving adaptations in a workplace, although the same basic ergonomics principles are used. The practical consequences, however, can be totally different. For this reason, we

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expect a more pronounced specialization in the provision of assistive technology, on the basis of both functional and environmental characteristics of the work involved in service provision. Finally, a sound judgement of the value of a proposed solution to the user is the key factor in the quality of the service. It will enable the service provider to recognize the user’s motivation and to suggest the right level of assistance and solutions, also in relation to the resources that can be made available, both by the user and the community. A consensus between the user and the supplier or service provider seems to be a necessity in situations where the agreed solution is also proposed to the community for complete or partial reimbursement. 9.4 Ergonomics in manual wheelchair propulsion: a multidisciplinary approach The freedom of action of any subject, which is fundamental to health, and determines the social range of action of the person, is mainly determined by the functionality of their locomotor system. A disability of the lower limbs, which confines a person to a wheelchair, reduces the range of action of that person to a relatively large extent. Their freedom will be determined by a number of factors generally classified into three major areas: the wheelchair, the wheelchair-user interface and the user themselves. The aim of this section is to provide the reader with a comprehensive overview of the existing research information related to the physiology and the kinesiology of manual wheelchair propulsion. 9.4.1 Wheel chair-related factors The coasting characteristics of a wheelchair are described in terms of gravitational force when propelling up an incline (Fincl), rolling resistance (Fr), internal energy losses in the wheelchair (Fi) and air drag (Fa). Consequently, power output (PO) is expressed as the sum of these external energy losses multiplied by the mean velocity (v) of the wheelchair-user system (van der Woude, 1989). Except for Fincl all the forces representing external energy losses are related to the characteristics of the wheelchair. These forces can become quite large, especially if the wheelchair is in a technically bad condition, which seems to be true for a large majority (van der Woude, 1989). As a consequence, mechanical efficiency (ME=[PO/Energy expenditure]×100) of manual wheelchair propulsion is low (11 to 14 per cent according to van der Woude et al. (1988a), Brattgard et al. (1970), Glaser et al. (1979), Gass and Camp (1987) and Vanlandewijck et al. (1994) compared to efficiency values of 23 per cent in bicycle ergometer work

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and up to 30 per cent in walking (Traut and Schmauder, 1991). This, together with the fact that only a small muscle mass is involved, will discourage proper wheelchair use and participation in physical activities, and will enhance disabling conditions, both in the cardiovascular and the musculo-skeletal system. A number of explanations for high physical strain and the generally low values of mechanical efficiency can be found in the coasting characteristics of the wheelchair. 9.4.1.1 Coasting characteristics of the wheelchair Rolling resistance. Rolling resistance arises mainly because the forces acting on the wheel ahead of the centre of the contact area (where the tyre and/or the wheel are deformed) are greater than those behind that point (where the deformation recovers). This causes a loss of energy, known as hysteresis loss, and results in the slight heating of the tyre material (Frank and Abel, 1991b). An increase in rolling resistance will increase physical strain during wheelchair propulsion. The ground surface, over which a wheelchair is propelled, plays an essential role in this respect. Rolling resistance on rough surfaces is generally higher than on smooth ones. Soft surfaces, like a carpet, can offer very high rolling resistance and therefore require higher PO levels (Glaser and Collins, 1981), and consequently induce higher cardiopulmonary stresses (Glaser et al., 1981b, Smith et al., 1983). Considering the tyre and wheel characteristics, the main determinants of rolling resistance are the bulk properties of the material, the radius of the tyre and the radius of the tread in cross section (Kauzlarich and Thacker, 1985). Pneumatic tyres have been found to have smaller hysteresis loss than solid tyres (Whitt and Wilson, 1982) and, for similar sizes, have better shock absorbtion (Frank and Abel, 1991a). Because of their relatively small radius, the castor wheels have a higher rolling resistance than the rear wheels. Therefore, the total rolling resistance of the chair can be minimized by moving the centre of gravity further back, in the direction of the rear axle. This is, however, a matter of individual choice (disability, security, and so on), as the tendency to tip backwards is increased. Rolling resistance also increases as the radius of the tread in the cross section increases. The tread radius is highly dependent on the inflation pressure in the tyres. It is also influenced by the total weight and weight distribution over the front and rear wheels. Misalignment of the rear wheels, known as toe-in or toe-out, results in a frictional drag force in the region of contact with the ground. A few degrees of deviation from true alignment can cause a dramatic increase in rolling resistance (O’Reagan et al., 1981). Castor wheels have tended to vibrate rapidly from side to side, once a certain speed is reached. Castor flutter can significantly increase rolling resistance (Frank and Abel, 1991b).

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The increased camber angle of the rear wheels is not only a fashion trend, that is seen more and more on daily-use wheelchairs, but it also presents a certain number of advantages. It increases lateral stability and offers less rolling resistance and a lower downward turning moment on lateral slopes. Indoors, the hands are protected when passing through doors or moving along a wall. However, narrow passages are more difficult to negotiate. The strain on the rear ball-bearings is greater and rolling resistance increases when the chair is tilted, as a result of the misalignment of the rear wheels. Values of rolling resistance for non-pneumatic wheelchair wheels, reported by Frank and Abel (1989), ranged from 2 to 6 N for a 200 N load and a constant speed of 1 ms−1. On a firm level surface the rolling resistance may be as low as 6 Newtons (N) or as high as 40 N, depending on tyres and alignment (McLaurin and Brubaker, 1991). Internal losses. Internal energy losses in the wheelchair occur mainly at three levels: friction in the wheel bearings, deformation of the wheelchair frame and losses in chain and lever transmission systems. For hand-rim wheelchairs, plain bearings are uncommon nowadays and most modern wheelchairs have annular bearings with revolving balls or rollers. If they are in good condition, they offer a coefficient of friction that is likely to be less than 0.001, that is, a drag force of less than one thousandth of the combined weight of the chair and the occupant (Frank and Abel, 1991b). Possible energy dissipation in hinges and folding mechanisms have not been quantified to date. Air drag. While for most wheelchair users, air drag is a minor problem and rarely encountered, it is an important consideration in wheelchair athletics, where travelling speed is higher. The drag force results from collisions of air molecules with the frontal area of a moving object, and from the friction between the object and the air moving round it (Frank and Abel, 1991b). It can be described by the equation below. Where F is the total air drag force, c is the drag coefficient, p is the density of the air, a is the frontal area of the object (the total cross-sectional area seen from the front) and v is the speed of the object relative to air. At atmospheric conditions, the density of the air is 1.23 kg m3. Using data from Hedrick et al. (1990) the frontal area of a wheelchair user will be between 0.394 and 0.756 m2, depending on body position. According to Coe (1979), the drag coefficient is approximately 1.4. Figures from Frank and Abel (1991b) indicate that at slow walking speed (1 ms−1) air drag is below 1 N, while at 5 ms −1 the drag force due to air resistance is about 14 N, which implies an average power output of 5×14=70 W for wind resistance only.

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9.4.1.2 Propulsion mechanism Lever, (hub) crank and hand rim propulsion mechanisms. Propulsion systems of hand-driven wheelchairs are of three kinds: hand rims, crank and lever propulsion mechanisms. Lesser (1986) and Gangelhoff et al. (1988) found that lever ergometry was superior to crank ergometry, in terms of mechanical efficiency and cardiorespiratory responses. Hand rim propulsion, however, is the most common system (85 per cent according to Traut and Schmauder, 1991), probably due to the effective propulsion interface which provides the user with maximum feedback and control (Brubaker et al., 1984). Hand rim wheelchairs have often been compared with the alternative propulsion mechanisms. Voigt and Bahn (1969), Brattgard et al. (1970), Sawka et al. (1980), Smith et al. (1983), Sedlock et al. (1990) and van der Woude et al. (1986, 1993) showed that crank propelled wheelchairs are more efficient and less stressful from the physiological point of view, compared with the hand rim propulsion mechanism. Lesser (1986), Engel and Seeliger (1986) and van der Woude et al. (1986, 1993), comparing a lever propulsion mechanism with a conventional hand rim wheelchair, have found a marked decrease in circulatory strain and energy consumption in favour of the lever system. Studies by Engel and Hildebrandt (1974) showed that levers moved back and forth to drive the wheels could increase the efficiency compared with hand rims. The double mode system (push and pull action) is very efficient because of the lack of idling strokes. The use of one arm in wheelchair propulsion is practically possible in a lever wheelchair and enables subjects with hemiplegia to propel themselves. The consequences for the cardiorespiratory system have not been extensively studied. The small muscle mass in the asymmetric task may lead to considerable strains. The stress on the cardiovascular system is probably elevated, because of high muscle force with a large static component (stabilizing the trunk, grip forces). This obviously enhances peripheral vascular pressure, which in turn may imply a serious health risk for those with cardiovascular disease or untrained subjects in general. Van der Woude et al. (1993, 1995b) have speculated about the explanations for the apparent relative efficiency of lever propulsion mechanisms. Differences in hand velocity, isometric muscular activity, segment trajectories and the magnitude and direction of force differ and may explain the differences in physiology. Other factors that may explain the higher efficiency in a lever propelled wheelchair are the continuity of motion, the effective use of the backrest and probably the larger muscle mass involved. For more effective everyday use, a redesign in terms of weight, lever configuration and gearing is required for existing lever wheelchairs. Unfortunately, there are practical difficulties associated with both levers and cranks which increase cost, weight and complexity. The crank studies were conducted using bicycle type cranks mounted in front of the user—a juxtaposition that is mechanically difficult and socially undesirable for the user.

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Typical lever systems rely on connecting rods to drive the wheels. This causes difficulties in maneuvring and in starting, particularly on slopes (McLaurin and Brubaker, 1991). Ergonomic and handling criteria of the various wheelchair propulsion systems are shown in Table 9.1. A recently developed propulsion mechanism is the hubcrank, a device which allows a continuous motion of the hand around the wheelhub of the rear wheels of a track wheelchair. The hubcrank has a well-fitted handgrip which rotates freely around an axle perpendicular to the crank and adapts itself to the orientation of the hand. In a comparison between the hubcrank device and a hand rim device, van der Woude et al. (1995a) demonstrated a significantly lower strain for the hubcrank and a significantly higher gross mechanical efficiency which reached values up to 3 per cent higher for the hubcrank over the hand rim propulsion mechanism. The positive effects of the hubcrank may be explained metabolically by a continuous Table 9.1 Ergonomic and handling criteria of various wheelchair propulsion systems (Seeliger 1991). Criteria

Wheelchair propulsion systems

Rim

Crank

Lever

Good ergonomic position Idling strokes Good efficiency Freewheel Dead points Turnable on the spot Steering with additional parts Kinetic brake required

No Yes No Yes No Yes No No

No/yes No Yes No No Yes/no No No

Yes No Yes No Yes No Yes Yes

circular motion, allowing both push and pull actions, reducing muscular fatigue and increasing the active muscle mass (van der Woude et al., 1995a). Furthermore, equilibrated work of both agonists and antagonists of hand-rim wheelchair propulsion may reduce shoulder injuries due to imbalance of the rotator cuff. Biomechanical advantages of the hubcrank mechanism could be (1) a more natural orientation of the hand and a less strenuous coupling of the hand to the propulsion mechanism; (2) the prevention of a negative gripping torque as is seen in hand-rim wheelchair propulsion and (3) the prevention of the braking torque at the start and the end of the push phase (see Section 9.4.3.2.4.). However, the wheelchair is hard to steer, and braking becomes more complicated (van der Woude et al., 1995a). Synchronous versus asynchronous propulsion. Wheelchair locomotion is normally seen as a synchronous form of locomotion. Modifications of the conventional wheelchair design may improve efficiency and reduce the physical strain of the wheelchair user. Glaser et al. (1980) used a wheelchair ergometer to

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evaluate the synchronous and asynchronous application of force to the hand rims. Nineteen able-bodied subjects propelled at a power output level of 30 and 60 kpm min−1. The asynchronous hand rim propulsion was found the most efficient. The advantage of the asynchronous mode compared with the synchronous mode was expressed in a significant lower (p<0.01) gross caloric output (kcal min−1) pulmonary ventilation and heart-rate values. These results on propulsion mode were supported by Engel et al. (1976) and Beal et al. (1981) for lever propulsion mechanisms. In a comparative study (12 able-bodied subjects) of propulsion mode (synchronous versus asynchronous) with a tricycle arm crank device on a motor driven treadmill, Bosmans (1995), however, found the synchronous mode to be superior with respect to metabolic parameters and mechanical efficiency. Contradictory results are dedicated to steering inaccuracy in the asynchronous mode, and the supportive action of the trunk musculature to the arm muscles. It has to be noted that the only paraplegic subject (T6) involved in this study showed inverse results. Mechanical advantage. Lever and crank propulsion mechanisms may be equipped with a gearing system, for example, in a tricycle arm crank wheelchair. Hand-rim wheelchairs, however, are usually not equipped with gears. The angular velocity of the wheels will thus always be equal to the angular velocity of the hand rims. Consequently, hand rim tangential velocity will always be proportionally lower than the propulsion velocity of the wheels and dependent on the radius of both rim and wheel. Mechanical advantage (MA) thus equals the ratio between hand rim radius and wheel radius (Veeger et al., 1992c). To study the physiological effects of rim size, van der Woude et al. (1988b) tested eight track athletes in a similar type racing wheelchair on a motor-driven treadmill. In five separate tests, five hand rims of different diameters were used, ranging from 0.30 (MA=0.43) to 0.56 m (MA=0.77). At equal external loads, cardiorespiratory responses were significantly higher (p<0.05) for the two bigger rims in comparison with the smaller ones. Gross mechanical efficiency showed an inverse relationship with hand rim diameter. However, a shift in the shoulderto-rim distance also occurred with varying rim size, as the seat height could not be adjusted. The authors indicate that both factors may have influenced their results. Gayle et al. (1990) also found significantly lower physiological responses for a smaller hand rim, but only at a speed of 8 km h−1 (2.22 m s−1). No rim diameter effect was found at 4 km h−1 (1.11ms−1). The possible causes for these findings are that the linear velocity of the hand increases with increasing rim diameter for a given propelling speed. This may lead to higher accelerations and decelerations of the different arm segments. In addition, increased angular excursions of the shoulder complex are observed with bigger rim sizes. These aspects may well explain the increased oxygen cost and physiological responses (van der Woude et al., 1988b). Veeger et al. (1992c) studied the effect of hand rim velocity on mechanical efficiency in wheelchair propulsion against constant power output levels. By

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testing nine able-bodied subjects on a stationary wheelchair ergometer (Niesing et al., 1990), they were able to confirm that mechanical efficiency decreased with increasing tangential hand rim velocity, which is related to the diameter. They suggest that an ineffective direction of forces on the rims might be a possible explanation for this (see Section 9.4.3.2. ‘Applied forces’). These findings would exclude the hypothesis of van der Woude et al. (1988b) that the effect of rim diameter on physiological parameters is caused by differences in shoulder-to-rim distances. Studies on mechanical advantage in manual wheelchair propulsion, as summarized in Table 9.2, have to be compared with caution, because of differences in power output level (varying or constant), subjects (able-bodied versus elite athletes), and test protocol (differences in slope and/or velocity). For example, comparing the results of Veeger et al. (1992c) and Vanlandewijck et al. (1994), a shift of the velocity-effect can be noticed. This shift could be explained by the high level of training and experience of the subjects in the latter study. In cycling, a considerable number of studies have examined the effect of pedalling frequency with reference to optimal performance. Many researchers have concluded that there are optimum pedal rates, which seem to be positively related to the level of training. Both authors (Veeger et al., 1992c; Vanlandewijck et al., 1994), however, support the inverse relationship between mechanical efficiency and mechanical advantage. The choice of the hand rim is related to the functionality of the user. A major practical consequence of the inverse relation between efficiency and hand rim diam Table 9.2 Mechanical advantage (MA) in hand-rim wheelchair propulsion and its effect on mechanical efficiency (ME) [* versus **: significant difference in ME] Authors

Speed m.s−1

Glaser et al. (1980)

0.97

van der Woude et al. (1988b)

0.83 m.s−1 +0.83 m.s−1 each stage

Gayle et al. (1990)

1.1 m.s−1 2.2 m.s−1 0.83 m.s−1 1.11 m.s−1 1.39 m.s−1 1.67 m.s−1 1.11 m.s−1 1.67 m.s−1 2.22 m.s−1

Veeger et al. (1992c)

Vanlandewijck et al. (1994)

MA

Results

1.62 1.86 2.10 0.43 0.50 0.54 0.67 0.77 0.36 0.59 0.43 0.58 0.72 0.87 0.59 0.88 1.17

* ** ** * * * ** ** Significant decrease in ME for 2.2 m.s−1 Significant decrease in ME over the velocity range

Significant decrease in ME from 1. 67 to 2.22 m.s−1

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eter or speed would be the choice of smaller rims. A smaller hand rim with a lower mechanical advantage, and thus a higher resistance, implies, however, the need for greater torques when negotiating slopes and steps. The final choice is therefore dependent on the functional capacities and muscular strength of the individual, as well as on factors like manoeuvrability and purpose of use. In wheelchair sports, the size of the rim is very task-specific. Thus, the larger rims used by basketball players have an advantage in quick acceleration and, therefore, in covering a short distance as rapidly as possible. Track wheelchair athletes usually use smaller rims. Since wheelchair athletes may travel at a speed of up to 30 km h−1 and there is a practical limit to the speed of muscle contraction (approximately 10×muscle length per second) it is not difficult to see the importance of small diameter hand rims for racing. In order to reach small diameter hand rims, the seat must be lowered, and the wheels cambered to permit the arms to reach comfortably over the wheels (McLaurin and Brubaker, 1991). Further biomechanical consequences of usage of different gear ratio’s are discussed in Section 9.4.3.2. ‘Applied forces’. Cross-sectional hand rim diameter. Hand rim characteristics can also vary in terms of cross-sectional diameter/profile and surface material. A number of studies focusing on these aspects revealed a tendency towards thicker tubes and forms, giving a greater contact surface between the hand and the rim, and a higher frictional coefficient, allowing a better force transmission (Jarvis and Rolfe, 1982; Lesser, 1986; Traut and Schmauder, 1991). According to Linden et al. (1995) it is not unlikely that force application on the hand rims is not primarily dependent on the cross-sectional diameter, but rather on the coupling action between hand and rim (that is grasping, stroking). In Linden et al.’s (1995) study, a tendency seemed to exist towards a more effective force application when using a hand rim tube with oval cross section and a larger diameter, compared with a hand rim with circular shape and smaller cross-section. However, this tendency was not significant. Considering the surface material used, the results of Traut and Schmauder (1991) clearly indicate that materials with a high frictional coefficient on the rims are unsuitable for the braking task and may induce burn injuries. Such materials can, however, be recommended for users with lower hand closing force and for selected uses in wheelchair sports. 9.4.2 The wheelchair-user interface The wheelchair-user interface is the area of study where the geometry of the wheelchair is analysed with respect to the user’s performance. To optimize the fit of the dimensional characteristics of the wheelchair to the individual’s functional capacities, certain factors of the interface must be studied. These include, for hand rim wheelchairs, camber of the rear wheels, hand rim characteristics and seat position. Seating adjustments are becoming more

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common in wheelchair design, but it should be remembered that any adjustment carries a penalty in cost, weight and strength. Common adjustments are seatback angle and seatback height. Seat angle and seat height adjustments are also available, but perhaps the most important adjustment is to allow the center of gravity of the user to be positioned correctly with respect to the main wheels (McLaurin and Brubaker, 1991). 9.4.2.1 Fore/aft orientation to the hand rim Considering the fore/aft position of the seat relative to the rear wheels, Brattgard et al. (1970) found a significantly higher efficiency with the wheels in a ‘posterior-high’ position compared with the ‘anterior-high’ position. Lesser (1986) recommends a lower and more forward position of the seat with respect to the wheels, which seems to be in accordance with the findings of Brattgard et al. (1970). As no precise definitions of the positions relative to anthropometric data are indicated, it is, however, difficult to compare these results. Traut and Schmauder (1991) recommend a hand rim position at which the hand rim vertex is 75 mm in front of the shoulder joint and 50 mm below the forearm when the elbow is flexed at an angle of 90°. The reason that the seat position affects efficiency is found in the mechanics of the arm during the power stroke and recovery. The optimum seating position is primarily dependent upon the position of the shoulder joint with respect of the axle, and the dimensions of the arm segments. This determines the geometry of the joint position and the range of motion of the muscles used in propulsion (see Section 9.4.3.2. ‘Applied forces’). One must remember, however, that changing the seat position relative to the rear wheels in order to optimize mechanical efficiency also induces some changes in the wheelchair characteristics, such as rolling resistance, manoeuvrability, overall length and danger of tilting. These factors must be considered when adapting a wheelchair to a person with respect to their functional capacities (disability, equilibrium, strength, purpose of use). 9.4.2.2 Shoulder-to-rim distance Van der Woude et al. (1989c) conducted a study on nine non-wheelchair users to find a relationship between seat height and arm and trunk dimensions. They used a basketball wheelchair on a treadmill to do four subsequent exercise tests at four different seat heights. The seat height was adjusted with respect to the elbow angle (respectively 100°, 120°, 140° and 160° elbow extension, 180° standing for full extension) and defined with the subject in a fixed standardized position with the hands on the top-dead-centre of the rims. Their findings showed that, in general, cardiorespiratory responses increased with increasing seat height, with significant effects for mechanical efficiency and oxygen consumption.

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These results were in line with those of a follow-up study by van der Woude et al (1990a), who had five non-wheelchair users perform on a stationary wheelchair ergometer (Niesing et al., 1990) at seat heights corresponding to 90°, 80° and 70° elbow extension. They found an increase in physical strain as the seat height decreased, with a statistically significant effect for oxygen consumption only. These two studies showed a dependence of efficiency on seat height in relation to the anthropometric dimensions of the wheelchair user. The optimum height corresponded to an elbow extension of 100° to 120° in the standardized position. Recently, these results were confirmed in a study of 12 subjects with spinal cord injuries in the course of their rehabilitation process (van der Woude et al., 1995b). 9.4.3 User-related factors The wheelchair-dependent individual is the engine of the wheelchair-user combination, and as such, their performance capacity determines their freedom of move ment. Performance capacity is usually related to maximal oxygen uptake and/or external power output, measured in a standardized wheelchair exercise test. Maximum power output in wheelchair ergometry is not merely a function of individual training, but also depends to a large extent on disabilityspecific factors, age and alterations in wheelchair design. Volume of action, speed, endurance and manoeuvrability will vary proportionally to performance capacity. Quality of life can be limited by the resources available (upper body strength, anaerobic capacity and aerobic power) to meet the challenges encountered in daily life, such as slopes, architectural barriers. User-related factors influencing physiological responses to wheelchair exercise also include propulsion technique. Propulsion-technique characteristics can be described in terms of timing parameters, movement patterns, muscular activity and force application. Exercise capacity and propulsion technique are discussed in the next section with special reference to spinal-cord injury. 9.4.3.1 Exercise capacity Wheelchair-bound subjects must depend on their upper body musculature for locomotion. This places the wheelchair user at a disadvantage because of the relatively small muscle mass of the arms compared with the legs. A greater oxygen uptake is elicited by arm-crank rather than leg-cycle exercise performed at the same submaximal power output. In addition, peak oxygen uptake is consistently lower during arm-crank than leg-cycle exercise (Sawka, 1986). The relatively smaller skeletal muscle mass involved during upper body exercise

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limits peak oxygen uptake by the smaller oxidative capacity and reduced ability to generate tension (Sawka et al., 1991), leading to early local muscle fatigue. A spinal cord injury, as in the case of quadriplegia, may even reduce the amount of upper body skeletal muscles that can be used to operate a wheelchair. Although there are significant variations between persons of different functional disability classes (Table 9.3), in terms of peak oxygen consumption and peak power output, Vanlandewijck (1994) finds no differences in mechanical efficiency in his test subjects (N=40), who are highly trained wheelchair athletes. Some studies suggest that, in general, wheelchair ergometry, compared with arm-crank ergometry, elicits similar peak oxygen uptake values (Wicks et al., 1977, 1983), but lower peak power output values (Glaser et al., 1980; Wicks et al., 1983). Sawka (1980) found that, at a given submaximal power output level, oxygen uptake, cardiac output, stroke volume, heart rate and blood pressure were generally higher during wheelchair than arm-crank exercise. Although cardiac output responses at a given submaximal oxygen uptake are similar for arm-crank and leg-cycle exercise (Sawka, 1986; Miles et al., 1989), there are marked differences in the heart-rate and stroke-volume relationships. Investigators consistently report a higher heart rate and lower stroke volume at a given submaximal oxygen uptake during arm-crank than during leg-cycle exercise (Sawka et al., 1991). Reduced skeletal muscle pump activity during upper body exercise probably reduces preload and therefore stroke volume. Paraplegics have a disturbed vasoregulation below the lesion, because the absence of the musculo-skeletal pump in the legs and the lack of sympathetic vasomotor regulation in legs and abdomen reduces vasoconstriction. This may cause blood pooling in the capacity veins below Table 9.3 Body mass, POmax and VO2-peak for spinal cord injured individuals, according to the International Stoke Mandeville Games Federation (ISMGF) classification. ISMGF class Veeger et al (1991a) I: n=1; II: n=6, III: n=10; IV: n=13; V: n=7 POmax (W) VO2-peak (ml.kg−1.min−1) Janssen et al. (1993) I: n=9; II: n=6; III: n=15; IV: n=12; V: n=2 POmax (W.kg−1) VO2-peak

I

II

III

IV

V

Body mass 60 (kg)

84 17.7

74 12.1

67 13.8

59 11.8

65.8 11.8 27.3 23.0 7.5 Body mass 81.2 (kg) 14.9

79.8 13.8 26.8 6.9 82.8 10.6

85.4 23.5 36.9 9.1 78.6 16

79.3 19.7 40.6 8.6 78.9 21.9

0.41 0.16 13.63

0.91 1.11 1.04 0.37 0.37 0.21 21.20 25.74 31.30

0.72 0.32 17.55

68.4

258 MOBILITY OF THE DISABLED

ISMGF class (ml-kg−1.min−1) Vanlandewijck et al. (1994) II: n=6; III: n=7, IV: n=12, V: n=7 POmax (W) VO2-peak (ml.kg−1.min−1)

I 3.05 3.97 Body mass (kg) 62.6 18.3 24.8 9.2

II 6.59 69.2 13.7 86.7 18.1 34.8 4.1

III 7.82 66.0 7.2 82.6 26.4 35.5 9.4

IV

V

67.2 14.3 105.0 22.8 40.3 4.3

64.2 15.6

the lesion, which, during exercise, may fail to facilitate venous return and decrease end-diastolic volume. Therefore, a reduced preload will cause the myocardium to contract on a less efficient part of the ventricular function curve. As compensation, heart rate is higher in paraplegics than in able-bodied subjects during arm exercise (Hopman et al., 1991). At lower exercise levels heart rate may compensate for the reduced stroke volume, but at higher exercise levels heart rate will reach a maximum. Functional neuromuscular stimulation of paralysed muscles, imitating the musculo-skeletal pump, and anti-gravity suits, applying external pressure on legs and abdomen, are possibilities to increase venous return and, thus, stroke volume in paraplegics (Hopman et al., 1991). The level of the spinal cord injury plays an important role in cardiovascular behaviour during exercise. Paraplegics with lesions above T6 may have a disturbed cardiac sympathetic innervation, so vagal innervation will overrule. For these subjects it is difficult to accelerate their heart rate during exercise, and they may reach their maximum heart rate, cardiac output and oxygen consumption at lower exercise levels than paraplegics with lesions below T6 (Hopman et al., 1991). Passive and active mechanisms of temperature regulation as well as temperature sensation in areas below the spinal cord lesion are impaired in quadri- and paraplegic subjects. Sweating, pilo-erection and autonomic control of muscle and skin vasculature are inactive below the level of the lesion. Therefore, the skin and body temperature of patients with spinal cord injuries are influenced much more by environmental temperatures than the able-bodied. This may lead to faster overheating and cooling when these subjects are exposed to extreme environmental conditions (Grunze et al., 1991). Sawka et al. (1989) suggest that the lack of vasomotor and sudomotor neural control of skin blood flow may, in addition to the venous pooling in paralysed leg muscles, contribute to altered cardiovascular performance. According to them, in people with spinal cord injury, temperature control must rely on dry heat exchange mechanisms to maintain homeostasis during prolonged exercise. To elicit sufficient dry heat exchange, more blood collects in the skin to maintain adequate heat loss to the ambient environment. This results in a reduced stroke volume and increased heart rate during prolonged physical activity.

Y.C.VANLANDEWIJCK, A.J.SPAEPEN AND D.THEISEN 259

Oxygen consumption, heart rate and ventilation during wheelchair exercise generally vary inversely with the level of the lesion. The lower the lesion, the higher the peak value for these variables (Coutts et al., 1983; Wicks et al., 1983; Lakomi et al., 1987; Eriksson et al., 1988; Glaser, 1989; Bhambhani et al., 1991). In addition, peak physiological responses are influenced by lifestyle and training (Glaser et al, 1981a; Eriksson et al., 1988), sex (Wicks et al., 1983) and age (Sawka et al., 1981). The physical capacity of persons with quadriplegia appeared to be dramatically lower than in those with paraplegia (Coutts et al., 1983; Eriksson et al., 1988; Burkett et al., 1990; Janssen et al., 1993). In several studies (DiCarlo, 1988; Cooney and Walker, 1986) a significant effect of regular training programmes was demonstrated on cardiovascular parameters in persons with cervical spinal cord injury. The results of the assessment of physical strain during an ordinary day indicate that the average strain for all subjects was low during the day (26 per cent heart rate reserve). This is only slightly higher than the results (15–24 per cent heart rate reserve) reported by Hjeltnes and Vokac (1979). Although the mean strain in the activities of daily living is low, the activity-related strain, such as making transfers, climbing a ramp and wheelchair propulsion outdoor, can increase to more than 50 per cent of heart rate reserve (Janssen, 1994). In Table 9.4, maximal oxygen uptake and peak power output values of elite spinal cord injuried athletes, performing different sports disciplines (wheelchair racing, wheelchair basketball, quad-rugby) are presented. All parameters were assessed by means of wheelchair ergometry. Exercise capacity standards for spinal cord injuries, however, based on these results, are difficult to determine, due to differences in exercise-testing protocol, and the variety in the level of disability, age, sex and training status. Sound conclusions on cardiorespiratory fitness in spinal cord injuries can only be drawn when exercise protocols are standardized, and inter-subject variables such as level of disability, age, sex and training status are controlled. Furthermore, from the viewpoint of ergonomics, ergometer devices have to be task-specific and controlled for reliability, validity and accuracy. There have been several types of ergometers employed for this purpose including mounting the wheelchair on a motor-driven treadmill or low-friction rollers and specialized devices used in research to closely simulate over-ground propulsion. The traditional disadvantages of wheelchair ergometer tests have included issues of reproducibility and validity when moving from one wheelchair device to another. Accurate quantification and reproducibility of power output characteristics between trials or among subjects of disparate body mass is still a major problem in low-friction rollers. From a biomechanics viewpoint, manual wheelchair propulsion on a motor-driven treadmill properly simulates over-ground wheelchair locomotion (see 4.3.2.4. ‘Three-dimensional dynamic modelling’). For people with spinal cord injury very few investigations concerning protocol dependency have been undertaken. Lasko-McCarthy and Davis (1991) have

260 MOBILITY OF THE DISABLED

investigated the effects of the size of the increment in intensity on peak-VO2 during wheelchair ergometry in men with quadriplegia. Rasche et al. (1993) compared different protocols in terms of (dis)continuity in men with paraplegia. Hartung et al. (1993) controlled the peak-VO2 dependency on grade and speed modalities of treadmill exercise-testing protocols in men with paraplegia. Systematic comparison to determine which test modalities and which test protocols yield the highest or most consistent values for peak-VO2 will lead to the determination of normative data on maximal exercise potential of spinal cord injuries. Standardized test protocols will also allow cooperation between laboratories, through which conclusions can be based on the results of large and homogenous experimental groups, which will reduce the high within-group variability. 9.4.3.2 Propulsion technique Oxygen consumption is an adequate parameter to evaluate the effectiveness of steady-state wheelchair ambulation with a certain propulsion technique. However, metabolic parameters themselves do not clarify how energy is transferred from the user to the wheelchair or why a certain technique requires more energy than another. These aspects can be studied by analysing related parameters such as timing, movement patterns, muscular activity and force application. Timing parameters. In recent studies (Sanderson and Sommer, 1985; Brown et al., 1990; Lees, 1991; Veeger et al., 1992a, b, d; Vanlandewijck et al., 1994), a number of timing parameters are used to describe propulsion technique in handrim wheelchair propulsion (Figure 9.1). The variations of these timing parameters have been extensively described in relation to different work conditions: Table 9.4 VO2-peak and POmax in spinal cord injured athletes performing wheelchair ergometry (A=athletics, B=basketball, Q=quad-rugby, NA=not available) Referenc e

Subjects (M/F)

Sports Type of lesion

Lesion level

Age (years)

VO2-peak POmax (ml.kg (W) −1.min−1)

Coutts and Stogryn (1987) Lakomi et al. (1987)

2M 2 M, 1 F

5A

Quad Para

C6–C7 T9–T12

25.0+1.4 25.7+4.7

17.1+0.3 38.9+11. 0

2 quad 10 para

C7 T4–L2

32.5+3.5 23.5+6.9

1.15+0. 09 L.min

12 M

−1

1.95+0. 38 L.min −1

28.5+13. 4 94.3+38. 5 NA

Y.C.VANLANDEWIJCK, A.J.SPAEPEN AND D.THEISEN 261

Referenc e

Subjects (M/F)

Sports Type of lesion

Lesion level

Age (years)

VO2-peak POmax (ml.kg (W) −1.min−1)

Coutts (1990) Cooper et al. (1992) Rotstein et al. (1994) Bhombh ani et al. 1994 Vanland ewijck et al. (1994) Campbel l et al. (1995) Dallmeij er et al. (1995)

4M

Para Para Para

NA

27.0+5.7 26.5+4.9 31+6

49.2+3.5 36.5+2.6 38.1+4.3

NA

11 M

2A 2B 11 A

4M

4B

Para

T4–L5

31.7+12. 4

19.8+3.6

NA

7M 6M

7A 6A

Quad Para

C5–C8 T5–L4

30+5 29+5

15.5+2.6 26.6+4.0

NA

22 M

22 B

Para

T3–L4

31.6+6.7

30.0+7.5

73.0+18. 8

19 M

19 A

Quad Para

C7–L5

31+7

32.3+7.1

NA

8M

8Q

Quad

C5–C8

NA

1.13+0. 49 L.min

29.4+15. 0

T3–T12

Figure 9.1 Propulsion technique parameters.

−1

NA

262 MOBILITY OF THE DISABLED

■ cycle frequency (CF)—number of propulsion cycles that the user performs per unit of time ■ push time (PT)—time during which the hand is in contact with the hand rim ■ recovery time (RT)—time during which the hand, after releasing the hand rim, is brought back to the starting position (start angle) ■ cycle time (CT)−CT=PT+RT ■ work per cycle—external work that is produced during one propulsion cycle ■ push angle (PA)—angular displacement of the hand on the hand rim between the beginning and the end of the propulsive phase, with respect to the wheel axis ■ start angle (SA)—angle at which the hand grips the hand rim at the beginning of the push ■ end angle (EA)—angle at which the hand releases the hand rim at the end of the push. These timing parameters have often been defined on basis of film analysis. Sanderson and Sommer (1985) suggest that the definitions of the propulsive and the recovery phase are, in such a case, more operational in nature rather than absolute. In fact, there could be times, especially at first-hand contact with the rim, when the hand might be moving more slowly than the wheel and impart a braking force. As will be seen later, this idea has been largely confirmed by studies on the curves of developed torque and forces on the hand rims. An increase in mean wheelchair velocity leads to an increase in cycle frequency (van der Woude et al., 1988a, 1989a, b). van der Woude et al. (1989b) studied the effect of propulsion technique on efficiency and cardiorespiratory parameters by systematic variation of the cycle frequency. Two groups of subjects (wheelchair sportsmen and non-wheelchair users) propelled their wheelchair on a treadmill at their own freely chosen cycle frequency and subsequently at four imposed frequencies. The investigators found that, for all velocities (0.55–1.39 ms−1) and both subject groups, efficiency decreased and the cardiorespiratory parameters increased significantly (p<0.05) at frequencies that were lower or higher than the freely chosen one. The timing parameters of the group of athletes showed a typical pattern with increasing cycle frequency: a decrease in recovery time, push angle and work/ cycle, whereas push time showed only a minor decrease. These adaptations of technique parameters are, however, different to those seen with respect to speed. A number of studies (van der Woude et al., 1988a, b; 1989a, b; Samuelsson et al., 1991; Veeger et al., 1989a, b, 1992c; Vanlandewijck et al., 1994) have shown that mere speed increase leads to a marked decrease in cycle time, predominantly caused by a decrease in push time. Only minor changes in recovery time and an increase in work/cycle and cycle frequency were found. Surprisingly, the push angle remains more or less constant, but shows a forward shift with increasing speed (Vanlandewijck et al., 1994). Accordingly, Veeger et al. (1991c) found that a lower angular velocity of the rims at higher

Y.C.VANLANDEWIJCK, A.J.SPAEPEN AND D.THEISEN 263

resistances allows for a longer hand contact and thus a longer push time. Nevertheless, an increase in the resisting force, but a constant velocity, leads to increases in work/cycle and cycle frequency, and subsequently to significant decreases in recovery time. Push angle and push time remain constant (van der Woude et al. 1988a; Veeger et al., 1989b). Veeger et al. (1992c) found that push angle and end angle do not increase with increasing speed at equal power output levels. High hand rim speeds are even likely to lead to a decrease in end angle, as was seen in wheelchair sprinting (Veeger et al., 1991c). This might be explained by the ‘geometrical constraint principle’ (Ingen Schenau, 1989) which describes the relationship between joint rotational velocity and translational velocity. The early termination of the push, well before maximal elbow extension is reached, results probably from the inability actively to follow the rims. In fact, the closer an angle nears full extension, the less effective the rotational velocity will be, in terms of the translation of the end-points. The reason why recovery time, often qualified as a ‘passive’ period, remains more or less constant as velocity increases is not clear at first sight. The findings of Vanlandewijck et al. (1994) give an explanation. He was the first to investigate propulsion technique concentrating on both the push and the recovery phase. He observed that, confronted with high velocities, experienced wheelchair users adapt their propulsion technique, not by changing their style, but by increasing the amplitude of their movements. In fact, ‘high’ displacement velocities require a higher segmental velocity of the upper limbs in order to effectively apply forces to the hand rims. Therefore, an increased backward arm swing is needed to generate a greater acceleration of the hand before the contact with the rim. Both the accelerated backward arm swing and the preparation for hand contact result in an increased muscular activity. This induces an increased energy consumption and, consequently, leads to a lower mechanical efficiency. Analysing the propulsive force of the wheelchair-user system, Vanlandewijck et al. (1994) found that the mechanical work produced during the recovery phase at velocities higher than 6 km h−1 (1.67 ms−1) could comprise more than one-third of the total mechanical work delivered during the whole propulsion cycle. This is due to an acceleration of the wheelchair-user system, caused by the increased backward arm swing. Subsequently the system is decelerated by the fast change of movement direction of the upper limbs and the acceleration of the hands towards the rims. Movement patterns. In a recent study on 19 endurance-trained wheelchair athletes, Campbell et al. (1995) observed that a number of individuals with relatively low VO2-peak values were able to push at fast speeds at a low oxygen cost. This may suggest that high-speed wheelchair propulsion, unlike running, does not necessarily require a high rate of oxygen utilization. It is suggested that this may be achieved through the development of an economical wheelchairpropulsion technique. The study of movement patterns involves the gathering of information about angular displacement, velocity and acceleration of the arm and trunk segments.

264 MOBILITY OF THE DISABLED

This is done by film or video analysis of the segmental motions during wheelchair propulsion. Markers on different anatomical landmarks make it possible to follow the movement of the upper limb and the trunk in the sagittal (and even the frontal) plane, while the person propels their wheelchair on a treadmill or works against an ergometer. Commonly used landmarks are C7 (seventh cervical vertebra), articulatio acromio-claviculare, epicondylus lateralis humeri, articulatio manus, caput ossis metacarpalia III and the rear wheel axis. Marker positions in each frame are digitized and smoothed. Sanderson and Sommer (1985) were some of the first investigators to use this technique. They analysed the kinematic features of the propulsion technique used by three male paraplegic world-class athletes, who were asked to propel their wheelchair on a motor-driven treadmill. At least three complete push cycles were filmed in the subjects’ sagittal plane, at a rate of 200 frames per second. Whereas intraindividual variations were very small and the style of pushing very consistent, intersubject analysis revealed dramatic differences. Physiological data did not show any major variations between the subjects, suggesting that these kinematic dissimilarities have no impact on physiological responses. Like Sanderson and Sommer (1985), Veeger et al. (1989b) found considerable intersubject differences in propulsion style for five well-trained wheelchair athletes. Movement patterns were classified as predominantly ‘circular’ to a ‘pumping’ technique. Although it has been suggested that the circular pushing style is superior to other techniques (Sanderson and Sommer, 1985; Veeger et al. 1989b). scientific conclusions with respect to a causal relationship between style and mechanical efficiency could not yet be reported. The pump arm action is actually more like the technique used by quadriplegic persons, to compensate for the loss of effective finger flexion (Sanderson and Sommer, 1985). Comparing five wheelchair-dependent (WCD) with five able-bodied persons (AB) during manual wheelchair ergometry, Brown et al. (1990) showed that there were basic physiological and biomechanical dissimilarities between the two groups under study. The significantly higher net mechanical efficiency of WCD over AB could be attributed, to a large extent, to biomechanical differences: the WCD had significantly greater shoulder and elbow extension angles at initial hand-to-rim contact. This resulted in a greater time spent in the pulling phase of the propulsion stroke, defined as the time from initial hand contact to the minimum elbow angle. The total hand-to-rim contact was the same in the two test groups, whereas the shoulder range of motion was significantly greater for the AB compared with the WCD. Thus, the significantly higher oxygen consumption of the AB might have been caused by the necessity of a better trunk stabilization. Some studies have measured trunk excursions during manual wheelchair propulsion, and generally found a forward shift of the trunk as the demand of activity increases (van der Woude et al., 1988b, 1989c; Veeger et al., 1989b; Lees, 1991). Vanlandewijck et al. (1994) found that only those subjects with a good sitting balance increased trunk inclination. Lees (1991) analysed the role of the trunk in more depth, focusing on the phasing of its oscillations with respect to

Y.C.VANLANDEWIJCK, A.J.SPAEPEN AND D.THEISEN 265

the push cycle. He observed two distinct forms of trunk use in nine competitive wheelchair athletes: the trunk is either brought forward and used as a stable base for the push phase, or the movement of the trunk is coordinated with the push phase. In the latter case the trunk acts as a moving rather than a stationary base, moving in the direction of the push. This seems to have some advantage in that the inertia of the moving trunk could be used to drive the push (Lees, 1991). The effect on performance of these techniques is, however, not clear and needs further study. As displacement velocity increases, the angular velocities of all the segments increase significantly (Veeger et al., 1989b; van der Woude et al., 1989c), whereas an increase in resistance leads to lower segmental velocities (Veeger et al., 1991c). The range of trunk and upper arm excursion is not significantly affected by an increase in speed (van der Woude et al., 1988b, Veeger et al., 1989b). However, the abduction of the upper arm was found to increase significantly (Veeger et al., 1989a, van der Woude et al., 1989c), as well as retroflexion (Veeger et al., 1989b). In a group of 40 highly-trained male wheelchair athletes, Vanlandewijck et al. (1994) found that the displacement of the hand during the recovery phase increased more than 20 per cent as velocity increased from 1.67 to 2.22 ms−1. This was due to a greater backward arm swing which is, as already mentioned, needed at high velocities, to generate a greater acceleration of the hand before the contact with the rim. In a study of Veeger et al. (1991c), six able-bodied subjects performed several 20-second sprint tests at different workloads. Their results showed that maximum elbow extension (closely related to the push time) increased with increasing resistance and, consequently, lower speed. Again, the ‘geometrical constraint principle’ (Ingen Schenau, 1989) provides a possible explanation for this observation (see the previous section). The lower angular velocity of the rims at high resistances allowed for longer hand contact and thus for greater elbow extension and a longer push time. The findings of Veeger et al. (1991c) suggest that elbow extension is inversely related to displacement (and consequently hand rim) velocity, especially as trunk flexion was found to be more or less constant. This is, however, not in line with results of other studies, where elbow range and angles were not found to be significantly influenced by speed (van der Woude et al. 1988b, 1989c; Veeger et al., 1989b). It must, however, be noted that the tests used in these investigations were all submaximal tests, where no extreme work conditions were reached. Muscular activity. Muscle activity is generally registered by means of surface electromyography. This technique is often used together with kinematic recordings, to describe the time-dependent role of different muscles and to determine their role in power production. The propulsion cycle in hand-rim wheelchair propulsion can be divided into different phases: pull phase, top-dead-centre, push phase and recovery phase. After the hand has made contact with the rim, the pull phase starts with an initial elbow flexion, accompanied by the activity of M. biceps brachialis (Lesser,

266 MOBILITY OF THE DISABLED

1986; van der Woude et al., 1989c; Veeger et al., 1991c). M. deltoideus anterior has a high activity at the beginning of rim contact, whereas M. pectoralis major has a more constant activity of longer duration (Veeger et al., 1992d). These two muscles are considered to be the prime movers in wheelchair propulsion (Lesser, 1986; Veeger et al., 1989a, 1991c, 1992d). Vanlandewijck et al (1994) finds that M. latissimus dorsi shows a similar activity pattern, stressing its importance during this phase. Although there is an increasing abduction of the arm, no activity of M. deltoideus medialis is registered (Lesser, 1986; Veeger et al., 1989a), suggesting that this shoulder abduction is not an active movement. It is assumed to be caused by the high activity of the prime movers, causing an anteflexing and endorotating torque. While the hands follow the rims, the elbows are forced outward as the result of a propulsive movement in a closed chain (Veeger et al., 1992d). At the top-dead centre, Vanlandewijck et al. (1994) observed a co-contraction of M. biceps and M. triceps brachialis, indicating a stabilizing action at the elbow joint. Some investigators analysed torque and power output curves during wheelchair propulsion and found a slope change or even a negative deflection about halfway in the torque curve (Samuelsson et al., 1989; van der Woude et al., 1989a; Veeger et al., 1992c). Veeger et al. (1991c) showed that, under strenous conditions (20-second sprint test), this period of smaller torque production was not caused by a change from elbow flexion to elbow extension, as suggested by Ross and Brubaker (1984). In fact, it coincided with a switch in muscular activity from M. biceps to M. triceps brachialis. Since the most effective direction of applied force is tangential to the rim, at least from a purely mechanical viewpoint (see Section 9.4.3.2. ‘Applied forces’), both elbow flexors and extensors are needed for a more optimally directed force. The dip in the torque curves appears at the time when a flexing moment around the elbow joint is no longer needed and an extending torque is more effective (Veeger et al., 1991c). During the push phase, M. deltoideus anterior and M. pectoralis major stay active, together with a highly active M. triceps brachialis (Lesser 1986; Veeger et al., 1990, 1991b). The recovery phase is characterized by the major activity of M. deltoideus pars medialis and posterior, and M. trapezius pars superior, which illustrates their prime mover function (Vanlandewijck et al., 1994). Towards the end of the recovery phase, M. deltoideus anterior, M. pectoralis major and M. latissimus dorsi are activated, to accelerate the hands before the contact with the rims (Vanlandewijck et al., 1994). The time-dependent role of different muscles and their role in power production during hand-rim wheelchair propulsion is well documented. However, few attempts have been made to put muscular activity in relation to other relevant parameters. To date, Vanlandewijck et al. (1995) are the only investigators to relate integrated EMG to metabolic cost, based on the electrical activity of the following eight muscles: M. biceps and triceps brachialis, M. deltoideus pars anterior, medialis and posterior, M. pectoralis major, M.

Y.C.VANLANDEWIJCK, A.J.SPAEPEN AND D.THEISEN 267

latissimus dorsi and M. trapezius pars descendens. As hand-rim wheelchair propulsion is mainly a concentric activity, Vanlandewijck et al. (1995) integrated muscular activity for each muscle separately in function of the corresponding concentric angular displacement. Doing so, he found a close relationship between the mechanical work performed and metabolic energy expenditure, with a mean correlation coefficient of r=+0.84 (rmin=+0.79, rmax= +0.90). This relationship was demonstrated only for subjects who did not show an extreme motion of the trunk while propelling the wheelchair, because abdominal and back muscular activity was not registered. Consequently, it may be concluded that concentric muscular work seems to be a valuable standard for energy consumption in hand-rim wheelchair propulsion. Applied forces. Measurement of forces in hand-rim wheelchair propulsion had until recently been limited to some studies on the effective force or torque on the hand rims (Jarvis and Rolfe, 1982; Lesser, 1986; Samuelsson et al., 1989; van der Woude et al., 1989a, 1990b). A high sampling rate of these torque values (up to 100 Hz) allows for analysis of within-cycle characteristics (van der Woude et al., 1989a). Thus, defined parameters may be measured, such as push time, recovery time, cycle time, peak torque and power, time-to-peak torque, mean torque and power of the push phase and of the complete cycle (van der Woude et al., 1990b). The individual torque curves frequently show a negative deflection at initial hand-to-rim contact, under steady state conditions (van der Woude et al., 1989a, Veeger et al., 1992a) as well as under the more extreme conditions of a sprint test (van der Woude et al., 1990b, Veeger et al., 1991c, 1992b). This is explained as a braking force, indicating a discrepancy between the momentary hand and rim velocity. In addition, a dip halfway in the torque curve is generally observed, as already mentioned. Although these studies may clarify certain aspects of force application, the different components of the applied hand force cannot be quantified. Niesing et al (1990) described a stationary wheelchair ergometer that allows for the measurement of the propulsive torque around the wheel axle, the threedimensional propulsive force applied on the hand rims and the velocity of the wheels. Based on these data, Veeger (1992c) defines a number of parameters. From the force components Fx (horizontally forward directed), Fy (outward directed) and Fz (downward directed), the total force vector Ftot is calculated (square root of the sum of squares). By dividing the effective torque (registered by the torque transducer) by the rim radius, the effective force on the hand rims Fm is found. From the values of Ftot and Fm the fraction of effective force can be determined.

If the hand position is known, the effective force component Feff of Ftot can be calculated from Ftot and hand position. The difference between the calculated torque produced by Feff and the propulsive torque around the wheel axle, as

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Figure 9.2 Forces occuring in wheelchair propulsion. Ftot=force applied on the hand rim, Feff= effective component of Ftot, M=torque on the wheel axle, Fm=torque/rim radius, Mh=torque applied by the hand on to the hand rim.

registered by the torque transducer, is defined as Mh and represents the theoretical torque of the hand onto the hand rim surface (Figure 9.2). At the beginning of the propulsive phase, Fy is negative and thus directed inward. It then becomes positive and reaches a maximum value during the last third of the propulsive phase. The horizontally forward directed component Fx increases progressively and becomes maximal when the hand is around the top-dead centre. An important and permanently present downward force component Fz is noticed. It constantly increases to become maximum towards the end of the propulsion phase. Although it has been suggested that the most effective force is directed tangentially to the hand rim at each position of the hand-to-rim contact (Veeger 1991b), forces applied to the hand rims are pointing too much in a vertical direction. A possible reason for this might be the necessity to apply sufficient force perpendicular to the rim to create a high enough friction component between the hand and the rim. Another explanation is that the elbow flexion torque is too small. The horizontally outward directed force component at the end of the push phase is the result of a too high elbow extension torque. This indicates that cambered rear wheels might be of advantage for a better force application and thus reduce physical strain. A study on the effect of rear wheel

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camber on mechanical efficiency and oxygen consumption could, however, not provide scientific evidence for this suggestion (Veeger et al., 1989a). The non-optimal direction of the free force components is also reflected in the relatively low values of FEF. This indicates that subjects cannot direct the forces they apply on the rims in the most effective tangential direction, which seems to explain to some extent the generally low mechanical efficiency in hand-rim wheelchair propulsion. Results from submaximal and maximal tests showed that mean FEF values did not exceed 81 per cent (Veeger et al., 1992a) and could reach a minimum of 50 per cent (Veeger, 1991b). In addition, FEF values, as well as mechanical efficiency, were found to decrease with speed, both for different gear ratios (at constant power output levels) (Veeger et al., 1992c, d) and for conditions where external power output increased with increasing speed (Veeger et al., 1992a). This might have been the result of a decrease in intermuscular coordination. The torque of the hand on to the hand rim surface Mh is found to be fairly small and contributes general negatively to the propulsive torque. Under lowresistance conditions it might especially be negligible relative to the forces concerned (Veeger et al., 1992a). This is, however, not the case under static conditions. Veeger (1991b) reported results from a series of tests where subjects were asked to develop isometric torques in different hand positions of the push arc. Values for Mh were found to be of considerable magnitude and highly dependent on hand position. Negative values were found at 30° and 60° hand position (0° standing for top-dead-centre), whereas Mh contributed positively at positions around the top-dead-centre. The positive values of Mh in these positions sometimes led to FEF values above 100 per cent, i.e. Fm was larger than Ftot. This means that the hands must have applied substantial torque onto the hand rim surface. Under static conditions, FEF values averaged over all hand positions varied between 88 and 95 per cent and were thus considerably higher than in submaximal and maximal tests. In addition, propulsive forces were directed too much upward, contrary to dynamic work situations, where a large positive Fz component was found. This suggests too strong an elbow flexion torque in positions around the top-dead-centre during the isometric tests. Three-dimensional dynamic modelling. Manual wheelchair propulsion is an increasingly demanding strenous effort on upper limb musculature and the evaluation of forces generated by the muscles, and interchanged at articular surfaces, should be a future major topic in preventive sports medicine. Threedimensional dynamic modelling (simulation) will be required to simulate manual wheelchair propulsion appropriately. Dynamic simulations of wheelchair propulsion could demonstrate which muscles are important in power generation around the shoulder mechanism, and which muscles are important for stabilization. Then the influence of factors affecting mechanical efficiency like discontinuity of force application, recovery phase, large muscle force and so on can be assessed. Design parameters like seat height and wheel camber can be

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adjusted. Maybe other types of propulsion mechanisms can be developed which will be more efficient than rim-type wheelchairs. Three-dimensional dynamic modelling will probably be the key to wheelchair-user interface optimization. The biomechanical complexity of dynamics at the shoulder joint, however, will have to be appropriately incorporated into this model. Furthermore, the model will have to be validated by means of propulsion modalities in realistic conditions, controlling force application, electromyographic activity and threedimensional movement patterns of the trunk and upper extremities. Although the wheelchair simulator described by Niesing et al. (1990) meet most of the reality criteria, simulation is not fully achieved, because of the stationary condition of the system. 1 Inertial forces acting on the wheelchair (caused by accelerations and decelerations of the trunk and arms) are neglected (Vanlandewijck et al., 1994). 2 Centre-of-gravity shifts, which will influence rolling resistance and wheelchair balance, are not considered. 3 The model will have to incorporate the functional capacity of the user and to address a variety of intended purposes such as safety, efficiency and manoeuvrability. First attempts at three-dimensional dynamic model development have already been made by Helm et al. (1991), and Veeger and van der Woude (1995), for hand rim propulsion mechanisms, and Brubaker (1986) for lever propulsion mechanisms. Veeger and van der Woude (1995) studied the relationship between force direction and net joint torques around the shoulder and elbow, calculated in three dimensions following the standard Newton-Euler method. Figure 9.3 shows that the application of the tangential force (in mechanical terms the most optimal force) might lead to a contradictory situation in which the elbow joint is extending while at the same time a flexing moment ought to be generated for mechanically optimal results. Therefore, it is likely that the human musculoskeletal system prevents such a situation as much as possible and ‘chooses’ for a, in mechanical terms seemingly sub-optimal, but physiologically more efficient direction of force application (Figure 9.3). However, since the musculoskeletal system also possesses bi-articular muscles, it is possible that M. biceps brachialis still produces positive power despite the fact that negative external power was calculated over the elbow joint. The coordinative principle demonstrated by Veeger and van der Woude (1995) illustrates that the improvement of wheelchair propulsion efficiency should not be sought in the development of new propulsion techniques, but should focus on the optimization of design instead (Veeger and van der Woude, 1995). The previous discussion is based on the assumption that the most effective force is directed tangential to the hand rim at each position of the hand-to-rim

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Figure 9.3 The relationship between force direction and calculated net joint torque’s around shoulder and elbow. Solid arrows represent joint torques. Dashed arrows are the directions of joint rotations (Veeger and van der Woude, 1995).

contact (Veeger, 1991b). By means of a two-dimensional mathematical model, however, Vanlandewijck (1992) demonstrated the beneficial effects of deviations from the tangential force direction. In the simplified example (Figure 9.4), a tangential force application (Figure 9.4) at handcontact −30° (trunk inclination=0°) is compared to an outward directed force application (Figure 9.4b) under equal geometrical conditions. In both situations a torque of 70 Nm is generated around the rear wheel axle. In Figure 9.4, the total force (Ftot) is composed by three forces acting on the elbow and shoulder joint: M. bicepsbrachialis (Fb), M. deltoideus pars posterior (Fpp) and M. trapezius pars superior (Ftr). Due to the outward direction of force application in Figure 9.4, an outward directed radial force (Fr) will be created. Fr will increase friction between hand and hand rim, and therefore reduce the torque of the hand onto the hand rim surface Mh (see Figure 9.2). Consequently, a redistribution of forces occur, resulting in a marked decrease of elbow flexion and shoulder retroflexion torque. The marked increase in force generation, produced by means of shoulder elevation (Ftr), is not dramatic since Ftr closely approaches an optimal situation with respect to the direction of M. trapezius pars superior contraction and the length-tension relationship of this muscle. This example demonstrates the different force application strategies available to the wheelchair user in each hand-contact position. The final choice of strategy will depend on the following: 1 the geometrical configuration of the wheelchair-user interface, such as seat height and fore/aft location of the centre of gravity,

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Figure 9.4 Comparison between a tangential directed force (a) and an outward directed force (b) on the hand rim generating a torque at the rear wheel axle of 70 Nm. Redistribution of forces is showed for M. trapezius pars superior (Ftr), M. deltoideus pars posterior (Fpp) and M. biceps brachialis (Fbi). (Feff)=effective force; Ftot=total force; Fr=radial force).

2 user-dependent characteristics, such as level of disability and handgrip (rim, or both rim and tyre), 3 environmental conditions, and 4 intended purpose. Influence of seat position on force generation. It is interesting to note that only a part of the forward motion is effective in driving the rim. During the early part of the stroke, the hand is accelerating to the speed of the rim. After rim contact, the hand continues to accelerate, providing input torque to the rim. After releasing the rim, the hand begins to decelerate before beginning the return stroke to the starting position. The pattern of the stroke varies with seat position. When the seat is high, the stroke is shorter because the hand cannot reach as far down the rim. When the seat is forward, the stroke acts on the forward part of the rim, and when the seat is to the rear it acts over the top of the rim. A lower seat allows a longer stroke over a large section of the rim. This means that the force input can be lower than for a high seat where the energy must be applied in a shorter time (McLaurin and Brubaker, 1991).

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The return or recovery stroke is worth considering. Even though no energy is imparted to the rim at this time, energy is required to move the arms backwards to the starting position. With a low seat, the elbow must be flexed for this action. With a high seat, this flexion is minimized, thus reducing the required energy. It has been postulated that one reason why levers are more efficient than hand rims is that the weight of the hand and forearm rests on the lever and hence less energy is needed for the return stroke (McLaurin and Brubaker, 1991). Changing the position of the user in the wheelchair will not only affect the range over which the user is able to apply forces on the hand rims, but will also influence the force-production capabilities of the upper limb muscles, by altering the range of motion of the arms and, subsequently, the length changes experienced by the arm muscles (length-tension relationship). Moreover, changes in arm position affect the muscle moment arms at each joint, so that the turning effect of each muscle is also altered. However, no study, to date, has related changes in force application on the hand rims to specific muscle length changes at varying seat heights. References BEAL, D.P., GLASER, R.M., PETROFSKY, J.S., SMITH, P.A. and Fox, E.L. (1981) Static component of handgrip muscles for various wheelchair propulsion methods (abstract), Federation Proceedings, 40, 497. BHAMBHANI, Y.N., ERIKSSON, P. and STEADWARD, R.D. (1991) Reliability of peak physiological responses during wheelchair ergometry in persons with spinal cord injury. Archives in Physical Medicine and Rehabilitation, 72, 559–62. BHAMBHANI, Y.N., HOLLAND, L.J. and ERIKSSON, P. (1994) Physiological responses during wheelchair racing in quadriplegics and paraplegics. Paraplegia, 32, 253–60. BRATTGARD, S., GRIMBY, G. and HOOK, O. (1970) Energy expenditure and heart rate in driving a wheelchair ergometer. Scandinavian Journal of Rehabilitation Medicine, 2, 143–8. BOSMANS, I. (1995) ‘Ventilatory parameters, mechanical efficiency and physical strain when propelling an arm crank wheelchair at different modes of propulsion and different gear ratios.’ Unpublished Master’s Thesis, Katholieke Universiteit Leuven, Leuven, Belgium, 61pp. BROWN, D.D., KNOWLTON, R.G., HAMILL, J., SCHNEIDER, T.L. andHETZLER, R. K. (1990) Physiological and biomechanical differences between wheelchairdependent and able-bodied subjects during wheelchair ergometry. European Journal of Applied Physiology, 60, 179–82. BRUBAKER, C.E. (1986) Computer model for the prediction and generation of a 3dimensional wheelchair propulsion cycle from anthropometric dimensions, in STAMP, N.G. and MCLAURIN C. (Eds) Wheelchair Mobility, pp. 2–12, Charlottesville, Virginia: Rehabilitation Engineering Center: University of Virginia.

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BRUBAKER, C.E., MCCLAY, I.S. and MCLAURIN, C.A. (1984) Effect of seat position on wheelchair propulsion efficiency. Proceedings of the Second International Conference on Rehabilitation Engineering, pp. 12–4, Ottawa, Canada. BURKETT, L.N., CHISUM, J., STONE, W. and FERNHALL, B. (1990) Exercise capacity of untrained spinal cord injured individuals and the relationship of peak oxygen uptake to level of injury. Paraplegia, 28, 512–21. CAMPBELL, I.G., WILLIAMS, C. and LAKOMI, H.K.A. (1995) Physiological characteristics and marathon performance of endurance trained wheelchair athletes, in VAN COPPENOLLE, H., VANLANDEWIJCK, Y., SIMONS, J., VAN DE VLIET, P. and NEERINCKX, E. (Eds) Proceedings of the First European Conference on Adapted Physical Activity and Sports: A White Paper on Research and Practice, pp. 83–7, Leuven: Acco. COE, P.L. (1979) Aerodynamic characteristics of wheelchairs. NASA Technical Memorandum 80191. COONEY, M.M. and WALKER, J.B. (1986) Hydraulic resistance exercise benefits cardiovascular fitness of spinal cord injured. Medicine and Science in Sports and Exercise, 18 (5), 522–5. COOPER, R.M., HORVATH, S.M., BEDI, J.F., DRECHSLER-PARKS, D.M. and WILLIAMS, R.E. (1992) Maximal exercise response of paraplegic wheelchair road racers. Paraplegia, 30, 573–81. COUTTS, K.D. (1990) Peak oxygen uptake of elite wheelchair athletes. Adapted Physical Activity Quarterly, 7, 62–6. COUTTS, K.D. and STOGRYN, J.L. (1987) Aerobic and anaerobic power of Canadian wheelchair track athletes. Medicine and Science in Sports and Exercise, 19 (1), 62–5. COUTTS, K.D., RHODES, E.C. and MCKENZIE, D.C. (1983) Maximal exercise responses of tetraplegics and paraplegics. Journal of Applied Physiology: Respiration and Environmental Exercise Physiology, 55, 479–82. DALLMEIJER, A.J., HOPMAN, M.T.E. and VAN DER WOUDE, L.H.V. (1995) Effect of quad rugby training on physical capacity and physical strain during standardised ADL in persons with a cervical spinal cord injury, in VAN COPPENOLLE, H., VANLANDEWIJCK, Y., SIMONS, J., VAN DE VLIET, P. and NEERINCKX, E. (Eds) Proceedings of the First European Conference on Adapted Physical Activity and Sports: A White Paper on Research and Practice, pp. 95–9, Leuven: Acco. DICARLO, S.E. (1988) Effects of arm ergometry training on wheelchair propulsion endurance of individuals with quadriplegia. Physical Therapy, 68 (1), 40–4. ENGEL, P. and HILDEBRANDT, G. (1974) Wheelchair design—technological and physiological aspects. Proceedings of the Royal Society of Medicine, 67, 409–13. ENGEL, P. and SEELIGER, K. (1986) Technological and physiological characteristics of a newly developed hand-lever drive system for wheelchairs . Journal of Rehabilitation, Research and Development, 23, 37–41. ENGEL, P., NEIKES, M., BENNEDIK, K., HILDEBRANDT, G. and RODE, F.W. (1976) Arbeitsphysiologische Untersuchungen zür Optimierung des Hebelantriebs und der Sitzanordnung. Rehabilitation, 15, 28–32. ERIKSSON, P., LÖFSTRÖM, L. and EKBLOM, B. (1988) Aerobic power during maximal exercise in untrained and well-trained persons with quadriplegia and paraplegia. Scandinavian Journal of Rehabilitation Medicine, 20, 141–7.

Y.C.VANLANDEWIJCK, A.J.SPAEPEN AND D.THEISEN 275

FRANK, T.G. and ABEL, E.W. (1989) Measurement of the turning, rolling and obstacle resistance of wheelchair castor wheels. Journal of Biomedical Engineering, 11, 462–6. FRANK, T.G. and ABEL, E.W. (1991a) A System for Measuring the Vibrational Characteristics of Wheelchairs. International Report 91/2, Scotland: School of Biomedical, University of Dundee. FRANK, T.G. and ABEL, E.W. (1991b) Drag forces in wheelchairs, in WOUDE, VAN DER, L.H.V., MEIJS, P.J.M., GRINTEN, VAN DER, B.A. and BOER, DE, Y.A. (Eds) Ergonomics of Manual Wheelchair Propulsion: State of the Art pp. 255–67, Milan, Italy. GAESSER, G.A. and BROOKS, G.A. (1975) Muscular efficiency during steady-rate exercise: effects of speed and work rate. Journal of Applied Physiology, 38, 1132–9. GANGELHOFF, J., CORDAIN, L., TUCKER, A. and SOCKLER, J. (1988) Metabolic and heart rate responses to submaximal arm lever and arm crank ergometry. Archives of Physical Medicine and Rehabilitation, 69, 101–5. GASS, G.C. and CAMP, E.M. (1987) Effects of prolonged exercise in highly trained traumatic paraplegic men. Journal of Applied Physiology. 63, 1846–52. GAYLE, G.W., DAVIS, G.M., POHLMAN, R.L. and GLASER, R.M. (1990) Track wheelchair ergometry: effects of hand rim diameter on metabolic responses, in DOLL-TEPPER, G., DAHMS, C., DOLL, B. and SELZAM, VON, H. (Eds) Adapted Physical Activity: An Interdisciplinary Approach, pp 101–7, Heidelberg: Springer-Verlag. GLASER, R.M. (1989) Arm exercise training for wheelchair users. Medicine and Science in Sports and Exercise, 21, 149–57. GLASER, R.M. and COLLINS, S.R. (1981) Validity of power output estimation for wheelchair locomotion. American Journal of Physical Medicine, 60, 180–9. GLASER, R.M., FOLEY, D.M., LAUBACH, L.L., SAWKA, M.N. and SURYAPRASAD, A.G. (1979) An exercise test to evaluate fitness for wheelchair activity. Paraplegia, 16, 341–9. GLASER, R.M., SAWKA, M.N., BRUNE, M.F. and WILDE, S.W. (1980) Physiological responses to maximal effort wheelchair and arm crank ergometry. Journal of Applied Physiology: Respiration and Environmental Exercise Physiology. 48, 1060–4. GLASER, R.M., SAWKA, M.N., DURBIN, R.J., FOLEY, D.M. and SURYAPRASAD, A.G. (1981a) Exercise program for wheelchair activity. American Journal of Physical Medicine, 60, 67–75. GLASER, R.M., SAWKA, M.N., WILDE, S.W., WOODROW, B.K. and SURYAPRASAD, A.G. (1981b) Energy cost and cardiopulmonary responses for wheelchair locomotion and walking on tile and on carpet. Paraplegia, 19, 220–6. GRUNZE, M.F., MULLIGAN, M.S., KAISER, R. and SCHULER, G. (1991) Clinical aspects of wheelchair racing, in WOUDE, VAN DER, L.H.V., MEIJS, P.J.M., GRINTEN, VAN DER, B.A., and BOER, DE, Y.A. (Eds) Ergonomics of Manual Wheelchair Propulsion: State of the Art, pp 109–26, Milan: Edizioni pro Juventute, IOS Press. HARTUNG, G.H., LALLY, D.A. and BLANCQ, R.J. (1993) Comparison of treadmill exercise protcols for wheelchair users. European Journal of Applied Physiology, 66, 362–5.

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HEDRICK, B., WANG, Y.T., MOEINZADEH, M. and ADRIAN, M. (1990) Aerodynamic positioning and performance in wheelchair racing. Adapted Physical Activity Quarterly, 7, 41–51. HELM, F.C.T., VAN DER and VEEGER, H.E.J. (1991) A shoulder model required? in WOUDE, VAN DER, L.H.V., MEIJS, P.J.M., GRINTEN, VAN DER, B.A. and BOER, DE, Y.A. (Eds) Ergonomics of Manual Wheelchair Propulsion: State of the Art, pp 157–68, Milan: Edizioni pro Juventute, IOS Press, 365 pp. HJELTNES, N. and VOKAC, Z. (1979) Circulatory strain in everyday life of paraplegics. Scandinavian Journal of Rehabilitation Medicine, 11, 67–73. HOPMAN, M.T.E. (1993) ‘Paraplegia and exercise: a study of cardiovascular behaviour during arm exercise in persons with paraplegia.’ Doctoral dissertation, Department of Physiology, University of Nijmegen, The Netherlands, CIP-Data Koninklijke Bibliotheek, Den Haag. HOPMAN, M.T.E., OESEBURG, B. and BINKHORST, R.A. (1991) Cardiovascular aspects in spinal cord injured subjects, in WOUDE, VAN DER, L.H.V., MEIJS, P.J. M., GRINTEN, VAN DER, B.A. and BOER, DE, Y.A. (Eds) pp. 103–8, Milan: Edizioni pro Juventute, IOS Press, 365 pp. INGEN SCHENAU, G.J., VAN (1989) From rotation to translation: constraints on multijoint movements and the unique action of bi-articular muscles. Human Movement Sciences, 8, 301–37. JARVIS, S. and ROLFE, H. (1982) The use of an inertial dynamometer to explore the design of children’s wheelchairs. Scandinavian Journal of Rehabilitation Medicine, 14, 167–76. JANSSEN, T.W.J. (1994) ‘Physical strain and physical capacity in men with spinal cord injuries.’ Doctoral dissertation, Faculty of Movement Sciences, Free University Amsterdam, The Netherlands, CIP-Data Koninklijke Bibliotheek, Den Haag. JANSSEN, T.W.J., OERS, C.A.J. VAN, HOLLANDER, A.P., VEEGER, H.E.V. and VAN DER, WOUDE, L.H.V. (1993) Isometric strength, sprint power and aerobic power in individuals with spinal and cord injury. Medicine and Science in Sports and Exercise, 25 (7), 863–70. KAUZLARICH, J.J. and TRACKER, J.G. (1985) Wheelchair tyre rolling resistance and fatigue. Journal of Rehabilitation, Research and Development, 22, 25–41. LAKOMI, H.K.A., CAMPBELL, I. and WILLIAMS, C. (1987) Treadmill performance and selected physiological characteristics of wheelchair athletes. British Journal of Sports Medicine, 21, 130–3. LASKO-MCCARTHY, P. and DAVIS, J.A. (1991) Protocol dependency of VO2max during arm cycle ergometry in males with quadriplegia. Medicine and Science in Sports and Exercise, 23, 1097–1101. LEES, A. (1991) Performance characteristics of two wheelchair sprint tests, in WOUDE, VAN DER, L.H.V., MEIJS, P.J.M., GRINTEN, VAN DER, B.A. and BOER, DE, Y.A. (Eds) Ergonomics of Manual Wheelchair Propulsion: State of the Art, pp. 13–20, Milan, Italy: Edizioni pro Juventute. LESSER, W. (1986) Ergonomische Untersuchung der Gestaltung antriebsrelevanter Einflu grö en beim Rollstuhl mit Handantrieb. Fortschrittberichte VDI Verlag, Reihe 17: Biotechnik Nr. 28, Düsseldorf, Germany. LINDEN, M.L. VAN DER, VALENT, L., VEEGER, H.E.J. and VAN DER, WOUDE, L. H.V. (1995) Het effect van hoepelbuisdikte op krachtleverantie in hand-aangedreven rolstoelen. Tijdschrift voor Ergonomic, 20 (4), 14–18.

Y.C.VANLANDEWIJCK, A.J.SPAEPEN AND D.THEISEN 277

MCLAURIN, C.A. and BRUBAKER, C.E. (1991) Biomechanics and the wheelchair, Prosthetics and Orthotics International, 15, 24–37. MILES, D.S., Cox, M.H. and BOMZE, J.P. (1989) Cardiovascular response to upper body exercise in normal and cardiac patients. Medicine and Science in Sports and Exercise, 21, 126–31. NIESING, R., EIJSKOOT, F., KRANSE, R., OUDEN, A.H. DEN STROM, J., VEEGER, H. E.J., VAN DER WOUDE, L.H.V. and SNIJDERS, C.J. (1990) Computercontrolled wheelchair ergometer. Medical and Biological Engineering and Computing, 28, 329–38. O’REAGAN, J.R., TRACKER, J.G., KAUZLARICH, J.J., MOCHEL, E., CARMINE, D. and BRYANT, M. (1981) Wheelchair dynamics, in Wheelchair Mobility 1976–1981, pp. 33–41, Rehabilitation Engineering Center, University of Virginia. POWERS, S.K., BEADLE, R.E. and MANGUM, M. (1984) Exercise efficiency during arm ergometry: effects of speed and work rate. Journal of Applied Physiology: Respiration and Environmental Exercise Physiology, 56, 495–9. RASCHE, W., JANSSEN, T.W.J., VAN OERS, C.A.J.M., HOLLANDER, A.P. and VAN DER WOUDE, L.H.V. (1993) Responses of subjects with spinal cord injuries to maximal wheelchair exercise: comparison of discontinuous and continuous protocols. European Journal of Applied Physiology, 66, 328–31. Ross, S.A. and BRUBAKER, C.E. (1984) Electromyographic analysis of selected upper extremity muscles during wheelchair propulsion. Proceedings of the Second RESNA Conference on Rehabilitation Engineering, pp. 7–8, Ottawa, Canada. ROTSTEIN, A., SAGIV, M., BEN-SIRA, D., WERBER, G., HUTZLER, J. and ANNENBURG, H. (1994) Aerobic capacity and anaerobic threshold of wheelchair basketball players, Paraplegia, 32, 196–201. SAMUELSSON, K.A., LARSSON, H. and TROPP, H.T. (1989) A wheelchair ergometer with a device for isokinetic torque measurement. Scandinavian Journal of Rehabilitation Medicine, 21, 205–8. SAMUELSSON, K.A., LARSSON, H. and TROPP, H.T. (1991) Power output and propulsion technique in wheelchair driving. International Journal of Rehabilitation Research, 14, 76–81. SANDERSON, D.J. and SOMMER, H.J. (1985) Kinematic features of wheelchair propulsion. Journal of Biomechanics, 18, 423–9. SAWKA, M.N. (1986) Physiology of upper body exercise. Exercise Sports Science Review, 14, 175–211. SAWKA, M.N., GLASER, R.M., LAUBACH, L.L., AL-SAMKARI, O. and SURYAPRASAD, A.G. (1981) Wheelchair exercise performance of the young, middle-aged and elderly. Journal of Applied Physiology: Respiration and Environmental Exercise Physiology, 50, 824–8. SAWKA, M.N., GLASER, R.M., WILDE, S.W. and VON LURTHE, T.C. (1980) Metabolic and circulatory responses to wheelchair and arm crank exercise. Journal of Applied Physiology: Respiration and Environmental Exercise Physiology, 49, 784–8. SAWKA, M.N., LATZKA, W.A. and PANDOLF, K.B. (1989) Temperature regulation during upper body exercise: able-bodied and spinal cord injured. Medicine and Science in Sports and Exercise, 21, 132–40. SAWKA, M.N., LATZKA, W.A. and PANDOLF, K.B. (1991) Upper body exercise: application for wheelchair propulsion and spinal cord injured populations, in VAN

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DER WOUDE, L.H.V., MEIJS, P.J.M., VAN DER GRINTEN, B.A. and DE BOER, Y. A. (Eds). Ergonomics of Manual Wheelchair Propulsion: State of the Art, pp. 151–62, Milan, Italy: Edizioni pro Juventute. SEDLOCK, D.A., KNOWLTON, R.G. and FITZGERALD, P.I. (1990) Circulatory and metabolic responses of women to arm crank and wheelchair ergometry. Archives of Physical Medicine and Rehabilitation, 71, 97–100. SEELIGER, K. (1991) Lever propulsion systems, in VAN DER WOUDE, L.H.V., MEIJS, P. J.M., VAN DER GRINTEN, B.A. and DE BOER, Y.A. (Eds) Ergonomics of Manual Wheelchair Propulsion: State of the Art, pp. 151–62, Milan, Italy: Edizioni pro Juventute. SMITH, P.A., GLASER, R.M., PETROFSKI, J.S., UNDERWOOD, P.D., SMITH, G.B. and RICHARD, J.J. (1983) Arm crank versus hand rim wheelchair propulsion: metabolic and cardiopulmonary responses. Archives of Physical Medicine and Rehabilitation, 64, 249–54. TRAUT, L. and SCHMAUDER, M. (1991) Ergonomic design of the hand-machine interface for wheelchairs, in VAN DER WOUDE, L.H.V., MEIJS, P.J.M., VAN DER GRINTEN, B.A. and DE BOER, Y.A. (Eds) Ergonomics of Manual Wheelchair Propulsion: State of the Art, pp. 335–48, Milan, Italy: Edizioni pro Juventute. VANLANDEWUCK, Y.C. (1992) Mechanische Efficiëntie van de Aandrijf- en Terugvoerbe-weging bij Rolstoelpropulsie, Doctoral thesis, Katholieke Universiteit Leuven, Leuven, Belgium. VANLANDEWUCK, Y.C., SPAEPEN, A.J. and LYSENS, R.J. (1994) Wheelchair propulsion efficiency: movement pattern adaptations to speed changes. Medicine and Science in Sports and Exercise, 26 (11), 1373–81. VANLANDEWUCK, Y.C., SPAEPEN, A.J. and LYSENS, R.J. (1995) Relationship between energy expenditure and muscular activity patterns in hand rim wheelchair propulsion. Proceedings of the 12th Triennial Congress of the International Ergonomics Association. 3, pp. 145–7, Toronto, Canada, Rehabilitation Ergonomics. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1989a) The effect of rear wheel camber in manual wheelchair propulsion. Journal of Rehabilitation Research and Development, 26, 37–46. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1989b) Wheelchair propulsion technique at different speeds. Scandinavian Journal of Rehabilitation Medicine, 21, 197–203. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1990) Krachtleverantie tijdens rijden in een hoepelrolstoel: enige theoretische aspecten. Bewegen en hulpverlening, 7, 127–34. VEEGER, H.E.J., HADJ YAHMED, M., VAN DER WOUDE, L.H.V. and CARPENTIER, P. (1991a) Peak oxygen uptake and maximal power output of Olympic wheelchair-dependent athletes. Medicine and Science in Sports and Exercise, 23 (10), 1201–9. VEEGER, H.E.J. (1991b) Biomechanics of manual wheelchair propulsion, in VAN DER WOUDE, L.H.V., MEIJS, P.J.M., VAN DER GRINTEN, B.A. and DE BOER, Y. A. (Eds) Ergonomics of Manual Wheelchair Propulsion: State of the Art, pp. 135–45, BME, Edizioni pro Juventute, IOS Press.

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VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1991c) Withincycle characteristics of the wheelchair push in sprinting on a wheelchair ergometer. Medicine and Science in Sports and Exercise, 23, 264–71. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1992a) A computerized wheelchair ergometer: results of a comparison study, in VEEGER, H.E.J. (Ed.) Biomechanical Aspects of Manual Wheelchair Propulsion, pp. 7–21, Academisch proefschrift, Amsterdam: Free University Amsterdam, Industriebond FNV, Amsterdam. VEEGER, H.E.J., LUTE, E.M.C., ROELEVELD, K. and VAN DER WOUDE, L.H.V. (1992b) Differences in performance between trained and untrained subjects during a 30-second sprint test on a wheelchair ergometer, in VEEGER, H.E.J. (Ed) Biomechanical Aspects of Manual Wheelchair Propulsion, pp. 77–91, Academisch proefschrift, Amsterdam: Free University Amsterdam, Industriebond FNV, Amsterdam. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1992c) Effect of hand rim velocity on mechanical efficiency in wheelchair propulsion against constant power output. Medicine and Science in Sports and Exercise, 24, 100–7. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1992d) Load on the upper extremity in manual wheelchair propulsion, in VEEGER, H.E.J. (Ed). Biomechanical Aspects of Manual Wheelchair Propulsion, pp. 57–75, Academisch proefschrift, Amsterdam: Free University Amsterdam, Industriebond FNV, Amsterdam. VEEGER, H.E.J. and VAN DER WOUDE, L.H.V. (1995) Force generation in manual wheelchair propulsion, in VAN COPPENOLLE, H., VANLANDEWIJCK, Y., SIMONS, J., VAN DE VLIET, P. and NEERINCKX, E. (Eds) Proceedings of the First European Conference on Adapted Physical Activity and Sports: A White Paper on Research and Practice, pp. 89–94, Leuven: Acco. VOIGT, E.D. and BAHN, D. (1969) Metabolism and pulse rate in physically handicapped when propelling a wheelchair up an incline. Scandinavian Journal of Rehabilitation Medicine, 1, 101–6. WALSH, C.M., MARCHIORI, G.E. and STEADWARD, R.D. (1986) Effect of seat position on maximal linear velocity in wheelchair sprinting. Canadian Journal of Applied Sports Science, 11, 186–90. WHITT, F.R. and WILSON, D.G. (1982) Bicycling Science. The MIT Press. WICKS, J.R., LYMBURNER, K., DINSDALE, S.M. and JONES, N.L. (1977–8) The use of multistage exercise testing with wheelchair ergometry and arm cranking in subjects with spinal cord lesions. Paraplegia, 15, 252–61. WICKS, J.R., OLDRIDGE, N.B., CAMERON, B.J. and JONES, N.L. (1983) Arm cranking and wheelchair ergometry in elite spinal cord-injured athletes. Medicine and Science in Sports and Exercise, 15, 224–31. VAN DER WOUDE, L.H.V., DE GROOT, G., HOLLANDER, A.P., VAN INGEN SCHENAU, G.J. and ROZENDAL, R.H. (1986) Wheelchair ergonomics and physiological testing of prototypes. Ergonomics, 29, 1561–73. VAN DER WOUDE, L.H.V., HENDRICH, K.M.M., VEEGER, H.E.J., VAN INGEN SCHENAU, G.J., ROZENDAL, R.H., DE GROOT, G. and HOLLANDER, A.P. (1988a) Manual wheelchair propulsion: effects of power output on physiology and technique. Medicine and Science in Sports and Exercise, 20, 70–8.

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VAN DER WOUDE, L.H.V., VEEGER, H.E.J., ROZENDAL, R.H., VAN INGEN SCHENAU, G.J., ROOTH, F. and VAN NIEROP, P. (1988b) Wheelchair racing: effects of rim diameter and speed on physiology and technique. Medicine and Science in Sports and Exercise, 20, 492–500. VAN DER WOUDE, L.H.V. (1989) Manual Wheelchair Propulsion: An Ergonomic Perspective. Doctoral Thesis, Amsterdam: Free University Amsterdam. VAN DER WOUDE, L.H.V., VEEGER, H.E.J. and ROZENDAL, R.H. (1989a) Propulsion technique in hand rim wheelchair propulsion. Journal of Medical Engineering and Technology, 13, 136–41. VAN DER WOUDE, L.H.V., VEEGER, H.E.J., ROZENDAL, R.H. and SARGEANT, A. J. (1989b) Optimum cycle frequencies in hand rim wheelchair propulsion. European Journal of Applied Physiology, 58, 625–32. VAN DER WOUDE, L.H.V., VEEGER, H.E.J., ROZENDAL, R.H. and SARGEANT, A. J. (1989c) Seat height in hand rim wheelchair propulsion. Journal of Rehabilitation, Research and Development, 26, 31–50. VAN DER WOUDE, L.H.V., VEEGER, H.E.J. and ROZENDAL, R.H. (1990a) Seat height in hand rim wheelchair propulsion: a follow-up study. Journal of Rehabilitation Sciences, 3, 79–83. VAN DER WOUDE, L.H.V., VEEGER, H.E.J., KOPERDAAT, J. and DREXHAGE, D. (1990b) Design of a static wheelchair ergometer: Preliminary results, in DOLLTEPPER, G., DAHMS, C., DOLL, B. and VON SELZAM, H. (Eds) Adapted Physical Activity: An Interdisciplinary Approach, pp. 441–6, Berlin Heidelberg: Springer-Verlag. VAN DER WOUDE, L.H.V., VEEGER, H.E.J., DE BOER, Y. and ROZENDAL, R.H. (1993) Physiological evaluation of a newly designed lever mechanism for wheelchairs, Journal of Medical Engineering and Technology, 17 (6), 232–40. VAN DER WOUDE, L.H.V., MAAS, K., ROZENDAL, R.H. and VEEGER, H.E.J. (1995a) Physiological responses during hubcrank and hand rim wheelchair propulsion: a pilot study. Journal of Rehabilitation Sciences, 8 (1), 13–19. VAN DER WOUDE, L.H.V., VEEGER, H.E.J. and ROZENDAL, R.H. (1995b) Ergonomie van hand-aangedreven rolstoelen: de rol van experimenteel gekombineerd bio-mechanisch en inspanningsfysiologisch onderzoek. Tijdschrift voor Ergonomic, 20 (2), 22–32.

CHAPTER TEN Wheelchair ergonomics RORY A.COOPER, RICK N.ROBERTSON, MICHAEL L.BONINGER, SEAN D.SHIMADA, DAVE P.VANSICKLE, BRAD LAWRENCE AND TIFFANI SINGLETON

10.1 An historical perspective on the development of wheelchairs The wheelchair, as we know it today, began developing in the early eighteenth century. It was styled like an armchair equipped with two large wooden wheels in the front and one caster at the rear for balance. The early wheelchairs were ornate, heavy, difficult to operate and provided little independence. With thousands of amputees left in the wake of the Civil War, lighter weight wheelchairs appeared with caned seats and backs and modern wheels of iron. These young veterans were typically shut away in state institutions or veterans’ homes. Their wheelchairs only served to reinforce the notion that they were ‘invalids’. World War I left legions of young Americans with disabilities. These veterans were given ‘advanced’ 50-lb wheelchairs made almost entirely of India reed, which were still impractical for independent mobility. The British government, alerted to the risk of wasting the lives of thousands of young veterans, revived spinner knob tricycles and issued them to veterans with disabilities (Bartolucci, 1992). A few years later the British Red Cross issued motorized tricycles to many veterans with disabilities. Similar vehicles can be seen today in many developing countries. In 1932, Herbert Everest, together with his friend and fellow mining engineer Harry Jennings, invented a sling-seat folding aircraft steel wheelchair in Everest’s quest for autonomy (Bartolucci, 1992; Wilson, 1992). This was a radical departure from previous designs and Everest, who had paraplegia from a mine collapse, became a rolling advertisement for their product. The E&J company continues to produce wheelchairs. During this same period, Franklin D.Roosevelt, who was affected by the 1931 polio epidemic, refused to be seen as anything but the vigorous man that he was. The White House respected his wishes and rarely showed his wheelchair in photographs. Roosevelt was unhappy with the selections of wheelchairs available to him and had several ordinary kitchen chairs equipped with wheels.

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World War II led to developments enabling many veterans with spinal cord injuries to live independently for the first time. However, veteran’s hospitals were still equipped with wheelchairs from the Civil War. Later many veterans were supplied with standard 18-inch seat width chrome Everest and Jennings model wheelchairs. It had not yet occurred to people that wheelchairs should fit the individual. They were quite simply chairs that provided users with some degree of mobility. Shortly after World War II, Sir Ludwig Guttmann and his colleagues originated wheelchair sports as a rehabilitation tool at Stoke Mandeville Hospital in England (Cooper, 1995). Wheelchair sports developed out of the need to provide exercise and recreational outlets for the large number of young people recently injured in the war. News of Guttmann’s success with the rehabilitation of his patients through the use of sports soon spread through Europe to the USA. In 1948, he organized ‘Games’ for British veterans with disabilities. In 1952, the Games developed into the first international wheelchair sporting competition for people with physical disabilities, with participants from The Netherlands, Germany, Sweden, Norway and Israel. The Vietnam conflict brought about dramatic changes in wheelchair design. Medical advances permitted great numbers of people with paraplegia and quadriplegia to live much longer lives. Efforts began to restore a sense of self and enable people to be more mobile. Wheelchair sports began to grow in popularity. During 1960 in Rome, Italy, athletes with disabilities competed for the first time in the same venues as Olympic athletes (Cooper, 1995). At the 1964 games in Tokyo, Japan, the word ‘Paralympics’ was coined. Since then the Paralympics have been held in conjunction with the Olympic games every four years, except 1980 and 1984. The wheelchair has, for most of its history, been a design that segregated instead of integrated. The wealthy have always been capable of obtaining conveyance. If the wheelchair could not go where they wished, servants could carry them. Some people had been fortunate enough to obtain wheelchairs through the government, charity or insurance. As for the poor, many languished and died from whatever illness or accident that created the disability. During the 1970s and 1980s many active wheelchair users began to heal the wounded sense of self so characteristic of people with disabilities. Physical activity and a strong desire for inclusion so empowered some wheelchair users that they started modifying their chairs with saws and welding tools to make the chairs better suited to their needs. The manual wheelchair evolved to be less than 20 lb (Briskorn, 1994). Some wheelchair users went on to form the own companies, which were responsive to consumers wishes, and revolutionized the industry.

