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Aging and productivity: some physiological issues
International Journal of Industrial Ergonomics 25 (2000) 535}545
Aging and productivity: some physiological issues Roy J. Shephard * Faculty of Physical Education and Health, Faculty of Medicine, University of Toronto, Canada Department of Public Health Sciences, Faculty of Medicine, University of Toronto, Canada Health Studies Programme, Brock University, St. Catharines, Ontario, Canada
Abstract Aging is associated with progressive decreases in aerobic power, thermoregulation, reaction speed and acuity of the special senses. These changes can reduce productivity, particularly in self-paced activities where the physical or mental input of the individual worker is the rate-limiting step in production. Many potential problems can be corrected by worksite modi"cation, employee wellness programmes and retraining. Given wide interindividual di!erences in the abilities of elderly employees, and the fallibility of most test methods, the setting of appropriate and non-discriminatory standards for recruitment and continued employment of older individuals remains a di$cult challenge for the industrial ergonomist. The social need for ever-increasing production also requires critical examination. Relevance to industry A progressive aging of working populations in the industrial nations poses important practical questions concerning the impact of these changes on productivity. What measures can be taken to extend the span of working life, and what is the best method of determining the age when retirement should occur? 2000 Elsevier Science B.V. All rights reserved. Keywords: Aerobic power; Age ceilings; Employee wellness; Employment standards; Reaction speed; Retirement; Retraining; Sensory deterioration; Thermoregulation
This paper examines the in#uence of aging upon productivity, focusing particularly on the "nal decade of working life, when issues of employee recruitment, continued employment and deteriorations in productivity are most vigorously debated. Speci"c concerns of the industrial ergonomist include appropriate de"nitions of aging and productivity, non-discriminatory methods of setting any necessary ceilings to both recruitment and con-
tinued employment, and the potential to extend productive working life through modi"cations of the working environment, speci"c retraining programmes and the introduction of worksite wellness programmes.
1. De5nitions 1.1. Aging
* PO Box 521, 41390, Dryden Rd. Brackendale, BC, V0N 1H0, Canada. Tel.: (604)-898-5527; Fax: (604)-898-5724. E-mail address: [email protected] (R.J. Shephard)
Most gerontologists consider that even `younga old age does not begin until the commonly accepted national age of retirement, 65 yr. Nevertheless,
0169-8141/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 9 - 8 1 4 1 ( 9 9 ) 0 0 0 3 6 - 0
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there are concerns because of the growing proportion of employees who have reached late middle age. The average age of the labor force is rising rapidly in many countries, in part because of the decline in birth rate over the past 20}30 yr, and in part because current technology is demanding ever-longer university and community college courses. The ILO has estimated that by the year 2025, the proportion of individuals over the age of 55 yr will be 32% in Europe, 30% in North America, 21% in Asia, and 17% in Latin America (ILO, 1992). In a number of developed nations, there has also been a progressive decrease in the average age of retirement; workers accumulate su$cient wealth to retire early, employers are unwilling to hire older workers, and senior members of the labor force are displace by technical change (McPherson, 1983). Thus, in many countries, participation in the labor market is now quite low among those aged 55}65 yr. However, the growing number of frail elderly is placing an ever-increasing pressure upon national systems of pensions and health care, so that a number of governments now have a strong interest in maximizing the productivity of older workers, and are considering an upward revision of any mandatory retirement age. The peak years of achievement in many professions are often thought to lie in the late 30 s or the early 40 s (Simonton, 1988). Individual studies and meta-analyses have shown surprisingly little relationship between aging and job performance (Hunter and Hunter, 1984; McEvoy and Cascio, 1989; Meier and Kerr, 1976; Schwab and Heneman, 1977; Waldman and Avolio, 1986). Nevertheless, the deterioration of biological function is a relentless life process; it begins in many organs at birth, and a progressive decrease in many biological functions can be detected from early adult life (Shock, 1967). Caution must be shown in extrapolating from laboratory tests to the work-site. However, eight of nine abilities tested by the general aptitudes test battery were found to decline with age (Droege et al., 1963). Moreover, such abilities seem strongly and causally related to job performance (Schmidt et al., 1986). Other papers in this symposium also point to a substantial impact of aging on the Work Ability Index, particularly in heavy physical work.
Population aging has increased the political power of elderly workers, and what previously seemed acceptable age-restrictions upon the recruitment, promotion, and retention of older employees have faced increasing challenge before quasi-legal regulatory agencies such as the Human Rights Commission in Canada and the Equal Employment Opportunities Commission in the United States (Shephard, 1987). The issue of the productivity of the aging worker is thus attracting considerable current attention.
1.2. Productivity Productivity may be considered as the output of goods and/or services per unit investment of human capital. Under conditions where the main production bottleneck is human productivity, the reported "gure thus re#ects the immediate input of human capital, the work-e!ectiveness of the individual employees, any immediate loss of time due to absenteeism, acute or chronic illness, and the long-term loss of human capital due to early retirement or premature death. Biological factors limit productivity less often than some investigators have assumed. Output may be determined simply by the pace of a conveyor belt. In self-paced work, much also depends upon personal initiative (Pyle, 1979; Vermeersch et al., 1979). Productivity varies with occupancy (whether the individual actively seeks work, or passively awaits instructions), on e!ectiveness (selection of an appropriate task), and on e$ciency (adoption of an optimum approach to a task). Performance often re#ects much more than the abilities, motivation, and experience of the individual employee. Output may be limited by absence or lack of cooperation from a key colleague, ine$cient management, union restrictions, a lack of essential equipment or materials, failure to invest in automation, a poor overall quality of the working environment, seasonal factors, or a lack of consumer demand for a product (Shephard, 1986a,b). In many real-life situations, immediate human resources limit neither quantity nor quality of production, and the age of a worker may be irrelevant except to the extent that accumulated experience
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allows older employees to determine some method of circumventing bottlenecks in production. Where the main determinant of productivity is the e!ort contributed by the individual worker, classical concepts have suggested a hyperbolic relationship linking the quality and the quantity of output (Shephard, 1974). More recent investigations have noted the in#uence of both working environment and experience on the quality versus quantity relationship. The younger worker may produce a somewhat larger quantity of the desired end-product in unit time (Droege et al., 1963; Yokizomo, 1985), but against this super"cial attraction, accumulated experience (Schmidt et al., 1986) and a di!ering work ethos (Rhodes, 1983) allow the older worker to produce goods of greater quality, sometimes also in equal amounts. The successful manager seeks to optimize the relationship between the quantity and quality of production for a minimum input of human capital, materials and/or equipment. In our present context, it is worth noting that in many industries today, the in#uence of minor age-related di!erences in physical productivity is far-eclipsed by e!ects from age-linked increases in salaries and fringe bene"ts. Furthermore, large gains in productivity per dollar of labor costs can often be realized through investment in automation or `out-sourcinga of components to countries where wage-rates are low for both young and older workers. Attempts to optimize the hyperbolic relationship between quality and quantity usually assume that both the quantity and quality of industrial output can be monitored accurately. However, it is di$cult to measure either aspect of production in many types of employment. Often, the end-product is the result of team work between good and bad workers, both young and old, so that it becomes almost impossible to assess the individual's contribution. Determinations of the quality of output are particularly di$cult, and indeed output is often expressed simply as a rate of production: the length of "rebreak cut per hour, the average time that an airline clerk takes to answer a telephone call, or the number of policies per hour that are processed by an insurance agent. Such an assessment tends to penalize older employees, since accumulated experience and judgment enhance the quality of their
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contribution relative to that of a younger person, but may slow the speed of response. Alternative bases of assessment include in some applications a self-rating of productivity, a consideration of supervisor ratings of performance, a history of commendations or merit pay awards, a scoring of `errors,a and the computer monitoring of an employee's speed and rhythm of working. This last technique is widely criticized as an invasion of privacy, and it usually leads to a deterioration in worker/supervisor relationships. 2. Functional changes and productivity 2.1. General considerations As aging progresses, various decreases in peak functional capacity may limit an employee's potential to engage in strenuous physical work. If a person's physical capabilities have become marginal, the quantity of production will diminish in self-paced work, and in machine-paced tasks excessive fatigue may lead to poor quality output, industrial disputes, accidents, injuries, absenteeism, a high employee turnover rate and demands for early retirement. Particularly in self-paced work, age-related decreases in muscular strength and endurance, anaerobic power and anaerobic capacity may threaten the productivity of older individuals (Monod, 1999). This paper will focus on other potential constraints that can limit the occupational performance of the older person, including a decrease in aerobic power, an impairment of thermoregulation, a slowing of reactions and a deterioration in the acuity of the special senses. If the rate of working is truly limited by some aspect of an employee's functional capacity, there is opportunity for the industrial ergonomist to address these physiological problems by modi"cation of the workplace, employee wellness programmes and retraining of the older worker. 2.2. Decreases in aerobic power Aerobic power declines progressively over working life, from around 50 ml/[kg ) min] in a young man and 40 ml/[kg ) min] in a young woman, to 25}30 ml/[kg ) min] in 65-yr-olds of either sex
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(Shephard, 1994). A corresponding decrease of productivity might thus be anticipated in tasks with a high aerobic demand. In self-paced heavy work, the average individual maintains an energy expenditure where there is little accumulation of lactate over an eight-hour working day; the critical intensity of e!ort is typically 40% of maximal oxygen intake (Hughes and Goldman, 1970); however, the 40% ceiling is situational. Values decrease from 50% under very favorable working conditions to around 35% if the environment is di$cult, rest periods are not practicable, and/or the task demands adoption of an awkward posture, the use of small muscle groups and intermittent peaks of more intensive physical activity (As strand, 1967); even lower percentages are usual in lifting tasks. With any pattern of activity, much also depends on the individual's motivation; substantially higher percentages of aerobic power are developed both during an occupational emergency and in an athletic competition such as an ultra-marathon run (Shephard and Kavanagh, 1975) than during normal daily work. Finally, although this point has yet to be tested, the ceiling may be somewhat higher in an old person, since the resting metabolism then accounts for a larger fraction of the 40% standard. The energy cost of individual work-site tasks can be estimated by devices such as a Kofranyi} Michaelis respirometer or an Oxylog recorder, but unfortunately employees may tend to accelerate their work-pace while their energy expenditure is measured. Further, on a normal work-day, the `heavya components of work described by such devices occupy only a fraction of an 8 h shift, although both management and unions may be reluctant to admit the extent of time lost through relaxation breaks, machinery failures and other causes. Analysis is further complicated by interindividual di!erences in both the energy cost of speci"c tasks and the work structure of a typical day (Shephard, 1974). In older employees, an agerelated increase in body mass tends to increase the cost of tasks where body mass must be displaced (Godin and Shephard, 1973), but this disadvantage is o!set by accumulated experience and resulting improvements in mechanical e$ciency in the older employee. Moreover, seniority rules may allow
older employees to choose physically easier subtasks within a given job category. In machine-paced tasks, the standard rate of working is commonly set at a pace which demands four-"fths of the 40% e!ort tolerance of the average employee, that is 32% of the presumed average maximal oxygen intake for the population (Shephard, 1974). However, this pace may have been agreed with unions when the average worker was male and aged 40 yr or younger. Let us assume that such a standard is indeed appropriate for a typical 40 yr-old male who is engaged in hard physical work for much of an eight-hour day. If employment continues through to the age of 65 yr, with a 10% loss of aerobic power per decade, and a 30}40% di!erence of aerobic power between men and women, then an average 65 yr old man will be working at 105% rather than the intended 80% of his 8-hr aerobic capacity. Likewise, a 65-yr-old female will be operating at over 140% of this standard, in other words at 56% of her peak aerobic power. There are a few occupations where aerobic demand remains high; examples include the infantry soldier (Hughes and Goldman, 1970) and the postal carrier (Shephard, 1982), both of whom may be required to walk long distances while carrying heavy loads. But in practice, there is only a weak relationship between aerobic power and job performance, and complaints of fatigue are relatively infrequent, even among older women who are engaged in such work. This is because: (i) The 80% standard was usually reached by union negotiation, and is less than the true, physiological 8-h ceiling for the average worker. (ii) Employees often choose heavy occupations or continue in such work if their initial physique gives an above average physical working capacity. (iii) In many physically demanding tasks, a substantial fraction of the energy cost is attributable to the displacement of body mass (Godin and Shephard, 1973). Performance thus depends on the relative rather than the absolute working capacity. This reduces the disadvantage of female employees relative to their male counterparts. (iv) Experience increases mechanical e$ciency. The energy cost of many occupational tasks is thus smaller in older employees who have
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accumulated many years of experience in a given occupation. (v) Heavy work may occasionally help to sustain aerobic "tness as a person becomes older, although the intensity of e!ort required in most occupations is insu$cient to have any marked training e!ect (Allen, 1966). (vi) Categorizations of jobs are crude. Promotion or seniority rules may thus allow those who are still classed as `heavy workersa to select less demanding types of employment as they become older. (vii) Those whose physical abilities no longer match task demands often seek lighter employment, part-time work or early retirement. 2.3. Thermoregulation In general, the literature suggests that individuals aged 46}65 have a poorer heat tolerance than younger adults, and su!er more physiological strain during heat acclimation (Pandolf, 1991, 1997). One adverse in#uence of aging is that the rate of sweating seems to be reduced for any given thermal load and vasodilatation is less well coordinated (Robinson, 1963). More importantly, when work is performed in a hot environment, the rise in core body temperature depends upon the relative rather than the absolute intensity of e!ort. Elderly employees are thus handicapped because their maximal oxygen intakes are low (Lavenne and Belayew, 1966; Strydom et al., 1971). In many older individuals, problems of heat dissipation are further exacerbated by chronic disease or because the average skinfold thickness increases by 4}5 mm over the course of working life; indeed (Pandolf, 1991,1997) has argued that in those over the age of 65 who are free of chronic disease and have maintained personal "tness, heat tolerance is unimpaired. Hot conditions a!ect productivity mainly by causing discomfort. Work becomes progressively more di$cult as the rectal temperature rises above 383C (Wyndham, 1974). The quality of output is reduced, and there is an increased likelihood of both industrial disputes and accidents (Vernon et al., 1927). Muscle blood #ow is reduced, in part because of the #uid lost in sweating, and in part because a substantial fraction of the available blood #ow is diverted from the working muscles to
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the skin. One consequence of these circulatory changes is that the worker can no longer operate at 40% of maximal oxygen intake throughout an 8-h day without developing severe fatigue. In some tasks such as deep mining, physical demands can also push core body temperatures to dangerously high levels where there are risks of heat collapse and heat stroke (Wyndham, 1974). Older workers are on average less productive and more vulnerable to heat stroke than their younger peers if working conditions are hot (Strydom et al., 1971). However, the handicap of the older employee depends on how far physical condition has been allowed to deteriorate. Lavenne and Belayew (1966) concluded that a peak oxygen intake of 40 ml/ [kg ) min] provided a useful dividing line between those who were able to tolerate a high temperature and those who were adversely a!ected by it. The e!ect of hot conditions on productivity can be examined using some calculations of Pugh et al. (1960); they evaluated the rate of heat exchange in cross-channel swimmers. Since the water was cold, their subjects were fully vasoconstricted. Given an energy expenditure of 10 metabolic equivalents (METS), Pugh et al. (1960) argued that the application of a 1 mm layer of grease external to the skin (an increase in thickness of the layer of super"cial fat from 10 to 11 mm) would augment the core-toskin temperature gradient by 10%, or 1.673C. Vasodilatation greatly reduces the initial thermal gradient from the core to the skin surface when a person is working in a hot environment. At an energy expenditure typical of a heavy worker (5 METS), the total thermal gradient is unlikely to exceed 23C. If aging leads to a 4 mm increase in skinfold thickness (a 2 mm increase in super"cial fat relative to the usual initial value of 6 mm in a young man), then this should increase the steady state core-to-surface temperature gradient by one third, or 0.73C. If environmental conditions are such that even young workers reach the safe limiting core temperature of 39.23C during the working day (Wyndham, 1974), then older workers who carry an extra 2 mm of super"cial fat will need to reduce their gross rate of energy expenditure by 33% (1.7 METs) in order to maintain thermal equilibrium. The corresponding decrease in net external energy expenditure is a substantial 42%.
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2.4. Reaction speed and special senses Age-related decreases in reaction speed and the acuity of the special senses are well-documented (Shephard, 1997). There are certain special categories of employment in which a deterioration of vision or hearing can substantially limit employment prospects * for example, a loss of near vision in a watchmaker, or a decrease of auditory acuity in a person who is using their hearing to check the performance of vacuum cleaner motors (Shephard, 1974). However, the magnitude of such problems is progressively being reduced by modern technology. It is now often cheaper to replace than to repair a watch mechanism, and the sound patterns associated with malfunction of a motor can be displayed on a VDT, rather than relying upon an acute sense of hearing in the diagnostician. Concern is often expressed regarding the impact of changes in reaction speed and sensory acuity upon an employee's susceptibility to accidents. Although overall injury rates for any given type of employment show little change with aging, Griew (1964) has argued that accident rates for a number of speci"c trades within an occupational category increase in older employees; the disability resulting from a given injury may also take longer to resolve in an older worker. There has been particular anxiety about the ability of older employees to operate public service vehicles such as buses safely. However, available statistics (Norman, 1960; Shephard et al., 1988) show that the number of accidents per vehicle per kilometer are fewer for 60}64 yr old drivers than for other age categories, even after control of the data for years of bus driving experience. The greater judgment and patience of the older worker, plus the progressive selecting out of `accident pronea personnel seem more than enough to compensate for any adverse e!ects from a slowing of reaction speed or a deterioration in vision. Detailed task analysis suggests that problems are more likely to arise from decreases in muscle strength. A loss of strength may prove a handicap when making fast turns in a bus that is not equipped with power steering, when loading wheelchair patients into vehicles that are only partially adapted for special populations, and when
carrying the fare-box back to the manager's o$ce (Shephard et al., 1988). In some types of o$ce work such as VDT data entry, the average employee may have a less than optimal productivity because the job is boring and arousal decreases over the course of the workday. Problems of this sort could be less likely in an older person, for two reasons. Any reduction of ability because of declining senses and out-dated skills makes a given task more challenging for the older person. This can increase stress in demanding employment, but in a boring job it helps to sustain arousal. Progressive job selection tends to match the individual's ability and task demands over the course of a working career, but this bene"t of aging is increasingly o!set by problems of redundancy and the need of displaced workers to accept any type of employment, irrespective of its demands. Many causes of occupational stress are environmental: excessive task di$culty, a lack of perceived control over operations, unclear job requirements, lack of social interactions, personality con#icts or inadequate feedback of performance (Shephard, 1988). Some of the items that cause such stress are relatively independent of age, but problems can be greater for older employees because of declining physical and mental abilities and an out-dating of skills by a rapidly changing technology (Robinson et al., 1985).
3. Maintaining productivity in an aging workforce Much can be done to sustain the productivity of an aging workforce through redesign of the workplace, the introduction of employee wellness programmes and speci"c retraining of individual employees. 3.1. Workplace redesign Mechanization and automation can reduce the energy demands of most tasks to the point that the age-related decrease in aerobic power is no longer an issue. If mechanization is still di$cult to organize, other options include the extension of workbreaks and the arrangement of job-sharing or part-time work for older employees; the usable
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fraction of peak oxygen intake increases progressively as the length of the working day is shortened (Bonjer, 1968). The average rate of energy expenditure can often be reduced to an acceptable level by a simple rearrangement of duties. For example, a shipping clerk may spend a part of each hour labelling rather than lifting boxes (Shephard, 1974), or a postal carrier may structure a mail delivery route so that the mailbag is heaviest while he or she is descending any hills on the route (Shephard, 1982). An excessive accumulation of body heat can be avoided by improvements in the design of protective clothing, by the installation of more powerful air-conditioning systems, or simply by a reduction in the standard rate of working. Likewise, if a task is proving stressful, the mental demands can be reduced by simpli"cation of the work-station and the development of clearer organizational guidelines. 3.2. Employee wellness programs The bene"ts of employee wellness programmes are discussed in an accompanying paper (Shephard, 1999), but certain salient points that are relevant to productivity will be underlined here. Corporate motivation for such programmes may re#ect either a belief that enhanced productivity will increase pro"ts, or an altruistic desire of a key executive to maintain employee health (Shephard, 1986a, b). The development of such programmes also serves to demonstrate to the Equal Employment Opportunity Commission that everything possible has been done to accommodate and sustain the e!ectiveness of older employees (Shephard, 1990). 3.2.1. Aerobic power A well-designed laboratory endurance training programme can enhance aerobic power by around 20%. Moreover, in percentage terms, the response of a 65-yr old is similar to that of a young adult (Shephard, 1997). A recent review has summarized the functional gains that result from worksite exercise programmes (Shephard, 1996). The early studies of Slee and Peepre (1978) and Cox et al. (1981) remain fairly typical of the work-site response. Both research teams found that a useful 13% in-
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crease of predicted aerobic power developed within a few months of initiating the programme. This was equivalent to a 13 yr reduction in biological age, but unfortunately gains were restricted to frequent programme participants, about 10% of the total work-force. Thus, when averaged across the entire company, there was only a 1.3% gain of maximal oxygen intake. Slee and Peepre (1978) and Cox et al. (1981) both examined o$ce workers, a group where aerobic power was unlikely to have limited job performance. But even if the work had been physically demanding, and the aerobic power of the oldest third of the labor force had initially been inadequate to meet task demands, the programmeinduced gain in oxygen transport would only have boosted productivity by 0.4% (1.3;0.33%) (Shephard, 1995). Blair et al. (1986) claimed that the average employee showed a 10.5% gain in aerobic power two years after inception of Johnson and Johnson's `Live for Lifea worksite wellness programme. However, gains were estimated from submaximal cycle ergometer tests, and control subjects who received only a health screening also showed a 4.7% increase of score. The net programme impact was thus a 5.8% increase in aerobic power. Moreover, the need to boost oxygen transport is greatest in those over 45 yr of age, and in this critical group the di!erence between experimental and control subjects was only 0.9%. Nevertheless, empirical data suggest that gains of work performance can be substantial, particularly under arduous conditions. Danielson and Danielson (1982) assessed productivity from the speed with which forestry workers cut a "re-break. On average, aerobically trained crews cut a 62% greater length per day than control crews. After covariance adjustment for age and experience, performance was signi"cantly correlated with the individual's maximal oxygen intake. Under hot summer conditions, the trained group had a 101% advantage of cutting speed over their untrained peers. 3.2.2. Thermoregulation There is some interaction between aerobic training and heat acclimatization. Worksite exercise programmes could thus enhance tolerance of hot
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conditions, especially in older employees whose tolerance of heat stress has become marginal. Acclimatization is maximized if subjects are exposed to a combination of heat and regular endurance exercise. Strydom et al. (1971) have used this technique to prepare recruits for deep gold mining in South Africa. It is less clear whether enhanced "tness increases the comfort of workers who are exposed to more moderate heat. Fit individuals sweat more readily, and this may actually increase discomfort under conditions where it is di$cult for sweat to evaporate (Aoyagi et al., 1997). In such situations, comfort may be as important to productivity as is overall thermal balance. 3.2.3. Self-ezcacy and mood-state Fitness programmes have a positive in#uence upon feelings of self-e$cacy, reducing both anxiety and depression (North et al., 1990; Landers and Petruzello, 1994). The response depends in part upon the initial disturbance of mood-state, and since depression is more common in older individuals, exercise programmes may be particularly helpful in boosting the mood-state of older employees. Given the subjective nature of occupational fatigue, an increased sense of self-e$cacy and/or an elevation of mood-state may in turn allow the completion of demanding tasks without complaints of tiredness. Early uncontrolled but objective studies suggested that "tness programmes decreased error scores in both manual telegraph operation and the inspection of textiles (LaPorte, 1970). A study of pharmaceutical workers found decreased self-perceptions of work load and fatigue and enhanced job satisfaction among exercise participants relative to social group controls (Rosenfeld et al., 1990; Shephard, 1995). Cox et al. (1981) compared work-times to previously established standards for a variety of o$ce tasks; 6 months after inception of a work-site wellness programme, there was a 7.0% gain of productivity at the experimental company, but * perhaps because of a Hawthorne e!ect * there was also a 4.3% gain at the control company. Likewise, Smolander et al. (1992) noted a 5.5% gain in performance of exercised subjects at a metal company, although there was also a 2.5% improvement in the performance of controls.
3.2.4. Healthy lifestyle A healthy lifestyle may be another important dividend of a worksite wellness programme. Terborg (1995) estimated that smoking was associated with a 1.8% loss of productivity, and alcoholism with a 30% loss. