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