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10.2 Wheelchair user disability etiology Disability involves limitations in actions and activities because of mental and physical impairments. Over 14 per cent of the US population is limited in selected activities, with some of these limitations making wheelchair use necessary. Each year the National Center for Health Statistics conducts a National Health Interview Survey on Assistive Devices. This survey showed that there were 1411000 wheelchair users in the USA in 1992 (National Center for Health Statistics, 1992). Arthritis is one of the leading causes of activity limitation in the USA and is second in prevalence to orthopedic impairments (LaPlante, 1991). The quantity and epidemiology of wheelchair user etiology has changed over the past 40 years. Between 1980 and 1990, alone, the use of wheelchairs has increased 96.1 per cent (McNeil 1991–92). Advances in the medical arena have lead to many methods of prolonging life, thus increasing the demand for wheelchairs. There are numerous grounds for a person to need wheelchair assistance. These causes fall into two major categories: traumatic injury and chronic and degenerative disease. The table below presents data obtained in a survey conducted by the British Ministry of Health which gave the diagnosis per hundred of patients who obtained wheelchairs in a controlled study. Condition Arthritis Organic nervous disease Cerebral vascular disease Other bone injuries and deformities Lower limb amputations Cerebral palsy Traumatic paraplegia Respiratory and cardiac disease

(Per cent affected) 28 14 13 11 9 8 7 5

It is estimated that 5 per cent of people over 70 years old are wheelchair users (Sonn and Grimby, 1994). This age-specific prevalence of disability is therefore higher for elderly persons, which places them in a large subcategory of wheelchair users (Morbidity and Mortality Weekly Report, 1994). For the elderly, the more common causes for wheelchair requirement are arthritis/rheumatism, hypertension, diabetes, cardiac and respiratory disease (Pickles and Topping, 1994). The most prevailing reason these patients give for requesting a wheelchair is arthritis and unsteadiness (18.2 per cent), with strokes and frequent falls ranked second and third respectively. Most of these patients (54.5 per cent) use their wheelchairs all the time (Brooks, 1994).

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10.3 Types of wheelchairs The wheelchair is the common mode of transportation and mobility for people with disabilities. Until the 1970s when disability rights laws were being passed, wheelchairs had varied little from the original designs of the 1930s and 1940s. From the 1970s to the present, wheelchair evolution has changed dramatically. Technical advances in engineering, material science and clinical feedback has led to state-of-the-art wheelchair manufacturing and improved client satisfaction (Cooper, 1995). Wheelchairs are either manually powered or electrically (battery) powered. Manual wheelchairs include amputee, depot, ultralight and foot-propelled wheelchairs. Power wheelchairs include conventional power chairs, power bases and scooters. 10.3.1 Manual wheelchairs The depot wheelchair is basically the original institutional wheelchair designed in the 1930s with some minor changes. Although institutional depot wheelchairs have become lighter in the last 50 years, their design has not changed significantly. These chairs are used mainly in hospitals, airports and convalescent homes. Although depot wheelchairs have some varying dimensions, they are not customized for the individual, but designed for many people to use over the life of the chair. These chairs are inexpensive, requiring minimal repairs, and are often propelled by an attendant. Among the few additions are removable armrests for comfort, swing-away footrests for patient transfer and solid tires to reduce maintenance instead of pneumatic tires. The Disability Rights Movement led to a more active and accessible lifestyle for disabled persons. This new lifestyle called for a wheelchair with more maneuverability and better performance to meet the needs of the users. The ultralight wheelchair provides a greater range in mobility. Its lighter frame is usually comprised of aluminum, titanium or composite material, with adjustments to customize the chair for the user. According to the user’s preferences, the user can change the wheelbase, wheel and caster size and type, axle position, camber, body support angle and wheel alignment to meet their needs. People with disabilities have a broad range of injuries, and each injury calls for a specific wheelchair design for the user’s injury. Amputee wheelchairs must be modified from conventional wheelchairs. Conventional wheelchairs are designed for ana-tomically intact users, but people with amputations have varying centers of gravity. Accompanying a lower limb amputation is a change in the person’s center of gravity. The center of gravity moves closer to the rear axle of a normal chair. Tipping could result if the center of gravity is too close to

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the rear wheel axle. Therefore, the rear axle must be extended rearwards without changing the overall strength or stiffness of the wheelchair. For those people with upper extremity paralysis or weakness, foot-propelled wheelchairs may offer more efficient wheelchair propulsion. Two techniques are used in foot-propelled propulsion; push or pull. If the user pulls themselves forward, a wheelchair with the footrests removed is adequate. If the user pushes themselves forward, the seat and rear wheels are in effect the front of the wheelchair. Design considerations include placement of the larger wheels to ensure stability, and placing the castors in a leading position in the direction of travel. 10.3.2 Power wheelchairs People with severe disabilities might need a power wheelchair for mobility purposes. Individuals who have a moderate level of trunk control can use a conventional power wheelchair. Conventional power wheelchairs contain a standard seat system as well as the power control system. Alternative seating systems have been designed to provide customized seating in the standard power wheelchair seat. Power bases are simply power wheelchairs consisting of the power-drive system on a mobile platform. Power bases are developed for those people with minimal trunk control who need a customized seating system mounted to the base. The conventional power wheelchair seating system does not fulfill their needs as individuals. Scooters are designed for those with limited walking ability and substantial body control. They are power bases with a mounted seat and usually a handlebar steering system. They are generally used by people with less serious disabilitative injuries. 10.4 Wheelchair-fitting considerations In today’s wheelchair market there are more types, styles and models of wheelchairs than ever before. As the importance of proper wheelchair prescription has become more recognized, the interface between the user and the wheelchair has been investigated to a greater extent. Biomedical engineers, biomechanists and rehabilitation professionals have all contributed to this area by more thoroughly investigating the anthropometric measurements, activities and skills that individuals with a disability possess and how they relate to comfort and overall physiological functioning.

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10.4.1 User dimensions Anthropometry is often defined as the study of the measurements of human beings (Winter, 1990). Anthropometric data has been used to assist with designing workspaces, automobiles and other types of devices that humans interact with on a frequent basis. The basic concept of anthropometry can also be applied to wheelchair development and prescription. Wheelchair-fitting considerations begin with measuring the user’s anthropometric dimensions. Anthropometric data is most often used to facilitate the development of products that can be utilized by a large percentage of the general population, while fitting considerations will entail prescribing a wheelchair for one particular individual, rather than a number of individuals. This is because each wheelchair user has their own unique anthropometric dimensions, which often vary depending on the user’s age, level of function, time of injury and/or specific musculoskeletal disorder. Measurements of the user’s sitting and acromial height, leg and foot length, shoulder, chest, waist, pelvic, knee and overall width and seating depth should be carefully measured (Trefler et al., 1993). The length of the individual’s arms is also another important anthropometric dimension to consider. A comprehensive anthropometric evaluation will greatly facilitate the proper wheelchair prescription. The age of the wheelchair user can influence the type and size of wheelchair to be prescribed. Children and elderly individuals generally have a smaller stature, compared with their adolescent and adult counterparts. This may necessitate a smaller wheelchair and associated components. The level of the wheelchair user’s functioning is also a primary concern when prescribing a wheelchair. An individual with a more severe disability will require more postural support and possibly additional technology in order to improve the overall level of functioning (Church and Glennen, 1992; Trefler et al., 1993). The time of the individual’s injury is also a consideration when fitting a wheelchair to a user. The individual’s anthropometric dimensions will change as the time of postinjury lengthens. This is because the muscular structure often atrophies as the extremity activity is greatly diminished. The specific type of injury or disorder is another important consideration when fitting a wheelchair. The primary users of wheelchairs are individuals with cerebral palsy, muscular dystrophy, spinal cord and head injuries and the elderly (Trefler et al., 1993). The more common skeletal deformities are kyphosis, lordosis, scoliosis of the spine and valgus and varus angles of the feet, knee and elbow (Church and Glennen, 1992; Trefler et al., 1993). The clinician must thoroughly understand the progression of the individual’s particular disorder in order to properly prescribe a wheelchair. The objectives of the wheelchair prescription depend on the prognosis, medical concerns, intelligence and overall seating goals defined for the individual. As a general rule, the more severe the injury or disorder, the more technology required to properly fit the wheelchair to the user.

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10.4.2 User activities The activity level of the individual with a disability greatly dictates the scope of the wheelchair prescription. The first consideration would pertain to the age of the individual. Children and adolescents may want a more ‘sporty’, more responsive wheelchair that can be used in various social and recreational settings. When recreational and ultra-light wheelchairs are prescribed, they are generally not prescribed with an abundance of postural support to control deformities or deficiencies. Hence, fitting considerations are minimal, resulting in greater mobility and independence for the user. Adults, elderly and more severely disabled individuals may desire a more conservative wheelchair, one that may be more stable, easy to maneuver and maintain (Axelson et al., 1994). As the severity and age of the individual increases, the likelihood of needing more postural stability also increases. Consequently, the wheelchair user would most likely be prescribed a rehabilitation wheelchair or a power wheelchair, as opposed to an ultra-light, sport-type wheelchair (Trefler et al., 1993). A rehabilitation wheelchair can be more easily customized in order to meet the needs of the individual who requires increased postural stability and support. In essence, as the severity of the disability increases, the probability of needing a wheelchair with specific fitting considerations also increases. A power wheelchair would be prescribed, over a manual wheelchair, to an individual who may not have sufficient amounts of strength or endurance to self-propel the manual wheelchair (Trefler et al., 1993; Axelson et al., 1994). Despite the disadvantages of being generally larger and needing periodic maintenance and repair, power wheelchairs do provide those individuals with more severe disabilities the advantage of greater independence. Ultimately, the prescribed wheelchair should be selected in order to complement the user’s abilities in order to fulfil all their daily needs. 10.4.3 User skills The user’s skill level is most often determinant on the severity of the individual’s disability. The extent of the individual’s disorder and/or deformity, in addition to muscular strength and functional range of motion, must all be considered when prescribing a wheelchair (Trefler et al., 1993). Wheelchair users often have disorders associated with head trauma, cerebral palsy, spina bifida and muscular dystrophy. Individuals with these disorders frequently have specific seating considerations that need to be met in order to provide the most functional seating position. When the individual is seated properly, they may have improved function of the extremities, in turn increasing the likelihood of improving the individual’s skill level (Church and Glennen, 1992). As the severity of the individual’s disorder increases, the probability of having orthopedic deformities

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also increases. Common orthopedic deformities are kyphosis, scoliosis and lordosis of the spine, valgus and varus deformities and windswept hips (Trefler et al., 1993). With the increased likelihood of having a disorder and/or orthopedic deformity, individuals often, in turn, lose the use of their musculature in its full capacity. Consequently, these individuals may have insufficient amounts of strength to efficiently and independently propel a manual wheelchair. This often necessitates a power wheelchair rather than a manual wheelchair. In contrast, the individual may have sufficient amounts of upper body strength and endurance, which may allow self-propulsion. Some individuals may even go as far as participating in wheelchair sports such as tennis, basketball, rugby or bowling. The user’s range of motion (ROM) may also be factor to consider when prescribing a wheelchair. The ROM of the user’s upper and lower extremities will determine the position and type of wheelchair that would be ultimately prescribed (Axelson et al., 1994; Church and Glennen, 1992). A reduced ROM may keep the individual from efficiently propelling a manual wheelchair and, in turn, may restrict the individual to a power wheelchair. This is often dependent on the severity of the individual’s disability. If the individual is lacking functional ROM, then they will ultimately be restricted to the types of activities that they can actively participate in. When fitting a wheelchair, all these concerns must be considered in order to properly fit a person with a disability. Issues such as whether the individual should self-propel a manual wheelchair, attendant propel, or use powered technology should also be considered. Often, this is dependent on the type of environment the individual most frequently interacts with and how efficiently the individual would function with the particular mode of mobility in this environment. 10.4.4 Wheelchair properties adjustments In addition to the wheelchair-fitting considerations from the user’s viewpoint, issues regarding the wheelchair’s adaptability must be addressed. A wheelchair with increased adaptability can be adjusted to a greater extent in order to properly fit the wheelchair to the individual. Accompanied by the advantage of creating a better fit for the user, the wheelchair can be further adapted to increase accessibility for various architectural and environmental situations. Accessibility concerns entail clearance under desks and tables, turning in stalls and halls, and traveling through doorways and other tight spaces. Wheelchair adaptability often entails adjustable backrests, footplates, casters, rear axles and seating arrangements. The adjustable backrest will allow changes in backrest height and angle. As a rule of thumb, the higher level of injury, the higher the backrest (Trefler et al., 1993). The angle of the backrest is also adjustable in order to accommodate each individual’s specific comfort needs. Footplates are primarily adjustable in the vertical direction. The vertical movement of the footrests facilitates the acquisition of the desired hip, knee and ankle joint angles (Church

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and Glennen, 1992). The proper adjustments of the footrest can ultimately provide a more stable and functional seating position. The appropriate caster selection, an instrumental component, can add increased comfort, maneuverability, stability and clearance for the wheelchair user. The smaller, 5 in (13 cm) polyurethane solid casters provide the user with increased height and turning clearance, in addition to a faster responding tire, opposed to its 7.5 in (19 cm) counterpart. The 8 in (20 cm) pneumatic casters provide a more comfortable ride, but necessitate proper maintenance and additional height and turning clearance. The rear axle of the wheelchair is the most important adjustment that can be used to manipulate the user’s center of gravity (COG), wheel camber, wheelbase width and seat height. The COG can be manipulated by sliding the rear axle in the fore and aft position and horizontally and vertically in order to achieve the most stable but responsive wheelchair (Brubaker, 1986; Axelson et al., 1994). The rear axle can also be adjusted to change the camber of the rear wheels. The increased camber can provide more lateral stability, responsive turning and greater access to the pushrim. The rear axle can also be changed to provide an increase or decrease in wheelbase width and toe-in and out. The change in wheelbase dimensions can improve accessibility, efficiency and can compensate for camber adjustments. The final and most critical adjustment is providing the user with proper seating. Seating technologies come in two distinct forms, planar and contoured designs (Trefler et al., 1993). These designs can be fluid filled, polyfoam, a hybrid of the two, or oscillating in nature (mechanical or air cells). The specialized seating technology provides the user with postural control, comfort, and deformity and pressure management. All of these wheelchair-adjustment features manipulated in a comprehensive manner will ultimately give the user the foremost comfort, maneuverability, function and independence possible. 10.5 Power wheelchair access systems The primary function of a power wheelchair access system is the control of the power wheelchair. Secondary applications are for use with environmental control systems and computer access. By using the same control interface for both the power wheelchair and the secondary systems, the seating position and control selection can be optimized for multiple purposes. 10.5.1 Joysticks Joysticks are the most common access system for power wheelchair systems. When a power wheelchair is ordered and nothing is specified, a joystick is almost always supplied by the power wheelchair manufacturer. Joysticks can either be switched or proportional. Switched joysticks respond to discrete

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positions of the joystick. Usually four switches are implemented. There are eight discrete with four positions defined by the activation of a single switch and four positions defined by the activation of two switches together. Proportional joysticks get their name because the control output sent to the wheelchair from the joystick is in proportion to how far the joystick is pushed from the center position. The control output can be one of several electrical signals. One particular joystick manufacturer uses a change in electrical resistance to indicate the position of the joystick. This type of joystick is called a resistive joystick. As the joystick is moved left, the electrical resistance is increased, and as the joystick is moved to the right, the electrical resistance is decreased. Another independent change in resistance is used to indicate the position of the joystick fore and aft. Another national manufacturer uses a change in voltage to signal the position of the joystick. Two independent voltages vary with the position of the joystick in the same manner that the resistance does with resistive type. Digital joysticks based on a new standard called M3S are being introduced in the European market. These joysticks offer improved immunity to interference from sources such as police radios, cellular phones, ham radios and even the electric motors of the wheelchair itself. 10.5.2 Sip-and-Puff Sip-and-Puff switches are used primarily by persons with quadriplegia or tetraplegia who do not have any functional use of their arms or hands. A Sip-andPuff consists of a replaceable straw located near the mouth. The wheelchair is controlled by a sequence of pulling and pushing air through the straw with the mouth. These systems can be set up in a variety of configurations. Generally, the user will sip a specific number of times to indicate a direction, and puff to confirm the choice and activate the movement of the wheelchair. It is common for an auxiliary display to be used with Sip-and-Puff to provide feedback to the user. This display is often an LCD flat panel which is capable of displaying about 20 characters. 10.5.3 Switches An array of switches can be used for the directional input of a wheelchair. The control scheme is similar to that of a switched joystick, except that the combination of switch activations are rarely used for directional input. Switches are indicated for individuals who have good control over an anatomical site not usually used to control a wheelchair. An individual with a disability might, for example, have better motor control over a foot than a hand. An array of large switches mounted to the footrest could then be used as a

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direction input. Switches are also the primary means for computer access. Often one switch is used to toggle between the functions of computer access and power wheelchair control. In computer access mode, the switches are used with any number of coding schemes. These coding schemes include International Morse Code, automatic scanning, step scanning, inverse scanning, array scanning and multilevel scanning. Morse code has the advantage of only requiring one switch (though two switches can be used), but generally places the highest cognitive demands on the user of all of the different types of coding schemes. The common feature of the scanning methods is that the selection choices proceed until the user chooses the correct function or if typing the correct character. The act of selection can be through a time delay or the activation of a switch. In automatic scanning, the choices are presented to the user on a computer screen or LCD panel with a preset time delay between each choice. When the desired choice is presented, the user must activate a switch before the next choice is shown. With step scanning the user employs the switch to move from one choice to the next with each press of the switch. A delay on any one choice indicates acceptance of that function or character. Inverse scanning is the reverse operations of automatic. The switch is held down until the desired choice is reached, and then released to finalize the selection. All three of the scanning methods can be further modified to use more than one method with an application. One such modification would be to use one switch to step through the choices and a second switch to accept the choice. Array scanning uses four switches to guide a cursor through an x-y grid of choices; a fifth switch with a time delay is used for the selection process. The switch arrangement in array scanning is highly applicable for both power wheelchair control and computer access. This is because of to the similarity in skills which are necessary to master each task. Multilevel scanning is similar to the above methods but, after the selection of a choice, a new menu is presented. The final function or character is entered from this new menu. The number of levels can also be increased. With all the possibilities for computer access and the ability to use unusual access sites, switches provide one of the most versatile power wheelchair control inputs. The disadvantage is the same as for a switched joystick. There is no proportional control of the wheelchair’s speed with switched control. 10.5.4 Ultrasonic and infrared Many of the input devices described in this section can be used for more than the control of power wheelchairs. Two common additional uses are environmental control and computer access. In some cases, the computer is mounted to the wheelchair, but often it is at a fixed site. In this case, there must be a method for the linkage of the computer to the control device. Older systems which were used primarily for environmental control used ultrasonic signals to transmit

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information. Newer designs are based on infrared for both environmental control and computer access. 10.6 Standard and custom seating system ergonomics 10.6.1 Cushions Individuals with a disability often lack sensation in their lower extremities. Furthermore, these individuals often have a reduced musculature in the lower extremity due to atrophy. The combination of the lack of sensation and atrophy can and often does lead to pressure sores and subcutaneous ulcers. If left untreated, these problems can even be life threatening. There are several methods based on cushion designs for the alleviation of pressure. The general goal is to distribute the pressure over the buttocks evenly without any areas of high pressure. It is also important to minimize the pressure in the regions of the bony prominences such as the ischial tuborosites. This can be accomplished with cut-outs in these areas. One of the oldest cushion designs is an air cushion with individual air cells. The advantage of this design is that it has excellent pressure-relief properties. The major disadvantage is that this type of cushion gives poor postural support. Another disadvantage of an air-floatation cushion is that it does not provide stable performance with changing outside temperature. The rubber bladders which make up air cells tend to crack in the cold and the air pressure changes with temperature. Modification to this design includes using various sized air bladders to provide some additional postural support. Another older type design which has proven to be extremely flexible is the use of foam. Originally these designs used foam laid on top of plywood backboards. Modern cushion designs have contours and multiple layers of different types and densities of foam. The contours can either be standard designs or custom designs. The custom designs are created by forming a mold to the anatomy of the individual. The cushion is then carved out of a block of foam by copying the mold with a panagraph type device. Another advantage of foam is the ability to make orthopedic additions to the seating design. For example, a foam wedge might be added between the legs to separate them. This separating device is called an abductor. Gel pads added to a foam design are generally called a gel cushion. Gel has the advantage of providing better pressure relief than a simple foam cushion, but not usually as good as a custom-contoured foam cushion. Gel cushions have, therefore, become a popular option where a custom-contoured design is not desired. However, gel does suffer from the problem of not being stable with changes in temperature, and can even freeze in very cold climates.

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10.6.2 Custom seating Custom seating systems are used for many of the same reasons that cushions are used except custom seating systems are generally used for more difficult cases. A custom seat can range from a custom-contoured seat cushion to a complete seating system including seat cushion, backrest, headrest, armrests and restraints. Design techniques which are available for custom seat designs are foam-inplace, vacuum bead molding, computer topography, and plywood and foam. The foam-in-place designs use a base of plywood or aluminum covered loosely with vinyl. The client is situated over the seat and foam is injected into the cavity formed by the vinyl. The foam cures and forms the padding and contouring for the seat. The final design can be hand finished by cutting out areas which are most susceptible to pressure or building up others with additional layers of foam. This type of system has the advantage of providing a finished product in a short period of time. Vacuum bead molding is a process where a temporary mold can be made. The method consists of situating the client over a seat and backrest made of a beadfilled bags. The appearance of these bags is similar to that of a bean-bag chair. The air within the bag is withdrawn which makes the seat rigid. A partial vacuum is used to form the mold around the client and the vacuum is intensified to hold the mold in place. Considerable modification to the shape can be made by moving the beads around by hand after the mold has been formed. The mold is cast with plastercasting material to form a positive image. This image is used to make the final cushion out of foam using a three-dimensional panagraph type foam cutter. Computer topography is now being explored as a replacement for foam-inplace and vacuum bead molding. An image is formed based on sensors which are in direct contact with the client. The client sits on what can best be described as a ‘comfortable’ version of a bed of nails (actuators). The displacement of each of these actuators is recorded by the computer and used to form a virtual image. A computer-controlled cutter is then used to carve the custom foam cushion. A backrest can be made using similar techniques. Computer control can also be applied to the force-displacement characteristics of each of the actuators. With this control mechanism, the pressure distribution can, in theory, be completely prescribed by the operator. The oldest method for making custom seating is to carve foam by hand. This method still has some advantages. For a skilled artisan, the pressure distribution can be prescribed, and many different densities of foam can be used with little additional work. Other types of custom seating are usually restricted to two or three densities of foam per design. Another advantage of a hand-formed cushion is that it can easily be modified. The disadvantage is that it takes several hours for a highly skilled technician to construct each design, and these skills are learned

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slowly which makes this method expensive and there is a high degree of variability in the final product. 10.7 Multiconfiguration and stand-up wheelchairs 10.7.1 Tilt-in-space Tilt-in-space wheelchair frames allow the user to redistribute their weight and center of gravity. As the seat-to-back angle remains constant, the tilt-in-space frame can tilt up to an angle of greater comfort for the user. People suffering from spasms, poor postural strength and skeletal deformities can benefit from tiltin-space frames. 10.7.2 Manual wheelchair-power wheelchair conversions No one type of wheelchair can be used satisfactorily in all types of circumstances. For example, an individual might want a power wheelchair for out of doors, but may prefer a manual wheelchair for indoor use. A manual wheelchair has the advantage of generally being smaller and more maneuverable, and the individual usually gains some cardiovascular benefits from manual wheelchair propulsion. A power wheelchair, however, can prevent overexertion for longer distances such as when the individual is outside, or in a shopping mall. A wheelchair which could fulfil both tasks would have an economic advantage, and would allow the use of the same seating system to be used for both powered mobility and manual propulsion. There have been some attempts at designs such as these. The designs center around one of two philosophies. The first is to modify a manual wheelchair with the addition of a power assist add-on device. This device can be an electric motor which turns a separate wheel in contact with the ground, or motor-wheel units which replace the standard rear wheels. In either case the wheelchair frame retains its manual wheelchair characteristics. Heavier-duty designs are centered around the philosophy of modifying a powered wheelchair to allow for the removal of the motors and batteries. In one design, the batteries, motors, gearbox assemblies and rear wheels are removable as a single unit. Manual propelled rear wheels are then attached to complete the conversion.

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10.7.3 Stand-up wheelchairs The act of standing has been shown to contribute to the slowing of osteoporosis in certain individuals with a disability. Standing also provides the practical abilities of reaching items on shelves, operating office equipment and holding conversations at eye level. There are two basic types of standing wheelchairs. The first is strictly a standing wheelchair and the second type can convert between either a power or manual wheelchair and a standing wheelchair. Designs of the first type generally consist of a cage structure around the lower extremity of the user. Padded supports can be added for the postural stability of the trunk if necessary. These supports can be adjusted by the standing wheelchair user to allow for bending at the waist. Propulsion is provided through a chain or lever mechanism to the rear wheels. The second type of standing wheelchair provides this standing function in addition to the function of either a manual wheelchair or a power wheelchair. Various standing mechanisms have been devised. Most of these designs use an electrically powered mechanism to raise and lower the individual regardless of whether the wheelchair is a manual or electric type. There is, however, at least one design which uses the push rims connected through a mechanism to raise and lower the wheelchair user. In this design, a lever is used to switch the function of the push rim between the functions of raising and lowering the wheelchair user and propelling the wheelchair. In both the electrically powered and manuallypowered lift designs, the lift sequence is similar. The tibia is supported near the head by a pad just below the knees and the trunk is supported either by a pad or a seat belt at the midline of the chest. The user is raised by a movement which is produced by the reaction force at the knees and the raising seat. At the highest position, the seat back, seat and leg rest fall in a line with pivoting taking place about the knees and hips of the wheelchair user. Potential problems can arise with this type of design because of the large forces applied to the tibia to raise an individual to a standing position. 10.8 Wheelchair-propulsion biomechanics The low efficiency and high strains seen in manual wheelchair propulsion have been associated with four conditions. 1 A discontinuous motion, with an idle recovery phase. 2 A complex hand-arm movement during the push phase, requiring additional coordinative muscular action. 3 A complex coupling of the hand to the push rim, leading to braking forces at the start of the push phase and a negative torque.

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4 The shoulder complex requires (static) muscular actions to stabilize and adjust the shoulder complex with respect to the trunk during the push phase (van der Woude et al., 1995). These factors, among others, may subject the upper extremity joint structures to forces and movement patterns which cause them to fail over time. An understanding of the kinematics and kinetics of wheelchair propulsion will allow the clinician and rehabilitation engineer to effect changes in wheelchair design, the user-wheelchair interface and stroke technique in order to reduce the potential for injury. The fol lowing sections outline research which has been reported on the biomechanics of wheelchair propulsion. 10.8.1 Kinematics The phases of the wheelchair-propulsion stroke have been described by a number of researchers. Flexion and extension of the joints of the upper limb are described as the main motion (Davis et al., 1988) produced each stroke or cycle time (CT). The stroke has generally been divided into propulsion or drive and recovery phase (Sanderson and Sommer, 1985; Davis et al., 1988; Ridgway et al., 1988; Veeger et al., 1989; Cooper and Bedi, 1990) which are referred to as push time (PT) and recovery time (RT), respectively. During the propulsive phase the hands are in contact with the push rim (Ridgway et al., 1988; Veeger et al., 1989) applying force in order to maintain velocity (Alexander, 1989; Davis et al., 1988; Veeger et al., 1989). The propulsive phase usually begins with the hands contacting the push rim close to top-dead center and ending when the hand is in a forward, downward position. During the recovery phase the arms are brought back into position to allow for the beginning of the next propulsive phase. The amount of time subjects spend in propulsion during the cycle has been reported close to 25 per cent for both adult and pediatric groups pushing an everyday wheelchair overground (Bednarczyk and Sanderson, 1994), between 30 per cent to 45 per cent for subjects pushing a wheelchair on a treadmill (Sanderson and Sommer, 1985) and between 33 per cent and 37 per cent for athletes pushing racing wheelchairs (Cooper and Bedi, 1990; Higgs, 1986). Robertson et al. (1991) divided the stroke into five phases based on racing wheelchair propulsion. These include: 1 hand drive forward and downward 2 push rim impact 3 hand on the push rim 4 hand off push rim and 5 elbow drive to the top.

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It is suggested that these phases might also be used for analysing the propulsion stroke for individuals pushing a commonly used everyday wheelchair. The range of motion and movement patterns of joint segments have been studied in relationship to various conditions of propulsion. Veeger et al. (1991) found that maximum elbow extension occurred at the end of the push phase with a greater extension angle as resistance increased, while trunk flexion stayed the same. Vanlandewijck et al. (1994) characterized the elbow movement while subjects pushed on a treadmill as a push-pull action, which involves a flexion at the elbow joint followed by extension. They noted that at lower speeds, half of the push time was equally divided over a pull-and-push phase while at higher speeds (2.21 m/s) only one-third of physical therapy was spent on elbow flexion. At hand contact with the push rim the shoulder joint was in maximum abduction, shoulder flexion occurred during the entire push phase and the increasing speed of propulsion increased shoulder flexion range of motion in the first 50 per cent of the stroke. During recovery they noted that the motion pattern was extremely variable. Van der Woude et al. (1989) showed that increasing seat height for subjects pushing on a treadmill resulted in decreased extension and adductionabduction of the arm at the shoulder. The kinematics for three experienced wheelchair users were shown to remain consistent within subjects during an 80minute test on a treadmill but considerable differences were found between subjects (Sanderson and Sommer, 1985). There were two distinct stroke styles found, circular and pumping. It was concluded that the circular stroking style was more advantageous because the subject can prolong the propulsive phase, producing a greater impulse to the push rim. Veeger et al. (1992a) studied nonwheelchair users versus wheelchair users and showed that the nonwheelchair users leaned further forward, started and ended the push with the arms further back and had greater arm extension during the stroke. Gaines et al. (1984) found that different wheelchairs produced differences in stroke patterns for the same subjects with paraplegia. Changes in the phases of the stroke have been described for different conditions of propulsion. Researchers have measured the effects on the stroke during protocols on a treadmill or a wheelchair ergometer and with changes in speed, seat height, resistance and power. Increasing seat height was shown to decrease push range (the amount of rotation the wheel undergoes PT) and PT (van der Woude et al., 1989). Fatigue was shown to minimally affect PT and recovery time (Rodgers et al., 1994). Changing speed and slope on a treadmill for two different workload strategies resulted in decreased PT with increasing speed but not with slope, while recovery time (RT) remained constant at higher speeds but decreased with increasing slope (van der Woude et al., 1988). Vanlandewijck et al. (1994) reported decreases in PT with increases in velocity while subjects pushed on a treadmill. It was also found that subjects shifted the start and end angles of the push range to the front of the hand rim without changing PA for increases in velocity of propulsion. Veeger et al. (1992b) investigated four different speeds of propulsion for two power outputs and found

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that subjects did not decrease the time of recovery phase or increase push range to increase push rim speed. Increases in resistance for a 20-second sprint test on a wheelchair ergometer caused increases in PT and cycle time (Veeger et al., 1991). This work and subsequent studies showed that increasing cycle frequency and the amount of work per cycle, while decreasing cycle time, caused an increase in mean power output (van der Woude et al., 1989). Different modes of propulsion have been investigated in terms of their influence on kinematics. A comparison of treadmill with ergometer modes of wheelchair propulsion demonstrated that there were only small differences in kinematics and both PT and cycle time decreased with increases in propulsion velocity (Veeger et al., 1992b). Lever versus push rim propulsion resulted in differences kinematically in upper extremity motion with push rim propulsion requiring less elbow motion, greater shoulder extension, less shoulder rotation and less arm abduction (Hughes et al., 1992). Seat position had a greater effect on joint range of motion for push rim propulsion than for lever propulsion with a forward seat position increasing shoulder abduction/adduction. A rear seated position increased shoulder flexion/ extension and a lower position increasing overall upper extremity motion. Analysis of the electrical activity of the upper extremity musculature during wheelchair propulsion revealed that the anterior deltoid and pectoralis major were highly active during the push phase (Veeger et al., 1991; Mâsse et al., 1992). The biceps brachii was active during the initial part of the push phase (pull motion) and during the latter part of the recovery phase. The triceps brachii was active during the end of the push phase. Seat position was shown to affect the activation pattern to the greatest extent in the triceps brachii, pectoralis major and posterior deltoid with the backward-low position having the lowest overall activity (Veeger et al., 1991; Mâsse et al., 1992). 10.8.2 Kinetics The complexity of developing a system for measuring push rim forces is evidenced by the paucity of data in the literature on the kinetics of wheelchair propulsion. A number of researchers have attempted to develop a force-sensing system with varying degrees of success. The wheelchair kinetic data reported in the literature can be divided into three categories: static force measurements; external devices for measuring forces and torques; and measurement of force components at the push rim—indirectly or directly. 10.8.2.1 Static force measurement Brauer and Hertig (1981) used a system of springs to restrain a push rim. Static torque was measured for wheelchair and non-wheelchair users at six different

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positions ranging from −10 to 40° relative to the vertical. Males were found to generate more torque than females. Ranges of torque values were from 27.9 to 46.6 Nm for males (wheelchair and non-wheelchair users) and 17.1 to 32.1 Nm for females. The authors concluded that the amount of torque produced by the user at the push rim varies with frictional characteristics of the push rim, grip location, handedness, grip strength and/or how well the wheelchair fitted the anthropometric measurements of each subject. Brubaker et al. (1982) measured static pushing and pulling force for four grip positions using strain-gauged beams mounted to the push rims. A movable sets allowed various seat positions. The range of forces between 500–750 N varied considerably by rim and seat position. 10.8.2.2 External devices for measuring forces and torques Tupling et al. (1986) used a force plate to measure the force generated during the initiation of wheelchair propulsion for the grab-and-start techniques. They found that the grab start was more effective in initiating the movement and that the individual’s strength determines their ability to generate an impulse. Samuelsson et al. (1989) described a wheelchair ergometer which was a wheelchair with a gear attached to the hub connected by a chain and gear to an isokinetic dynamometer. This device allowed torque and power output to be calculated. Results of a pilot study showed that subjects could produce peak torque values in the range of 70 Nm at 120°/sec. Ruggles et al. (1994) tested three different wheelchairs through a roller system connected to a Cybex Isokinetic Machine. Peak torque, angular displacement, work and angular impulse were compared. Differences among wheelchairs were found and the authors suggest that wheelchair design and dimensions relative to the anthropometry of the user have a great influence on the mechanical characteristics of propulsion. These studies and the static studies have provided useful information; however, they can only estimate the actual forces at the push rim during propulsion and they do not allow for the calculation of joint moments. 10.8.2.3 Measurement of force components at the pushrim Niesling et al. (1990) described a stationary ergometer capable of measuring pushrim forces using a three-dimensional force transducer mounted on the support brackets. This device has been used in a number of studies of wheelchairpropulsion biomechanics (van der Woude et al., 1989; Veeger et al., 1992a, b; Dallmeijer et al., 1994). Using this device Veeger et al. (1992a, b) developed a parameter known as the fraction of effective force (FEF) which is the ratio of tangential force to total force at the push rim. In a study (Veeger et al., 1992b) utilizing nine non-wheelchair using subjects at different speeds of propulsion, they showed that the Fx (forward) forces were considerably smaller than the Fz

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(vertical), while Fy (medial/lateral) had a more consistent pattern with a large outward component at the end of the push phase. This resulted in a total force component which was directed predominantly downward. It was also found that FEF decreased significantly with speed and that the forces increased with external power output, while FEF parameters did not. Roeleveld et al. (1994) tested nine wheelchair athletes during a 30-second sprint test on the same system. Results showed that the fraction of effective force was low for these subjects and only slightly higher than what was found for less experienced subjects. This was attributed to the total force not being tangentially directed and to the geometry of the wheelchair. Utilizing a similar protocol on the device, Dallmeijer et al. (1994), in addition to physiological measurements, compared forces applied to the push rim by a group of spinal cord injured (SCI) subjects during a 30-second sprint test. FEF was also found to be low in this study and although a number of differences were found in performance between the high-lesion group (C4–C8) and the other lower-lesion groups, FEF was not different. This and other studies by Veeger and van der Woude’s group concluded that the FEF was adversely affected by non-optimal wheelchair dimensions, ineffective propulsive technique and the need for friction between the hand and the push rim. Rodgers et al. (1994) used a force-sensing push rim to compare changes in propulsion biomechanics with fatigue. No changes in joint reaction forces with fatigue were found, although kinematic changes were seen (Rodgers et al., 1994). Strauss et al. (1989, 1991) have reported technical difficulties developing devices capable of measuring forces at the push rim during propulsion. Cooper and Cheda (1989) described a force-sensing push rim to dynamically measure racing wheelchair push rim forces and torques. A slotted disk was used to mount different size push rims which mounted to the hub with three beams instrumented with strain gauges. A later version of this force-measuring wheel; SmartWheel (Watanabe et al., 1991; Cooper et al., 1992; Asato et al., 1993) allows measurement of three-dimensional push rim forces and moments. The unique quality of this device is that it can be mounted to the user’s own everyday wheelchair. Measurement of push rim forces with this device has shown that a large radial and vertical component of force is apparent in the stroke of most individuals, an impact spike is seen early in the propulsion phase, and the magnitude of these forces are dependent on experience using a wheelchair (Robertson and Cooper, 1993). 10.9 Net joint forces and moments Joint forces have been studied by few authors. Larger joint moments have been noted with increases in external power output, with the highest moments occurring at the shoulder during flexion and adduction with the anterior deltoids and pectoralis major acting as primary movers (Veeger et al., 1991). Fatigue was

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shown not to affect the magnitude of joint moment or joint reaction forces; joint moments and joint power measures were highest during shoulder joint flexion (Rodgers et al., 1994). Shoulder joint moments were found to be much higher than at the wrist or the elbow, when subjects pushed a wheelchair on a treadmill. Higher speed and greater slope resulted in greater loads on the three joints, with the effect of slope being more significant than that of speed (Su et al. 1993). Robertson et al. (1995a, b) have shown a larger moment at the shoulder than either the wrist or elbow, a large component of vertical reaction force at the shoulder and differences between wheelchair users and non-wheelchair users in terms of peak values and when these values occurred during the propulsion stroke. Much more work must be completed on assessing push rim forces and the concomitant joint moments and forces in order to develop an understanding of the factors which dictate whether an individual will sustain a propulsion injury. Three-dimensional push rim forces in relationship to the kinematics of the propulsive stroke should be studied in detail along with concomitant net joint forces and moments. The influence of seating position, speed of propulsion, different conditions of propulsion such as speed changes, ramps and directional changes, and different levels of impairment must be investigated in order to determine the causes of the high incidence of injury experienced by manual wheelchair users. 10.10 Overuse injuries related to wheelchair propulsion Prolonged wheelchair use is associated with secondary musculoskeletal and neurologic upper extremity injuries. The most commonly reported site of musculoskeletal injury in manual wheelchair users (MWUs) is the shoulder. Surveys of MWUs show the prevalence of shoulder pain to be between 31 and 73 per cent (Bayley et al., 1987; Gellman et al., 1988b; Wylie and Chakera, 1988; Pentland and Twomey, 1991; Sie et al., 1992). Sie et al. (1992) interviewed 103 patients with paraplegia, 36 per cent reported shoulder pain. He found prevalence increased over time until 20 years post-injury, when it decreased slightly. Nichols et al. (1979) in a survey of MWUs, found a 51.4 per cent prevalence of shoulder pain. He reported that the frequency of shoulder pain increased with time since the onset of the disability. Pentland and Twomey (1991) reported on pain complaints, strength and range of motion in 11 women with paraplegia and 11 healthy controls. This study found 73 per cent of women with paraplegia less than 15 years out from their spinal cord injury (SCI) experienced shoulder pain during activities. Gellman et al. (1988b) interviewed 84 subjects with paraplegia and found 100 per cent of the subjects more than 15 years out from an SCI had shoulder pain as compared with 20 per cent of those less than 15 years out from injury.

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Bayley et al. (1987) studied 94 veterans with complete paraplegia. Each veteran had a physical examination focusing on the upper extremity. Thirty-one patients reported a history of shoulder pain and 23 were found to have signs of impingement on examination. All 23 subjects with pain on examination had Xrays and arthrography which revealed rotator cuff tears in 65 per cent and aseptic necrosis of the humeral head in 22 per cent. No comment on the association of time since injury and shoulder problems was made. Although this study includes objective evidence of shoulder pathology, testing was only performed on symptomatic subjects, and thus subclinical pathology was probably missed. Wylie and Chakera (1988) reviewed the medical and surgical records of 51 individuals who were all over 20 years out from an SCI. He found radiographic shoulder abnormalities in 32 per cent of the subjects. He also reported that patients with greater activity levels had fewer complaints of pain. The type of radiographic abnormality was not reported and shoulder films were not present on all subjects. Although the shoulder is the most common site of musculoskeletal injury in MWUs, elbow, wrist and hand pain are also commonly reported (Gellman et al., 1988b; Pentland and Twomey, 1991; Sie et al., 1992). Sie reported elbow, wrist and hand pain in 16, 13 and 11 per cent respectively. This did not include patients with CTS. In addition, Sie further defined significant pain as that which required analgesia, occurred with two or more ADLs or required cessation of activity. Using this definition, the prevalence of all upper extremity pain complaints was 20 per cent, 5 years post-injury and 46 per cent from 15 to 19 years post-injury. Other studies have shown the prevalence of forearm, wrist and hand pain to be between 8 and 55 per cent (Gellman et al., 1988b; Pentland and Twomey, 1991). In all the studies on upper extremity pain, the authors felt the pain was related to overuse of the arm during transfers or wheelchair propulsion and that additional work aimed at prevention strategies is needed. The possible mechanism of injury to the rotator cuff has been extensively explored in the non-disabled population. Fu et al. (1991) and Frieman et al. (1994) provide two thorough reviews of this literature. Mechanisms of injury to the rotator cuff have been divided into intrinsic and extrinsic factors. Intrinsic factors relate to the anatomy of the tendon itself, whereas extrinsic factors relate to surrounding structures. The most commonly cited intrinsic factor associated with rotator cuff disease is a critical zone for injury at the insertion of the supraspinatus tendon into the humeral head. This critical zone has been found to have decreased vascularity (Rathbun and Macnab, 1970). In Bayley and coworkers’ (1987) study of shoulder pain in MWUs he found that interarticular pressure was over two times arterial pressure when performing a transfer. He believed that this increased pressure further stressed the vasculature of the rotator cuff tendon. The most commonly cited extrinsic factor is impingement of the rotator cuff by surrounding structures. Neer (1972, 1983) reported changes in the undersurface of the structures forming the coracoacromial arch which he related

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to impingement. He attributed 95 per cent of all RCT to impingement, and stated that this impingement took place with the arm abducted and forward flexed. Bigliani et al. (1986) reported that specific shapes of the acromion correlated with an increased risk for tears of the rotator cuff. Of note, Wylie and Chakera (1988) reported that 18 per cent of active wheelchair users had joint space narrowing in the shoulder. Although both these theories of pathophysiology have come into question recently (Ozaki et al., 1988; Iannotti et al., 1989), it is likely that both the shape of the coracoacromial arch and the vascularity of the rotator cuff tendons contribute to pathology. Any activity which forces the humeral head further into the glenohumeral joint can cause impingement under the acromioclavicular arch and thus inflammation. In the majority of the literature, the humeral head is placed in close proximity to the acromioclavicular arch during overhead activities. In MWUs the vast majority of activity is not overhead; however, there are forces which tend to drive the humeral head up into the glenohumeral joint. These forces occur during transfer activities and during wheelchair propulsion when a downward force is necessary to create friction against the push rim. Another extrinsic factor leading to impingement and RCT is the instability of the glenohumeral joint (Hardy et al., 1986; Jobe et al., 1989). The instability is thought to relate to a combination of attenuation of supporting structures of the glenohumeral joint, such as the glenoid labrum, and to muscle imbalance. Muscle imbalance, caused by overuse, is thought to lead to abnormal biomechanics and thus injury. The most common disparity in strength associated with RCT is an imbalance between the internal and external rotators of the shoulder (McMaster et al., 1991; Hinton, 1988). Burnham et al. (1993) was able to demonstrate muscle imbalance in a group of wheelchair athletes and was able to correlate this imbalance to shoulder pain. Combined epidemiologic and ergonomic studies show a correlation between the incidence of shoulder pain and type of job (Herberts et al., 1981, 1984; Bergenudd et al., 1988; Stenlund et al., 1992, 1993). These studies have correlated the extrinsic factors of exposure to vibration, high static and dynamic forces and overhead activity with shoulder pain. Increased pressures in the shoulder joint from heavy lifting are thought to compromise the vasculature of the rotator cuff tendon (Herberts et al., 1984). The most common neurologic cause of upper extremity pain in MWUs is CTS. The prevalence of CTS in this group is between 49 and 73 per cent (Aljure et al., 1985; Gellman et al., 1988a; Tun and Upton, 1988; Davidoff et al., 1991; Sie et al., 1992; Burnham and Stead ward, 1994). In addition to CTS, ulnar nerve damage has been reported by a number of investigators (Stefaniwsky et al., 1980; Tun and Upton, 1988; Burnham and Steadward, 1994). Gellman et al. (1988a) in a study of 77 individuals with T2 or below paraplegia, found 49 per cent had signs and symptoms of CTS. Sie et al. (1992) interviewed 103 subjects with paraplegia and found historical or physical examination evidence of CTS in

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66 per cent. Both these large clinical series found the incidence of CTS increased with the increased duration of paralysis. To add objective criteria to the diagnosis of CTS, a number of investigators have performed nerve-conduction studies (NCS) on this population. Aljure et al. (1985) studied 47 patients with a SCI below the T2 level and found electrodiagnostic evidence of CTS in 63 per cent and clinical evidence of CTS in 40 per cent. This study also found an increased prevalence of CTS with duration of paralysis. Tun et al. (1988) found that 50 per cent of individuals with paraplegia below the T1 level had slowed motor conduction of either the ulnar or median nerves at the wrist (Tun and Upton, 1988). Forty-four per cent of patients with electrical abnormalities were asymptomatic. Davidoff et al. (1991) studied 31 patients with paraplegia below the T1 level and found electrodiagnostic evidence of CTS in 55 per cent and symptoms of numbness or tingling in the hand in 74 per cent. Burnham and Steadward (1994) studied the incidence of nerve injury in a group of 28 wheelchair athletes. Exhaustive nerve-conduction studies were performed and the prevalence of electrically diagnosed CTS was found to be 46 per cent. It is important to note that by clinical criteria only 23 per cent of the athletes had nerve damage. Stefaniwsky et al. (1980) studied 12 patients with various levels of SCI and found slowed conduction velocity in the ulnar nerve. Slowing of the ulnar nerve was seen in both the above-elbow to below-elbow segment and the below-elbow to wrist segment. In this small study there was no correlation between time since injury and ulnar nerve damage. In three of the studies described above, electrodiagnostic evidence of ulnar nerve injury was also documented (Burnham and Steadward, 1994; Davidoff et al., 1991; Aljure et al. 1985). The prevalence of ulnar nerve injury in these studies varied between 15 and 40 per cent. CTS is generally thought to be caused by compression of the median nerve within the carpal tunnel. Extremes of wrist flexion and extension have been shown to greatly increase the pressure within the carpal tunnel, more so in patients with CTS (Gelberman et al., 1981; Lundborg et al., 1982; Werner et al., 1983). Gellman et al. (1988a) studied patients with spinal cord injuries and found that pressures in the carpal tunnel were higher in wrist flexion in this group than in a group of controls. Thickening of the flexor tendon sheaths secondary to repetitive motion has also been implicated as a cause for compression of the median nerve (Moore, 1992; Werner et al., 1983). The majority of authors who have investigated CTS in MWUs have implicated the repetitive activity of propelling the chair as a causative factor. There is a large body of epidemiologic and ergonomic literature relating CTS to worksite risk factors. A number of studies has shown that high force-high repetition jobs are associated with a high incidence of CTS (Armstrong et al., 1982; Silverstein et al., 1987; Delgrosso and Boillat, 1991; Hagberg et al., 1992; Loslever and Ranaivosoa, These studies indicate that the higher the force and the greater the degree of wrist flexion, the greater the likelihood of developing CTS. These studies also indicate that high repetition is more important than high force

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in the development of CTS and that anatomic or congenital factors are also important—CTS is commonly bilateral. Additional studies have implicated exposure to vibration as a strong risk factor for CTS (Delgrosso and Boillat, 1991; Silverstein et al., 1987). Although little can be done about the high repetition involved in wheelchair propulsion, modification of the chair or user stroke may be able to reduce forces, the amount of and type of wrist motion and the amount of vibration that occurs when the hand strikes the wheel. 10.11 Wheel chair-related accidents and injuries Falling and tipping-related accidents are the primary accidents connected to wheelchair use. In a study involving 651 records collected by the Food and Drugs Administration (FDA) between 1975 and 1993, types of wheelchair injury and engineering factors leading to injury were examined (Kirby and AckroydStolarz, 1995). Table 10.1 (Kirby and Ackroyd-Stolarz, 1995) gives the breakdown of recorded wheelchair injuries, and Table 10.2 (Kirby and AckroydStolarz, 1995) lists the recorded engineering factors involved in injury. Axle position, camber, the position of the user and the location of any added masses directly affect the tipping angles of the wheelchair. Making the proper adjustments to the wheelchair can help prevent falling and tipping-related accidents. Most wheelchairs offer rear wheel adjustability. This feature allows the user to position the rear axle to their own personal preference. Moving the rear wheels rearward increases uphill stability and decreases the chance of a tipping accident. Camber is the degree of angling of the rear wheels outward at the bottom of the chair and inward where the user’s hands contact the hand rim. Greater camber increases sideways wheelchair stability, and is important in helping users’ negotiate cross slopes. Table 10.1 Breakdown of recorded wheelchair injuries

Fracture Laceration Contusions/abrasions Concussions/subdurals Dislocation Dental injury Puncture Strain/sprain Burns, thermal Other

Number

(Per cent)

143 70 63 9 5 4 4 4 4 8

45.5 22.3 20.1 2.8 1.6 1.3 1.3 1.3 1.3 2.6

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The user can change the wheelchair’s stability themselves, according to upper body strength and mobility. Rearward stability can be increased by the user leaning forward, and forward stability can be increased by the user leaning backwards. A user with good upper-body strength might opt for a less stable and more maneuverable wheelchair adjustment, relying on their trunk mobility to avoid tipping. If the user has a varying body-weight distribution or poor trunk control, the wheelchair can be modified by adding weights where needed. By calculating the center of gravity of the wheelchair and user, weights can be placed at appropriate points on the wheelchair to make it safer. Some wheelchair accidents occur as a result of poor design. Wheelchair stability, frame and component material strength, environmental interaction, and braking ability are important factors in designing a safe wheelchair. The American National Standards Institute (ANSI)/RESNA and the International Organization for Standards (ISO) have developed standardized tests for wheelchairs for disclosure to the public. These standards allow the user to select a wheelchair based upon performance, safety and dimensions. The standards serve as a guide to avoid designrelated accidents that may occur, based upon the disclosed information. The static stability test measures how stable a wheelchair is on a sloped angle. Rearward, forward and sideways-tipping angles are measured and disclosed. The user can use this information to avoid slopes that prove to be greater than the wheelchair’s tipping angles. The determination of seating and wheel dimensions standard helps to provide a customized fit for the user. A good fit between the wheelchair and the wheelchair user is crucial to prevent the user from slipping or falling out of the wheelchair. Standards for the effectiveness of wheelchair brakes are tested on manual and powered wheelchairs. In addition to tipping on a slope, the wheelchair may have a Table 10.2 Recorded engineering factors involved in injury

Mechanical/frame Electrical/electronic Brakes Motor

Number

(Per cent)

305 48 24 18

77.3 12.2 6.1 4.6

tendency to slip or slide, creating a dangerous situation. The angles at which slipping occurs is measured and disclosed, similar to the stability tests. Static, impact and fatigue strength tests measure the wheelchair’s susceptibility to different loads. These loads approximate normal everyday wheelchair use, such as dropping off a curb, running into objects and riding over

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uneven terrain. The information gathered by these tests can be used to select a wheelchair that will not suffer a sudden or catastrophic failure. These standards are continually revised as researchers and clients provide feedback for the effectiveness and efficiency of the tests. The writing of wheelchair standards will continue to be an ongoing process as wheelchair technology and wheelchair designs advance. References ALEXANDER, M.J.L. (1989) Aspects of performance in wheelchair marathon racing, Journal de l’ACSEPL, Jan.–Feb., 26–32. ALJURE, J., ELTORAI, I., BRADLEY, W.E., LIN, J.E. and JOHNSON, B. (1985) Carpal tunnel syndrome in paraplegic patients. Paraplegia, 23, 182–6. ARMSTRONG, T.J., FOULKE, J.A., JOSEPH, B.S. and GOLDSTEIN, S.A. (1982) Investigation of cumulative trauma disorders in a poultry processing plant. American Industrial Hygiene Association Journal, 43, 103–16. ASATO, K.T., COOPER, R.A., ROBERTSON, R.N. and STER, J.F. (1993) SMARTWheel: development and testing of a system for measuring manual wheelchair propulsion dynamics, IEEE Transactions on Biomechanical engineering, 40 (12), 1320–4. AXELSON, P., MINKEL J. and CHESNEY, D. (1994) A guide to wheelchair selection: How to use the ANSI/RESNA wheelchair standards to buy a wheelchair. Washington DC: Paralyzed Veterans of America. BARTOLUCCI, M. (1992) Making a chair able by design, Metropolis, 12 (4), 29–33. BAYLEY, J.C., COCHRAN, T.P. and SLEDGE, C.B. (1987) The weight-bearing shoulder. The impingement syndrome in paraplegics. Journal of Bone and Joint Surgery—American Volume, 69, 676–8. BEDNARCZYK, J.H. and SANDERSON, D.J. (1994) Kinematics of wheelchair propulsion in adults and children with spinal cord injury, Archives of Physical Medicine and Rehabilitation, 75 (12), 1327–34. BERGENUDD, H., LINDGARDE, F., NILSSON, B. and PETERSSON, C.J. (1988) Shoulder pain in middle age: A study of prevalence and relation to occupational work load and psychosocial factors. Clinical Orthopaedics and Related Research, 231, 234–8. BIGLIANI, L.U., MORRISON, D.S. and APRIL, E.W. (1986) The morphology of the acromion and its relationship to rotator cuff tears. Orthopaedic Transactions, 10, 216. BRAUER, R.L. and HERTIG, B.A. (1981) Torque generation on wheelchair hand rims, Proceedings 1981 Biomechanics Symposium, ASME/ASCE Mechanics Conference, Colorado, pp. 113–16. BRISKORN, C.N. (1994) Composing the composite, Team Rehabilitation Report, 5 (2), 35–9. BROOKS, L. (1994) Use of devices for mobility by the elderly. Wisconsin Medical Journal, 93 (1), 16–20.

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BRUBAKER, C.E. (1986) Wheelchair prescription: An analysis of factors that affect mobility and performance. Journal of Rehabilitation Research and Development, 23 (4), 19–26. BRUBAKER, C.E., Ross, S. and MCLAURIN, C.A. (1982) Effect of seat position on hand rim force, Proceedings of 5th Annual Conference on Rehabilitation Engineering, Houston, Texas, p. 111. BURNHAM, R.S. and STEADWARD, R.D. (1994) Upper extremity peripheral nerve entrapments among wheelchair athletes: Prevalence, location and risk factors. Archives of Physical Medicine and Rehabilitation, 75, 519–24. BURNHAM, R.S., MAY, L., NELSON, E., STEADWARD, R. and REID, D.C. (1993) Shoulder pain in wheelchair athletes: The role of muscle imbalance. American Journal of Sports Medicine, 21, 238–42. CHURCH, G. and GLENNEN, S. (1992) The Handbook of Assistive Technology, San Diego, CA: Singular Publishing Group, Inc. COOPER, R.A. (1995) Rehabilitation Engineering Applied to Mobility and Manipulation, London, UK: Institute of Physics Publishers. COOPER, R.A. and BEDI, J.F. (1990) Gross mechanical efficiency of trained wheelchair racers, Proceedings of the 12th International Conference of IEEE Engineering in Medicine and Biology Society, 5, 2311–22. COOPER, R.A. and CHEDA, A. (1989) Measurement of racing wheelchair propulsion torque, Proceedings of the 12th International Conference of IEEE Engineering in Medicine and Biology Society , 5, 2311–22. COOPER, R.A., ASATO, K.T., ROBERTSON, R.N. and STER, J.F. (1992) Twodimensional kinetic analysis of manual wheelchair propulsion with an improved SMARTWheel, Proceedings IEEE-EMBS of the 14th International Conference, Paris, France, 14 (4), pp. 1544–5. DALLMEIJER, A.J., KAPPE, Y.J., VEEGER, D.H., JANSSEN, T.W. and VAN DER WOUDE, L.H. (1994) Anaerobic power output and propulsion technique in spinal cord injured subjects during wheelchair ergometry, Journal of Rehabilitation Research and Development, 31 (2), 120–8. DAVIDOFF, G., WERNER, R. and WARING, W. (1991). Compressive mononeuropathies of the upper extremity in chronic paraplegia. Paraplegia, 29, 17–24. DAVIS, R., FERRARA, M. and BYRNES, D. (1988) The competitive wheelchair stroke, NSCA Journal, 10 (3), 4–10. DELGROSSO, I. and BOILLAT, M.A. (1991). Carpal tunnel syndrome: Role of occupation, International Archives of Occupational and Environmental Health, 63, 267–70. FRIEMAN, B.G., ALBERT, T.J. and FENLIN, J.M., JR. (1994). Rotator cuff disease: A review of diagnosis, pathophysiology and current trends in treatment, [Review]. Archives of Physical Medicine and Rehabilitation, 75, 604–9. Fu, F.H., HARNER, C.D. and KLEIN, A.H. (1991). Shoulder impingement syndrome. A critical review, [Review]. Clinical Orthopaedics and Related Research, 269, 162–73. GAINES, R.F., ZOMLEFER, M.R. and ZHAO, W. (1984) Armstroke patterns of spinal cord injured wheelchair users, Archives of Physical Medicine and Rehabilitation, 65, 616.

RORY A.COOPER ET AL. 309

GELBERMAN, R.H., HERGENROEDER, P.T., HARGENS, A.R., LUNDBORG, G.N. and AKESON, W.H. (1981) The carpal tunnel syndrome. A study of carpal canal pressures. Journal of Bone and Joint Surgery—American Volume, 63, 380–3. GELLMAN, H., CHANDLER, D.R., PETRASEK, J., SIE, I., ADKINS, R. and WATERS, R.L. (1988a) Carpal tunnel syndrome in paraplegic patients. Journal of Bone and Joint Surgery, 70, 517–19. GELLMAN, H., SIE, I. and WATERS, R.L. (1988b) Late complications of the weightbearing upper extremity in the paraplegic patient. Clinical Orthopaedics and Related Research, 233, 132–5. HAGBERG, M., MORGENSTERN, H. and KELSH, M. (1992) Impact of occupations and job tasks on the prevalence of carpal tunnel syndrome, [Review]. Scandinavian Journal of Work, Environment and Health, 18, 337–45. HARDY, D.C., VOGLER, J.B. and WHITE, R.H. (1986) The shoulder impingement syndrome: Prevalence of radiographic findings. American Journal of Roentgenology, 147, 557–61. HERBERTS, P., KADEFORS, R., ANDERSSON, G. and PETERSEN, I. (1981) Shoulder pain in industry: An epidemiological study on welders. Acta Orthopaedica Scandinavica, 52, 299–306. HERBERTS, P., KADEFORS, R., HOGFORS, C. and SIGHOLM, G. (1984) Shoulder pain and heavy manual labor. Clinical Orthopaedics and Related Research, 166–78. HIGGS, C. (1986) Propulsion of racing wheelchair, in SHERRILL, C. (Ed.) Sport and Disabled Athletes, Champaign, Il: HumanKinetics Publishers Inc. HINTON, R.Y. (1988) Isokinetic evaluation of shoulder rotational strength in high school baseball pitchers. American Journal of Sports Medicine, 16, 274–9. HUGHES, C.J., WEIMAR, W.H., SHETH, P.N. and BRUBAKER, C.E. (1992) Biomechanics of wheelchair propulsion as a function of seat position and user-to-chair interface, Archives of Physical Medicine and Rehabilitation, 73 (3), 263–9. IANNOTTI, S.P., SWIONTKOWSKI, M.F. and ESTERHAI, J.L. (1989) Intraoperative assessment of rotator cuff vascularity using laser Doppler flowmetry. Fourth International Conference on Surgery of the Shoulder, New York, NY. JOBE, F.W., KVITNE, R.S. and GIANGARRA, C.E. (1989) Shoulder pain in the overhand or throwing athlete: The relationship of anterior instability and rotator cuff impingement. Orthopaedic Review, 18, 963–75. KIRBY, R. and ACKROYD-STOLARZ, S. (1995) Wheelchair safety-adverse reports to the United States Food and Drug Administration. American Journal of Physical Medicine and Rehabilitation, 74 (4). LAPLANTE, M. (1991) The demographics of disability, Milbank Quarterly, 69 (1–2), 55–77. LOSLEVER, P. and RANAIVOSOA, A. (1993) Biomechanical and epidemiological investigation of carpal tunnel syndrome at workplaces with high risk factors. Ergonomics, 36, 537–55. LUNDBORG, G., GELBERMAN, R.H., MINTEER-CONVERY, M., LEE, Y.F. and HARGENS, A.R. (1982) Median nerve compression in the carpal tunnel-functional response to experimentally induced controlled pressure. Journal of Hand Surgery, 7, 252–9. MCMASTER, W.C., LONG, S.C. and CAIOZZO, V.J. (1991) Isokinetic torque imbalances in the rotator cuff of the elite water polo player. American Journal of Sports Medicine, 19, 72–5.

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McNEIL, J.M. (1991–92) Americans with disabilities. Data From the Survey of Income and Program Participation, P70, 33. MÂSSE, L.C., LAMONTANGE, M. and O’RIAIN, M.D..(1992) Biomechanical analysis of wheelchair propulsion for various seating positions, Journal of Rehabilitation Research, 29 (3), 12–28. MOORE, J.S. (1992) Carpal tunnel syndrome, [Review]. Occupational Medicine: State of the Art Reviews, 7, 741–63. MORBIDITY AND MORTALITY WEEKLY REPORT (1994) Prevalence of Disabilities and Associated Health conditions: United States, 1991–1992. MMWR 43 (40) (The On-line Journal of Current Clinical Trials) NATIONAL CENTER FOR HEALTH STATISTICS (1992) National Health Interview Survey of Assistive Devices 1990, NCHS, (Hyattsville, Maryland). NEER, C.S., II (1972) Anterior acromioplasty for the chronic impingement syndrome in the shoulder: A preliminary report. Journal of Bone and Joint Surgery, 54, 41–50. NEER, C.S., II (1983) Impingement lesions, Clinical Orthopaedics and Related Research, 173, 70–7. NICHOLS, P.J., NORMAN, P.A. and ENNIS, J.R. (1979) Wheelchair user’s shoulder? Shoulder pain in patients with spinal cord lesions. Scandinavian Journal of Rehabilitation Medicine, 11, 29–32. NIESLING, R., EIJSKOOT, F., KRANSE, R., DEN OUDEN, A.H., STORM, J., VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and SNIJDERS, C.J. (1990) Computercontrolled wheelchair ergometer, Medical & Biological Engineering & Computing, 28 (4), 329–38. OZAKI, J., FUJIMOTO, S., NAKAGAWA, Y., MASUHARA, K. and TAMAI, S. (1988) Tears of the rotator cuff of the shoulder associated with pathological changes in the acromion: A study in cadavera. Journal of Bone and Joint Surgery, 70, 1224–30. PENTLAND, W.E. and TWOMEY, L.T. (1991) The weight-bearing upper extremity in women with long term paraplegia, Paraplegia, 29, 521–30. PICKLES, B. and TOPPING, A. (1994) Community care for Canadian seniors: an exercise in educational planning. Disability and Rehabilitation, 16 (3), 181–9. RATHBUN, J.B. and MACNAB, I. (1970) The microvascular pattern of the rotator cuff. Journal of Bone and Joint Surgery, 52, 540–53. RIDGWAY, M., POPE, C. and WILKERSON, J. (1988) A kinematic analysis of 800 meter wheelchair racing techniques, Adapted Physical Activity Quarterly, 5 (2), 96–107. ROBERTSON, R.N. and COOPER, R.A. (1993) Kinetic characteristics of wheelchair propulsion utilizing the SMARTWheel, Proceedings of the 17th Annual Meeting of the American Society of Biomechanics, pp. 202–3, Iowa City, Iowa, USA. ROBERTSON, R.N., COOPER, R.A. and BALDINI, F.D. (1991) Kinematics of wheelchair propulsion , National Wheelchair Athletic Association Newsletter, 10–11. ROBERTSON, R.N., COOPER, R.A., ENSMINGER, G. and BONINGER, M.L. (1995a) Characterization of upper extremity joint kinetics during wheelchair propulsion, Proceedings of the 18th Annual RESNA Conference, pp. 358–60, Vancouver, BC, Canada. ROBERTSON, R.N., COOPER, R.A., ENSMINGER, G. and BONINGER, M.L. (1995b) Joint kinetic-kinematic relationships during wheelchair propulsion, Proceedings of the 19th Annual Meeting American Society of Biomechanics, pp. 231–2, Palo Alto, CA, USA.

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RODGERS, M.M., GAYLE, G.W., FIGONI, S.F., KOBAYASHI, M., LIEH, J. and GLASER, R.M. (1994) Biomechanics of wheelchair propulsion during fatigue, Archives of Physical Medicine and Rehabilitation, 75 (1), 85–93. ROELEVELD, K., LUTE, E., VEGGER, D., GWINN, T. and VAN DER WOUDE, L.H. (1994) Power output and technique of wheelchair athletes, Adapted Physical Quarterly, 11, 71–85. RUGGLES, D.L., CAHALAN, T. and AN, K. (1994) Biomechanics of wheelchair propulsion by able-bodied subjects, Archives of Physical Medicine and Rehabilitation, 75, 540–4. SAMUELSSON, K., LARSSON, H. and TROPP, H. (1989) Wheelchair ergometer with a device for isokinetic torque measurement, Scandinavian Journal of Rehabilitation Medicine, 21 (4), 205–7. SANDERSON, D.J. and SOMMER III, H.J. (1985) Kinematic features of wheelchair propulsion, Journal of Biomechanics, 18 (6), 423–9. SIE, I.H., WATERS, R.L., ADKINS, R.H. and GELLMAN, H. (1992) Upper extremity pain in the postrehabilitation spinal cord injured patient, Archives of Physical Medicine and Rehabilitation, 73, 44–8. SILVERSTEIN, B.A., FINE, L.J. and ARMSTRONG, T.J. (1987) Occupational factors and carpal tunnel syndrome. American Journal of Industrial Medicine, 11, 343–58. SONN, U. and GRIMBY, G. (1994) Assistive devices in an elderly population studied at 70–76 years of age, Disability and Rehabilitation, 16 (2), 85–93. STEFANIWSKY, L., BILOWIT, D.S. and PRASAD, S.S. (1980) Reduced motor conduction velocity of the ulnar nerve in spinal cord injured patients. Paraplegia, 18, 21–4. STENLUND, B., GOLDIE, I., HAGBERG, M. and HOGSTEDT, C. (1993) Shoulder tendinitis and its relation to heavy manual work and exposure to vibration, Scandinavian Journal of Work, Environment and Health, 19, 43–9. STENLUND, B., GOLDIE, I., HAGBERG, M., HOGSTEDT, C. and MARIONS, O. (1992) Radiographic osteoarthrosis in the acromioclavicular joint resulting from manual work or exposure to vibration. British Journal of Industrial Medicine, 49, 588–93. STRAUSS, M.G., MALONEY, J., NGO, F. and PHILLIPS, M. (1991) Measurement of the dynamic forces during manual wheelchair propulsion, Proceedings of the American Society of Biomechanics 15th Annual Meeting. STRAUSS, M.G., MOEINZADEH, M.H., SCHNELLER, J. and TRIMBLE, J. (1989) The development of an instrumented wheel to determine the hand rim forces during wheel chair propulsion, Proceedings Annual Winter Meeting ASME, San Francisco, CA, 10–15 December, pp. 53–4. Su, F.C., LIN, L.T., WU, H.W., CHOU, Y.L., WESTREICH, A. and AN, K.A. (1993) Three-dimensional dynamic analysis of wheelchair propulsion, Chinese Journal of Medical and Biological Engineering, 13 (4), 329–42. TREFLER, E., HOBSON, D.A., JOHNSON TAYLOR, S., MONAHAN, L.C. and SHAW, G.C. (1993) Seating and mobility for persons with physical disabilities. Therapy Skill Builders, Tucson, Arizona. TUN, C.G. andUPTON, J. (1988) The paraplegic hand: Electrodiagnostic studies and clinical findings, Journal of Hand Surgery, 13, 716–19.

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TUPLING, S.J., DAVIS, G.M., PIERRYNOSKI, M.R. and SHEPARD, R.J. (1986) Arm strength and impulse generation: initiation of wheelchair movement by the physically disabled, Ergonomics, 29 (2), 303–11. VAN DER WOUDE, L.H.V., VEEGER, H.E.J., ROZENDAL, R.H. and SARGEANT, T. J. (1989) Seat height in hand rim wheelchair propulsion, Journal of Rehabilitation Research, 26 (4), 31–50. VAN DER WOUDE, L.H., V., VAN KRANEN, E., ARIENS, G., ROZENDAL, R.H. and VEEGER, H.E.J. (1995) Physical strain and mechanical efficiency in hubcrank and hand rim wheelchair propulsion, Journal of Medical Engineering and Technology, 19 (4), 123–31. VAN DER WOUDE, L.H.V., HENDRICH, K.M.M., VEEGER, H.E.J., VAN INGEN SCHENAU, G.J., ROZENDAL, R.H., DE GROOT, G. and HOLLANDER, A.P. (1988) Manual wheelchair propulsion: effects of power output on physiology and technique, Medicine and Science in Sport and Exercise, 20 (1), 70–8. VANLANDEWIJCK, Y.C., SPAEPEN, A.J. and LYSENS, R.J. (1994) Wheelchair propulsion efficiency: movement pattern adaptations to speed changes, Medicine and Science in Sports and Exercise, 26 (11), 1373–81. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1989) Wheelchair propulsion technique at different speeds, Scandinavian Journal of Rehabilitation Medicine, 21, 197–203. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1991) Withincycle characteristics of the wheelchair push in sprinting on a wheelchair ergometer, Medicine and Science in Sports and Exercise, 23 (2), 264–71. VEEGER, H.E.J., LUTE, E.M.C., ROELEVELD, K. and VAN DER WOUDE, L.H.V. (1992a) Differences in performance between trained and untrained subjects during a 30-s sprint test in a wheelchair ergometer, European Journal of Applied Physiology, 64, 158–64. VEEGER, H.E.J., VAN DER WOUDE, L.H.V. and ROZENDAL, R.H. (1992b) A computerized wheelchair ergometer: result of a comparison study, Scandinavian Journal of Rehabilitation Medicine, 24 (1), 17–23. WATANABE, K.T., COOPER, R.A. and STER, J.F. (1991) Proceedings IEEE-EMBS of the 13th International Conference, Orlando, Florida, pp. 1817–18. WERNER, C.O., ELMQVIST, D. and OHLIN, P. (1983) Pressure and nerve lesion in the carpal tunnel, Acta Orthopaedica Scandinavica, 54, 312–16. WILSON, A.B. (1992) Wheelchairs: a Prescription Guide, New York, NY: Demos. WINTER, D.A. (1990) Biomechanics and Motor Control of Human Movement, Second Edition, New York: John Wiley. WYLIE, E.J. and CHAKERA, T.M. (1988) Degenerative joint abnormalities in patients with paraplegia of duration greater than 20 years, Paraplegia, 26, 101–16.

CHAPTER ELEVEN Assistive technology MARCIA J.SCHERER AND JAN C.GALVIN

For most people, technology makes things easier. For people with disabilities, however, technology makes things possible. Mary Pat Radabaugh, IBM National Support Center for People with Disabilities Technology is the totality of the means employed to provide objects necessary for human sustenance and comfort Webster’s Dictionary 11.1 Background Technology is pervasive in today’s society. Our lives have been shaped and eased by computers, personal appliances, telecommunications, sound and videoelectronics and medical and diagnostic and treatment techniques to name just a few. The technologies we take for granted today have not been around that long. The first flush-ing toilet in the late 1800s, the first automobile in the 1890s, the first personal computers and automatic teller machines in 1970. All these technologies have made our lives more comfortable and have enabled us to do our jobs easier and faster. Information technology, telephones, facsimile machines and electronic mail are becoming more sophisticated every day. In the medical world, virtual surgery is becoming commonplace. This technology allows surgeons to practise delicate sur-geries in a simulated or virtual operating room with a virtual patient, before doing the real thing. Telephone/video hospital/ patient hook-ups are being tested in many rural areas of the USA where a patient has blood pressure, blood sugar, temperature and weight monitored twice a day by the doctor—even though the patient and doctor may be 200 miles apart. Technology is beneficial to everyone. Each of us has used some type of technology device or service in everyday life activities. Items such as can openers, computers, telephones, dryers, remote controls, shopping carts, calculators, luggage carts, ramps and power doors are all examples of assistive devices that help people get through their day with less difficulty. Individuals

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with disabilities use these and other specialized technologies, assistive technology devices, for a variety of reasons: ■ ■ ■ ■ ■ ■ ■

to achieve maximum independent functioning to increase mobility to help with communication to increase success or abilities in the job market to increase functional abilities to increase self-esteem (Wright, 1980). Assistive technology enhances the lives of persons with disabilities on an individual basis. All individuals with disabilities, regardless of age, regardless of disability, would have increased control over themselves and their environments, and would have greater freedom of movement, exploration and participation along side their peers at home, school, work and in the community, with the use of appropriate technology. (Rubin and Roessler, 1987)

At its most fundamental level, assistive technology systems represent someone (a person with a disability) doing something (an activity) somewhere (within a context). The major goal for an appropriate assistive technology device is that it meets the individual’s specific needs, is consistent with their skills and accomplishes unique functions within the context of that person’s daily life. 11.2 Evolution of the term ‘assistive technology’ In the USA, the concept of technology for people with disabilities was recognized in a number of major legislative enactments during the mid-1980s (for example, The Rehabilitation Act Amendments of 1986. Yet no consistent or standardized nomenclature emerged until the passage of The Technology-Related Assistance for Individuals with Disabilities Act (The Tech Act) of 1988. Adopting the terms assistive technology devices and assistive technology services, the statute defined them as follows. Assistive technology device means any item, piece of equipment, or product system, whether acquired commercially off-the-shelf, modified or customized, that is used to increase, maintain or improve the functional capabilities of an individual with a disability. Assistive technology service means any service that directly assists an individual with a disability in the selection, acquisition, or use of an assistive technology device, including… evaluation of the needs of an individual…; Purchasing, leasing or otherwise providing for the acquisition by an individual with a disability of an assistive technology device; Selecting, designing, fitting, customizing,

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adapting, applying, maintaining, repairing or replacing assistive technology devices;… Training and technical assistance… (29 USC Sec. 2201) Since 1988 the Tech Act terminology has been incorporated in a succession of US statutes (including the Individuals with Disabilities Education Act, The Rehabilitation Act Amendments of 1992, and The Developmental Disabilities and Bill of Rights Act Amendments) as they were enacted or reauthorized. The concept of the rehabilitation engineering process is closely related to AT and its application. This process is ‘the application of scientific knowledge to practical purposes. It makes use of devices and techniques or strategies to remove or reduce barriers or obstacles to physical, behavioral or cognitive performance confronted by individuals with disabilities’ and to enhance the safe interactions among person, technology and environment. To further clarify the meaning of assistive technology, some researchers make a distinction between high technology and low technology. High technology usually refers to complex, electrical and electronic devices such as computers, augmentative communication boards and environmental control systems. Low technology generally refers to simpler interventions such as custom-designed hand tools, workstation modifications and simple, easier to use, less expensive devices. ‘Often, low technology involves the application of ‘ergonomics’ or human factors in which the workplace or home is designed to fit the person instead of making the person fit into a fixed design’ (McQuistion, 1989). Often, when addressing the issue of technology, people tend to think of talking computers, robots, laser optics and spy satellites; but not door levers, canes, telephone headsets or job sharing. It is often assumed that bigger, newer and more sophisticated means better. We tend to look to hightechnology solutions for every situation. However, ‘low technology alternatives can be just as effective and more easily integrated into a person’s lifestyle’ (Galvin and Phillips, 1990). Utilization of this more uniform wording in a succession of statutory frameworks has contributed to greater clarity in the understanding and awareness of what we mean when we speak of assistive technology (AT). This uniformity has also facilitated comparing various funding streams and strategies, as well as contrasting various administrative models in terms of their responsiveness to and utilization of AT. However, such has been the nature of recent developments in our technology that the line of demarcation has become progressively harder to draw between ‘assistive’ and what, for lack of a better term, we will call ‘mainstream’ technology. As written and applied, the Tech Act definition of AT, together with the subsequent laws and regulations that have adopted it, presuppose a fairly clear juxtaposition between mainstream and assistive technology. The Tech Act definition of assistive technology is predicated on the existence of devices or systems that are distinguishable from other technologies by reason of their design or use to facilitate access or function by people with disabilities. In the conventional view, AT devices are added to, substituted for, or used in

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conjunction with, mainstream equipment. The hand controls are used to operate an automobile, the speech synthesizer is employed to capture the output of a computer screen, the eyegaze computer input system is designed to operate an environmental control unit, the telecommunications device for the deaf (TDD) is designed to permit the use of the phone. All these represent classic illustrations of assistive technology according to the static model of AT. So too do the variety of prosthetic and orthotic devices designed literally to replace or substitute for the function of numerous body organs, and sensory, motor or cognitive functions (Mendelsohn, 1996). In many cases, the design of today’s electronic devices and systems does not permit the use of any add-ons or the substitution of components. Because the accessibility and usability of a growing array of electronic devices will be determined by whether they were designed according to principles of inclusiveness and universal access, the concept of ‘assistive technology’ has little meaning in relation to them. Would we call an automated teller machine an assistive device because it had builtin speech output to facilitate its use by blind persons? Would we describe a new TV set as assistive technology because it has a built-in decoder chip to facilitate access to the audio by persons who are deaf? On the one hand, the answer might logically be yes, but unless our paradigm for defining and funding AT is broad enough to include accessible technology, funding streams that uphold a narrow definition of what technology is ‘assistive’ may prove decreasingly relevant to the day-to-day issues and compelling access needs in the lives of those they aspire to serve. 11.3 New and emerging technologies It is also important to understand the changing nature of the technology that surrounds us. For example, the origins of e-mail go back to the 1960s when Western Union developed their computer-based messaging system. However, it is only in the past seven years that e-mail has blossomed. In the early 1980s very few of us were using computers at work, let alone at home. Today, 20 million people are on e-mail. The number of e-mail users is increasing daily. Thousands of discussion groups are available on the Internet on a host of subjects of interest to individuals with disabilities, researchers and providers. Individuals who access discussion groups can read various notes from others on the list, receive regular newsletters, keep up with the latest in medical breakthroughs, experimental drug treatments, consumer evaluations of products, conference agendas, Federal government requests for proposals, research papers and reports. Children in early intervention programs are accessing computers as young as 18 months old through simple switches. By kindergarten they are accessing VCRs and computer games. Students at schools and universities are able to learn and research more easily, quickly and comprehensively than ever before. No longer

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do we need the Encyclopedia Britannica filling all our book shelves, it is on disc. Technology—especially computer technology—can enhance or amplify different human abilities: text-processing systems, for example, allow us to explore enormous volumes of written material very quickly. And, because computer technologies can work with visual, auditory or tactile output, they can equalize informationprocessing opportunities for people with sensory limitations. Other technologies, however, such as the graphical user interface, rely heavily on a particular modality— vision in this case. These make it hard for people with visual disabilities to use computers. Meanwhile, specific assistive technologies are being developed to enable persons with disabilities to deal effectively with the new digital environments. From the point of view of assistive technology, looking to the future involves understanding basic computers and the related infrastructure, powerful tool-level developments such as object-oriented technology, knowledge-based systems and neural networks, virtual reality and nanotechnology (Orr, 1996). Information is the currency of the twenty-first century. The Information Superhighway brings together interactive multimedia (phone, TV, computer, video—a marriage of text, pictures and sound) in digital form (letters, numbers, sounds and images reduced to a sequence of zeros and ones), traveling over fiber optic cables in order to provide information to people in their homes, at schools and at work. The full potential of the Information Highway is still in the future. However, all the pieces are in place and efforts are being made through mergers of phone, cable and entertainment companies to capitalize on both the process and the product that will move along it. It is important that individuals with disabilities are actively involved in influencing the direction of the highway, to ensure the on-ramps, highways and byways are accessible to all. The advent of comprehensive computerization in the business world bodes well for people with disabilities. The more sophisticated the computers, the more extensive the networks, the more easily they will accommodate adaptive devices and programs. By the year 2000, speaker-independent voice-recognition systems at reasonable prices will be available. Speech will replace pens and keyboards as the main form of interaction with computers. Language-translation programs will have also improved. Perhaps the most striking impact of technology on the ‘office’ is that it will obviate the need for a physical gathering place. This will have major importance for individuals with disabilities. By some estimates, as many as 40 million Americans now work either full-time or part-time at home—many of them by telecommuting. Already telephone, videoconferencing, e-mail and voice mail are replacing face-toface meetings. As imaging and OCR systems improve, the need for physical access to files goes away (Orr, 1995). Distance learning, as defined by the US Office of Technology Assessment in 1989, is the ‘linking of a teacher and students in several geographical locations via technology that allows for interaction’. Since no one has to be in the same

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place at the same time to participate in the lecture or conference, distance learning provides a maximum of schedule flexibility for students and teachers alike. An added benefit of distance learning is that students are more likely to have greater self-confidence and not worry about stereotypes, of ethnicity, appearance or disability (Coombs, 1988; Keefe et al., 1996). Virtual reality will obviate the need for a person in a wheelchair to get the wheelchair on to a factory floor. People who need to work in dark environments can move around safely. Models and simulations of those environments can be created and experiments run on the computer. Computers may well be the most important ally of the individual with a disability in tomorrow’s world. Computer technology will bring about environments tailored to individuals, in which the significance of their particular disability is diminished or neutralized. This changing face of technology requires that new and emerging technologies are accessible to everyone, regardless of whether there is a disability involved. 11.4 Who uses assistive technology? Persons with disabilities comprise the single largest minority group ever defined. Furthermore, the population is extremely heterogeneous. The definition and estimation of its size has been based on demographics research by Census and survey that shows variation both in the severity of disability and in the identification of persons as having a disability, whether by self-assessment or assessment by others (LaPlante, 1991). The Americans with Disabilities Act 1990 has provided a definition of disability: 1 A physical or mental impairment that substantially limits one or more of the major life activities of such individual 2 A record of such an impairment 3 Being regarded as having such an impairment Section 504 of the Rehabilitation Act of 1973 only used the definition that follows. A physical or mental impairment that substantially limits one or more of the major life activities of such individual. The ADA goes further, however, by including individuals who have a record of impairment or who are regarded as having an impairment. Persons who consider themselves disabled but are not considered by others to be so are implicitly included in the ADA definition.

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According to the National Health Interview Survey (NHIS) of the total noninstitutionalized population in the USA 34.2 million (14.1 per cent) were limited in activity due to a chronic health condition in 1989. Of people limited in activity due to a chronic health condition, 10.1 million were unable to perform their major activity. 13.2 million were limited in amount or kind of the major activity they could perform, and 10.9 million were limited in non-major activity. Limitation in activity increases with age. Of the population aged 70 and over, 7.5 million (39 per cent) were limited in activity. Of children under 18 years of age, 3.4 million (5.3 per cent) were limited in activity. Recent developments in public policy have emphasized the significant contribution of assistive technology for individuals with disabilities, and the need for statistics on the use of that technology. In response to that need, the National Institute on Disability and Rehabilitation Research (NIDRR) and the National Center for Health Statistics (NCHS) co-sponsored a survey on assistive technology devices and homes with accessible features as part of the National Health Interview Survey of 1990. The survey shows that in 1990 more than 13.1 million Americans, about 5.3 per cent of the population, were using assistive technology devices: 7.1 million people, nearly 3 per cent of the population, lived in homes that were adapted to accommodate impairments. Between 1980 and 1990, the number of persons using anatomical or mobility assistive technology devices increased at a more rapid rate than did the general population. More people use assistive technology devices to compensate for mobility impairments than any other general type of impairment: 6.4 million use some kind of mobility technology and 4.4 million use a cane or walking stick, the single most used assistive technology devices. Other prevalent assistive technologies are hearing aids (3.8 million), walkers (1.7 million), wheelchairs (1. 4 million) and back braces (1.2 million). Of the 7.1 million people living in homes that have special equipment, the most common adaptations are hand rails (3.4 million), ramps (2.1 million), extra wide doors (1.7 million) and raised toilets (1.3 million). Among persons who use any assistive devices, the majority are over 65, reflecting the higher prevalence of impairments in that population. However, for some specific assistive technologies, a significant proportion of users are under age 25: foot braces (38 per cent), artificial arms or hands (35 per cent), adapted typewriters or computers (25 per cent) and leg braces (24 per cent). 11.5 Legislation of assistive technology The Technology-Related Assistance for Individuals with Disabilities Act of 1988 (PL 100–407) The Tech Act was the first federal legislation to specifically address the expansion of the availability of assistive technology devices and services to individuals with disabilities. The Tech Act for the first time provides a definition of assistive technology devices and services. The Tech Act provides

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under Title I, direct grants to states for the development of consumer-responsive assistive technology services, with emphasis on interagency cooperation, developing flexible and effective funding strategies and meeting the assistive technology needs of individuals with all disabilities throughout the life-span; and, under Title II, programs of national significance to identify barriers or facilitation of access to services and devices. Programs funded under Title II included the National Assistive Technology Information amd Referral Feasibility and Desirability Study, the Study on the Financing of Assistive Technology Devices and Services for Individuals with Disabilities and Project Reaching Out, RESNA’s curriculum development for outreach to minority populations. The reauthorization of this Act in 1994 (PL 103–218) extends congressional support through 1998. The amendments continue support to the states but requires states to perform six specific systems change and advocacy activities and provide a specific amount of their Title I funds to a protection and advocacy agency. The six priority activities focus on systems change, advocacy and outreach to underrepresented and rural populations. All fifty states are funded under Title I plus the District of Columbia, American Samoa and Puerto Rico. The definition of assistive technology devices and services as set out in the original Tech Act is now used in the Individuals with Disabilities Act (IDEA), the Vocational Rehabilitation Act and the Developmental Disabilities Act. 11.5.1 The Americans with Disabilities Act (ADA) of 1990 The Americans with Disabilities Act (PL 101–336) is a federal antidiscrimination law. Like the Civil Rights Act of 1964 that prohibits discrimination on the basis of race, color, religion, sex and national origin, the ADA seeks to ensure equal access to and opportunity in employment, transportation, public accommodations, state and local government and telecommunications for individuals with disabilities. Reasonable accommodations, which may include assistive technology, are required in every aspect of employment for a qualified individual with a disability. Access to local government, transportation and public accommodations such as shops and hospitals includes readily achievable modifications and effective means of communication. Once again, assistive technology is one means of providing access to the wide variety of services covered by the ADA. The Reauthorization of the Education for All Handicapped Children (PL 94– 142) in 1991 renamed the law, Individuals with Disabilities Education Act (IDEA). This reauthorization extends assistive technology device and service definitions in education, adding new language that includes the same definition as in the Technology Related Assistance for Individuals with Disabilities Act as well as mandating local education agencies to provide assistive technology devices and services if required as part of the child’s educational program and written into the Individual Education Plan (IEP).

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11.5.2 The reauthorization of the Rehabilitation Act of 1973 Congress reauthorized the Rehabilitation Act in 1992 (PL 102–569). The legislation brings the Rehabilitation Act more in line with the ADA. Rehabilitation technology is defined to include both assistive technology and rehabilitation engineering. Each state must specify how assistive technology devices and services are to be provided. The individualized written rehabilitation plan (IRWP) must include the provision of rehabilitation technology services to assist in the implementation of intermediate and long-term goals. The Rehabilitation Act also includes the funding for NIDRR to continue support for Rehabilitation Engineering Research Centers (RERCs) and other core areas of research and development. 11.6 Service delivery systems Assistive technology services are provided to the individual with a disability in a number of different settings depending on the specific service delivery system, that is, a school-age child or a disabled veteran. Often, because of gaps in the service or funding systems, geographic area, age, or type of disability, a person may have to access more than one system to acquire all the services they need. Direct consumer service delivery settings include the following. 1 Rehabilitation setting. Assistive technology services are part of a comprehensive rehabilitation program; they may be part of one of the therapy departments or its own department. The primary purpose is to support the other services of the rehabilitation setting; therefore, there is usually multidisciplinary team involvement. Typical populations served are spinal cord injuries, head injuries, cerebral vascular accidents and amputees. Services are usually billed to third-party health insurance payers. 2 University based. Programs in this setting have largely evolved from a research component and may provide direct consumer services as well as education and training. Staff usually consist of personnel capable of performing clinical, research and educational duties. The professionals involved in the team will depend upon the functional areas addressed by the setting. Those settings conducting research provide a national service. The direct consumer service component is usually regionally oriented. Funding is largely grant and contract related (particularly for the research component), although portions of the direct consumer services may be billed to third-party payers. 3 State agency program based. State agency-based programs are usually a part of vocational rehabilitation departments or special education departments. Those programs, based in vocational rehabilitation

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departments, are statewide programs developed for the purpose of providing assistive technology services to individuals who need it for attaining or sustaining employment. The purpose of programs under special education departments is to facilitate the education of school-age children. In some instances, school districts have their own multidisciplinary team. In other cases, there may be a team that covers the entire state. Administration of these programs varies and may be statewide or on a local level. Funding is usually mandated at a state or federal level and designated for these agencies. 4 Private practice. A small number of assistive technology providers have gone into private practice. They may provide consultation to state agencies or rehabilitation centers. The population and functional service area varies and depends upon the professional backgrounds of those involved in the business. Operated as a for-profit, small business venture with fees for services charged. They are usually based in one local area. 5 Durable medical equipment (DME) supplier. Usually a for-profit agency that addresses a range of equipment needs. Typically, it provides walking aids, bathing and toileting aids, wheelchairs and seating systems. Some suppliers may provide communication and environmental control equipment. The supplier is reimbursed by third-party payers. The DME supplier is known for its technical resources and ability to provide repair and maintenance services. There are some DME suppliers who operate on a nationwide basis; others are local operations. 6 Veterans’ Administration (VA). Assistive technology services are provided at many Veterans’ Administration hospitals. There is usually a multidisciplinary team approach. Research in the field of assistive technology is a large component of the services provided by the Veterans Administration and significant contributions have been made in this area. The population served is restricted to veterans with service-related disabilities. Veterans with spinal cord injury have been a major group served by the VA. 7 Local affiliate of a national non-profit disability organization. National organizations such as United Cerebral Palsy Association (UCPA), Easter Seal Society, Muscular Dystrophy Association (MDA), Association for Retarded Citizens (The ARC), and the American Foundation for the Blind provide assistive technology services through their local affiliates. The purpose of each of these organizations is often to serve individuals with a particular disability; therefore, the populations served and the functional areas are geared primarily toward that disability group. Programs of the local chapters are usually administered at the local level and assistive technology services vary among affiliates. Some local chapters may have a complete assistive technology team to provide services, whereas others may only loan equipment. Funding for these agencies is through grants, contracts, donations and fundraising events.

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8 Volunteer programs. Volunteer organizations in the USA that provide assistive technology services include groups such as the Telephone Pioneers of America, the Volunteers for Medical Engineering and the Rehabilitation Volunteer Network. Most of these groups have developed out of private industry and have as their purpose the provision of a philanthropic service. These groups usually provide services on a local or regional basis. The functional areas served depends upon the expertise of the volunteers involved (Smith, 1987; Hobson and Shaw (1987)). 11.7 Examples of AT in employment In the USA, employers are prohibited by law from discriminating against qualified individuals with disabilities in any aspect of employment, from the interview and hiring process, to workplace accommodations, to advancement and other related activities. To ensure non-discrimination, the Americans with Disabilities Act requires employers to focus on the essential functions of the job to determine whether a person with a disability is qualified. In order for a person with a disability to be qualified, they must have the requisite skills, education, experience and certifications necessary for the job. If a person with a disability cannot perform one or more essential functions of a job because of their disability, but is otherwise qualified, the employer must consider whether there are modifications or adjustments that can be made that would result in the individual successfully performing the essential functions of the job. Such modifications or adjustments are called ‘reasonable accommodations’. Reasonable accommodations include the use, where appropriate, of assistive technology. These assistive technology devices range from a simple telephone headset amplifier to a voice-activated computer (Peterson, 1996). Some of Peterson’s specific examples of accommodations are listed in Table 11.1. How these translate into the workplace is illustrated below. 11.7.1 Illustrations A lawyer who is a quadriplegic uses a personal computer with a voicerecognition system to control such software programs as word-processing, databases, spread-sheets, telecommunications and other applications. Its extensive vocabulary and ability to learn new words enables the lawyer to speak to the computer as you would type in your words. Verbal commands are also recognized such as delete, print and merge. The workstation consists of a raised height desk so that the user can roll right up to the desk (Galvin and Caves, 1995).

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For an individual who is deaf, the computer revolution and the upsurge in communications can be frustrating. There may be no difficulty accessing a regular comTable 11.1 Specific examples of accommodations Physical accessibility

Job restructuring

Workstation modifications

Provision of assistive devices

Environmental changes

Parking spaces with access aisles Wider doorways Bathrooms with adequate floor space Elevator controls with appropriate signage Accessible workstations Accessible drinking fountains Visual and audio fire alarms Signage with Braille and raised lettering Flexible time off Job sharing Focusing on outcomes rather than traditional methods of doing the job Modified equipment Ergonomic furniture and equipment Special jigs and fixtures to provide better access Telephone headsets and speaker phones TTYs Assistive listening devices Braille printers Computer peripherals Changes in lighting Better ventilation Noise abatement

puter, but they need audible communications made visual so they can see the spoken word. An individual who is deaf may use a telephone device for the deaf (TDD), a relay service or facsimile machine to communicate. Modems linked to personal computers allow a wider range of communication alternatives such as electronic mail. Computer-aided transcription can provide instantaneous hard copy printouts of meetings. Software is available that teaches American Sign Language. Captioning translates the spoken word into text, making television programming and videos more accessible. Visual alarm systems provide a means to monitor the environment.

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11.8 Examples of assistive technology in education Assistive technology can be beneficial to students at all levels of the education process, from pre-school to post-secondary. Computers are providing powerful learning tools and more equitable access to the educational process. In early intervention programs, toddlers (18–36 months) with multiple disabilities are using brightly colored large single switch access modes to operate computerized games and nursery rhymes. Assistive technology and adaptive computer technologies are not just used in special education classrooms, but also in the regular classroom. From pre-school to college the computer can be both a teaching tool and a way for individuals with disabilities to learn, communicate and express themselves in a broad variety of ways (Albaugh and Fayre, 1996; Keefe et al., 1996). Technology is a tool that can be used to make the learning environment more accessible and enhance individual productivity. Computerized technology can facilitate access and interaction with teachers and peers. People can use it to manipulate their environment by controlling tape recorders and electrical appliances. Computers are helping students prepare for future vocational settings and children access computer-related technologies for play, recreation and leisure. Video games such as Nintendo with adaptive controllers allows the child to have fun on an equal footing with non-disabled peers (Galvin and Caves, 1995). In the past three years there has been a sizeable increase in the number of devices and software available to help children with reading, writing and computational skills. Computers in school allow students to work at their own pace and receive immediate feedback. Computers can help motivate students and help compensate for their disabilities. Triffiletti et al. (1984) analysed the effects math drills and tutoring had on proficiency for a group of students with disabilities. They found that 40 minutes of computerized tutoring and math drills was more than twice as effective as an equivalent amount of teacher-delivered math instruction. Jones et al. (1987) found that computer-based instruction in reading enabled students to increase their reading speed by 26 per cent as opposed to a 4 per cent increase for students taught by teacher-based instruction. 11.9 Examples of AT for augmenting communication Communication means exchanging, transmitting and receiving information, thoughts, feelings and ideas. Technology is having a profound effect on how and how often we transmit and receive information. Computer components and fiber optics have made it possible to communicate effectively and efficiently

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with almost everyone, everywhere, at any time and in any form (Blackstone, 1996). There are many individuals who have difficulty communicating verbally. For example, people with cerebral palsy, neuromuscular disease, traumatic brain injury, or stroke can have difficulty producing speech. Communication boards, which contain letters, icons or pictures and an individual pointing to them to communicate, are a common method for communicating basic needs. However, for many individuals the communication board is insufficient. The advent of computers has lead to the development of computerized augmentative or alternative communication systems (AACs)(Galvin and Caves, 1995). Augmentative communication devices have developed rapidly over the past few years. Over 250 augmentative communication hardware and software items are currently on the market. Sophisticated AAC systems can offer speech synthesis in up to ten age- and gender-appropriate voices and foreign languages. These offer access by touch, pointer, switch, infra-red scanning or even ocular eyegaze monitors which electronically measure eye movements (Vanderheiden and Lloyd, 1986). Wordprediction software can assist a user in recognizing and predicting keystrokes, building upon a dictionary of words and phrases. This can speed up the entry process and enable the user to communicate faster. AAC systems for children can teach communication through play. Games, bedtime stories, prayers, descriptive concepts, basic math and core vocabulary programs make learning and communicating fun. Stephen Hawking, who has a form of amyotrophic lateral sclerosis and little muscle control, dictated his recent bestseller, A Brief History of Time, using a personal computer adapted for singleswitch scanning access, with speech output through a speech synthesizer. AAC technology is complex, and evaluating a non-vocal individual for a communication system has become equally complex. The individual’s expressive language skills, receptive language skills, symbol-recognition skills and functional ability to access the technology all have to be evaluated to ensure an appropriate match between the person and the device (Galvin and Caves, 1995). 11.10 Examples of AT (orthotics and prosthetics) Devices that augment function rather than replace it are termed orthoses or orthotics. Originally this term only applied to braces, now it is used more broadly to describe any item that augments or assists function. Prosthetics or prosthetic devices are devices that replace a body part both structurally and functionally. Today orthotic and prosthetic advancements are emerging from research laboratories that include experimental aircraft and aerospace industries. Lightweight plastics and carbon-graphite fiber orthotics and prosthetics were developed from the aerospace industry. These new materials offer decreased

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weight and increased strength, leading to decreased energy consumption and better mobility. Computer-assisted design (CAD) and computer-assisted manufacturing (CAM) are influencing all areas of technology but they are of significant importance in the orthotic/prosthetic field where customized prostheses and orthoses are made individually for each client. These new advancements have led to prosthetic ankles that accommodate a full range of motion. They can be unlocked for complete dorsi- and plantar flexion, then locked for standing and walking, and prosthetic feet that provide energy storage and multi-axis functions through a double spring design. Control and interface strategies have become increasingly sophisticated and play an important role especially in upper extremity prosthetics. Myoelectric technology uses sensitive electronic sensors to amplify and transfer human nerve impulses into electrical current. This current is then transferred to a motor in the prosthetic device. Research is ongoing in the development of myoelectric lower extremity protheses. Advances in orthotics and joint protection methods include the development of functional electrical stimulation to aid muscle re-education, strengthening and joint motion and orthotics that provide constant passive predetermined motion. These orthotics are available for the knee, shoulder, elbow, hand and ankle. The growing sophistication of the prosthetic and orthotic fields with advancements in CADCAM design, lightweight strong materials, myoelectrics and FES is providing individuals with disabilities with more ergonomic customized devices, leading to improved health, function and independence. 11.11 Assistive technologies for aging individuals The push to keep aging persons home and out of hospitals or nursing care facilities for as long as possible means that more technology is entering American homes. Many of these individuals, however, show an aversion to replacing more and more interpersonal interactions with technical functions. As technologies are being developed to replace the need for expensive, intrusive and often unreliable assistance from other persons, many individuals resent reduced contact with concerned, supportive others and having their care reduced to a technical task. They prefer human understanding and the human touch. To try to replace interpersonal elements with technical ones is felt by many persons of all ages to be dehumanizing and detrimental to quality of life. The concomitant emphasis today on consumerism (self-determination, making choices) and independent living leaves the person and family more in charge and with more responsibilities than ever before. Some crucial considerations in the beginning stages of matching an aging person with technology are as follows (Scherer, 1996).

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1 Knowledge of and comfort with technology. Aging women in particular were not brought up to feel comfortable with and knowledgeable about machines and technical devices. Find out what technologies the person is already using and try to present new technologies that are similar in operation. 2 There may be few incentives for the aging person’s enhanced independence. Aging persons may no longer be interested in employment, further education, and other typical goals of rehabilitation. Their special needs and interests are only now starting to be recognized. 3 Difficulties in obtaining personal assistance. Continuous frustrations in obtaining reliable personal assistance are incentives in learning to use a new technology but also remind the person of dependence on others. 4 Added stress on already burdened caretakers. Family members and other caretakers who devote a major portion of their day to the care of their loved ones with a disability may feel overwhelmed by the heightened need for medical and technological interventions. When, in spite of such assistance, they see the individual continue to deteriorate or become depressed, they may experience their own sense of helplessness and despair. 5 New device and equipment needs. Aging persons with disabilities undergo changes in their physical capabilities and general health that require modifications in devices and heightened attention to their special needs. Rehabilitation engineering efforts will also need to address functional declines and the preservation of as much previous functioning as possible. An all-too-common stressor is that the equipment that worked so well in the rehabilitation facility is not working out in the home. The power wheelchair is tearing up the carpet or the cane is never in the same room as the person needing it. The failure of assistive technology to fit well in the home environment is a major reason for technology being abandoned. Another common reason for abandonment is that assistive technology use was forced upon the individual as a condition for being discharged to home and the assistive technology (AT) immediately became a focal point for resentment. The following are examples of considerations regarding one category of equipment. ■ Mobility devices. The most frequently encountered mobility ATs in the home environment are walkers, canes, manual and powered wheelchairs, leg braces and crutches. ■ Hoyer lifts (a canvas seat attached a large swing arm used to help people get in and out of bed, tubs and so on), elevators and ramps are typical accompaniments. ■ The use of a mobility AT creates the need for easy access around the house, as well as the ability to get in and out of the home easily. Transportation often has to be (re)arranged, steps and stairs eliminated, carpeting removed. It is important to try out ATs in the home and involve all family members so that the best AT with the minimal amount of home modification can be

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recommended and everyone feels they are involved in making choices around home accommodations. ■ In addition to the stress of a need for a mobility AT, family members may feel stress from changes made to the home. Not only are there disruptions to the familiar home environment, but in individuals’ daily routines. There may be resistance to change, resentment towards the individual with a disability, and anxiety, insecurity and depression at the loss of familiar routines and surroundings. 11.12 Waste in assistive technology remains a problem In spite of the federal mandates for comprehensive, consumer-responsive assistive technology and technology-related services, obtaining such devices and services remains an arduous task for both the individual and the professional. As indicated in the previous section, the match of person and technology requires attention to aspects of the environments in which the technology will be used, the needs and preferences of the user, and the functions and features of the technology. If the match is not a quality one from the viewpoint of the customer, the technology will not be used. This section concentrates on issues that can be easily or more easily resolved by improved interaction between the individuals delivering the services and the individuals receiving the services. Recent studies and reports show a high level of dissatisfaction and non-use of technology by consumers. Technology abandonment arises from a mismatch of person and technology in several areas (Table 11.2) and can have serious repercussions (Scherer 1991, 1996). For individuals, non-use of a device may lead to decreases in functional abilities, freedom, independence and increases in monetary expenses. On a service delivery level, device abandonment represents the ineffective use of limited funds by federal, state and local government agencies, insurers and other provider organizations. A better understanding of how and why technology users decide to accept or reject a device is critical to improving the effectiveness of assistive technology interventions and enhance consumers’ satisfaction with devices. One major factor associated with technology abandonment is significant—lack of consideration of user opinion. A small body of literature addresses the acceptance or use of technology versus rejection or non-use of technology. The literature includes clinical reports, case studies and survey studies conducted by researchers representing a number of different disciplines. A range of age and disability groups are covered. This area of research is growing and illustrates how complex and personal the interface between a person and a technological device can be. Broad generalizations about patterns of assistive technology use and non-use are presented below based on a review of this literature. Studies of abandonment reveal that rates of abandonment range from 8–75 per cent. On average, about one-third of all devices provided to consumers are

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abandoned. We have no information about the numbers of people who must continue to use devices they are unhappy with because they cannot abandon them without more severe repercussions. Most abandonment occurs within the first year (especially the first three months), or after five years of use. These figures suggest that users find out relatively quickly whether or not a device works for them. If it does not, it is discarded. If it does, they may keep it until it needs to be replaced. The major reasons devices are not used by consumers (in no particular order) are: ■ ■ ■ ■ ■ ■ ■ ■

lack of consumer involvement in selection change in consumer’s functional abilities or activities lack of consumer motivation to use the device or do the task lack of meaningful training in the use of the device (especially for elderly, cognitively impaired) ineffective device performance accessibility problems lack of access to and information about repair and maintenance device was unnecessary.

Most of these issues can be addressed appropriately in a comprehensive selection process. There are some gaps in service delivery that are beyond individual control, but we can teach consumers to deal with these problems until the situation improves. We also need to be sure to consider ongoing needs and take a long-term Table 11.2 Influences on use of assistive technology Milieu

Personality

Use Support from family, peers, Proud to use device or employer Motivated Realistic expectations of family or employer Setting/environment fully supports and rewards use Good coping skills Pressure for use from family, peers, or employer Generally positive life experiences

Cooperative

Technology Goal achieved with little or no pain, fatigue, discomfort, or stress Compatible with or enhances the use of other technologies

Optimistic Is safe, reliable, easy to use and maintain Patient Has the desired Self-disciplined transportability Best option currently available

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Milieu Has the skills to use the device Perceives discrepancy between desired and current situation Willing to challenge self

Personality

Technology

Lack of support from family, peers, or employer

Fear of losing own abilities or becoming dependent

Unrealistic expectations of others Setting/environment disallows, prevents, discourages or makes use awkward Unmotivated Requires assistance that is not available or angry Intimidated by technology Medical status inhibits or limits use of device

Embarrassed to use device

Perceived lack of goal achievement or too much strain or discomfort in use Requires a lot of set-up

Non-use

Depressed

Perceived or determined to be incompatible with the use of other technologies

Uncooperative, resistant, hostile, Long delay for delivery Overwhelmed by changes required with device use Does not have skills for use Training not available Poor socialization and coping skills

Too expensive

Other options to device use are available Has been outgrown Is inefficient Repairs or service not timely or affordable

This is an abbreviated version of a table from Living in the State of Stuck: How Technology Impacts the Lives of People with Disabilities. This version is reprinted from: Guidelines for the Use of Assistive Technology: Evaluation, Referral, Prescription (American Medical Association, 1994, p. 23)

view of assistive device use to make more effective selection decisions. Some typical comments from a recent survey on abandonment supports this factor. Talk to the user. Be a little more considerate of the end-user… Don’t assume anything—ask the consumer… Listen to me! I know what works for me. (Galvin and Phillips, 1990) It is evident from these recent studies that services designed to involve consumers and accommodate long-term technology needs will enhance consumer satisfaction with assistive technology and reduce device abandonment. A good way to begin involving the consumer in the decision-making process is to have them answer the questions listed in Table 11.3.

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Table 11.3 Am I choosing the right device? Goals and tasks Have I identified my needs clearly? Can I change my activities so I can do them without a device? Is there a device that can help me meet my needs? Will I need assistance to use the device? Will an assistant need to use the device? Abilities and preferences What is my disability? Is it stable or changing? Do I have the physical and mental abilities to use the device? What technology do I currently use? How do I currently manage my daily activities? Is it important to me to do things as independently as possible? Does technology help me to be more independent or dependent? Am I comfortable using technology? Environment Where will I use the equipment? At home, work, community, all of these? Is the environment architecturally accessible? Is transportation available? Can my environment support the technology? Are people available to assist if needed? Could the environment disrupt device performance, i.e., electronic interference? How would the device affect other people in my environment? Device What kind of device do I prefer? Does the device reflect my lifestyle, age, personality, values? Have I considered all the devices available? How well does the device work? How much will it cost to buy and take care of? Will it be easy to use and take care of? How long is it likely to last? Will I be able to try it before I buy it? Excerpted from Evaluation, Selection and Use of Appropriate Assistive Technology 1995.

11.12.1 Key considerations for matching people and technology The steps used in selecting assistive technology are similar to the steps used in any selection or decision-making process. The specific issues may be different and unfamiliar for assistive technology. With a systematic, consumer-oriented approach and comprehensive questions, the most appropriate product can be identified (Mann and Lane, 1995; Read, 1990). Step 1 Identify consumer goals and tasks. Determine general goals and activities to be accomplished. Then conduct a task analysis of the

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activities to look at the components of the activity and what actions are required to do it. Step 2 Get comprehensive information. Get information about the person, the environment and the devices. Assess the consumer’s functional abilities and personal preferences; environmental barriers and resources; and product availability. This step is often ongoing until the final decision is actually made. Table 11.4 depicts a form used in the Matching Person and Technology Model (Scherer, 1991a) to begin to organize information in these areas. Step 3 Establish criteria for a successful choice. Based on information gathered in Steps 1 and 2, identify objective criteria by which to judge the likely success of an intervention or product. Step 4 Make final selection. Apply the criteria to possible solutions to weed out and narrow down the options. Determine which of these solutions best meet the criteria. Although these steps are presented as a linear process, it is really an iterative (cyclical) operation. Information gathered at each step may require adjustments of decisions made in earlier steps. For example, you may have decided that one of your criteria for a scooter was that it cost under $2000. However, in gathering information about available scooters, you find scooters that meet your performance criteria cost between $2300 and $2600. Then you must weigh the issues related to performance and price and decide how you can compromise. You must also consider the effects a device selected for one activity may have on another activity. For example, in a work setting handheld typing sticks may be the best method for typing. However, if the user must also answer the phone, will the typing sticks interfere with or make that activity more difficult? Again, you must weigh the benefits and drawbacks within the larger context. 11.13 Promoting choice in selection These steps can be carried out prescriptively or collaboratively. A provider can accomplish these same steps without consumer involvement. Traditional medical and human services systems tend to encourage prescription and recommendations based on the professional’s expertise. However, this reliance on professionals is also subject to their biases and natural tendency to recommend what has worked previously. One of the keys to successful technology outcomes is using a collaborative approach in selection. Individuals with disabilities who are involved in the decision Table 11.4—(Continued) in a meaningful way will generally be more cooperative, more active and independent in using the device, and more satisfied with services overall. Some tips in approaching this process in a collaborative manner are outlined below. Consider the relationship a partnership—a collaborative interpersonal business relationship (Rehab Brief, 1990). The partnership is characterized by equality. Partners are recognized for their ability to contribute their unique information and experience. For example, consumers know their goals, interests, dislikes, priorities and practical aspects of their living situation. Professionals

In which of the following does the individual experience a limitation (check all that apply)? For each limitation, indicate goals as well as potentially desirable technologies, environmental accommodations and other interventions for this person.

Table 11.4 Worksheet for the Matching Person and Technology (MPT) model.

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know about systems, have experience matching technology and people, and have access to a variety of resources. The partnership encourages shared responsibility. Each partner completes certain tasks, provides information and makes certain decisions. With responsibility comes concern for the outcome. The partnership exists for a purpose. Focus on solving the problem and reaching the goal. Remember both parties are trying to achieve the same thing. When disagreements arise, go back to the shared goal and reinforce the areas of accord (Grady et al., 1991). In most cases, evaluation of functional capabilities will rest with clinical professionals such as occupational and physical therapists. Counselors can stimulate discussion of the consumer’s current adaptive and technological behaviors and personal aspects related to device use such as lifestyle, motivation, adjustment to disability, attitude toward technology and values. Together, consumers and counselors can explore how these issues relate to technology use. A comprehensive evaluation of the consumer’s environment is also essential. Clinicians conducting functional evaluations need to consider environmental issues. Based on the consumer’s goals, abilities, and preferences, identify specific, objective criteria by which to judge potential solutions. Determine the basic necessities and the desired features for a device. Write down the agreedupon criteria so both the consumer and the professional will have a concrete criteria checklist that can be revised as necessary. Divide and conquer when it comes to finding information about devices. There are a number of resources to check: people who use the type of product you are considering, occupational therapists, physical therapists, rehabilitation engineers, technology information specialists, product manufacturers and vendors, product catalogs and local demonstration centers. The consumer, family members and the professional can each take responsibility for checking out certain resources. This encourages active involvement and stimulates learning about technology. Share the collected information with each other and brainstorm as many options for solving the problem as possible. It can be difficult to sort out all of this new information in a limited amount of time. Be aware of overloading people with information, getting too little information, or providing information too quickly. When brainstorming, accept any and all ideas, then go back to look at each of them systematically using your criteria. Before you make the final decision, you may have to make adjustments or compromises. In some cases, you may have to go back and redefine the problem. By the time you reach the last step in the process it is usually obvious that one or two of the options really meet the criteria better than the others. Because you developed the options together it is not too difficult to settle on one choice, or agree on two possibilities and leave the final decision to the consumer. One means developed to record and document progress in matching the person with the most appropriate technology is the Matching Person and Technology (MPT) Model and accompanying assessment instruments (Scherer 1991a, 1996). The three primary areas assessed are as follows:

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■ determination of the milieu/environment factors influencing use ■ identification of the consumer’s needs and preferences, and ■ description of the function and features of the most desirable and appropriate technology. Assessing milieu influences. In situ trials of equipment that involve everyone affected by the assistive technology have proven to be cost effective in the long term because obstacles to optimal technology use are identified before ‘bad habits’ can form. When trials are videotaped, the entire rehabilitation team can then participate in identifying solutions to potential obstacles to optimal technology use. Assessing characteristics and preferences of the person. Proper timing is of the essence. So is privacy. It is best to ask individuals about preferences, needs and capabilities when their significant others are not present. Significant others want to be helpful and should be involved, but let them know that they will have opportunities to express their preferences at another time. Assessing features of and comparing technologies. An assistive technology is abandoned when it is perceived as not being worth the effort required to set it up and operate, is never there when needed, and is costly or inconvenient to maintain. Selecting the most appropriate technology with all the right features is a complex process. A technology must have enough features to be useful and expandable, but not so many that the user becomes overwhelmed. Overload is a concern when an individual already uses or is being matched with more than one technology. Multiple technology use can bring overload of many types— including power, cognitive and willingness to tolerate technical assistance. It has become increasingly difficult to keep up to date with new assistive technologies and improvements in existing ones. For this reason, the Technology Related Assistance for Individuals with Disabilities Act was passed in 1988 to help establish state assistive technology centers. A major responsibility of these centers is to provide information about technologies and help individuals to obtain them. Equipment loan and trial programs, user/peer networks and equipment funding assistance exist in many parts of the USA. 11.13.1 Assessing the outcomes of AT service and device utilization Professionals working with assistive technologies need to demonstrate that what they do makes a difference to the lives of persons with disabilities. Insurance companies and other payors are increasingly asking for documentation showing the effectiveness of all AT services—also known as ‘quality assurance’. A major part of quality assurance is being able to assess and document outcomes of an intervention. Definition of outcomes. Outcomes are the result of an intervention. Examples of outcomes are employability, performance of ADL and consumer satisfaction

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or subjective quality of life. The latter encompasses the person’s sense of wellbeing, comfort, happiness and satisfaction with such specific areas of functioning as work, social relationships and finances. ‘Outcomes assessment’ has been defined as: what rehabilitation services ought to achieve for the persons [emphasis added] receiving them…and how those achievements can be identified and measured (Fuhrer, 1987, p. 1). In their 1995 Standards Manual and Interpretive Guidelines for Behavioral Health, the Commission on the Accreditation of Rehabilitation Facilities (CARF) discusses outcome-based evaluation and the need for organizations to: demonstrate that systems have been established to measure outcomes including effectiveness, efficiency, and satisfaction of the persons served. (CARF, 1995, p. 6) Table 11.5 Examples of Currently Available Outcome Measures 1.

2.

OT FACT is a computerized functional assessment instrument which solicits practitioner or consumer judgments on the perceived level of functional performance. The instrument contains five domains of function: Role Integration, Activities of Performance, Integrated Skills of Performance and Components of Performance, as well as Environment Performance. The entire question set includes over 900 trichotomous scaled computer branching questions. Efficiency is managed by using global screening questions which request detail only in needed areas. Also, the question set can be customized by users to minimize the overall depth of the assessment. OT FACT specifically addresses the area of assistive technology by allowing consumer or practitioner scoring, producing performance scores with and without the use of assistive technology for side-by-side comparison, and prompting the scorer to identify the specific technologies used. Optimizing reliability and validity has been key to the design of OT FACT which led to the computerized dynamic questioning approach used. As a dynamic question set, however, reliability and validity determination has challenged traditional instrument test procedures. Thus, a multi-directional set of classical and more modern reliability and validity measures have been and are continuing to be administered to document the effectiveness of the computerized question structure on which OT FACT is based. For more information on OT FACT, contact the Trace Center in Wisconsin. The Functional Independence Measure (FIM) is an 18-item, seven-level ordinal scale developed to provide uniform measurement of disability and rebailitation. The FIM is designed to measure changes in a person’s functioning over the course of comprehensive medical rehabilitation and is appropriate for a wide variety of physical disabilities. It can

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Table 11.5—(Continued)

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11.13.1.1 Measuring outcomes Outcomes measures are used to demonstrate that particular goals established for a consumer have been identified and then achieved. One outcome measure is the difference over time in capability and performance (effectiveness). That is why many functional assessment measures (with their focus on employability, performance of activities of daily living and so on) are being viewed as means of demonstrating outcome achievement. Without the use of functional assessment measures, the determination of rehabilitation effectiveness can be affected by incongruence in views held by consumers and therapists regarding ‘disability, rehabilitation success’, and so on (Scherer, 1996). For example, professionals tend to define independence in terms of physical functioning whereas consumers more often equate independence with social and psychological freedoms. Outcomes vary among individuals and one must obtain the consumer’s perspectives of the most desired outcomes as well as the perspectives of secondary consumers (family members, caretakers) payors, vendors and one’s employer. Once the goals of the intervention are specified, a timeline for goal achievement needs to be established. Table 11.5 list three examples of outcome measures related to assistive technologies. 11.13.1.2 How important is quality of life? To many people the acid test of outcome achievement is the subjective sense of well-being and comfort the person has when in the community. Quality of life has come to mean global happiness and satisfaction as well as satisfaction with specific areas of life functioning such as work, social relationships and finances. A person’s view of their quality of life is influenced by such psychological factors as mood and outlook, physical factors like pain, and the person’s perceptions of a broad array of external factors including available social support, money and transportation. Furthermore, all of these factors are interrelated: pain influences mood which, in turn, influences perceived resources and needs. When looking at outcome achievement from a quality of life perspective, one means of assessing a person’s quality of life is to have the individual prioritize their desired outcomes and then rate over time progress in achieving them. This is the system used in the Assistive Technology Device Predisposition Assessment. In this way, outcomes are measured in terms of changes in, for example, the person’s satisfaction in being able to get to where they want to go, whether by walking or some other means, rather than just by the functional capability to do so. Functional capability, however, is an essential means to quality of life achievement.

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11.13.1.3 How to evaluate: Is quality of life measurable? Quality of life is a highly variable and unstable construct, making its global measurement difficult and imprecise. One approach might be to measure its component parts. This, however, brings such measurement problems as the need to square (or match) success in achieving one component with a related negative effect on another component. For example, getting a job requires a geographic move that dissociates the individual from their social support network which heightens anxiety. While this may be a temporary phenomenon, it may also lead to the person leaving their job and returning to the security of family and friends. 11.13.1.4 What to do with evaluation data: Is quality of life enough? We operate in a climate of ‘expenditure crisis’. Quality of life enhancement is the ultimate outcome for most professionals working in assistive technology service delivery. Professionals want to make a positive difference in people’s subjective view of their quality of life; they want them to feel—and be—more capable, more independent, able to exercise more choice and take advantage of a wide range of opportunities. Professionals do it—they just need to be able to show it, to prove it. That is what outcomes evaluation can accomplish. Outcomes evaluation as servant, not master; as helping match person and technology, not defining or limiting the service delivery process. 11.14 Conclusion While some technologies are meant to be used for only a short time, premature assistive technology abandonment is costly both in terms of dollars and outcome achievement regardless if the abandoned equipment is low or high-tech. Equipment also becomes wasteful when it does not enhance the person’s quality of life—even if it is used. Partial, reluctant or inappropriate use are issues equally deserving of assessment and intervention. Professionals in ergonomics are experts at designing technologies to best correspond with human anatomy and physiology. The usability of technologies without fatigue or pain, the selection of the best components and materials, have greatly contributed to overall consumer satisfaction with today’s technical products. Now ergonomics professionals must also become skilled in assessing user preferences and predispositions to the use of particular technologies. To this end, this chapter was written to provide some initial guidelines and areas to consider.

ASSISTIVE TECHNOLOGY 343

References ALBAUGH, P.R. and FAYNER, H. (In press) The BTPA for predicting technology success with learning disabled students. Lessons from a multimedia study, Technology and Disability. BLACKSTONE, S.W. (In press) Evaluating, selecting and using communication devices, in GALVIN, J.C. and SCHERER, M.J. (Eds). Evaluating, selecting and using appropriate assistive technology. Gaithersburg, MD: Aspen Publishers, Inc. COMMISSION ON THE ACCREDITATION OF REHABILITATION FACILITIES. (1995) 1995 Standards Manual and Interpretive Guidelines for Behavioral Health. Tucson, AZ: Author. COOK, A.M. and HUSSEY, S.M. (1995) Assistive Technologies: Principles and Practice, St Louis: Mosby. COOMBS, N.R. (1988) Using distance education technologies to overcome physical disabilities. Paper reprinted in Mindweave, New York: Pergamon Press. FUHRER, M.J. (1987) Rehabilitation Outcomes: Analysis and Measurement. Baltimore: Paul H. Brookes. GALVIN, J.C. and CAVES, K.M. (1995) Computer assistive devices and environmental controls, in BRADDOM, R.L. (Ed.). Physical Medicine and Rehabilitation, pp. 493–501, Philadelphia: W.B.Saunders. GALVIN, J.C. and PHILLIPS, E. (1990) What is Appropriate Technology? Washington, DC: National Rehabilitation Hospital, Rehabilitation Engineering Center. GALVIN, J.C. and SCHERER, M.J. (Eds). (1996) Evaluating, Selecting and Using Appropriate Assistive Technology. Gaithersburg, MD: Aspen Publishers, Inc. GRADY, A., KOVACH, T.., LANGE, M. and SHANNON, I. (1991) Promoting choice in the selection of assistive technology devices, in MURPHY, H. (Ed.). Proceedings of the Sixth Annual Conference, Technology and Persons with Disabilities, pp. 8315–24. Los Angeles: Office of Disabled Student Services, California State University, Northridge. HOBSON, D.A. and SHAW, C.G. (1987) Program development and implementation, in Rehabilitation Technology Service Delivery: A Practical Guide. Washington, DC: RESNA Press. JONES, K., TORGESEN, J. and SEXTON, M. (1987) Using computer guided practice to increase decoding fluency in learning disabled children: A study using the hint and hunt I program. Journal of Learning Disabilities, 20, 122–8. KEEFE, B., SCHERER, M.I. and MCKEE, B.J. (In press). Maine Point: outcomes of teaching American Sign Language via distance learning, Technology and Disability. LAPLANTE, M.P., HENDERSHOT, G.E. and Moss, A.J. (1992) Assistive technology devices and home accessibility features: Prevalence, payment, need and trends. Advance Data (National Center for Health Statistics), No. 217. MANN, W.C. and LANE, J.P. (1991) Assistive Technology for Persons with Disabilities: Second edition. Bethesda, MD: The American Occupational Therapy Association, Inc. MENDELSOHN, S. (1996) Funding assistive technology, in GALVIN, J.C. and SCHERER M.J. (Eds). Evaluating, Selecting and Using Appropriate Assistive Technology. Gaithersburg, MD: Aspen Publishers, Inc.

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ORR, J.N. (1996) Technologies of the future, in GALVIN, J.C. and SCHERER, M.J. (Eds). Evaluating, Selecting and Using Appropriate Assistive Technology. Gaithersburg, MD: Aspen Publishers, Inc. PETERSON, W.A. (1996) Transportation, in GALVIN, J.C. and SCHERER, M.J. (Eds). Evaluating, Selecting and Using Appropriate Assistive Technology. Gaithersburg, MD: Aspen Publishers, Inc. READ, R.F. (1990) Client evaluation and equipment prescription, in MURPHY, H. (Ed.). Proceedings of the Fifth Annual Conference, ‘Technology and Persons with Disabilities, pp. 553–64, Los Angeles: Office of Disabled Student Services, California State University, Northridge. RUBIN, S.E. and ROESSLER, R.T. (1987) Foundations of the Vocational Rehabilitation Process, 3rd edn, Texas: Pro-Ed, Inc. SCHERER, M.J. (1991a) Matching a Person and Technology (mpt). Model and Assessment Instruments. Rochester, NY: Author. SCHERER, M.J. (1991b) Assistive technology use, avoidance and abandonment: What we know so far, in MURPHY, H. (Ed.). Proceedings of the Sixth Annual Conference, Technology and Persons with Disabilities, pp. 815–26, Los Angeles: Office of Disabled Student Services, California State University, Northridge. SCHERER, M.J. (1993) ‘Living in the state of stuck: How technology impacts the Lives of people with disabilities. Cambridge, MA: Brookline Books. SMITH, R.O. (1987) Models of service delivery in rehabilitation technology, in Rehabilitation Technology Service Delivery: A Practical Guide, Washington, DC: RESNA Press. TRIFILETTI, J.K., FRITH, G.H. and ARMSTRONG, S. (1984) Microcomputers versus resource rooms for learning students with a disability: A preliminary investigation of the effects on math skills. Learning Disability Quarterly, 7, 69–76. US CENSUS BUREAU. (1990) National Health Interview Survey on Assistive Devices (NHISAD), Washington, DC. VANDERHEIDEN, G. and LLOYD, L.L. (1986) Communication systems and their components, in BLACKSTONE, S. and RUSKIN, D. (Eds). Augmentative Communication: An Introduction. Rockville MD: ASHA Press. WRIGHT, G.N. (1980) Total Rehabilitation. Boston: Little, Brown.

CHAPTER TWELVE Anthropometry for the needs of disabled people EWA NOWAK

12.1 Introduction The aim of this chapter is to present anthropometry as a set of measuring techniques and methods, and to prove its usefulness for the needs of the disabled. Anthropometry originates from anthropology and is directed towards obtaining the measurements of man. Anthropology is the science about man. It deals with the changeability of physical characteristics of man in time and space, particularly with race differentiation, individuals’ differentiation, ontogenesis and phylogenesis. In the English and American approach anthropology embraces the complete knowledge of man and can be divided into physical (biological) anthropology and cultural anthropology. There are other types of anthropology including social and criminal. Physical anthropometry is particularly useful for practical purposes. According to the accepted division used most often, physical anthropology can be separated into the following three basic parts. ■ Population anthropology (known earlier as race anthropology) that studies the intraspecies differentiation of man—including living conditions, history and the present state, ■ Ontogenetic anthropology that studies the ontogenesis of man. ■ Phylogenetic anthropology that deals with the phylogenesis of man, that is, the origin of our species. Anthropology is related in its research to biology and the humanities (archaeology, prehistory, psychology and pedagogic) as well as the technical sciences. In contact with technology and engineering, ergonomic anthropology appears and develops. Ergonomic anthropology deals with man as the basic unit of the man-technique system. Together with other disciplines (including physiology and psychology) it aims at obtaining the best conditions for this system to function.

346 ANTHROPOMETRY FOR THE DISABLED

Ergonomic anthropology makes use of the scientific output of phylogenetic, ontogenetic and population anthropology, and as a result of the problems it concentrates on, it benefits from various sections of medicine and psychology. An anthropologist dealing with ergonomics makes use of classical anthropological science and develops this science for the needs of technology and engineering. Thus, he or she utilizes classical anthropometry, that is, the basic research methods applied to anthropology. As ergonomics develops and in compliance with its needs anthropometry develops new methods that can be called ergonomic anthropometry. Many of these methods, concerning both classical and ergonomic anthropometries, can be applied to rehabilitation ergonomics (Kumar, 1992) that can be divided into two parts: ■ the first part is strictly connected with ergonomics, where anthropometry provides data for designing and shaping work and life environment of the disabled; ■ the second part embraces all methods and measuring techniques that assist the rehabilitation process. These two spheres will be discussed later. 12.2 Aims and tasks of anthropometry 12.2.1 Measuring methods Basic anthropometric measurements of man include: ■ ■ ■ ■

linear measurements; angular measurements; circumferences; force measurements.

Linear measurements include breadth, height and length measurements. These are measured between anthropometric points that are determined. Angular measurements are carried out between planes and lines that cross the human body. Body movements in the sagittal plane are called flexion and extension. Figure 12.1 illustrates head movement ranges in this plane. Back and head movements in the sagittal planes are called bending to the right and to the left, and extremities movements are called adduction and abduction (Morecki et al., 1971). According to these extremities, movements in the transverse plane are called pronation and supination, and back movements are called left turn and right turn. Figure 12.2 presents head movements in the frontal plane and

EWA NOWAK 347

Figure 12.1 Movement ranges of the hand in sagittal plane (after Wołoszyńska); (a) flexion; (b) extension.

Figure 12.3 shows hand movements in the transverse plane. Circumferential measurements of the body are mainly carried out for the needs of clothing design and for physical assessment. The basic measurements include head, neck, chest, hips, arms, thighs and shins circumferences. Force measurement is done in order to define the physical predispositions of man. In general, force is defined in relation to force exerted by the hand and foot. Moments of forces are used as data applied to designing hand and foot control systems. The basic aim of classical anthropometry is to provide objective and precise data on the somatic structure of man. In population anthropology, for example, anthropometry is used as a set of methods applied to defining biological differences that occur between human populations. Figure 12.4 shows the differences between the upper and lower extremities as well as back measurements of the white, black and yellow races. Anthropometry in ontogenetic anthropology serves to assess the ontogenetic development of man, and provides data for defining the development process, the process of puberty and the aging process. Following the development of the body segments in particular ontogenetic periods, anthropometry describes changes in proportions of the human body. Figure 12.5 presents proportions of the newborn and the adult body. The proportions of the head equal 2:1, of the back 3:1, of the upper extremity 4:1 and of the

348 ANTHROPOMETRY FOR THE DISABLED

Figure 12.3 Movement ranges of the hand in transverse plane (after Wołoszyńska); (a) adduction; (b) abduction.

Figure 12.2 Movement ranges of the head in frontal plane (after Wołoszyńska); (a) bending to the right; (b) bending to the left.

lower extremity 5:1 respectively. This means that during the physical development of man, head measurements increase twofold, trunk measurements threefold, and the measurements of extremities four- and fivefold. The aim of anthropometry is not only to define differences in the body structure of man in relation to age, but also in relation to the type of somatic structure and sex (Figure 12.6). Significant differences can be found in somatic characteristics in men and women (Figure 12.7). In general women are about 8–15 per cent smaller than men and are physically weaker. Following the development of successive generations anthropometry assists in defining and foreseeing developmental trends of populations. These concern

EWA NOWAK 349

Figure 12.4 Differences between the body dimensions depending on the race (after Diffrient et al., 1974).

such phenomena as development acceleration and secular trend. These phenomena result in significant differences between generations in somatic, morphological and functional characteristics. Anthropometry describes the above differences and provides data of somatic changes that occur in a given population. Pediatrics and ergonomics make use of these changes and facts described. Pediatrics applies data about populations as biological standards to the evaluation of individuals. Ergonomics on the basis of somatic characteristics of a given population creates products adjusted to its body structure. The development in ergonomics resulted in the development of methods and measuring techniques applied to anthropometry. New techniques especially for the needs of ergonomics which may be called ergonomic anthropometry have been gradually developed. The main aim of ergonomic anthropometry is to obtain data that describe the physical predispositions of man to design work and life environment. This objective imposed the need to modify methods applied up to the present and to develop new ones. In ergonomics, for example, many anthropometric measurements are performed on the basis classical anthropometric points and new fixed references basis. The main reference basis in classical anthropometry for height measurements is the horizontal place of the footrest—Basis (B). An additional vertical plane basis—Basis dorsalis (Bd)—was introduced for the needs of ergonomics. This basis is mainly applied in determining body dimensions in the sagittal plane. These dimensions include depth measurements and reaches. To measure the body in the sitting position two additional reference planes were introduced. These are the horizontal seat plane—Basis sedilis (Bs)—

350 ANTHROPOMETRY FOR THE DISABLED

Figure 12.5 Proportions of the body of the newborn and the adult.

and the vertical plane—Basis sedilis dorsalis (Bsd) (Figure 12.8). Many times ergonomic anthropometry has developed reference systems to solve definite problems in order to meet the requirements of the constructors and designers of technical machines and appliances. This way of thinking was applied to determining dimensions of the spatial zone of upper extremities reaches (Damon et al., 1966; Bullock, 1974; Nowak, 1976, 1979). According to assumptions adopted by Nowak (1976, 1979) the measuring system was based on acromial points. These points are used to determine the length measurements of the upper extremities, and at the same time to define the position of the extremities in space regardless of the body position. The upper extremities zone was defined as the spatial curve area that could be determined according to the Cartesian system. Thus, the measuring system of the above zone was determined with the use of the measuring plane tangential to the back, central sagittal plane and horizontal plane crossing the acromial points (Figure 12.9). The point of intersection of these perpendicular planes marked the origin of the coordinate axes of the measuring system. Thus, recording the reach zones on 10 horizontal levels and recording the hand positions every 15° on each level, a set of geometrical points that constitute the spherical area of the upper extremities work zones was obtained (Figure 12.10). The system makes it possible to determine the reach zone for any position of the body and therefore is very useful. In Damon et al. (1966) and Bullock (1974) studies it was assumed that the measurement should refer to the sitting position typical for the pilot since the

EWA NOWAK 351

Figure 12.6 Differences between the body dimensions depending on the somatic type (after Diffrient et al., 1974).

studies aimed at providing data for the design of spatial structures of airplane cockpits. The origin of the measuring coordinate system was determined by the seatback plane and the seat plane. The seat reference point (SRP) constitutes the reference basis most often used for measuring the human body in the sitting position. The methods mentioned earlier are used to measure the healthy population and can also be applied to studies of the disabled. These methods, however, require a complicated set of measuring devices and can, therefore, be arduous in carrying out investigations of disabled people. In section 12.3.1.2 a simplified method of the reach zones determination recommended for this group of people is presented. At the initial stage of ergonomic anthropometry development the adult was its main subject since ergonomics dealt at that time with the work environment of man. As ergonomics develops its interests increase and deal with the life environment of man and include home ergonomics and leisure ergonomics. The role of ergonomics also increases and contemporary anthropometry used for the

352 ANTHROPOMETRY FOR THE DISABLED

Figure 12.7 Differences between the body dimensions of the man and the woman (after Diffrient et al., 1974).

benefit of ergonomics provides data of man in each stage of his development. Assuming ontogenetic periods as criteria for division we can distinguish anthropometry for children and young people, adults and the elderly (Figure 12.11). Anthropometry applies adequate measuring techniques for investigating each of these groups. For example, the length measurements of children aged up to one year old are done in the lying position by means of a special type of liberometer. The same measurements of the adult population are performed in the sitting position by means of the vertical anthropometer. The majority of methods and measuring techniques applied in anthropometry is used for measuring disabled people. Some of these, however, are modified or simplified to consider the difficulties in obtaining measurements. For example, special measuring chairs are constructed to investigate people with lower extremities dysfunction since they can be studied only in the sitting position (Molenbroek, 1987; Nowak, 1989; Jarosz, 1993). The methods applied by classical anthropometry are not easy to investigate the disabled. They require a great deal of experience from those performing experiments since the measurements should be taken very quickly. The

EWA NOWAK 353

Figure 12.8 Measuring planes.

measuring methods that make it possible to carry out investigations at a distance are most convenient both for the subject and the investigator, and are called nontactile methods. This type of method was applied by the Swedish researchers Thoren and Gustavsson (1994) in carrying out measurements of a group of the disabled. A set of mirrors and cameras properly arranged and interrelated to CAD/CAM software made it possible to obtain anthropometric data in a spatial system very quickly. The photogrammetric methods are being applied most often in the measurements of disabled people. These make it possible to define deformities and changes in the body structure, dislocations of bones segments and to define the shape and dimensions of the body regardless of the body position and of its changes in time (Bujakiewicz and Majde, 1978; Das and Kozey, 1994). It should be mentioned that these kinds of methods are relatively expensive and not all research units can afford to apply them.

354 ANTHROPOMETRY FOR THE DISABLED

Figure 12.9 Arrangement of a measuring system for determination of the space of arm reach areas.

Summarizing the above it can be stated that the sets of measuring techniques and methods of the classical and ergonomic anthropometry can be applied to the measurements of the disabled. Some of these methods, however, require verification from the point of view of the arduousness of investigations. 12.2.2 Statistical methods Individuals with various body dimensions (tall and short) and various body proportions (long or short extremities, or long or short trunk) live in every population. In order to characterize a given population, that is to evaluate it in terms of numbers, anthropometry utilizes basic statistical characteristics. Usually anthropometric features have the normal distribution and are arranged according to the ‘Gaussian distribution’. Figure 12.11 illustrates such distribution. It presents the body height of Warsaw boys aged 18 (Nowak, 1993). The values of this feature were presented on the frontal axis, and the frequency of occurring (possibility) on the horizontal axis. Two basic statistical parameters are used to determine the distribution of features in a population. One of these parameters is the mean (m). It tells where the distribution is located on the horizontal axis. The other is a quantity known as the standard deviation (S) which is the index of the degree of variability in the population concerned—the ‘width’ of the distribution or the extent to which individual values are scattered about or deviate from the mean. Mean values (m) and standard deviations are used to determine the statistical characteristics called percentile. They are useful both in developing biological standards, and preparing standards for the needs of ergonomics.

EWA NOWAK 355

Figure 12.10 The measuring system of arm reach areas.

Assuming that the features investigated in the random test of the population have the normal distribution (Figure 12.11) we can call percentile (Cp) the value of the feature that does not exceeds p% of individuals. The values of particular percentiles (Cp) are calculated according to the following formula:

356 ANTHROPOMETRY FOR THE DISABLED

Figure 12.11 The frequency distribution for the stature of Polish boys (18 age) after Nowak, 1993. This is an example of the normal of Gaussian distribution.

per cent are taller. In this distribution the mean is equal to the 50th percentile. Other percentile values are also marked on the horizontal axis. The fifth and 95th percentile are used for the needs of designing. The fifth percentile located closer to the frontal axis means that the 5 per cent of the boys are shorter. Similarly, an

where Cp is the characteristics value on the level of the p percentile; m is the mean; S is the standard deviation; z is the constant for the percentile concerned (look it up in statistical tables). In order to obtain a better percentile interpretation we should come back to Figure 12.11. The height measurement of the investigated population of boys aged 18 distributes in a symmetrical way (Nowak, 1993). Its highest point is the average stature, otherwise known as the mean. Since the curve is symmetrical, it follows that 50 per cent of the population of boys are shorter than average and 50

EWA NOWAK 357

Figure 12.12 Designing an interior for the disabled using the wheelchair (after MirowskaSkalska, 1995).

equal distance from the mean towards the right of the chart is a point known as the 95th percentile. Then we could say only 5 per cent of the boys are taller. Ninety per cent of the population are between the fifth and 95th percentile in stature. Using the values of the fifth and 95th percentile and applying the rules of ergonomics, products for 95 per cent of the population are designed. These principles are also used to design for the disabled. Figure 12.12 presents the way of applying percentile values to designing interiors meant for the wheelchair user. In order to determine the reach limit accessible for 90 per cent of the disabled population the values of the upper reach for the fifth percentile for the woman was applied.

358 ANTHROPOMETRY FOR THE DISABLED

12.3 Application of anthropometry for the needs of disabled people 12.3.1 Ergonomics—data for designing 12.3.1.1 Somatic characteristics of the disabled The influence of disabilities on shaping the body structure has been studied by numerous anthropologists (Floyd, 1966; Pheasant, 1986; Boussena and Davies, 1987; Goswami et al., 1987; Goswami, 1994; Laubach, 1981; Molenbroek, 1987; Nowak, 1988, 1989, 1994; Samsonowska-Kreczmer, 1988; Jarosz 1988, 1990, 1994; Mięsowicz, 1990; Łuczak et al., 1993; Das and Kozey, 1994; Lebiedowska et al., 1994). The largest disproportions between the healthy and the disabled population can be found in a group of people with motor dysfunction. This is understandable since dysfunction results from the past or currently developing diseases that lead to joint disturbances of the osseous, ligament and joint, muscular and nervous systems. These disturbances lead to deformities and somatic changes of particular parts of the body. This then affects the final shape and dimensions of the body and its motorics. Other factors that restrain the development and growth of the body include restriction of motion activities, neglected nursing, improper or lack of rehabilitation, as well as stresses connected with pains, frequent stays in hospitals and rehabilitation centers and which accompany the pathological process. Descriptions of investigations of people with the lower extremities dysfunction are usually found in the literature. They are usually wheelchair users. It should be realized, however, that this group embraces people with various degrees of motor-efficiency limitations. This depends not only on the type and stage of a disease but also on the time of its appearance. Therefore, researchers dealing with this problem face great difficulties in selecting subjects, and in describing results scientifically. This may be the cause of the small number of studies undertaken in this field. This particularly concerns studies where the results are to provide data for designing. Few characteristics of the disabled have been described in the literature in this field. These include: ■ anthropometric measurements of the petraplegics and tetraplegics in the UK using a wheelchair (Floyd; 1966 after Pheasant, 1986); ■ anthropometric measurements of clients of the Employment Rehabilitation Center (ERC) in the UK for the needs of seat, workstands and tools design in this center (Boussena and Davis, 1987);

EWA NOWAK 359

■ anthropometric studies of Indians with lower extremities disabilities resulting from spinal injuries and Heine-Medina disease, for the needs of wheelchair design (Goswami et al., 1987); ■ anthropometric measurements of elderly men using wheelchairs—clients of the Administration Veterans Medical Center in Dayton, Ohio (Laubach, 1981); ■ anthropometric measurements of elderly people in The Netherlands—data for the model of the man (CAD model) as a system of the Anthropometric Design Assessment Program (ADPS) (Molenbroek, 1987); ■ anthropometric studies of Polish young people with lower extremities dysfunction for the needs of designing and furnishing interiors (Nowak, 1989; Jarosz 1990) and clothing design (Samsonowska-Kreczmer, 1988); ■ anthropometric studies of the Polish adult population with lower extremities dysfunction for the needs of interior design (Jarosz 1993); and ■ anthropometric studies of people with spine injuries using the wheelchair— the Canadian population (Das and Kozey, 1994). Table 12.1 presents source data including anthropometric data of disabled people and Tables 12.2, 12.3 and 12.4 anthropometric measurements collected on the basis of accessible data published in the ergonomic literature (Pheasant, 1986; Boussena and Davies, 1987; Goswami et al., 1987; Laubach, 1981; Molenbroek, 1987; Nowak, 1989; Jarosz, 1990, 1993; Das and Kozey, 1994). Only data comparable with respect to the application of the same research methodology were presented. Unfortunately, much data must have been omitted. This concerns, for example, the upper and lateral reaches. The lateral reach can be measured in these studies in relation to the shoulder joint (Goldsmith, 1967), to a side of the wheelchair (Floyd, Table 12.1 Reported anthropometric data of disabled people. Year of Population Source investigatio author n

Type of disability

Male

Female

Male

Female

1966

British

1987

British

Floyd * Boussena and Davies

Wheelchair users Injuries and deformatio n of the spine, upper limbs, lower limbs and other

Age

Sex

Number

Under 45 years of age 20–40 years of age

+ +

91

36

+ +

177

26

360 ANTHROPOMETRY FOR THE DISABLED

Year of Population Source investigatio author n

Type of disability

Male

Female

Male

Female

1987

Indian

Goswami et al.

Suffering from lower limb

1987

Dutch

1988

Polish

Molenbroe k Nowak

1983

Polish

Jarosz

1984

Canadian

Das and Kozey

Wheelchair users Wheelchair users Spinal cord injuries / SCI/

Age

Sex

Number

Adults

+

61

Elderly people 15–18

+ +

197

625

+ +

32

45

18–39

+ +

101

69

Adults

+ +

42

20

734 963 496 717 468 676 108 312 −

−

* After Pheasant, 1986. Table 12.2 Structural anthropometric data for males with respect to the seat. Dimension (mm)

per

Author

Boussena and Molenbroek Nowak Jarosz Das and Davies Kozey

Goswami et al.

Seated stature Eye height

769 960 667 857 495 682 144 297 468 605 383 513 180 340 461 636 353 425 1028 1324

Shoulder height Elbow height Knee height Popliteal height Trunk depth Popliteal depth Shoulder breadth Overhead reach

5 95 5 95 5 95 5 95 5 95 5 95 5 95 5 95 5 95 5 95

824 761 − − 177 269 483 586 381 473 − 421 522 383 482 −

919 962 643 810 520 649 168 289 − 401 503 211 344 401 525 − 828 1214

744 972 630 857 474 647 158 289 453 572 386 502 165 270 435 555 337 439 1022 1320

− 198 281 − 354 439 1072 1415

− 330 564 136 212 − 343 465 − 356 447 − −

EWA NOWAK 361

Dimension (mm)

per

Author

Boussena and Molenbroek Nowak Jarosz Das and Davies Kozey

Goswami et al.

Reach forward

653 840

5 95

568* 677*

−

668 861

−

−

* Measured from the acromiale point.

1966 after Pheasant, 1986), to the body axis as a half of the lower extremities span (Nowak, 1989; Jarosz, 1993). The forward reach can be measured in relation to the shoulder joint (Floyd, 1966 after Pheasant, 1986), to the front of the trunk (Goldsmith, 1967) or to the vertical plane of the seat back—Bsd (Nowak 1988, 1989; Jarosz, 1993). It turns out that height measurements are measured in relation to various reference bases. This fact creates a difficulty not only for comparable purposes, but also for designers who would like to utilize investigation results. A synthesis of existing data was done for design purposes. Tables 12.2 and 12.3 comprise height measurements measured in relation to the seat plane (Bs) and Table 12.4 to the floor level (B). Anthropometric data differs significantly, regardless of the fact that these concern various populations. The influence of diseases resulting in the necessity of using the wheelchair affects shaping the body figure. Pheasant (1986) indicates that the body proportions of wheelchair users resemble those of elderly people aged over 65. This was confirmed by results of investigations carried out by Molenbroek (1987). Not only anthropometric measurements of the disabled are important for the needs of design but also differences between the disabled and healthy population. The majority of authors indicate that the body structure of disabled men and Table 12.3 Structural anthropometric data for females with respect to the seat. Dimension (mm)

per

Boussena and Davies

Molenbroek Nowak Jarosz Das and Kozey

Seated stature

5 95 5 95 5 95 5 95

Eye height Shoulder height Elbow height

Author 794 912 − − 176 266

702 858 585 763 479 601 156 270

708 890 592 783 461 592 139 309

668 894 570 789 433 619 133 281

647 857 546 744 423 597 105 257

362 ANTHROPOMETRY FOR THE DISABLED

Dimension (mm)

per

Boussena and Davies

Molenbroek Nowak Jarosz Das and Kozey

Knee height

5 95 5 95 5 95 5 95 5 95 5 95 5 95

Popliteal height Trunk depth Popliteal depth Shoulder breadth Overhead reach Reach forward

Author 450 539 364 453 − 418 516 368 434 − 552x 630x

− 361 460 219 368 405 524 − 733 1113 −

442 532 371 462 182 286 424 545 316 410 963 1195 617 768

407 530 315 454 191 315 418 571 310 394 882 1192 558 713

− − 143 182 − 291 355 947 1090 −

x measured from the acromiale point. Table 12.4 Reported anthropometric data of disabled people with respect to the floor. Dimension (mm)

per

Floyd

Author Jarosz

Men

Women

Men

Women

Floor to vertex

5 95 5 95 5 95 5 95 5 95 5 95 5 95

1260 1410 1150 1290 965 1100 625 745 620 680 120 180 1550 1785

1180 1355 1080 1235 910 1065 610 730 565 635 165 215 1460 1680

Floor to eye Floor to shoulder Floor to elbow Floor to top of height Floor to top of foot Floor to vertical grip reach

1299 1490 1197 1387 1025 1212 674 827 607 672 −

1198 1424 1100 1319 963 1149 663 811 598 667 −

1558 1854

1412 1722

women differs significantly from the able-bodied population (Pheasant, 1986; Samsonowska-Kreczmer, 1988; Nowak, 1988, 1989; Jarosz, 1990, 1993; Das

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Figure 12.13 Anthropometric model (the 5th percentile) of disabled men (right side) and able-bodied men (left side) in the sitting position (after Jarosz, 1993).

and Kozey, 1994). This problem was illustrated in the example of data on the Polish population (Jarosz, 1993). Using the threshold values of the fifth percentile a linear anthropometric model of disabled men and women in the sitting position was drawn. These models were compared with the models of the fifth percentile of the able-bodied (Figures 12.13 and 12.14). The following measurements were marked on each model: Seated stature (Bs-v) Eye level (Bs-en) Shoulder height (Bs-a) Elbow height (Bs-r) Popliteal height (B-ppl) Popliteal depth (Bsd-ppl) Arm overhead reach (Bs-ph III) Arm reach forward (Bsd-ph III). It appears that these measurements show smaller values for the disabled than for healthy people. The differences are significant and amount to 110 mm for the

364 ANTHROPOMETRY FOR THE DISABLED

Figure 12.14 Anthropometric model (the 5th percentile) of disabled women (right side) and able-bodied women (left side) in the sitting position (after Jarosz, 1993).

seated stature (Bs-v), for eye level (Bs-en) to 113 mm, for shoulder height (Bs-a) to 126 mm, and for elbow height (Bs-r) to 57 mm. For arm reach measurements the differences amount for arm reach forward (Bs-phIII) to 204 mm, and to 90 mm from arm overhead reach (Bsd-phIII). Similar results were obtained by Nowak (1988, 1989), by comparing the population of disabled young people aged 15–18 with lower extremities dysfunction, with the young of the same age representing the Polish population (Nowak, 1988) (Table 12.5).

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Table 12.5 Structural anthropometric data for boys and girls/disabled and able-bodied/— 5th percentile. Boys

Girls

Dimension (mm)

Disabled (Nowak, 1989)

Ablebodied (Nowak, 1988b)

Difference Disabled (Nowak, 1989)

Ablebodied (Nowak, 1988b)

Difference

Seated stature (Bs-v) Eye level (Bs-en) Shoulder height (Bsa) Elbow height (Bsr) Arm overhead reach (BsphIII) Arm reach forward (BsdphIII)

744

902

−158

708

814

−106

630

716

−86

592

690

−98

474

531

−57

461

541

−53

158

206

−48

139

207

−68

1022

1204

−182

963

1118

−155

688

738

−70

617

691

−74

Floyd (1966), Bouisset and Moynot (1985) indicate that the smaller seated stature (Bs-v) measurements of the disabled may result from the deformities of the osseous system as well as from the fact that as a result of back muscles paralysis, difficulties with maintaining the straight position of the body appear. This problem seems to be very serious for paraplegics. A similar interpretation can be accepted for reach measurements. According to Pheasant (1986) the same analogies of changes in body proportions occur in wheelchair users and elderly people. In old age, similarly to people with motor organs dysfunction, deficient muscular tonicity of the chest and belly appears. This results in an increase in pectoral kyphosis. At the same time the processes of intervertebral cartilages flattening and back shortening occur. This leads to the C shape of the spine (Nowak, 1980, 1988). Samsonowska-Kreczmer (1988) indicated that the stooping back and sunken chest occur in young people with motor organs dysfunction. Another reason for diminishing the seated stature measurement is the buttock and thigh muscles atrophy resulting from immobility of the back and lower extremities. Studies conducted by Jarosz (1993) indicate that for 55 per cent men and 65 per cent of women thigh thickness measurement is below the lower limit of the healthy population standard. Similar results concerning adults

366 ANTHROPOMETRY FOR THE DISABLED

were obtained by Goswami et al. (1987), and the young by Nowak (1988, 1989) and Mięsowicz (1990). In comparison with the stature and reaches characteristics, shoulder breadth characteristic (a-a) appears different. Most scientists confirm the fact that the value of this characteristic is bigger for wheelchair users than for the healthy population (Goswami et al., 1987; Boussena and Davies, 1987; Nowak, 1989; Jarosz, 1993) (Table 12.6). Wężyk (1989) and Mięsowicz (1990) point out the fact that children with celebral palsy have bigger values of shoulder breadth in comparison to those of healthy children. It is supposed that the increase in this characteristic value is caused by the bigger motor activity of the upper extremities. As a comparatively efficient motor organ, the upper extremities are used to carry the whole body while changing the position and displacing the body from a wheelchair to a chair or other piece of furniture. The same concerns moving with the assistance of all kinds of orthopedic aids (such as crutches). Particularly great activity connected with physi Table 12.6 Differences between shoulder breadth values/in mm/of the disabled population and the healthy population according to different authors. Author

Population

Age

Male

5

95

5

95

percentile

percentile

percentile

percentile

Nowak (1989)

Disabled Able-bodied Difference Disabled Able-bodied Difference Disabled

Jarosz (1993)

Boussena and Davies (1987)

Able-bodied Difference

15–18

19–65

15–35

Female

357 349 +8 353 305 +48 383

439 414 +25 425 419 +6 482

316 324 +8 310 271 +39 368

410 384 +26 394 373 +21 434

365 +18

435 +47

330 +38

390 +56

cal effort is shown in the case of upper extremities driving the wheels of the wheelchair—in this case they are in a sense the propulsive force. Although the development of electronics is changing the method of wheelchair steering, ensuring greater comfort for the disabled person, in many countries old generation wheelchairs, requiring the work of muscles, are still in production and use. Furthermore, the development of the osseous and muscular system of the shoulders is influenced by sports activities of the disabled. Nowadays this is a widespread and common practice. An additional factor of development can be the intensive training of these muscles during rehabilitation. It is supposed that

EWA NOWAK 367

the above factors can stimulate the growth of clavicles in their length, the more so as the ossification of parasternal epiphysis of clavicles takes place in man latest of all in comparison with other long bones. According to Wolański (1983), this process can last until the age of 25 or 27. The stimulating impact of physical training on the increase in bone length was confirmed by Malina (1980) on the basis of the investigations embracing the young. Buskirk et al. (1956) also proved that a one-sided load of the upper extremity with physical training or work stimulates the increase in its length. It was stated that the bones in the forearm and hand of professional tennis players were longer in a dominant extremity than in a non-dominant one. Preivs (1969) noticed lateralization in people practising sports or performing professional activities loading one side of the body. There are recorded facts of functional lateralization caused by performing one-sided, repeated work (Malinowski et al., 1985; Nowak, 1976). Analogically, it can be assumed that in the disabled, who at the same time show intensive motor activity of the upper extremities, it should be stimulation of clavicles growth, and as a result increase the values of shoulder breadth. This characteristic is important for clothing design and the fact that its values are bigger in case of the disabled is of importance for designers. It is an instruction to make necessary changes and corrections in the existing tailoring tables. Essential characteristics exerting an influence on workspace shaping are functional characteristics of the upper extremities, i.e. reaches. Values observed in these characteristics (Tables 12.2 to 12.4) are significantly lower in persons with lower extremities dysfunction, although their upper extremities are qualified as ‘efficient’. Lower values of reaches result not only from lower values of arm and forearm length, but also from limitations in shoulder and elbow joints. In connection with the above the disabled have difficulty in performing the movements of abduction and extension (Nowak, 1968). Grabowska et al. (1986) found that in people suffering from rheumatoid arthritis the workspace of the upper extremity is 7–10 per cent lower if a shoulder joint is constrained and 25– 33 per cent lower when there is the constraint of elbow joint movements. It is clear that disorders of these two joints increase the limitation of the upper extremity movements and thus the efficient workspace is significantly reduced. This is confirmed by investigations conducted by Nowak (1988, 1989) and Jarosz (1990, 1993). It should be pointed out that particular values of reaches of the disabled refer to the straight position of the body. Thus they can be increased through the trunk movements forward and lateral. Floyd’s investigations (1966) proved that the difference between the reach forward of disabled women in the straight position of the body and the same reach in the position of maximum bend forward amounted to 142 mm, and in case of the lateral reach with the trunk lateral bend it is 135 mm. Reaches forward of the disabled are limited by the footrest of the wheelchair. The difference between the point of reach of disabled women investigated and the beginning of the wheelchair amounted to 242 mm, that is, it exceeded the difference between reaches in the straight position and reaches in the bend forward stated by Floyd. This means that the

368 ANTHROPOMETRY FOR THE DISABLED

wheelchair user is not able to reach any devices in the frontal position if there is not enough free space for the wheelchair under the working plane. While designing the functional space for a paraplegic, one should bear in mind that they have difficulty with the stability of position and they can easily fall out of the wheelchair if they bend forward too much (Przybylski, 1979). Upper extremities moving forward disturb the balance of the body, which is more difficult to redress in consequence of the paralysis of the muscles of the spine and pelvis, stabilizing the body in the sitting position (Bouisset and Moynot, 1985). Molenbroek’s investigations (1987) provide data determining the values of the reach of the elderly. Limitation of the movement range of particular joints and decrease in the values of reach increase as age increases. Molenbroek (1987) proved that differences between the values of the arm reach overhead for 50year-old and 95-year-old Dutchmen amount (for the value of the 5th percentile) to approximately 300 mm. Table 12.7 presents the values of the arm reach overhead for this population (Molenbroek, 1987). These data are used for designing living interiors meant for elderly people. They help the person reach the top shelf of a wardrobe, reaching the highest buttons in lifts or reaching window handles. These data prove that while designing for people aged 50–110 we should place all kinds of switches at a height not exceeding 1474 mm. Above this height the elderly have difficulty operating them. According to Pheasant (1986), a wheelchair user (whose upper extremities are unimpaired) can reach a zone from around 600 to 1500 mm in a sideways approach, but considerably less ‘head on’. It may well be that the location of fittings within this limited zone will prove entirely acceptable for the ambulant users of the building, but in the case of working surface heights no such easy compromise is possible. Karagelis (1982), using a number of performance criteria, demonstrated that the optimal kitchen worktop height for wheelchair users was around 700 mm. Hamilton (1983) on the basis of a fitting trial, recommended a similar figure for the bottom shelf of an oven. Kitchen equipment installed at the 700 mm level for the benefit of a wheelchair user would be highly unsatisfactory for an ambulant spouse or helper. This problem is particularly acute in the case of elderly couples where one partner is a wheelchair user and the other, although ambulant, has diminished adaptive capacity. The stationary wheelchair user occupies up to 1445 mm×645 mm of floor space compared with 380 mm×630 mm for a standing person. They have a turning circle of between 1500 and 1700 mm diameter and require a minimum clear width of 800 mm for motion in a straight line, whereas the ambulant person is generously accomodated at 650 mm and can squeeze through 400 mm without much difficulty. Swing doors can be a problem especially if they are heavily spring loaded and/or mounted in consecutive pairs with inadequate space between them. Revolving doors are insurmountable obstacles as, of course, are steps and kerbs. Another task is determining appropriate steps and handrails adjusted to the dimensions of the disabled, who can move without aid. Petzall (1993)

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Table 12.7 Reach height in cm (after Molenbroek, 1987).

recommends installing a handrail at the height of 900 mm above the floor. Based on investigations of different steps variants, I suggest the height of a step within limits of 150– 200 mm and the width from 250 to 300 mm. Petzall (1983) determined placing handrails in a bus adjusted to the needs of ambulant disabled people (Figure 12.15) on the basis of anthropometric data, research tests and observations, as well as the size of seats and the distance from one to another (Figure 12.16). Petzall (1993) presents the following design requirements of seating for ambulant disabled people. ■ Seats should have a sitting height of approximately 430–500 mm above the floor and a seat depth of about 400 mm. The lower sitting height gives better sitting comfort when the passenger is to be seated for a long period, while the higher sitting height makes it easier to rise and can be used in city traffic, where the passenger sits for shorter times. ■ Seats are to be placed in such a way that there is a free distance of at least 230 mm from the foremost part of the seat cushion to the rearmost part of the seat in front. ■ Handgrips at the seat should have a horizontal member and be placed approximately 230–300 mm in front of the foremost part of the seat cushion and approximately 850–1100 mm above the floor. Vertical members can also be of use. ■ The cross section of the handgrips should be approximately 30 mm (25–35 mm) in diameter and well rounded off.

370 ANTHROPOMETRY FOR THE DISABLED

Figure 12.15 Recommended dimensions in mm for steps and handrails in a bus (after Petzall, 1993).

■ Armrests should be placed approximately 200–250 mm above the seat. It should be possible to fold armrests back so that they are out of the way. Anthropometric investigations aimed at determining the dimensions of the seat for the elderly were conducted by the Canadian scientists Holden and Fernie (1989). As the result of investigations and appropriate tests the authors obtained data for design and on this basis they developed a three-dimensional model of the seat. The dimensions of the seat are presented in Table 12.8. It should be mentioned that the seat was designed for elderly people, who spend long periods of time in the sitting position, rarely going out.

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Figure 12.16 Recommended dimensions in mm for seats in a bus (after Petzall, 1993).

As the review of investigations has proved, the body structure of disabled men and women differs considerably from that of the healthy population. Anthro Table 12.8 Dimensions of a chair for the elderly in institutions (after Holden and Fernie, 1989). Chair feature

Recommended

Minimum Maximum

Seat height (front) Seat rake (angle to horizontal) Seat depth Seat width Angle of backrest to seat Armrest height (front) Armrest height (back) Armrest separation Armrest protrusion from front seat to edge Armrest width Footrest angle

470mm 9° 430 mm 500mm 102° 730mm 250mm 460 mm 120mm 120mm 9°

470mm ? 430mm ? 100 720mm 230mm ? ? ? 6°

490mm 9° 450 mm 500 mm ? ? 250mm ? ? ? 9°

pometry, providing data concerning the body structure of disabled people, makes it possible to adjust designs of products and spatial structures to the possibilities and predispositions of this group of users. 12.3.1.2 Methods of reach zones determination Methods of reach zones determination used in anthropometry have mainly concerned the healthy population (Damon et al., 1966; Bullock, 1974; Nowak, 1978). Investigations were done on specially designed measuring stands and the

372 ANTHROPOMETRY FOR THE DISABLED

results of investigations constituted data for designing workstands (Nowak, 1978) or cockpits and control desks of aircraft (Damon et al., 1966; Bullock, 1974). It seems that investigations of this kind would be too arduous for the disabled. For that reason Das and Grady’s (1983) method appears to be very useful in this case. The method determines workspace within two planes— sagittal and transverse. Using the results obtained for the healthy population by means of experiment (Nowak, 1978), it was possible to modify the above method (Nowak, 1989) and use this method for the needs of the disabled. Though the method determines the upper extremities reach zones within two planes only, it is very simple, and helps determine the above zones by several simple anthropometric measurements without using expensive apparatus. The following somatic measurements were used to determine workspace for arm movements in the sitting position: A—Stature G—Trunk depth M—Arm overhead reach N—Arm reach forward W—Lateral reach Following Das and Grady (1983), a similar principle using percentile values was accepted. Thus the fifth percentile was used for arm overhead reach (M), arm reach forward (N) and lateral reach. The values of the 95th percentile were used for stature and trunk depth (G). The method determines workspace in the transverse and sagittal planes. The maximum reaches comprise the following planes: maximum transverse reach (MTR) and maximum sagittal reach (MSR). Figures 12.17 and 12.18 show the graphic way to determine maximum transverse reach (MTR) and maximum sagittal reach (MSR) planes. In order to describe the two reaches we should calculate reach radius (K) and determine the pivoting point (P). Reach radius (K) was calculated as the difference between the dimensions of arm overhead reach (M) and one-half of trunk depth (G). P point is an empirically determined starting point of reach radius (K) and constitutes the hypothetical pivoting axis in the shoulder joint. Its position in relation to the plane of the back of the seat (Bsd) is determined by a line parallel to the plane and drawn in the distance of one-half of trunk depth (G). The position of P point in relation to the body axis is measured by K radius drawn from the extreme value of lateral reach while determining MTR and from the extreme value of arm overhead reach while determining MSR. Consistently using the principles of the above discussed method, MTR and MSR were drawn for motor-efficient youth of the same age group (15–18 years old). All-Polish data obtained by Nowak (1988) were used. The comparison of the two reaches is presented in Figures 12.17 and 12.18. The difference between MTR, MTR’ and MSR, MSR’ reaches was marked with lines. The differences in maximum reach measurements were significant and amounted for the fifth percentile to 30 cm. Results of the study were used for

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Figure 12.17 Maximum Transverse Reach for the disabled population (MTR) and allPolish population MTR’).

ergonomic analysis at school and for designing school workshops, laboratories and rehabilitation centres. This method can be recommended for workspace design for the disabled. It is simple and easy to use. Using only five anthropometric characteristics we can obtain the graphic representation of the workspace of any population or individual. 12.3.2 Rehabilitation 12.3.2.1 Assessment of physical development Assuming efficiency as a criterion of evaluation, with regard to psychical and physical characteristics, the population can be divided into three groups: ■ people of high efficiency ■ people of ‘normal’ efficiency ■ disabled people. From the viewpoint of anthropometry, each one of these groups has a different somatic structure. The differences between the body structures of the able-bodied and people with disabilities have been discussed previously. The aim of this section is to show the role of anthropometry in the assessment of the physical development of children, including those who are disabled. In order to check and assess the process of children’s physical development biological reference systems, the so-called standards, are developed. The values of standards are determined on the basis of population investigations, embracing

374 ANTHROPOMETRY FOR THE DISABLED

Figure 12.18 Maximum Sagittal Reach for the disabled population (MSR) and all-Polish population (MSR’).

people qualified as ‘normally’ efficient. Standards are prepared with the use of mathematical and statistical methods. The statistical population standard is considered the range that comprises the majority of individuals and thus they occur most often within the population values of particular characteristics. The m-3S value is considered to be the physiological boundary value of the statistical population standard. It is the conventional limit of normality. However, it should be mentioned that there is practically no distinct boundary between normality and pathology. Besides, there is a wide range of subpathological states. In order to assess physical development of children’s populations or individuals, developmental standards are prepared. These standards can represent national or regional populations (countryside—cities, industrial areas and rural areas). Also, the so-called target standards are developed (for example, in Poland). They are prepared on the basis of selected data, considering social and economic conditions of the chosen population (for example, in Poland these are cities with large populations). Target standards reflect the maximum genotype values of the population, which develop in optimum environmental

EWA NOWAK 375

conditions. Thus this is the model to aim at, applying adequate preventive activities in order to level-up environmental differences. Developmental standards are presented in the form of percentile nets (see Section 12.2.2). For the needs of pediatrics two border regions of developmental standards are distinguished: ■ the so called narrow developmental standard, comprising values between the 25th and the 75th percentile and covering 50 per cent of all observations; ■ the so-called wide standard, comprising values between the 10th and the 90th percentile and embracing 80 per cent of the observations (children included within these limits need the observation and concern of a pediatrician). Developmental standards can also be used to assess the physical development of disabled children. Rehabilitation activities include, among others, the monitoring of somatic development, aimed at the assessment of the child’s biological potential. The development of a child depends not only on his genetic potential, but also on environmental conditions. As the result of disadvantageous events, which can take place during the ontogenesis, injuries inducing disturbances in the nervous system activity, growth or functioning of the whole body or its part can occur. Biological reactions of the body depend first on the releasing factors, that is, diseases and personal injuries. These factors have a direct effect on the development of the body, but reactions of the body are also indirectly influenced by other factors, such as the type of medicine and the schedule of its application, as well as undertaking rehabilitation. Important factors, which influence the process of development, are the time of disorder occurring and the kind of factor that caused the disorder. Approaching the assessment we should analyse and determine possible ways of the child’s physical development. Developmental standards can be helpful in a single assessment of a child, as well as in continuous investigations; they can also be used in determining the differences between the development of the body structure characteristics of the children with deviation and those of healthy children of the same age. The assessment is usually done with the use of the percentile nets representing the height and body mass characteristics. In a single assessment of the child’s development we determine the position of the child on the percentile net for the above characteristics and we determine the channel, in which this point is located. Based on the values of the two characteristics we can determine normality or disorders in the body proportions, for example, the child can have big body mass (it is in the channel between the 97th and 90th percentile) and low height (between the 10th and the 25th percentile). If we test the child regularly, we obtain the individual curve of their development. Figure 12.19 shows the example of the curve of development of a child, who at the age of 10 fell ill with poliomyelitis.

376 ANTHROPOMETRY FOR THE DISABLED

Percentile nets are also used to illustrate the differences between the disabled population and the population qualified as biological standard. Figure 12.20 presents the values of the seated stature of boys with celebral palsy against the values of the all-Polish population (Wężyk, 1989). The majority of authors conducting investigations of the disabled children (Samsonowska-Kreczmer, 1988; Nowak, 1988, 1989; Mięsowicz, 1990; Łuczak et al., 1993; Lebiedowska et al., 1990) emphasize the fact of their somatic dissimilarity in comparison with healthy children of the same age. Children with motor dysfunction are shorter, have very narrow hips and laterally flattened chest. They are similar to healthy children in that they have the same shoulder dimensions. They have a low body mass, and this deficiency increases with age. Łuczak et al. (1993), on the basis of their investigations of children with celebral palsy, proved that mass deficiency in 18-year-olds amounts to approximately 25 per cent. The majority of the authors cited above stress the fact that narrow hips and laterally flattened chest are undoubtedly conditioned by limitation of motor functions and by the taking over of these functions by the upper extremities in the case of a wheelchair or orthopedic device use. It should be added that such shape of the chest causes certain health difficulties. It was found that children with celebral palsy (Łuczak et al., 1993) fall ill with infections of the upper respiratory tract more often than other children of the same age. This fact can have a negative effect on the whole of the developmental process. Mięsowicz (1990) and Łuczak et al (1993) proved in their investigations that there is a correlation between the motor dysfunction and the deviation from the standard values of the somatic characteristics. The bigger degree of the motor dysfunction is correlated with the bigger values of standard deviations. The improvement of this function in the rehabilitation process influences in a indirect way the whole of the physical development. Scientists from the Child Health Center in Warsaw developed mathematical models allowing the objective assessment of the child’s development as the result of the conducted rehabilitation process (Lebiedowska et al., 1994). The mathematical models were based on the experimental data of the measurements which had been performed on healthy children aged 6 to 18 years. This method is being applied in the Center both by pediatricians and persons who carry out rehabilitation. In conclusion we can state that anthropometry is useful in the process of the physical development assessment of disabled children. The assessment is based on biological reference bases, that is, standards developed in the form of percentile nets or mathematical models.

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Figure 12.19 Curve of the development of the child with poliomyelitis.

12.3.2.2 Methods of assessing rehabilitation progress Rehabilitation is a complex and complicated process. It consists of restoring, to the maximum possible degree, the motor efficiency of the human body. Rehabilitation employs many means and research techniques used in various fields of science, such as medicine, sociology, psychology, mechanics and

378 ANTHROPOMETRY FOR THE DISABLED

Figure 12.20 Body height of the boys with celebral palsy against the all-Polish population (after Wężyk, 1989).

biology. It would seem that rehabilitation processes could also benefit from drawing more freely on the achievements of anthropometry. The objectives of this section are to present the methods of dynamic anthropometry used in ergonomics and put forward proposals for suitable modification of those methods to satisfy the requirements of rehabilitation processes.

EWA NOWAK 379

Anthropometry can be particularly useful in diagnosing and assessing the motor efficiency of the human body. Rheumatic diseases and mechanical injuries result in pathological changes in joints, ligaments, tendons, muscles, and lead to considerably restricted movement ranges. Thus, the assessment of motor efficiency of the affected joints is essential for monitoring the rehabilitation processes. The simplest way of assessing motor efficiency is by comparing a restricted motion range of an affected joint with its initial range of motion, that is, before injury or disease. Unfortunately, after injury or disease has already prevailed, it is impossible to determine what was the initial motion range in the healthy patient. It may hardly be expected that a rehabilitated patient had his initial motion ranges measured just before the injury. Thus, motor efficiency of a rehabilitated patient can only be assessed based upon data of the healthy population. A method based upon this kind of data and allowing the quantitative assessment of rehabilitation progress was developed by Nowak (1992). The results of investigations conducted for the needs of ergonomics were used. The investigations comprised ranges of motion of arm, leg, hand, foot and head. The following maximum movements were measured: ■ flexion and extension of the arm and leg ■ flexion and extension, adduction and abduction, supination and pronation of the extended hand ■ flexion and extension, supination and pronation of the grasping hand ■ flexion and extension, adduction and abduction of the foot ■ flexion and extension, bending to the right and left, turn right and left of the head. Motion ranges for these movements were measured by means of a set of measuring devices. One example of the device is shown in Figure 12.21. The investigations embraced 355 men and 215 women aged 18–65. The results of the investigations were used to calculate standards, that is, biological bases of reference for particular motion ranges. Standards were developed for three age categories and adequate subordinate classes of movements. These are: Age groups 1 18 to 30 years 2 31 to 40 years 3 41 to 65 years Motion classes 1 Wide range of motion (W) 2 Average range of motion (A)

380 ANTHROPOMETRY FOR THE DISABLED

Figure 12.21 Measuring of movement ranges of the hand.

3 Small range of motion (S) The following formulae were used to calculate the ranges of motion in three classes (Batogowska, 1977): W—Wide range of motion A—Average range of motion S—Small range of motion Values of for i=0, 1, 2, 3 were found from equations:

Where: P5—value of the fifth percentile

W=( 1, 2,) A=( 2, 3,) S=( 3, 4,)

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P95—value of the 95th percentile x—average value s—standard deviation Angular values of movement ranges of the hand are shown in Table 12.9. It includes the values attained by a healthy population of adults aged between 18– 65. The values of movement ranges are grouped in three motion classes, that is, from the maximum to the minimum value—classes ‘W, A and S’. In each class minimum and maximum extreme values are given, calculated according to formulae given earlier. Three age categories are subordinated to the classes of movement shown. The youngest persons, aged 18–30, belong to class W, characterized by the maximum values. Class A includes adults aged 31–40, and class S includes the eldest subjects, aged 41–65, whose movement range in particular joints has the smallest values. The values of movement ranges for particular classes shown in the table can be practically applied in the rehabilitation process. If the age of a patient is known we can read from the table the value of a range of movement in a given joint that can be attained by the joint, the range of movement that it should have prior to their injury. The maximum value is particularly significant in our case. It shows the angular value that should be aimed at in the rehabilitation process. The maximum value of range movement provides a basis for the evaluation of rehabilitation progress in a selected age group and is expressed by . After assessing the value , the value of the range of movement of a subject investigated before the rehabilitation process should be defined. This state is denoted by the symbol ’and is indicated by measurement, using a suitable protractor. The final step is to define the ‘decrease in the movement range’. Knowing the values and ’ we can calculate the absolute decrease in the movement range (Ar), and a percentage decrease in the movement range (Pr) using the following formula:

The value of a percentage decrease in movement range (Pr) is inversely proportional to the ability of movement (Ab) which can be defined by the equation: The above values Ar, Pr and Ab provide a basis for a direct evaluation of the progress of the rehabilitation process. Based upon the above the motion ability can be assessed in many various stages of rehabilitation. This assessment may be employed in: ■ diagnosing a disease ■ evaluating progress and monitoring the rehabilitation process and ■ determining a permanent decrease in movement ranges.

382 ANTHROPOMETRY FOR THE DISABLED

Figure 12.22 Ankle joint rehabilitation process.

The assessment may be either continuous or administered at random, depending upon the requirements. The application of the method described above is presented on a graph (Figure 12.22) which shows the rehabilitation process of an ankle joint. Considerable movement restriction was caused by injury to the Achilles tendon and surgery followed the injury. Measurements were taken by the protractor for measuring foot movements in sagittal plane-type KPS. The results of systematically taken measurements of foot extension, shown in Figure 12.22, illustrate a process of gradual improvement. Percentage angular decrease in the range of foot extension was 14 per cent. Thus, the ‘post-injury’ efficiency of the ankle joint can be determined as 86 per cent. Motion efficiency of individual movements can be assessed using different scales, depending upon requirements, disease and general mobility. The scale is also dependent upon individual preferences of an assessor. Scales of three, five or ten grades may be used in assessing the motion efficiency. A five-grade scale may be considered optimal after Zeyland-Malawska et al. (1968): ■ very good: decrease up to 20 per cent—efficiency from 80 per cent; ■ good: decrease up to 40 per cent—efficiency from 60 per cent; ■ poor: decrease up to 60 per cent—efficiency from 40 per cent;

EWA NOWAK 383

■ very poor: decrease more than 60 per cent—efficiency less than 40 per cent. The above proposal does not preclude applications of other assessment scales, which may be found convenient. The measurement of force is, beside motion ranges, one of the parameters determining the efficiency of man. Ergonomics studies the amount of force exerted by the hand or foot. The results of investigations are used in designing hand- or footoperated control devices. Some of the results can be used in rehabilitation, for example, for the assessment of the efficiency of an impaired organ or organ with dysfunction resulting from a disease. The assessment is based, as in the case of motion ranges, on the standards of force range, developed with the use of data concerning the healthy population. These standards make biological bases of reference to be striven for by a person increasing the efficiency of an impaired organ. Investigations conducted by many scientists confirm the fact that there is a correlation between the exerted force and circumferential measurements as well as body weight (Laubach and McConville, 1966; Hunsicker and Greey, 1970; Sulisz, 1975; Malinowski, 1975; Nowak, 1980, 1989; Jarosz, 1993; Łuczak et al., 1993; Batogowska, 1993). Persons with motor dysfunction (as shown in Section 12.3.1.1) have lower values of somatic characteristics—the same concerns children and young people. Rehabilitation makes it possible to increase the efficiency of particular motor organs and activate respective groups of muscles. Measurement of force can be an excellent indicator of rehabilitation progress. Following such drift of thoughts, the measuring stand to test hand efficiency was developed in the Institute of Industrial Design in Warsaw (Nowak, 1995). This efficiency is determined, among others, by measuring the force exerted by hand grasping a cylindrical grip. The principle of measurement is based upon the hydraulic system. The measuring system cooperates with a computer unit. The appropriate program makes it possible to calculate and visualise tested parameters. The subject can watch the effect of measurement on the monitor. This can increase motivation to achieve better results when the stand is used as a rehabilitation device, creating natural biofeedback. In the case of children, rehabilitation progress can be stimulated by games. There is a special computer program developed for this purpose. The increase of motor efficiency is an important factor in the rehabilitation of children with celebral palsy. Myszkowski and Stçzala (1989) put forward a proposal of an interesting testing stand. It consists of a set of control devices— manipulators using the handgrip function to perform repeated movements. The set of manipulators and the respective psychomotor computer tests allow the investigation and rehabilitation of children regardless of the degree of motor dysfunction of the hands. The examples reported here prove that the methods used in anthropometry are useful in the rehabilitation process. These methods as well as the results of

384 ANTHROPOMETRY FOR THE DISABLED

investigations can be used for assessing an impaired or injured organ. Measuring stands can serve as rehabilitation devices. 12.4 Conclusion As the system of measuring methods and technologies, anthropometry in its classical form acts for the benefit of anthropology. Ergonomics takes advantage of the practical application of anthropometry. Developing together with ergonomics, anthropometry has created new measuring technologies and methods. Based on them, anthropometric data are being developed. They constitute a basis for designing products adjusted to the physical abilities of contemporary man. Anthropometry, providing data about man, participates in shaping the working and living physical environments of man. On the grounds of methods used in classical and ergonomic anthropometry, new research technologies, aimed at the disabled man, are developing. Anthropometry is widely used in the field of rehabilitation ergonomics. Providing data about the body structure of the disabled, anthropometry ensures the adjustment of designed products and spatial structures for the possibilities and predispositions of this group of users. This is the field of equalization, one of the three phases of the World Program of Action for the benefit of the disabled, developed by the World Health Organization (WHO). Anthropometry is also useful in another very important phase of this program, called rehabilitation. This concerns all anthropometric methods and findings allowing the quantitative assessment of the rehabilitation process and the assessment of the physical development of disabled children. References BATOGOWSKA, A. (1993) Hand force quantities of children and the young. Institute of Industrial Design. Works and Materials, 147, Warsaw. BOUISSET, S. and MOYNOT, C. (1985) Are paraplegics handicapped in the execution of a manual task? Ergonomics, 28 (7), 299–308. BOUSSENA, M. and DAVIES, B.T. (1987) Engineering anthropometry of employment rehabilitation centre clients. Applied Ergonomics, 18 (3), 223–8. BUJAKIEWICZ, A. and MAJDE, A. (1978) Biostereometry, i.e. medical application of photogrammetry. Polish Medical Weekly, XXXIII (11), 451–4. BULLOCK, M.J. (1974) The Determination of Functional Arm Reach Boundaries for Operation of Manual Control Ergonomics, No 3, pp. 375–88. BUSKIRK, E.R., ANDERSEN, K.L. and BROZEK, J.. (1956) Unilateral activity and bone and muscle development in the forearm. Research Quarterly, No. 27, pp. 344–56. DAMON, A., STAUDT, H.W. and MCFARLAND, R.A. (1966) The Human Body in Equipment Design. Cambridge: Harvard University Press.

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DAS, B. and GRADY, M. (1983) Industrial work place layout design. An application of engineering anthropometry. Ergonomics, 26 (5), 433–47. DAS, B. and KOZEY, J. (1994) Structural Anthropometry for Wheelchair Mobile Adults, Toronto: 12th Triennial Congress of IEA, vol. 3 (Rehabilitation Ergonomics) Human Factors Association of Canada, 63–5. DIFFRIENT, N., TILLEY, A.R. and BARDAGJY, J.G. (1974) Humanscale 1/2/3, Cambridge (Massachusetts): The MIT Press. FLOYD, W.F. (1966) A study of the space requirements of wheelchair users. Paraplegia, 1 (4), 24–37. GOLDSMITH, S. (1967) Designing for the Disabled. London: RIBA Publications. GOSWAMI, A. (1994) Application of anthropometry in mobility aid design a developing country perspective. 12th Triennial Congress of IEA, Toronto, vol. 3 (Rehabilitation Ergonomics), pp. 55–7, Toronto: Human Factors Association of Canada. GOSWAMI, A., GANGULI, S. and CHATTERJEE, B.B. (1987) Anthropometric characteristics of disabled and normal Indian men. Ergonomics, 30 (5), 817–23. GRABOWSKA, Z., SALWA, J. and SEYFRIED, A. (1986) Studies on the work zone limitation in patients with rheumatoid arthritis. Informative Newsletter, Research Department of ZSI , 5, pp. 7–11. HAMILTON, N. (1983) ‘Optimal location of ovens for wheelchair users: an ergonomic approach’. MSC Dissertation, Ergonomics Unit, University College London. HOLDEN, J.M. and FERNIE, G. (1986) Specification for a mass producible static lounge chair for the elderly. Applied Ergonomics, 20 (1), 187–99. HUNSICKER, P. and GREEY, G. (1970) Studies in human strength. Research Quarterly, 2, 109–22. JAROSZ, E. (1990) Anthropometric data of the young with motor organ dysfunction. Institute of Industrial Design News—Design, 2, pp. 6–9, Warsaw. JAROSZ, E. (1993) Anthropometric data for workspace design for the disabled using the wheelchair. Institute of Industrial Design, Works and Materials, 146, Warsaw. JAROSZ, E. (1994) Anthropometric data of wheelchairs users for designers. 12th Triennial Congress of IEA, Vol. 3 (Rehabilitation Ergonomics), pp. 60–62, Toronto: Human Factors Association of Canada. KARAGELIS, J. (1982) ‘An ergonomics evaluation of proposed kitchen worktops for wheelchair disabled.’ MSC Dissertation, Ergonomics Unit, University College London. KUMAR, S. (1992) Rehabilitation: An ergonomic dimension. International Journal of Industrial Ergonomics, 9 (2) 97–108. LAUBACH, L.L. (1981) Anthropometry of aged male wheel-dependent patients. Annals of Human Biology, 8 (1), 25–9. LAUBACH, L.L. and MCCONVILLE, J.T. (1966) Muscle strength, flexibility and body size of adult males. Research Quarterly, No. 3, 384–92. LEBIEDOWSKA, M.K., GRAFF, K., SYCZEWSKA, M., KALINOWSKA, M., POLISIAKIEWICZ, A. and LEBIEDOWSKI, M.J. (1994) Mathematical models as a method of child growth process assessment. 12th Triennial Congress of IEA, Toronto, vol. 3 (Rehabilitation Ergonomics), pp 52–4. ŁUCZAK, E., MIĘSOWICZ, I. and SZCZYGIEŁ, A. (1993) Somatic characteristics of children and the young with celebral palsy. AWF Cracov, Scientific Annals, XXVI, 121–42.

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MALINA, R.M. (1980) Influence of physical training on selected tissues, dimensions and functions of the body during ontogenesis. Physical Training and Sports, No. 1, 3–35. MALINOWSKI, A. (1976) Differentiation of muscular force of the right and left hand in adult men and women according to the age. Poznań, Academy of Physical Training Mono-graphs, No. 8. MIĘSOWICZ, I. (1990) Somatic development of handicapped children. Annals of Special Pedagogics , 1. MIROWSKA-SKALSKA, A. (1995) ‘Set of furniture for storing with regard to the disabled’. Academy of Fine Arts, Warsaw, (Doctor’s thesis, unpublished). MOLENBROEK, J.F.M. (1987) Anthropometry of elderly people in The Netherlands, Research and Applications. No. 18.3, pp. 187–99. MORECKI, A., EKIEL, J. and FIDELUS, K. (1971) Movement Bionics. Warsaw: PWN. MYSZKOWSKI, R., and STĘŻAŁA, D. (1989) Scientific system for measuring the level of psychomotoric efficiency of children with celebral palsy, Technical Tasks of Medicine, XX (3), 166–76. NOWAK, E. (1976) Determination of the upper extremities workspace for the needs of workstands design. Institute of Industrial Design, Works and Materials, 30, Warsaw. NOWAK, E. (1978a) Dynamic anthropometry for the needs of rehabilitation. Institute of Industrial Design, Works and Materials, 47, Warsaw. NOWAK, E. (1978b) Determination of the spatial area of the arms for workplace design purposes. Ergonomics, No 7, 493–507. NOWAK, E. (1980) Minimum foot forces for designing foot operated control devices, Institute of Industrial Design, Works and Materials, 55, Warsaw. NOWAK, E. (1988a) Workspaces for the disabled. Data for design purposes, Institute of Industrial Design, Works and Materials, 129, Warsaw. NOWAK, E. (1988b) Physical development of children and the young aged 4–18. Data for design purposes. Institute of Industrial Design, Works and Materials, vol. 75, Warsaw. NOWAK, E. (1988c) Method of workspace determination. Institute of Industrial Design News, 1, 3–8. NOWAK, E. (1989) Workspace for disabled people. Ergonomics, 9, 1077–88. NOWAK, E. (1990) Ergonomics for needs of elderly and disabled people. Collegium Antropologicum, 14 (2), 293–301. NOWAK, E. (1992) Practical application of anthropometric research in rehabilitation. International Journal of Industrial Ergonomics, 9, 109–15. NOWAK, E. (1994) Anthropometric measurements of the young for the needs of clothing design. 12th Triennial Congress of IEA, Vol. 3 (Rehabilitation Ergonomics), pp. 58–9, Toronto: Human Factors Association of Canada. NOWAK, E. (1995) Workstand for measuring hand efficiency. Materials of the Conference of PTF Physiotherapeutists of the Hand, Poznań, September 21–23. PETZALL, J. (1993) Ambulant disabled persons using buses: experiments with entrances and seats. Applied Ergonomics, 24, 313–26. PHEASANT, S. (1986) Bodyspace. Anthropometry, Ergonomics and Design. London and Philadelphia: Taylor & Francis. PRIVES, M.G. (1969) Influence of labour and sport upon skeletal structure in man. Anatomical Record, 1, 51–62. PRZYBYLSKI, B. (1979) Flats for the Disabled. Warsaw. Publishing House of CZSBM.

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SAMSONOWSKA-KRECZMER, M. (1988) Measurements of disabled young people. Data for clothing design. Institute of Industrial Design News, 4, 5–8. SAMSONOWSKA-KRECZMER, M. (1990) Anthropometric Measurements of Children with Celebral Palsy. Warsaw: Institute of Industrial Design. STEENBEKKERS, L.P. and MOLENBROEK, J.F.M. (1990) Anthropometric data of children for nonspecialist users. Ergonomics, 33, (4) 421–9. SULISZ, S. (1975) Determination of the young men and women general force with the use of the dynamometric method. Anthropological Materials and Works, 89, 49–80. THOREN, M. (1994) Clothing Made to Fit the Disabled Users. 12th Triennial Congress of IEA, Toronto, vol. 3 (Rehabilitation Ergonomics), pp. 187–9, Toronto: Human Factors Association of Canada. WĘŻYK, E. (1989) ‘Physical development of children and the young with celebral palsy’. Master’s thesis, Wrocław: Department of Anthropology of Wrocław University. WOLAŃSKI, N. (1983) Biological Development of the Man. Warsaw: PWN. WORLD PROGRAM OF ACTION FOR THE BENEFIT OF THE DISABLED. Problems of Occupational Rehabilitation, CNB CZSI, No. 4. ZEYLAND-MALAWSKA, E., GŁADKOWSKA, E., HENICZ, T. and DOMAŃSKA, B. (1968) Method of investigation and assessment of motion range and usefulness of the land. Physical Culture, 6, 246–56.

CHAPTER THIRTEEN Anthropometry of people with disability ASIS GOSWAMI

13.1 Introduction Awareness of human anatomical limitations in designing the machinery for human use has grown very fast over the last few decades. This has led researchers to measure the physical dimensions of different people and their application of body dimensions in the design process. The process of rehabilitation has many facets depending upon the nature of disability. It is important to understand that the demands of a blind person and a paraplegic with visual ability will not be the same in respect to the mobility aid. This incongruity prevailing in rehabilitation has made it difficult to render the research work from one type of disabled person to another. The major concern in rehabilitation is to provide suitable aids for mobility and other daily living activities. The development and design of aids for the disabled require data regarding the loss of functional abilities in them and the physical dimensions. Despite scattered attempts in some specific areas, the data about the physical dimensions of the physically disabled is not sufficient (Floyd et al., 1966; Goswami et al., 1987; Nowak, 1989). This is probably due to the wide variations in the nature of disabilities encountered and the frequent need for the personalized designs of aids. However, personalized designs of aids like a wheelchair or tricycle would affect the demand and supply chain negatively and might leave many people nonrehabilitated in the end. This is a good reason for making such aids with average body dimensions in mind. Some important areas, relating to the anthropometric characteristics of the disabled, will be discussed in the following sections. The chapter has been divided into three major parts: the first deals with measurement techniques; the second describes the available literature and data on the disabled. The third part deals with the application of anthropometric data in various design processes. In addition, a special section has been added to examine the suitability of classification methods for the disabled.

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 389

13.2 Techniques of anthropometric measurements for the disabled 13.2.1 Representative population It is difficult to assess the relative presence of a particular disability in the world population. It is estimated that in the orthopedically disabled population the highest percentage is contributed by the lower extremity disabled. Most of the studies relating to the anthropometry of the disabled had focused on persons with lower extremity involvement only (Table 13.1). Since the percentage of the disabled persons is low, they remain extremely scattered in the normal population. It is difficult to locate them unless they appear in rehabilitation centers. This becomes a constraint to include several disabled persons in the measurement process. Sometimes the observer has to travel long distances with measuring devices to cover a representative population (Goswami, 1987). Nearly all the studies reported were restricted to one rehabilitation center (Nowak, 1989; Floyd et al., 1966) or one city (Atreya, 1988; Nag et al., 1982) and relate to a specific subject, for example, work space requirement. The only study which tried to induct statistical techniques to select appropriate sample size was by the Institute for Consumer Ergonomics (1981). This study had provided insight on the selection of representative populations and the size of the population, although it was also restricted to a zone of the UK. The sample size was highest in this study (n=502). In a recent presentation, data on 170 disabled persons was reported on a Polish population (Jarosz, 1994), but this was Table 13.1 Demographic information from various studies on the anthropometry of the disabled. Studies

Total number of disabled

Number of males

Number of females

Age group (yrs)

Nature of disability

Floyd et al., 1966 Institute for Consumer Ergonomics, 1981* Nag et al., 1982 Goswami et al., 1987

127

76 15 Not known

28 8 Not known

18–70

Paraplegic Tetraplegic Lower extremity disabled

9 2 61

−

22.2 (1.4) 24.4 (3.8)

502

11 61

−

<65

Post-polio paraplegic Post-polio spinal cord injury

390 A.GOSWAMI

Studies

Total number of disabled

Number of males

Number of females

Age group (yrs)

Nature of disability

Atreya, 1988

30

18

12

16–50

Nowak, 1989

77

32

45

15–18

Das and Kozey, 1994 Jarosz, 1994

62

42

20

20–64

Lower extremity disabled Systemic deformity, motor organ diseases Spinal cord injury

170

101

69

18–39

Spinal injury, cerebral palsy and muscular dystrophy

* The publication referred to does not provide details.

also from only one rehabilitation center. The number of persons included in the study by Goswami et al. (1987) was higher than the other two from India. Considering the total population of India the sample may not represent the target population. The anthropometric data were described for both the male and female groups separately. Exceptions are found in the studies reported from India. Two studies had included only a male group (Nag et al., 1982; Goswami et al., 1987) and one study had reported mixed data (Atreya, 1988). The existence of significant differences between the male and female in anthropometric dimensions was established in many studies. Mixed data will possibly be poor in applicability, especially where the sample size is small. In addition, the age group of the disabled persons covered under these studies varied to a large extent (Table 13.1). In only one study the adolescent age group was considered (Nowak, 1989). The age of the disabled is an important consideration which had been overlooked in anthropometric studies. Obviously a person becoming disabled due to neural diseases at a pre-adolescent age will differ in body dimensions to a person with a similar affliction at postadolescent age. Anthropometric data taken on different age groups are not thus comparable except to highlight the differentiation in growth patterns. The available data on anthropometric dimensions has encompassed a large age group and therefore could not be a model data to provide good design solutions. It is also not possible to suggest the degree of hypertrophy or atrophy due to disturbances in development or training effect.

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 391

13.2.2 Body dimensions Anthropometric studies on disabled persons provide a variety of methodological problems. It has been commonly said that they require special measuring equipment or the dimensions measured differ from the normal population measurements. A comparison of the body dimensions measured on the disabled population in several studies is given in Table 13.2. A total number of 58 different dimensions were measured in the reported studies. Most interestingly, not a single measurement was found common to all six studies. A large number of measurements were found in only one study. This shows a selective nature of requirement by the disabled persons (Nowak, 1994). Among these studies only one was targeted to identify characteristic differences of the disabled from the normal population (Goswami et al., 1987). The rest were concerned with specific design-related anthropometric dimensions. Design of the facilities and the supporting aids for the disabled require special consideration to accommodate the functional shortcomings. This is one reason for the variation of technique and dimensions measured in different studies. It is also clear that the reported studies have differences in the measurement terminology. It is a fact that as a result of disease or trauma the body parts of the disabled person become deformed and subcutaneous fat distribution changes (Feeney and Galer, 1984). Standard landmarks used for the normal population becomes inappropriate for the disabled person. It is also doubtful that a person with severe lower limb muscle wasting and concomitant contracture will be able to stand erect to allow a stature measurement. Unfortunately, not a single study could be found which had made an attempt to standardize the landmarks and measurements. Available studies have either used the definitions of the measurement applicable to normal persons or have devised a new Table 13.2 Comparison of anthropometric dimensions measured on disabled persons in various studies. Floyd et al., 1966

Institute Nag et for al., Consume 1982 r Ergonom ics, 1981

Goswami Atreya, et al., 1988 1987

Nowak, 1989

Das and Kozey, 1994

Jarosz, 1994

Stature

Seated stature

Stature

Stature Palm height Floor to vertex

Body height sitting

Sitting height

392 A.GOSWAMI

Floyd et al., 1966

Floor to eye

Institute Nag et for al., Consume 1982 r Ergonom ics, 1981 on the floor SP to back of the head SP to C7 SP to eye

Floor to shoulder

Floor to elbow

Floor to thigh

Goswami Atreya, et al., 1988 1987

Acromia l height SP to lowest back contact SP to max. lumber concavit y SP to undersid e of elbow Thigh thicknes s

Nowak, 1989

Das and Kozey, 1994

Jarosz, 1994

Eye height

Eye height

Eye height

Shoulde r height

Shoulde r height

Shoulde r height

Elbow rest height

Elbow height

Fore arm height

Elbow height

Thigh clearanc e

Thigh thicknes s Knee height

Knee height

Thigh thicknes s Knee height

Eye level height Acromi on height Subscap ular height Lower lumber height

Elbow rest height

Vertical seat height

Popliteal height Points of back contact BP to back of head

Popliteal height

Popliteal height

Popliteal height

Popliteal height

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 393

BP to C7 BP to max. lumber concavity Maximum abdominal protubera nce BP to back of buttocks Back of elbow to wrist Back of elbow to knuckles Horizontal seat depth Buttock knee length Buttock knee length Total arm length Upper arm length Lower arm length

Trunk depth

Buttock popliteal length Buttock popliteal length

Trunk depth

Trunk depth

Buttock popliteal length

Radial arm length Foot length

Floyd et al., 1966

Institute Nag et for al., Consume 1982 r Ergonom ics, 1981

Shoulde r width

Width across the shoulder s Width across the outside

Goswam Atreya, i et al., 1988 1987

Shoulde r width Bideltoi d breadth Elbow to elbow breadth

Bideltoi d width Chest width Waist width Elbow width

Nowak, 1989

Das and Kozey, 1994

Jarosz, 1994

Shoulde r breadth

Acromi on width Bideltoi d width

Shoulde r breadth

Elbow breadth

Elbow width

Elbow breadth

394 A.GOSWAMI

Floyd et al., 1966

Institute Nag et for al., Consume 1982 r Ergonom ics, 1981 of elbows

Goswam Atreya, i et al., 1988 1987

Nowak, 1989

Das and Kozey, 1994

Maximu m elbow breadth Hip width

Sitting hip/thigh width

Hip breadth

Buttock width

Jarosz, 1994

Elbow span Hip breadth

Olecran on breadth Radioulner breadth Hand breadth at thumb Hand breadth at metacar pal Foot breadth Vertical reach (max and com)

Maximu m arm grasp (v) Arm grasp (max) Arm reach from wall

Arm over head reach

Over head reach

Arm overhead reach

Maximu m arm grasp (h)

Total arm span

Arm reach forward Arms span Lateral reach

Arms span Lateral reach

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 395

Arm reach down Chest circumfer ence Arm biggest circumfer ence Waist circumfer ence Hip circumfer ence Wrist circumfer ence Thigh circumfer ence

Chest circumfer ence Midbicep circumfer ence

Arm reach down

Hand thickness at met. III Hand grip diameter (outside) Hand grip diameter (inside) Toe projection Lower leg length SP—Seat plane; Max.—Maximum; Ht.—Height; BP—Back plane; Max.—Maximum; Ht. —Height.

variable. In addition, a number of dimensions were given different nomenclature, for example, Eye level height (Nowak, 1989) was termed as seat plane to eye (Institute of Consumer Ergonomics, 1981) and Eye height (Jarosz, 1994) in contrast to floor to eye (Floyd et al., 1966). This type of change in nomenclature leads to difficulty in the comparison of data and can well be confusing (e.g. elbow rest height and its equivalents as given in Table 13.2). A number of measurements like body height (sitting on floor) (Nag et al., 1982) were possibly taken for specific reason and although such measurement could be compared with the sitting height taken by Atreya (1988) and Floyd et al. (1966), they were not the same. In the study by Nag et al. (1982) the disabled persons were polio

396 A.GOSWAMI

affected in the lower limbs. Due to severe wasting of the muscle in the lower body, such disability may hinder sitting in the chair without a foot and back support. Probably this had compelled the scientists of this study to take the sitting height from the floor. Again a number of measurements described by Das and Kozey (1994) seem to be confusing as the exact definition is not provided (for example, maximum reach height, normal reach). It is clear that a standard method of measurement and variables to be measured for the disabled population are non-existent. It seems that there is ample scope for discussion regarding the standardization of measurement dimensions; a consensus must be reached to enable comparability. Since the research data on the anthropometric characteristics of the disabled is not sufficient, a consensus on the standardization of measurements has not yet been agreed. 13.2.3 Instrumentation To compensate for the difficulties in standardizing measurement dimensions the Institute for Consumer Ergonomics developed a mobile table ISAT (Institute for Consumer Ergonomics, 1981). Because of the presence of adjustable backrest, footrest and removable armrests, this table provided the facility to position the disabled person for measurement and also ease of operation to the measurer. However, it is surprising that none of the subsequent studies took the benefit of this type of equipment. The anthropometric board as described by Floyd et al (1966) provides better fixation of the disabled person while in the chair or wheelchair, but for a large number of body measurements the anthropometer is the best answer. Photographic method utilized by Das and Kozey (1994) may not be as accurate (a few measurements were expressed as negative values) compared with direct measurement. 13.3 Studies on anthropometry of the disabled Anthropometric studies reported so far could be classified in two groups—those related to the body composition and strength and structural anthropometry for design purposes. Works on the first category are more in number although of recent times. 13.3.1 Body composition and strength All the studies with these characteristics were made for the purpose of evaluating the athletic abilities of the disabled persons and were started after the Olympiad for the Physically Disabled, held in Toronto, Canada, in 1976. It has been stated that paraplegics show a decrease in lean tissue with associated increase in body

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 397

fat (Cowell et al., 1986; Hjeltness, 1977). Contradictory findings to this view were also reported. According to Kofsky et al. (1986) the values of body mass and body fat of wheelchair-confined persons resemble those of normal persons. Coutts (1986) had found higher muscle mass and fat in disabled basketball players than in marathon runners. The body fat reported in these studies were calculated using the methods for normal individuals. Such calculation procedure is questionable since body fat distribution among the disabled may be influenced by the pathology, patterns of habitual activity and also on selection of the group (Shephard, 1988). It is expected that the strength of the upper body of the lower extremity disabled would be higher since they are used for moving the wheelchair or the body. Hypertrophy of the shoulder region was reported in a number of studies (Nakamura, 1973; Stoboy and Wilson-Rich, 1971; Kofsky et al., 1986). Higher grip strength of wheelchair athletes than able-bodied persons was also found (Gass and Camp, 1979). Differences in strength between active and non-active wheelchair-confined persons was reported by Davis et al. (1986). Some of the body composition and strength data are given in Table 13.3. 13.3.2 Structural anthropometry A compilation of anthropometric data on disabled persons has been presented in Table 13.4. To make the comparison possible the data reported by Floyd et al. (1966) was converted to the nearest centimeter and in some measurements the height of the chair has been deducted. In general, the body dimensions of the Indian population is found to be lower than the European population. Racial characteristics may be one of the reasons (Goswami et al., 1987); the contribution of the differences in the nature of disability cannot be ruled out. The Indian population mostly consisted of post-polio persons whereas the European’s was dominated by paraplegics related to neural injury. However, comparison of different studies on the Indian population indicate only minor differences in most dimensions. A similar trend is found in the European population, except in a few instances where the values presented by Das and Kozey (1994) were significantly different from the others (for example, elbow breadth). It is possible that the measurements describe a comfortable posture rather than a strict anthropometric measurement posture. Another reason for this variation may be explained by the differences in the technique, the negative values of toe height and the unusually low values of knee height found in the above study. A consensus finding among the studies is that the body dimensions of the disabled persons were smaller than normal except for the dimensions of the shoulder region. The reason for this change was attributed to the overuse hypertrophy (Goswami, 1994; Nowak, 1989). The possibility of changes in the proportional relationship of the body dimensions cannot be ruled out, specially in lower and upper part ratios (Goswami et al., 1987). The correlation between the

398 A.GOSWAMI

measurements of the disabled was found to differ as compared with normal. The presence of acquired deformity has also been reported. These deformities were the result of poorly designed mobility aids or simply for remaining mobile without any mobility aid (Goswami, 1987). Deformities among the disabled may also lead to uneven force Table 13.3 Body composition and muscular strength of disabled persons. Variables

Nag et al., Coutts, 1981. 1986. Marathon

Coutts, Davies et 1986. Non- al., 1986. Marathon Less active group

Davies et al., 1986. Active group

Kofsky et al., 1986. Male/ female

Body mass (kg)

39.7 3.2

71.6 12.6

75.1 15.3

58.6 3.4

64.1 3.5

68.4 13.8 57.8 12.0

Lean body mass (kg) Sum of four skin folds (mm) Average of four skin folds (mm) Hand-grip strength (N) Right Left Elbow flex (N.m)

33.3 2.6 27.7 3.7

30.2 7.1

45.2 2.9

39.8 5.4

32.8 2.8

Elbow ext (N.m)

Shoulder flex. (N.m) Shoulder ext. (N.m)

11.5 5.7 14.5 5.8 582 120

464 44.1

546 93.3 73 3.5 64 10.8 49 5.7 46 8.6 69 6.9 61 4.1 121 11.9 123 5.4

451 21.3 51 12.2 49 14.6 50 12.6 45 2.8 61 14.6 66 15.1 101 17.7 95 17.6

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 399

development in some joints which could be taken care of by the specific changes in clothing design. However, measurements of body circumferences has only been reported by Nag et al. (1982) and Nowak (1994). 13.4 Classification of disabled people The classification of the disabled arose mainly from the medical point of view and since the field is dominated by medical influence, ergonomists are at a disadvantage Table 13.4 Comparison of body dimensions of physically disabled persons reported in different studies. Dimensio Floyd et Nag et Goswam Atreya, n (cm) al., 1966. al., 1982. i, 1987. 1988. Male/ Male Male Mixed female Stature Sitting stature

Eye height

Shoulder height

Acromio n height Subscapular height Elbow rest height Lower lumber height Thigh clearanc e height

Nowak, 1989. Male/ female

Das and Kozey, 1994. Male/ female

Jarosz, 1994. Male/ female

85.8 6.9 79.9 5.5 74.4 6.9 68.7 5.8 56.1 5.3 52.6 4.0

84.8 7.0 75.2 6.4 73.5 6.7 64.5 6.0 57.2 6.3 51.0 5.3

86.4 5.9 78.2 5.8 76.2 5.8 67.9 6.7 58.8 5.7 52.6 5.7

22.3 3.9 22.4 5.2

21.2 6.2 18.1 4.8

22.1 4.7 20.7 4.5

139.2 17.5 84.8 5.1 79.8 5.3 73.9 5.3 69.6 5.6 55.3 3.8 51.5 4.6

21.1 3.8 19.6 5.3

76.8 2.2

76.7 5.9

66.0 6.9

47.3 6.8

45.7 5.8 38.1 4.5

18.1 2.3

17.7 3.8

17.3 2.0 16.2 3.3 14.5

9.1 3.0

12.2 2.3 12.3

10.9 2.0 10.2

400 A.GOSWAMI

Dimensio Floyd et Nag et Goswam Atreya, n (cm) al., 1966. al., 1982. i, 1987. 1988. Male/ Male Male Mixed female 3.1

Nowak, 1989. Male/ female

Das and Kozey, 1994. Male/ female

1.8

Jarosz, 1994. Male/ female 2.1

Table 13.4 (continued) Dimensio Floyd et Nag et Goswam Atreya, n (cm) al., 1966. al., 1982. i, 1987. 1988. Male/ Male Male Mixed female Lower arm length Lower leg length Foot length Shoulder width

Nowak, 1989. Male/ female

Das and Kozey, 1994. Male/ female

Jarosz, 1994. Male/ female

38.8 3.1 36.3 2.9

39.6† 2.6 35.5† 3.9 51.0 3.5 46.9 5.3

39.3 2.4 35.3 2.6

46.7 4.7 42.8 4.9 75.2 7.2 66.5 5.3

62.6 5.7 59.3 7.8

48.1 2.1 43.4 4.3 84.8 7.8 74.9 7.6

26.8 0.5 43.9 2.5 41.1 2.8 22.0 3.0 42.7 3.8 38.4 2.5

Bideltoid width Chest width Waist width Bi-elbow width

Maximu m elbow breadth

Knee height

34.9 1.6

40.2 2.1

38.1 3.2

38.2 2.7

27.1 3.3 21.9 3.5 38.8 5.2

51.2 3.6 48.7

42.5‡ − 37.1‡

53.7 4.2 46.9

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 401

Popliteal height

38.4 3.4

39.2 4.0

Trunk depth

Buttock knee length Buttock popliteal length

Total arm length Upper arm length

Hip breadth

48.4 2.6 39.9 2.8

51.4 4.1 42.5 4.4

28.3 2.2

31.8 4.9

2.8 44.4 3.5 41.6 2.7 21.7 3.2 23.4 3.2

−

24.0 2.5 18.2 2.3

49.5 3.7 48.5 3.7

3.8 44.8 3.9 34.8 4.2 26.0 4.9 25.3 3.8

54.8 5.2 49.5 4.6

74.6 1.2 34.9 0.9 35.8 3.1 36.3 4.6

Olecranon breadth Rt./lt.

32.9 8.5 32.9 3.9

8.1 0.2 8.3 0.3 9.1 0.2 8.9 0.2

Radio ulner breadth Rt./lt.

Table 13.4 (continued) Dimensio Floyd et Nag et Goswam Atreya, n (cm) al., 1966. al., 1982. i, 1987. 1988. Male/ Male Male Mixed female Hand breath at thumb Hand breadth at met. Foot breadth

9.3 1.4 8.0 0.6 8.6 1.2

Nowak, 1989. Male/ female

Das and Kozey, 1994. Male/ female

Jarosz, 1994. Male/ female

402 A.GOSWAMI

Dimensio Floyd et Nag et Goswam Atreya, n (cm) al., 1966. al., 1982. i, 1987. 1988. Male/ Male Male Mixed female

Nowak, 1989. Male/ female

Das and Kozey, 1994. Male/ female

Jarosz, 1994. Male/ female

Maximu m arm grasp (v)

117.1 9.1

124.3 10.4

117.6 9.0

107.9 7.1

109.0 8.7

103.7 9.4

149.6 13.4

143.9 8.4

145.6 9.8 123.4 10.0 74.7 5.7 63.6 4.7 72.8 4.9 61.8 5.0

9.8 3.8 8.7 2.4 88.5 − 88.9 – 27.7 − 25.8 − 80.2 − 77.3 − 94.3 − 92.6 − 44.1 −

4.7 4.3 4.1 6.3

125.2 5.8

112.5 10.5

116.3 8.4 Maximu m arm grasp (h) Total arm span

67.9 5.7

Forward arm reach

79.9 4.9

66.8 6.6 159.6 13.9

76.4 5.9 69.2 4.6 74.8 6.7 71.9 4.2

Lateral arm reach

Downward arm reach

Chest circumference

81.3 1.8

Mid-bicep circumference

24.9 1.1

Waist circumference

Hip circumference

Thigh circumference

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 403

44.9 − Hand thickness at met. III Toe projection

2.6 0.1 12.9 2.3 10.4 2.3

* The values were converted to ‘cm’ from ‘inch’. † The measurement was acromion width in original reference. ‡ The value was calculated from other dimensions given in the article, met.=metacarpal.

to target their developments for the varied nature of disabilities. Clinical classification dates back several decades. The classification terms are mainly developed to ensure correct medical and therapeutic treatment procedures and for the purpose of determining the compensation terms and job priority (Feeney and Galer, 1981). These classification methods do not provide a basis for the categorization of physical abilities and structural aspects. It is possible that persons with varied medical conditions may have similar function loss or structural changes. For example, muscular dystrophy, which produces reduction in muscle mass, may occur from poliomyelitis or from neural damage caused by trauma. In any of the cases there will be marked changes in anthropometric parameters. An attempt was made by the World Health Organization to classify the disabilities from the functional point of view (Wood, 1976). Despite the fact that this classification is very extensive, the problem arises as to how it may be related to the data which are classified in medical terms. Research studies on the classification of disability became widespread specially in the surge of athletics activities by them (Weiss and Curtis, 1984; Strohkendl, 1994; Sherrill et al., 1984; Lindstrom, 1984). However, these works are not useful for the purpose of anthropometric applications due to their specific nature. The anthropometric data available so far has been described in medical terms only. Since the purpose of classification is to provide a basis to decide the process of the design and evaluation of rehabilitation aids, an overall taxonomical approach may be needed. Such a classification method as of today is not properly elaborated. A broad-based classification which takes care of both the medical and structural aspects is given below. It is important to consider the duration of the disabling affliction and the age group. The disabled population could be divided in three categories based on the nature of physical dysfunction. 1 Amputees. Amputees are persons with the loss of a portion of limb. They resemble the normal population except for the lost portion of the body. This group may deviate from normal because of the wasting of muscular tissue (disuse atrophy) and acquired deformities, if they remain untreated for longer

404 A.GOSWAMI

duration. This class of persons could be arranged in subgroups depending on their age group and the duration of suffering. 2 Neural function loss. These are persons with loss of body functions due to malfunction of nervous system from inborn error, accident or disease. This type of disabled vary greatly in the nature of their disability and can be broadly classified in three categories: ■ Injury or damage occurring after adolescence. In these cases, at the initial stages, the body part dimensions appear like normal persons. The changes in body dimension of this group of disabled depends upon the disuse atrophy and acquired deformities. Changes in this direction becomes slow, in case the person undergoes regular treatment/physical therapy. In developing countries most of this population compound their disability because of the non-availability of suitable treatment and also increase the speed of the age-related reduction of body function. Improper aids add to secondary deformity. ■ Injury or damage occurring before adolescence. When a person is disabled because of neural damage, the growth of body parts become dispro-portional and this has been shown in our study (Goswami et al., 1987). The nature of anthropometric changes is widely variable and a variety of deformity is encountered. ■ Inborn errors in the nervous system. Spastics are the most difficult group among the disabled requiring aids for mobility. In this group, sometimes there is no apparent change in body dimensions as compared with normal individuals. However, the functional characteristics are frequently altered. Data regarding this group is rarely available. 3 Miscellaneous group. A number of growth disturbances which do not resemble the above groups can be included in this group. They include systemic deformities and developmental anomalies. The nature of structural change may vary within the group. On the basis of this classification it becomes clear that anthropometric measurements in relation to design and other ergonomics application is required for mainly the second and third categories. Anthropometric data required for the first group can be taken from the normal population; especially, the design of artificial limbs requires individualistic attention. The data arranged according to this classification will also be helpful in the identification of growth abnormalities.

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 405

13.5 Design applications for the disabled It has been pointed out by Feeney and Galer (1984) that ergonomics application is required in three major areas of daily living activities of the disabled. These are transport, the home environment and the work environment. Varied degrees of applicability of anthropometric data can be found in these areas. The approaches to the design of the aids and environment for the disabled concern the basic question of the goodness of fit with the body dimensions and physical working capacity of the disabled. The space requirement of wheelchair users is one area which had received attention from the beginning. Studies have reported the space requirement data for the purpose of maneuvering the wheelchair around doorways, corridors and bathrooms (Floyd et al., 1966; Ownsworth, 1973; Ownsworth et al., 1974). These studies indicated important criteria for the design of the home and work area, especially the differences in the use of fifth and 95th percentile values. It was argued that inclusion of the structural limitation of the disabled population in the design may not disturb their use by the general population. However, later studies did not confirm this view. In some of the anthropometric dimensions the 95th percentile value of the disabled were found to be lower than the fifth percentile value of the general population (Nowak, 1989; Das and Kozey, 1994; Jarosz, 1994). In this respect, mobility aids received the highest attention. The most researched mobility aid for the lower extremity disabled is the artificial limb (Ganguli, 1973; Ghosh, 1981; Mohan et al., 1985; Goswami, 1987). Almost all the studies have indicated compatibility of the prosthesis, presently available, with the user. Appar-ently there is no need for specialized population anthropometric data for the design of prosthesis, except in both limb involvement. Persons with bilateral above knee amputation prefer wheeled aids rather than a prosthesis. The gait abnormality after fitting the prosthesis may be linked to the changes in the distribution of fractional body weight in the prosthesis, since a higher foot weight is inducted in the design to allow swing effect (Goswami, 1987). Anthropometric data is currently insufficient to deal with this particular problem. The axillary crutch is the most common mobility aid in any country, since even people with a temporary disability are obliged to use this aid. An interesting aspect of crutch usage is the increase in the effective length of the limbs, which has been found useful in fast walking but becomes uneconomic in slow walking (Goswami, 1987). The available designs of crutches were found to incorporate adjustment in length. The possibility of contribution by anthropometric data in the design of the crutch seems to be low and specific data for this is not available. People with confining disabilities commonly use wheelchairs for indoor/ outdoor movements and, in many countries, tricycles for outdoor purposes. A typical example of the utilization of anthropometric dimensions in the design and evaluation of wheeled aids can be found in the studies by Goswani et al. (1986a,

406 A.GOSWAMI

b). Two types of tricycles are in use in different states of India: one has the arm crank in the middle front position of the user, while the other has the crank either at the right or left positions, or sometimes one each on the both sides of the user. The compatibility of Indian tricycles with these data was studied and a number of modifications in the sitting arrangement in the existing design were suggested. The provision of a single crank in the middle front position was advocated and has concurrence with the study by Nag et al. (1982) on similar tricycles. There have been attempts to design the wheelchair considering the physical limitations of the disabled (Kenward, 1971). This study discussed the seat design for the wheelchair. In another study, four types of wheelchairs, which were available in India, were evaluated, keeping in mind their anthropometric dimensions. None of the seats of the four types were found to provide comfort to a larger percentage of disabled user (Goswami et al., 1986b). The reason was attributed to the use of European data in the design of these wheelchairs. The study has indicated the provision of armrests and modification of the seat design for better suitability. Although the evaluated designs were of adjustable type, the procedures for adjustment were so cumbersome that none of the users were found to take the benefit of adjustment. In the hand-rim propulsion system the space between the hand rim and the wheel was also inadequate. However, these recommendations do not apply to the design of wheelchairs for sports purposes (Shephard, 1988), where comfort is sacrificed in favor of speed and stability. 13.6 Lacunae in the application of anthropometry? Considering the studies reported in the field of mobility-aid design and evaluation so far, it becomes clear that population anthropometric data has mostly been used for studying wheeled aids only. The reason lies in the requirement of such data. It is imperative that unclassified anthropometric data on the disabled population will probably lead to more complications rather than providing comfort and ease of operation. Again, one major difficulty in the collection of anthropometric data on the disabled population lies in the dispersed distribution of the individuals. The anthropometric investigations reported on disabled persons is in no way sufficient to form a common pattern for various design applications. There has also been few utilizations of anthropometric data in the design process. It is possible that several anthropometric surveys on the disabled have not been published, or have been published for a limited circulation only (for example, the data published in a report by the Institute of Consumer Ergonomics). Obviously, a larger survey on the anthropometric profile of disabled persons is required to identify the specific deformities, the effect of pre- and postadolescence disability on growth and development, the possible changes in dimension due to training effect (by use of specific mobility aids), and the effects of mobility without any aids which is the most probable situation in industrially

ANTHROPOMETRY OF PEOPLE WITH DISABILITY 407

developing countries. A larger compilation of the anthropometric database on the world disabled population, as a whole, may be more helpful for ergonomics practitioners. Acknowledgments The author is grateful to Professor R.N.Sen, Department of Physiology, University of Calcutta, for his enlighting suggestions. Thanks are due to Mr R.Iqbal, SAI Research Fellow, for his help in the preparation of the manuscript. It was the encouragement of Professor Shrawan Kumar, Canada, and Professor Eva Nowak, Poland, which led to the preparation of this chapter. References ATREYA, V. (1988) ‘Residential design consideration for physically handicapped homeusers’. Master’s Dissertation, SNDT University, Bombay, India. COUTTS, K.D. (1986) Physical and physiological characteristics of elite wheelchair maarathoners, inSHERRILL, C. (Ed.) Sport and Disabled Athletes, pp. 157–161, Champaign, Ill; Human Kinetics Publishers. COWELL, L.L., SQUIRES, W.G. and RAVEN, P.B. (1986) Benefits of aerobic exercise for the paraplegic: a brief review. Medicine and Science in Sports and Exercise, 18, 501–8. DAS, B. and KOZEY, J.W. (1994) Measurements of structural anthropometry for wheelchair mobile paraplegics. Proceedings of the 12th Congress of IEA, Vol 3, Rehabilitation Ergonomics , S.Kumar (Ed.) pp. 63–65. DAVIS, G.A., TUPLING, S.A. and SHEPHARD, R.J. (1986) Dynamic strength and physical activity in wheelchair users, in SHERRILL, C. (Ed.) Sports and Disabled Athletes, pp. 139–45, Champaign, Ill: Human Kinetics Publishers. FEENEY, R.J. and GALER, M.D. (1981) Ergonomics research and the disabled. Ergonomics, 24 (11), 821–30. FLOYD, W.F., GUTTMAN, L., WYCLIFFE-NOBLE, C., PARKES, K.R. and WARD, J. (1966). A study of the space requirements of wheelchair users. Paraplegia, 4 (1), 24–37. GANGULI, S. (1973) ‘Bioengineering investigation on orthopaedic rehabilitee-appliance man-machine systems’. Doctoral thesis, Jadavpur University, Calcutta, India. GASS, C.G. and CAMP, E.M. (1979) Physiological characteristics of trained paraplegic and tetraplegic subjects. Medicine and Science in Sports, 11, 256–65. GHOSH, A.K. (1981) ‘Selection of clinically suitable tests/methods for ergonomic/ physiological evaluation of lower extremity handicapped persons’. Doctoral thesis, Calcutta University, Calcutta, India. GOSWAMI, A. (1987) ‘Bioengineering/ergonomic evaluation of different types of mobility aids for lower extremity handicapped’. Doctoral thesis, Calcutta University, Calcutta, India. GOSWAMI, A. (1994) Application of anthropometry in mobility aid design—a developing country perspective. Proceedings of the 12th Congress of IEA, Vol. 3: REHABILITATION, 55–57, Toronto, Canada, August 15–19.

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GOSWAMI, A., GANGULI, S. and CHATTERJEE, B.B. (1987) Anthropometric characteristics of disabled and normal Indian men. Ergonomics, 30 (5), 817–23. GOSWAMI, A., GANGULI, S., BOSE, K.S. and CHATTERJEE, B.B. (1986a) Anthropometric analysis of tricycle designs. Applied Ergonomics, 17 (1), 25–9. GOSWAMI, A., GANGULI, S. and CHATTERJEE, B.B. (1986b) Ergonomic analysis of wheelchair designs. Clinical Biomechancis, 1 (3), 135–9. HJELTNES, N. (1977) Oxygen uptake and cardiac output in graded arm exercise in paraplegics with low level spinal lesions. Scandinavian Journal of Rehabilitation Medicine, 9, 107–13. INSTITUTE FOR CONSUMER ERGONOMICS (1981) Seated anthropometry: the problems involved in a large scale survey of disabled and elderly people. Ergonomics, 24 (11), 831–45. JAROSZ, E. (1994) Anthropometric data of wheelchair users for designers. Proceedings of the 12th Congress of IEA, Vol. 3: REHABILITATION, 60–61, Toronto, Canada, August15–19. KENWARD, M.G. (1971) An approach to the design of wheelchairs for young users. Applied Ergonomics, 2, 221–5. KOFSKY, P.R., SHEPHARD, R.J., DAVIS, G.A.. and JACKSON, R.W. (1986) Fitness classification tables for lower-limb disabled individuals, in SHERRILL, C. (Ed.). Sports and Disabled Athletes, pp. 147–155, Champaign, Ill: Human Kinetics Publishers. LINDSTROM, H. (1984) Sports classification for locomotor disabilities: Integrated versus diagnostic systems, in SHERRILL, C. (Ed.). Sports and Disabled Athletes, pp. 131–6, Champaign, Ill: Human Kinetics Publishers. MOHAN, D., RAVI, R. and SETHI, P.K. (1985) Jaipur AK prosthesis: Results of mathematical modelling and field trials. RESNA 8th Annual Conference, MEMPHIS, Tennesse. NAG, P.K., PANIKAR, J.T., MALVANKAR, M.G., PRADHAN, C.K. and HATTERJEE, S.K. (1982) Performance evaluation of lower extremity disabled people with reference to hand cranked tricycle propulsion. Applied Ergonomics, 13 (3), 171–6. NAKAMURA, Y. (1973) Working ability of the paraplegic. Paraplegia, 11, 182–93. NOWAK, E. (1989) Workspace for disabled people. Ergonomics, 32 (9), 1077–88. NOWAK, E. (1994) Anthropometric measurements of the young for the needs of clothing design. Proceedings of the 12th Congress of IEA, Vol. 3: REHABILITATION, 58–59, Toronto, Canada, August 15–19. OWNSWORTH, A. (1973) Housing for the disabled: Part One: An ergonomics study of the space requirement of wheelchair users for doorways and corridors. Loughborough: Institute for Consumer Ergonomics. OWNSWORTH, A., GALER, M.D. and FEENEY, R.J. (1974) Housing for the disabled: Part Two: An ergonomics study of the space requirement of wheelchair users for bathrooms. Loughborough: Institute for Consumer Ergonomics. SHEPHARD, R.J. (1988) Sports medicine and wheelchair athlete. Sports Medicine, 4, 226–47. SHERRILL, C., ADAMS-MUSHETT, C. and JONES, J.A. (1984) Classification and other issues in sports for blind, cerebral palsied, Les autres and amputee athletes, in SHERRILL, C. (Ed.). Sport and Disabled Athletes, pp. 113–30, Champaign. Ill: Human Kinetics Publishers.

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STOBOY, H. and WILSON-RICH, B. (1971) Muscle strength and electrical activity, heart rate and energy cost during isometric contractions in disabled and nondisabled. Para plegia, 8, 217–22. STROHKENDL, H. (1984) The new classification systems for wheelchair basketball, in SHERRILL, C. (Ed.). Sport and Disabled Athletes, pp. 101–12, Champaign. Ill: Human Kinetics Publishers. WEISS, M. and CURTIS, K.A. (1984) Controversies in medical classification of wheelchair athletes, in SHERRILL, C. (Ed.). Sport and Disabled Athletes, pp. 93–100, Champaign, Ill: Human Kinetics Publishers. WOOD, P. (1976) Classification of Impairment, Disability and Handicap. Geneva: World Health Organization.

CHAPTER FOURTEEN A new approach to clothing for disabled users MARIANNE THORÉN

14.1 Background Since ready-made clothes took over the clothing market many customers have had difficulty in finding suitable clothing. This is primarily the case for people whose bodies are not considered stereotypical. Their figures do not fit into clothes made according to the available size systems. 14.1.1 Today’s clothing market Most of our clothes are sold either in multiple-stores or in shops of different sizes. The customers are free to choose where they want to do their shopping. In the clothing market there is a great variety of designs and sizes. But who decides what is on the market? Multiple stores usually have their own designers. This gives them the opportunity to adapt their choice of styles to their customers. Smaller shops, on the other hand, have to choose among the styles offered them from various production-lines, which gives the customers less influence on the choice of the market. The design and pattern-construction is generally computerized and based on size systems. Most countries have their own size systems based on body dimensions of the population in each country, which is intended to cover around 95 per cent of the population. Therefore, the size systems are not the same all over the world. This makes it difficult for customers to choose the correct size when the clothes are imported. ISO standards (1991), which are intended to be part of an international size system, are available, but the market does not yet seem ready to adapt to them.

M.THORÉN 411

14.1.2 Who does not fit in? Many people with physical impairments do not fit into current size systems. Most of them are in need of individual adaptation of their clothing. Also, all sizes are not represented on the market. Some people with unusual body dimensions have to rely on the system of made-to-measure clothing, where the manufacturing is based on a single-ply production. This involves a production where the cutting is made on a single layer of material, since the pattern is adjusted to a single customer. The patterns used derive from the size systems and only minor changes are allowed, because of the stipulated limits in the production line. These limitations still leave out the more unusual body shapes. A 1993 issue of Applied Ergonomics deals with the importance of designing products for disabled and elderly people. In one of the papers (Benktzon, 1993) these users are arranged into a pyramid. The lower portion of the pyramid (Figure 14.1) represents the able-bodied or fully capable users. In the middle and top of the pyramid the critical users in the clothing system are to be found (shaded). They will be referred to as disabled users. At the top of the pyramid are severely impaired people who need help with many daily activities. In both these sections people with unusual body dimensions as well as people with different types of impairments will be found. Their body dimensions may differ from those represented in the size system, that is, they do not fit into ordinary-sized clothing. They can be tall, short, fat or skinny or they may have a scoliosis or kyphosis. They can also suffer from different types of impairments such as a paralysed arm or leg or they may have other impairments which gives them difficulties with their clothing. There may not be many disabled users in every city or out in the countryside, but when you look at it internationally you will find that they represent quite a large group of people. In Sweden alone, there are more than 200 000 people who are in need of crutches or a wheelchair in order to be able to get around (Handikappinstitutet, 1989). An impairment like this is enough to put them in the middle part of the triangle as members of our group of disabled users. 14.1.3 What has been done so far? Many efforts have been made throughout the years in order to help disabled users with their clothing problems. The most common effort is to start a business of special clothing where disabled users can buy clothes adjusted for their impairment. Successful firms are using mail order to reach their customers, who live far apart. Sewing courses are given, especially for parents who want to learn how to make clothes for their disabled children. Clothing patterns for different kinds of impairments have been produced, for example, patterns adapted for persons

412 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

Figure 14.1 The users’ pyramid.

Figure 14.2 The conventional system for the manufacturing and marketing of ready-made clothes.

sitting in wheelchairs, unusually big or small bodies or with different kinds of impairment. The most successful method for making these patterns is presented in a book by Frost (1987). In research at the Department of Consumer Technology, we have done some work to help the constructors of clothing for disabled people. A survey has been conducted (Benktzon, 1980) on how to make functional clothes for different groups of disabled people. Clothing for elderly people (Rosenblad-Wallin and Karlsson, 1986) and clothing fasteners for long-term-care patients (Sperling and Karlsson, 1989) have also been presented. We have for some years applied our method for user-oriented product development. (Rosenblad-Wallin, 1985) Our aim is to make the products more adapted to the user. By user here we mean the end-user of the product. The new definition of quality for the user reads: ‘All the properties of a product put together, which enables it to fulfil expressed and implicit needs’ (ISO

M.THORÉN 413

standard 8402, 1986). This implies that today’s ready-made clothing for disabled users is of poor quality. When available clothing is not suitable for disabled users, the quality is poor from their point of view. The quality could also be expressed in terms of use value (Rosenblad-Wallin, 1985). The use value of a product comprises both functional and symbolic values. Important examples regarding clothing are: ■ Functional values: protection, comfort, ease of dressing and undressing, care. ■ Symbolic values: self-esteem, group membership, decoration, fashion. 14.1.4 Which questions should be studied? Most of the earlier work on clothing for disabled users has not been successful. The question is why? Our recent experience tells us that when it comes to solving the clothing problem of the disabled, we have not had a proper communication with the user. The problem for disabled people is not only the end-product. There is also the question of the ability to choose among what is available on the market and how the products are offered to disabled customers. In order to get a clear view of the market structure for ready-made clothing, the easiest way may be to regard it as a system. In its most simple form this system will have a hierarchical structure (Figure 14.2). We have been studying these aspects and make the following proposals. 1 The manufacturers must have a thorough knowledge of their customers. By interviewing final users, their requirements for clothing can be determined. 2 The focus has earlier been on the final product only. The problem must, however, be addressed from a systems view. 14.2 Method 14.2.1 User-oriented product development In our research we have developed a method for user-oriented product development (UPD) (Rosenblad-Wallin, 1983; Dahlman, 1986). The method applied to functional clothing is described earlier (Rosenblad-Wallin, 1985). However, our study involves a new approach by studying the system for the clothing trade as a whole including manufacturing, marketing and end-use. In order to understand the function of the whole system it should be studied from both the user’s point of view as well as from that of the manufacturers and

414 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

retailers. This will give the study the design of a multiple case-study (Yin, 1989). However, the emphasis was put on the case of the end-user, as current knowledge was limited in this matter. 14.2.2 Soft systems methodology (SSM) According to Checkland and Scholes (1991) this is a case where soft systems methodology (SSM) should to be applied. The process of SSM has been summarized by von Bulow (1989): SSM is a methodology that aims to bring about improvement in areas of social concern by activating in people involved in the situation a learning cycle which is ideally never ending. The learning takes place through the iterative process of using system concepts to reflect upon and debate perceptions of the real world, and again reflecting on the happenings using system concepts. The reflection and debate is structured by a number of systematic models. These are conceived as holistic ideal types of certain aspects of the problem situation rather than as accounts of it. It is taken as given that no objective and complete account of a problem situation can be provided. The process of SSM is shown in Figure 14.3. Like in all systems partly based on human activity, there are no two identical systems. When we try to find a new system as a solution to a problem, even this solution cannot be static. Checkland and Scholes (1991) show that in changing a system according to the SSM, we have to consider two important streams of analysis; the logic-based and the cultural. According to the logic-based stream, models of a new system can be made based on some relevant changes. The cultural stream, however, considers that the situation is a part of human affairs. As such we have to consider the intervention in itself. It has to be looked at as a ‘social system’ as well as a ‘political system’. It is clear that the logic-driven stream and the cultural stream will interact. Overall, the aim of SSM is to take seriously the subjectivity which is always a part of human affairs. When applying the method of UPD, the subjectivity of the users is treated in somewhat the same way. It is handled seriously and considered. Important bases and characteristics for this method are as follows. 1 The user perspective, that is, the basis, is the end-user’s needs and demands. 2 The system-approach, that is, to study the conditions of the total system including the production, marketing and the end-use of a product. This may lead to the conclusion that there is a need to change the system rather than the product.

M.THORÉN 415

Figure 14.3 The process of SSM, from Checkland and Scholes (1991) Soft Systems Methodology in Action.

3 Formulation of demands, aiming at the use-value of the product/system: that is, the syntheses of the functional as well as the symbolic values. 14.3 Case study 14.3.1 Method A detailed knowledge of the final user is required, of their capacity and limitations, problems, needs and wishes, conditions and actual resources. This combination of objective and subjective data on the user has been collected

416 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

through questioning. Sixty-five people were interviewed. One part of the interview was formal and the other had an informal structure: that is, questions with open answers. Criteria for the choice of subjects of the interviews were to cover a wide field regarding type of disability, age, place of living and to keep an even distribution between sexes. Important conditions regarding the disabled users were that: ■ they should be familiar with their disability; ■ they should be more than 15 years of age and ■ their disability should be causing them problems in getting hold of wellfitting, ready-made clothing. The whole system for the manufacturing and marketing of ready-made clothes for disabled users should be studied. The following areas of the user-demands need to be examined: ■ ■ ■ ■

functional and symbolic values of their clothing shopping dealing with their present problems changing the system in the future. 14.3.2 Results 14.3.2.1 Interviews with the users

From 65 interviews with users (Thorén, 1992) three important groups with somewhat different demands on clothes and the clothing-market were identified (Figures 14.4 and 14.5). Three alternatives were allowed in the questionnaire for Figure 14.4 and four of them for Figure 14.5. We found that quite frequently two alternatives go together, for example, reduced hand function and using a wheelchair in Figure 14.5 and short combined with scoliosis or kyphosis in Figure 14.5. Considering these combinations of impairments we found that most of our subjects belonged to the following three groups: 1 Height <1.5 m 2 Users of a wheelchair 3 Users of a wheelchair paralysed in one or both arms Total:

Number 24 16 20 60

M.THORÉN 417

Figure 14.4 Different kinds of disabilities.

The first group is a good representative of the larger group among the disabled users; people with divergent body-forms, who do not fit into clothes now available on the market. Members of the second group need comfortable clothing and a special fit below the waist whereas members of the third group have the same demands combined with a need of special functions for dressing and undressing. 14.3.3 Functional and symbolic values of the clothing An important part of the whole investigation is to learn about the needs and wishes of disabled users regarding their clothing. Do they have any preferences regarding the fashion and/or function? Which type of clothing do they prefer? In the first group 70 per cent work outside the home taking part in social life. In the second group 63 per cent are employed outside the home and in the last group only 35 per cent can manage to work outside the home. Since clothing is a way of signalling who you are—or would like to be—it is likely that when you mix in society you may be interested in your clothing. However, your clothing can also enhance your self-esteem even when you are not in a social situation. Our investigation shows that the attitude towards the functional and symbolic values of clothing is very much dependent on the disability. Some of the members of the last group are very disabled. Symbolic values are to them fairly irrelevant. The most important questions for them are that clothes should be comfortable to wear and easy to handle for the staff helping them to dress and undress. In the first and second groups, however, the attitudes were much more varied; some of the users wanted to be dressed according to the latest fashion whereas others were quite happy as long as the clothes were comfortable.

418 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

Figure 14.5 Disproportion in the figure.

Conclusion 1. The difference regarding preference of functional or symbolic values of clothing is just as big among the disabled users as in any other group of people. Only in the last group, where several members are very disabled, is there a greater need of functional clothing. 14.3.4 Shopping The shopping procedure can be divided into some well-defined stages which have to be analysed: ■ Transportation to the stores. ■ Get access to a fitting-room. ■ Find clothes with a good fit, perhaps through a few alterations. The shopping procedure can be a major challenge to many disabled users. An interesting task is to find out how they manage. Every step that seems natural to the able user can involve great difficulty for the disabled. Figures 14.6 and 14.7 show a comparison between the user-groups ‘short statured’, represented by group 1 and ‘wheelchair’, represented by groups 2 and 3 together. It is obvious that they all have difficulties doing their shopping, but the difficulties vary between the groups. The ‘short statured’ usually manage to get around to different stores which means that they can find out what is on the market. They also manage to try the clothes on, although some of them have difficulties in reaching up far enough to be able to see themselves in the mirror. Very few clothes are made to fit their bodies. The clothes are too big and usually the proportions are all wrong. This makes it impossible to make any easy adjustments.

M.THORÉN 419

Figure 14.6 Problems with shopping for ready-made clothing.

Figure 14.7 Problems regarding ready-made clothing.

Most of the members in the ‘wheelchair’ group find it difficult to get around to see what is on the market. They also find it difficult to try the clothes on in the store, as most of the fitting rooms are too small for a customer in a wheelchair. They may be allowed to bring a few clothes home in order to try them on, but then they must return them to the shop. Not all garments cause difficulties: trousers, skirts and overcoats are the most difficult. The most disabled users in the last group do not usually manage to visit the shops. They have someone to do the shopping for them, or they can shop for disabled users clothing through the mail-order system. Surprisingly few disabled people use the mail-order system. Most do not want to buy special clothes for disabled people. They seem to be afraid of getting a label on them through their clothing.

420 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

Conclusion 2. The criteria of user demands regarding shopping are not fulfilled for any of the three different groups. All three stages within the shopping procedure are difficult for disabled users. It is obvious that they all need better service. 14.3.5 Dealing with their current problems This area is linked to the two previous ones. Some open questions about how they are dealing with their situation today has confirmed their previous answers. Some disabled users are to some extent very able users. They have a vivid mind and find their own ways of solving their problems. The creativity regarding special functional needs for their clothing can sometimes be very good. Their ideas should be taken notice of and passed on to others, who are in need of the same solutions. Surprisingly few are interested in learning how to sew their own clothes. Quite a few are fortunate enough to have relatives who know how to sew, but they realize that this help will not last for ever. Very few are willing to pay a higher price for having clothes made to measure. In most cases their budget does not allow them to spend a lot of money on clothing. Conclusion 3. The creativity among the disabled users regarding solutions of their functional needs of clothing is in some cases remarkably good. It needs to be taken notice of and passed on to others. Our investigation also shows that disabled users do not make their own clothes to any large extent, partly because of their lack of interest, partly because of their disability. 14.3.6 Changing the system in the future Disabled users often have difficulties in finding the clothing they really want, but they may have ideas of how they would like to have the system changed in order to solve their problems. The dominating wish among disabled people, who are able to mingle in society, is to be able to choose among the clothes available on the market, just as any other citizen. They want better service regarding: ■ individual patterns; ■ clothes made to measure; ■ adaptations of clothes from the market.

M.THORÉN 421

They would also like to find that staff in the stores are better informed about their problems and able to adapt the clothing according to their needs. Conclusion 4. It is obvious that disabled users do not want to be treated as a special group regarding clothing. They want to be able to make their own choice among the clothes available on the market. In order to get a good fit most of the clothes will have to be adjusted or made to measure. 14.3.7 Interviews with manufacturers In Sweden, we have only a few manufacturers specializing in clothing for disabled users. Informal interviews have been conducted with some of them. Some of the manufacturers of clothing for disabled users have mail-order businesses. They regard it as an easy way to cover a much wider area of the market. It is obvious that there is a lot of knowledge regarding clothing for disabled users collected among the producers of clothing for this group. They have all started with the aim of helping this group of people, but they have all found that it is not easy to succeed. Very few have been successful over the years. The main difficulties they have come across seem to be the following. Table 14.1 Priorities in different groups of users and manufacturers, respectively From the viewpoint of

Design priority Individual pattern

Shopping system

Symbolic values Not important

Important

Open market

Not important

Mail-order

Symbolic values Too Expensive

Too Expensive Mail-order

Users 1. 2.

Length < 1.5 m Symb./func. values Functional values

In wheelchairs 3. 2+limpn. in arm Manufacturers Ready-made-clothes Clothes for the disabled

Functional values

Open market

Open market

■ To make individual patterns for disabled people is a very difficult and timeconsuming process. It is too expensive. ■ It is necessary to concentrate on functional clothing for a limited group of disabled users in order to get a profitable production.

422 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

■ It is difficult to find a way of communicating with the customers as Sweden is quite a large country and the customers live far apart. 14.3.8 Comparison of the results If we look at the manufacturing and merchandizing of clothing as a system seen respectively by the eyes of different user-groups of disabled people and by different groups of manufacturers, it is obvious that these priorities do not coincide. Table 14.1 gives a summary of important priorities for the different groups. The three groups of users are the ones we identified in our interviews, whereas the manufacturers are represented by the ordinary type of manufacturer of readymade clothes and the typical Swedish manufacturer of clothes for disabled users. The only two groups where the interests coincide are group 3 and the manufacturers of clothing for the disabled. According to the interviews with disabled users most of them share the opinion that when you have to order your clothes through mail-order from the manufacturers, who specialize in functional clothing for disabled users, you lose a bit of your personal integrity. 14.4 Discussion Neither the disabled users nor the manufacturers of clothing are satisfied with the current solutions. 14.4.1 Use value When studying the use value the conflict between the end-user and the manufacturer becomes obvious. The results of the interviews with the end-users show that the manufacturers of clothing for disabled users have not taken the symbolic values of the clothing into serious consideration. This gives us reason to believe that our first proposition is correct. The manufacturers must have a thorough knowledge of their customers. By interviewing final users, their requirements for clothing can be determined. According to the SSM method it is obvious that the dominating stream of analyses for the manufacturers has been logic-based, whereas the cultural stream has been almost neglected. Very few disabled users want to buy their clothes from the special manufacturers of clothing for disabled people. There seems to be a barrier for all those who are able to live a normal social life, They do not want to accept their

M.THORÉN 423

disability when it comes to clothing. They want to be able to choose their clothes just like anyone else. Our results show that it is wrong to talk about disabled users as one single group. We found three different groups. The user demands were different between the groups. This implies that the manufacturer must identify the different categories of end-users in order to be able to analyse their user demands. 14.4.2 System thinking The methods used to study the problems have proven to be effective. The case study is a basic method for getting acquainted with objective as well as subjective factors. When using the user-oriented product development (UPD) and the soft systems methodology (SSM) all these factors can be taken into consideration. However, the SSM shows us that there will never be a perfect and final solution to the problem. There is a need to constantly keep trying to adapt the system to the users’ needs and to the available technique. We have, however, found our second proposition to be correct. The focus has been on the final product only. The problem must, however, be addressed from a systems view. We have found it to be essential not to focus on the final product only but to look at the problem as a system consisting of: ■ manufacturing ■ marketing ■ end-use. 14.4.3 New possibilities make room for new efforts In recent years there has been a change from the production society to the information society. This transformation opens up new opportunities to give better service and make better products. Despite this very little has been done in order to change the manufacturing system of clothing for disabled users. Information technology (IT) makes room for new efforts. A computer network combining the manufacturing and marketing of clothing with a databank of clothing for the disabled will make it possible to improve service to customers. Some very important work has been done by taking three-dimensional measurements from range images of the human body (Gustavsson and Thorén, 1993; Petersson and Sölvelid, 1993). This method offers a new way of handling the problem of how to forward measurements from the customer to the producer

424 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

when you are thinking in terms of made-to-measure clothing, which can be a good and possible solution for disabled users. In our work we are introducing tools that will be available when sufficient research and development is done. 1 Make all the information of the construction of functional clothing for disabled users easily available. This can be done by optic storage on a CDROM disk. When the information is available in an instructive way, it will be easily accessible for anyone being trained as a tailor. 2 The body measurements of disabled users should be communicated to a person capable of constructing an individual adaption of patterns for people with unusual body shapes. They should all be able to get a computerized adaption of patterns to their body. As mentioned earlier, some work has been done (Gustavsson and Thorén, 1993; Petersson and Sölvelid, 1993) on 3D measurements from range images of the human body and there is now enough data to present a paper on this matter. 3 Individual adaptions of patterns and access to sewing instructions for functional clothing will make it easier and more cost-effective to give a better service to disabled users. A better service includes a more flexible production-line in the manufacturing of clothing. However, in an agile production, which is the new trend in more or less every production, a better service is a word of honour. 14.5 Conclusions 14.5.1 A systems view is necessary Our investigation shows without doubt that disabled users cannot be helped with their clothing problems unless there is a change in the entire system. Their problem is a combination of communication, opportunity to choose, getting clothes with a good fit and function and all at a cost acceptable to them. 14.5.2 IT provides new possibilities Information technology can be of great help. IT opens up the possibility of communication between customer and expert. The experts on pattern construction and model shaping of clothing for disabled users are few. They will be able to help all customers who can get a range image of their body. This could be arranged at service centres.

M.THORÉN 425

Figure 14.8 A model of a new system for made-to-measure clothing.

Service centres can be an extra service preferably given by different stores for clothing. The disabled users will primarily need service about the following. 1 Getting their body measurements, preferably by a range image. 2 Ordering individual patterns. These can be computer based and owned by the customers. 3 Adapting clothing according to functional needs. 4 Advice regarding model shaping in order to get a good fit on a body with deformations. 5 Ordering made-to-measure clothing. With the knowledge of how disabled users look upon their clothing problems combined with the new possibilities of producing made-to-measure clothing it is possible to synthesize a new system (Figure 14.8). This model needs further elaboration. Most likely it is necessary to coordinate the interests in different countries. The research and development work needed can be done in cooperation. The possibilities of putting the user in the centre will improve if there is a big market waiting for manufacturers who are willing to provide a better service to disabled users. References BENKTZON, M. (1980) Kläderoch handikapp, STU inf. nr. 173. BENKTZON, M. (1993) Designing for our future selves: the Swedish experience Applied Ergonomics, 24 (1), 19–27. VON BULOW, I. (1989) The bounding of a problem situation and the concept of a system’s boundary in soft systems methodology, Journal of Applied Systems Analysis 16, 35–41.

426 A NEW APPROACH TO CLOTHING FOR DISABLED USERS

CHECKLAND, P. and SCHOLES, J. (1991) Soft Systems Methodology in Action. John Wiley, Chichester. DAHLMAN, S. (1986) User requirements. A Resource for the Development of Technical Products, Doktorsavhandling Instituut för Konsumentteknik CTH. FROST, E. (1987) Grunnrisskonstruksjon-Klaer for funksjonshemmede, Oslo: Yrkesopplaering i sömnad. GUSTAVSSON, T. and THORÉN, M. (1993) Clothing made to measure for people with divergent figures, Proceedings of the Ecart 2 Conference. Stockholm: The Swedish Handicap Institute. HANDIKAPPINSTITUTET (1989) Hur Många, Statistik om Handikapp. ISBN 91– 86310–56–9. INTERNATIONAL ORGANISATION FOR STANDARDIZATION. (1991) Clothing Size. Body Measurement Tables for Clothing. PETERSSON, K. and SÖLVELID, M. (1993) Utveckling av Mjukvara för Tredimensionell Måttagning med Avståndskamera, Instituut för Tillämpad Elektronik, CTH. ROSENBLAD-WALLIN, E. (1983) Människa-Beklädnad-Miljö; Metod för Utveckling av funktionell Beklädnad. Doktorsavhandling Instituut för Konsumentteknik, CTH, Göteborg. ROSENBLAD-WALLIN, E. (1985) User-oriented product development applied to functional clothing design, Applied Ergonomics, 16 (4) 279–87. ROSENBLAD-WALLIN, E. and KARLSSON, M. (1986) Clothing for the elderly at home and in nursing homes. Journal of Consumer Studies and Home Economics, 10, 343–56. STERLING, L. and KARLSSON, M. (1989) Clothing fasteners for long-term-care patients, Applied Ergonomics, 20 (2) 97–104. THORÉN, M. (1992) Individanpassad Konfektion för Personer Med Fysiska Handikapp och Avvikande Kroppsproportioner Instituut för Konsumentteknik, CTH, Göteborg. YIN, ROBERT, K. (1989) Case Study Research; Design and Method. London: Sage.

Index

accessibility 160, 252, 279, 323–4 accommodation ergonomic 163–4, 204, 282 near-point 42, 45 activities of daily living 7–9, 15 aerobic capacity 104, 105, 111 see also functional capacity exercise, 6, 101, 108, 110, 111 power functional (FAP) 102 maximal (MAP) 6, 101 age difference and stress 37–8, 50–1 physiological 40, 51–2 aging 1–14, 34–9, 40 definition 34, 35 and disability 15–17, 22 at work 34–67 and functional decline 4–6, 7–11, 41– 51 see also elderly American College of Sports Medicine 104 Americans with Disabilities Act (1990) 97, 98, 145, 151, 163, 277, 279, 281 Americans with Disabilities Act (1993) 157 amputation 167 amputee 249, 354 anaerobic work capacity 109 ankle joint motion 189, 334 anthropology 302–3 ontogenetic 304, 310 anthropometer 310, 346 anthropometric board 346 data

children 318–19 disabled 314, 316, 340 gait 177 gender difference 341 for product design 211 seat reference 315, 316, 318 see also body dimensions measurement technique 340–6 anthropometry 302–36, 339–57 elderly 313 racial 347 statistical methods 311–12 structural 347–8 wheelchair user 250–1 see also body dimensions arm ergometry 107 arm-crank ergometry 224 arthritis 13–14, 20–1, 247, 248, 321 assembly line 66 assistive technology 25, 154, 167, 211, 247, 273–300 abandonment 286–90, 296, 300 assessing device utilization 296–9 for augmenting communication 283–4 definition 274–6 design and development 339, 341 in employment 281–3 funding 30, 280–1 home-based 285–6 legislation 274–6, 278–80 manufacturer 214 orthotics and prosthetics 284–5 selection 287, 291–6 service delivery system 213, 216, 280–1 outcome 296–9 427

428 INDEX

users 277–8, 287–90 visual impairment 56–8 Assistive Technology Device Predisposition Assessment 298, 299 auditory code 82–5, 90 display 80–1, 83–5 hybrid 84–5, 90 user controls 82 visually impaired 69–70, 90 oscilloscope 84 avoidance control 201–4 back injury 4, 124, 126–7, 225 back (continued) pain, low 26–7, 127, 128, 136–8 see also spine; spinal balance 7, 13, 197–8, 201–4, 251 control system 204–6 measure of 23 perturbations to 197 see also center of gravity; postural; posture bank teller 136 Beck Depression Inventory (BDI) 114 Behavioral Health, 1995 Standards and Interpretive Guidelines for 297 biomechanical efficiency 232 gait model 177, 188–9 link segment model 189 blindness see visual impairment blood pressure 112–14 body composition 9, 346–7, 348 body dimensions 305, 306, 307, 335, 341– 6, 348 disabled people 349–53 wheelchair user 315, 317, 320 see also anthropometric; anthropometry body weight 9, 335 body-ground interaction 204 bone loss 10, 12

strength in elderly 6 Braille 72, 73–4, 77, 80 volatile display 81 breathing as index 52 Bruce protocol 104 bus access 323–4 CAD/CAM 159–60, 284–5 cadence 170, 196 camera 58, 88, 166, 186, 187–8 captioning 283 cardiac patient classification 19–20 performance 110, 112–14 rehabilitation 95–109 epidemiological change 115 health care cost 115–16 outcome 114–15 program 89–109 risk factor reduction 116 cardiology, nuclear 99 cardiovascular function 11–12, 18–20 carpal tunnel syndrome (CTS) 265–6 carrying see load carrying center of gravity shift 42, 44–5 see also balance; postural; posture central nervous system 177, 180, 183 see also nervous; neural cerebral cortex, activity level 42 cerebral palsy 174, 185, 320, 328, 330, 335 children 250, 251, 279 anthropometric data 318–19 computer 283 gait analysis 166–7 motor dysfunction 329–30 physical development assessment 327– 31 somatic characteristics 328–30 chronic heart disease effects of exercise 95–117 psychological and social concerns 97 risk factors 109 Chronic Obstructive Pulmonary Disease (COPD) 18

INDEX 429

cine with manual digitization 186 circumferential measurement 335, 348 closed-circuit television 87 clothing 127, 129, 360–73 design 321, 348 fasteners 362 functional and symbolic values 366–7 made-to measure 366, 373 mail order 361, 368 manufacturer 369–70 ready-made 362, 368, 373 size system 360 system model 366 user 361, 368–9, 370 communication 276 augmenting with assistive technology 283–4 board 284 deaf 282–3 with visually impaired 69, 90 compensation status 26 computer 153, 276–7 access 81, 82, 253, 254, 255 aids for deaf 283–4 CAD/CAM 159–60, 284–5 children 283 for visually impaired 74, 76, 80, 81 workstation 55–6, 89, 161 computer-aided transcription 283 concentration, maintaining 42, 45 conditioning 104 contact stress, localized 128–9, 138 contrast 88–9 cool-down 108 coordination of movement 183 coronary artery disease (CAD) 96, 117 counseling 152, 159, 160 crank device 218–19, 220, 224 criteria checklist 295 Critical Fusion Frequency value 45–7 crutch, axillary 356 cycling 107 database, population 22 deafness 24, 283–4 deformity 250, 347–8 demographic change 1–4, 22

dental hygienist 132–6 development, physical 327–31, 341, 355 Development Disabilities Act 274, 279 developmental standard 328 dexterity, reduced 86–7 diabetes 71 Dictionary of Occupational Titles 133–4, 136–7, 139 diet 39 disability 14–21 and age 15–17, 22, 34–67 classification 18–21, 23, 348, 354–5, 365–7 definition 145–6, 277–8 distribution and severity of 14–15 managing 30, 124–41 population 145–50, 340–1 reasons for using assistive technology 273–4 see also disabled Disability Rights Movement 249 disabled anthropometry 312–35, 349–53 athlete 346–7, 348 clothing 360–73 design applications 355–6 somatic characteristics 312–25 sports 321 see also disability discrimination 147, 151, 281 disease and systemic change 11, 12 door design 323 dynamic stability 197–8, 201–4 see also balance; center of gravity; postural; posture earning capacity 53 education 101, 151, 152–3, 277, 279 special 75, 280, 283 efficiency biomechanical 232 mechanical 220–2, 223, 224, 232 motor 331–5 ejection fraction 110 elderly 6, 90, 206, 322, 362

430 INDEX

anthropometry 313 assistive technology 278, 285–6 body proportions 315, 320 and falls 197 hand movement range 333 population growth 1–4 reach 322 seat design 324–5 vision 35 wheelchair use 248 workplace support 52–3, 64–7 see also age; aging Electrodynogram 174 electrogoniometer 186 Electro-Mechanical Spinal Model 27 electromyography 183–5, 285 eligibility determination 152, 155, 158, 159 e-mail 276 embossed print 73 EMED system 174 employment and disability 17–18, 97, 155, 313 Employment Rehabilitation Centre (ERC) 313 endurance 6, 23, 28 training 109–17, 114–15 energy consumption 11, 102–4 engineering 153–4, 156–7, 274, 286 environment 27–30, 147 evaluation 88–9, 295 environmental control system 253 Equal Employment Opportunity Commission (EEOC) 97 equalization 336 equilibrium function, index of 42 ergometer 101, 227 ergonomic anthropology 302–3 anthropometry 307 evaluation 158 intervention 132, 136, 138, 141, 299 job analysis (EJA) 131–2, 133–4, 136– 7, 139–40 risk factor 126 stressor 126, 135, 137, 139–40 ergonomics definition 25, 155, 210–1

rehabilitation see under rehabilitation systems 212, 215–6 ergonomist, role of 41, 163–4 Euler method 188–9 exercise 6–7, 206 aerobic 6, 101, 108, 110, 111 and aging 40 associated risk 108–9, 116–17 capacity of wheelchair user 224–7 and chronic heart disease 95–117 home-based 109 maintenance program 6–7, 30, 98, 109 secondary prevention 108–9 test 101–4 graded see graded exercise test tolerance test (ETT) 103, 110 training 98, 104–8, 321 contraindications 99, 117 eye height 346 fall 196–207 falling 13, 266 fatigue 47, 48–51, 128 electromyography 184–5 recovery from 35 wheelchair 262 fitness 6 follow-up 134–6, 138, 141, 166 force generation 184, 189, 262–3 see also under wheelchair measurement 335 plate dynamometer 174, 175 forceful exertion 127, 138, 141 Formboard with a Brain 85 forward lean 12 fraction of effective force (FEF) 234–6, 262 F-scan system 174 fulfilment 53 function, maintenance of 6–7, 30, 98, 109 functional assessment 7–9, 214, 297 capacity 5–6, 24, 110–12, 295, 299 evaluation 131, 132, 136, 138–9 see also physical capacity; work capacity

INDEX 431

decline 4–6, 286 demand 23 independence 12 restoration approach 124 space design 322 Functional Aerobic Power (FAP) 102 Functional Capacity Evaluation (FCE) 131, 132, 136, 138–9 Functional Independence Measure (FIM) 297–8 gait 177–83, 196 abnormality 356 adjustment 204 age-related change 13, 206 analysis 166–89 kinematics 172–4, 177 kinetics 176–7 system methodology 186–9 terminology 170–2 biomechanical modeling 177, 188–9 cycle 167–70 electromyography 183–5 predictive control 201 temporal parameters 170 see also locomotion games recreational 108 video 283 gender difference anthropometric data 341 arm ergometry 107 disability 16 employment 17–18 somatic characteristics 10, 305, 307 spatial layout 80 gerentology 52 see also age; aging; elderly glare 89 gloves 127, 129 graded exercise test (GTX) 99, 101, 105, 109 symptom limited (SL max GTX) 102, 108 graphics 74–80, 84, 89–90

grip strength 347 ground reaction force (GRF) 174–6 growth disturbance 355 guidance 152 hand dual role of 69 efficiency 335 forceful exertion 127 movement range 304, 305, 332–3 rim propulsion 218, 219–23, 230, 235, 237, 239, 260–2 tool 126, 127 handedness 73–4 handgrip 324 handrail design 323–4 haptics see tactile; touch Hawking, Stephen 284 head movement range 304 health management 37 perceived 7 Health and Activity Limitation Survey (HALS) 14–15, 16 hearing impairment 24, 283–4 heart disease, chronic see chronic heart disease heart rate 6, 101, 105, 110, 112 height measurement 310, 315 home control, electronic 25 equipment 278, 285–6, 323 exercise 109 interior design 322 hospitalization 98 housework 8, 13, 29 Hoyer lift 286 hubcrank propulsion 219–20 Human Factors and Ergonomics Society (HFES) 156 hybrid display (auditory/tactile) 84–5, 90 icy surface 204, 206 illuminator, portable 89 image enhancement 87–8 independence 12, 297–8 individual difference 37

432 INDEX

Individual Education Plan (IEP) 279 Individual Written Rehabilitation Plan (IWRP) 155, 159, 280 Individuals with Disabilities Education Act (IDEA) 279 inspection task 56–8 Institute of Electrical and Electronics Engineers (IEEE) 156 intellectual impairment 148–50 intervention, ergonomic 132, 136, 138, 141, 299 job ability to perform 39, 40–1 analysis, ergonomic 131–2, 133–4, 136–7, 139–40 classification 6 demand 6, 28, 52 placement 163–4 redesign 23, 41, 54–65 jogging 106–7 joint disease 20–1 force and moment 189, 262–3 power 177 protection method 285 stability 197–8 joystick 24, 253–4 kinematics gait analysis 172–4, 177 wheelchair 259–61 kinesthetic system 198, 205 kinetics gait analysis 176–7 wheelchair 261–2 kitchen equipment 323 knee jerk response 183 joint motion 189 labor management 6 late recovery period 98 laterally 73–4 leg ergometry 107 lever ergometry 218–19 liberometer 310

life satisfaction 114 lifestyle for elderly 6 lifting 128, 158 light probe 84 lighting 88–9, 207 limb elevation control 203 linear perspective in blind people 76–9 load carrying 8, 58–65, 127, 207 cumulative and back injury 4 local pattern generator 180 localized contact stress 140 locomotion see also gait locomotion control 181, 183, 204 locomotor pattern 203 low back pain 26–7, 127, 128 case study 136–8 low friction surface 204, 206 low vision see visual impairment magnification, electronic 87–8 magnifier 56–7, 86 maintenance of function 6–7, 30, 98, 109 map 76, 79–80, 81 see also navigational assistance marker system 187–8, 231 Master Touch system 82 Master Voice ECU 24 Matching Person and Technology Model 291, 292–4, 296 maximal oxygen uptake (VO2 max) 101, 104, 106, 111, 227 measuring chair 310 stand 335 table (ISAT) 346 mechanical efficiency 219–22, 223, 224, 232 medical condition 148 rehabilitation 156 memory, short-term 42 mental function and age 37 restoration service 153

INDEX 433

metabolic energy consumption (MET) 102– 4 meter reader, dynamic 84 minifier 87 mobility 333–4 aid 85–6, 286, 355 auditory 69–70 electronic/ultrasonic 85 for visually impaired 69–70, 80, 90 impairment 148–50 assistive technology 278 workstation design 159–61 predictor of 7 research on 8 moment analysis 177, 189, 262–3, 303 monosynaptic reflex 198 morale 65, 367 morphological change with age 9–11 motion 3D analysis 186, 188, 189, 334 range of 23, 304, 305, 332–3 tracking system, automated 187 see also movement motor dysfunction 24, 312, 329–30, 335 efficiency assessment 331–5 children 335 movement, voluntary 180 neuron 179, 181–3 MouseStick 24 movement coordination 183 range measurement 332–4 see also motion muscle change in mass 10 crosstalk 184 power source 206 tension 181–3 muscle-timing error 185 muscular strength 6, 35, 36, 58–65 musculoskeletal control of dynamic stability 197–8 pain, ergonomic factors 124–41 stress analysis 158 myoelectric technology 183–5, 285

National Center for Health Statistics 247, 278 National Health Interview Survey on Assistive Devices 247, 278 National Institute of Occupational Safety and Health 127 National Institute on Disability and Rehabilitation Research (NIDRR) 278 Naughton protocol 104 navigational assistance 80, 85–6 nervous system 11, 117, 177, 180, 183, 205, 206 neural control 177–81 function loss 354–5 pathway 178, 183 neuromuscular disorder 167 Newton’s Law 176–7 night viewing device 88 NIOSH Work Practices Guide (WPG) for Manual Lifting and Biomechanical analysis 158 Nomad system 81, 84 occupational musculoskeletal disorder (OMD) 124– 41 rehabilitation 124 case study 132–41 ergonomics 131–41 treatment approach 130–1 stress 45–51 Optacon 74 optical aids and devices 86–7 optoelectric system 187 organizational work factors 129–30 orientation display 85–6 orthopedic impairment 107, 247, 251 orthotic device 275 orthotics 153, 167, 284–5 osteoporosis 12 OT FACT 297 outcome 114–15, 296–9 achievement 26, 299 definition 296 measure 297–8 overload 37

434 INDEX

paediatrics see children pain 13, 124–41, 299 palpation 26–7 paraplegia 227 athlete 231 body composition 347 exercise 226 functional space design 322 patient management 166–7 patient-environment interface 27–30 perceived burden 47–8 perception, tangible picture 75 peripheral nervous system 177 neuropathy 205 photogrammetric method 187, 311 physical capacity 6–7, 28, 37, 111 see also functional capacity; work capacity restoration service 153 therapist 25–7 physiological effects of exercise training 110 function and aging 41–52 and occupational stress 45–8 response 6, 226 physiological age 40, 51–2 physiology and gait 177–83 pilot 308 placement service 152 polysynaptic reflex 198 post-employment service 155 post-operative follow-up 166 postural change, age-related 12–13 control 45, 205 stability 197, 251 stress 126 sway 12–13 posture 126, 134, 137, 141 constrained 140 poor 58–65 sustained or static 128 see also balance; center of gravity shift power

loss 10 tool 129 predicted maximal heart rate (PMHR) 101 predictive control 201 pressure sensitive insole system 174 pre-treatment evaluation 166 product design 211 Profile of Mood States (POMS) 114 prolonged activity 127–8, 134, 138, 141 propulsive power, locus of 204, 206 prosthesis design 355–6 prosthetics 153, 167, 275, 284–5 psychiatric impairment 147–9 psychological function 41, 45–8, 97 impairment 148–50 psychophysiological function 42 psychosocial assessment 131 functioning 28, 101, 114, 297 work factors 129–30 pulmonary conditions 18, 19 pushrim see hand rim quadriplegia 226–7, 231, 282 quality definition 362 of life 114, 299 raised-line drawing 75, 78 ramp 90 range of motion 23 rate-pressure product (RPP) 112–13, 115 rating of perceived exertion (RPE) 105, 106 reach 308, 309, 310, 313–15, 322 zone determination 325–6 reading machine 82 recovery period, late 98 time 230 at work 4–5 reference basis 307–8 reflex 198, 199 rehabilitation cardiac see under cardiac definition 25, 331

INDEX 435

engineering 153–4, 157, 274, 286 ergonomics 22, 25, 156, 303 model of 26 theoretical framework 29 vocational 155–64 goal of 25 inpatient 99–100 medical 148 occupational see under occupational outpatient 98, 100–9 progress 326–35 technology 153–4, 156–7, 159, 279–80 vocational see vocational rehabilitation Rehabilitation Act 163 Rehabilitation Act (1920) 150 Rehabilitation Act (1973) 97, 151, 152, 153, 278, 279–80 Rehabilitation Act (1993) 153 Rehabilitation Act Amendments (1986, 1992) 274 Rehabilitation Engineering Research Center 280 Rehabilitation Engineering Society of North America (RESNA) 156 repetitive work 28, 127–8 respiratory function 11, 52 rest period 5, 6, 128 return to work (RTW) 109, 124 cardiac patients 117 occupational musculoskeletal pain 131 risk factor 108–9, 116–17, 126 rope skipping 107–8 rowing 107 safety 4, 90, 127 scale marking, tactile 85–6 scooter 249 seat design 140, 324–5 reference point (SRP) 308, 315, 316, 318 see also under wheelchair secretary, legal 138–41 self-esteem 367 sensory aid 69 impairment 148–50

see also deafness, visual impairment system, age-related change 11 triggered reflex 198–201 service provider 215 shoe 106 shopping 8, 367–8 shoulder breadth 320–1, 347 injury 220 Sickness Impact profile 114 sign language software 283 sip-and-puff 254 SKERF-Pad 82 sliding scale method 104, 105 slip 196–207 Smith-Fess Act (1920) 150–1 Smith-Huges Act (1917) 150 Social Security Act (1935) 151 Society of Automotive Engineers (SAE) 156 soft systems methodology (SSM) 363–5, 371 soleus H-reflex, gain of 198, 199 somatic characteristics 305, 307, 312–25, 328– 30 gender difference 10, 305, 307 motor dysfunction 335 function 41 spatial cognition 69, 71–4, 89 concept learning 81 layout 79–80 sensor 80, 85 task performance 73 special education 75, 280, 283 speech 284 display 81–3 hybrid 82–3 output 80, 81–3, 90 quality vs speed 81–3 spinal central pattern generator 181 cord injury 225, 227, 265 motor control 180 mobilization 27 model 27

436 INDEX

see also back spine compressive force in 127 see also back sports disabled 321 wheelchair 247, 252, 356 injury 167 medicine 104 stability see balance stair climbing 8, 107 standard computer workstation 161 ergonomic 21 stature 310, 315 step dimensions 323 stimuli and health effects 37 strain, physical 227 strategy, enabling 22–5 strength 6, 23, 35, 36, 346–7, 348 loss 10 physical 58–65 score 7, 40 stress 6, 126 due to aging 37–8, 50–1 localized contact 128–9, 138 mechanical 128 metabolic analysis 158 mood 48–51 occupational 45–51 testing 101 Stress Arousal Checklist (SACL) 48 stressor ergonomic 126, 135, 137, 139–40 load 39 stroke volume 110, 112 support equipment for elderly, development of 64–7 surface properties 204, 206 surgical decision making 166 Swedish agency for special education 75 swell paper 76 switch height 322 systemic change 11–12 systems ergonomics 212, 215–16 Tact Tell system 85

tactile display 73, 74–5, 76–9, 80–1, 84, 85–6 hybrid 84–5, 90 drawing 81 sensitivity and age 90 see also touch tactual pattern perception 71–4 TAF-test 42, 45–7 tailoring table 321 Talking Signs system 85 Tampere Longitudinal Study on Aging 8, 12 tangible picture see under tactile target heart rate (THR) 105 task management 54–65 regain 211 technology abandonment 286–90 Technology-Related Assistance for Individuals with Disabilities Act, The (1988) (Tech Act) 274, 278–9, 296 telecommunication device for the deaf (TDD) 275 service 153 telecommuting 277 telemetry 184 telephone device for the deaf (TDD) 283 telescope design 86–7 television camera 58 temperature extreme 129 texture gradient 76 therapist-patient interface 26–7 threshold age 4 threshold heart rate (THR) 106, 108 toe clearance 203 touch 69, 75, 76, 78, 82 tablet 76, 82 and visual impairment 71–4, 85–6 see also tactile training effect 105 service 152 see also exercise transport 153–4, 156, 161–3, 323–4 treadmill protocol 99, 103, 227 walking 106 treatment

INDEX 437

goal 132–3, 136, 139 outcome 26 tricycle 356 trip 196–207 response to 199, 200 understimulation 37, 38 upper body strength 347 upper extremity pain 138 problem 126, 127, 264–5 workspace 321–2 usability in assistive technology 214 user attitude towards technology 295 auditory display control 82 user-oriented product development 363, 371 variable pitch code 83–4 VDT task and visual function 55–6 vehicle modification 161–3 private 153–4, 156 verbal ‘label’ 84 vertical load curve 175 vestibular system 198 Veteran’s Administration 153, 161, 281 vibration 129 vibrotactile device 74 video game 283 technology 186 virtual reality 88, 277 tactile map 76 vision and age 35 visual alarm system 283 function 54–8 impairment 56–8, 86 auditory display 69–70, 80–5, 90 computer aid 74, 76, 80, 81, 276–7 definition 70 graphics 74–80, 84, 89–90 see also tactile linear perspective 76–9

low vision aid 6 impairment (Continued) mobility 69–70, 88–9, 90, 205 and rehabilitation 69–90 vocational assessment 158 rehabilitation 145–64, 280 charitable organizations 150 counselor 159, 160 ergonomics 155–64 see also under rehabilitation history 150–1 legal basis 150–1, 279 pre-employment 158–64 system 150–5 Vocational Education, Federal Board of 151 Vocational Rehabilitation Act 279 voice recognition system 277, 282 voluntary response 198 walking 13, 106 Walter Clarity Telephone 24 warm up 104 water exercise 107 wheelchair accessibility 160, 252 brakes 267 coasting characteristics 216–18 crank propulsion 220 design 214, 222–4, 237, 247, 248–9, 251–3 ergonomics 212–15, 220, 221, 224, 228, 246–68 financing issues 214–15 foot-propelled 249 force generation 220, 234–6, 237, 239, 260–3 hand rim 218, 220–3, 229–30, 235, 237, 239, 260–2 lever propulsion 220, 237, 239, 260 manual 210–39, 246–7, 248–9 manual-power conversion 257 mechanical efficiency 216–17, 220–2, 224, 235 power 249, 251, 253–5 prescription 212–13, 215–16, 250–3

438 INDEX

propulsion 204, 206, 216–39, 258–62 modelling 236–9 quality control 212–14 seating 222–3, 239, 251, 253, 255–7, 260, 356 shoulder-rim distance 223–4 simulator 236 stability 249, 266, 267 standard test 267 stand-up 258 tilt-in-space 257 usability 213–14 use 247–8, 356 user 224, 233–4, 250–2, 315, 317, 320– 1 accidents and injuries 263–8 body composition and strength 347, 348 comfort 213–14 disability etiology 247–8 exercise capacity 224–7 position stability 232, 252–3, 312, 322 space requirement 323, 355 see also under exercise weight 247, 249 wheel 217, 252 camber 217, 234, 253, 267 wheelchair-lift design 162–3 wheelchair-user interface 222–4 Wide Angle Mobility Light 88 word prediction software 284 work break 5, 6, 128 capacity 4–6, 9, 52, 109, 111 see also functional capacity; physical capacity demand 4–6 desire to 41, 53 disability 124, 125 classification 148–50 industrial distribution 149–50 occupational distribution 148, 149 population 145–7 hardening 109 and occupational stress 45–51 organization 134, 138 WorkAbility Index (WAI) 9

workload 6, 59 Workmen’s Compensation statute 150 workplace computer 55–6, 89, 161 design 56, 89, 126, 159–61, 206–7, 282, 322–3 support for elderly 52–3 workspace determination 322, 325 of upper extremity 321–2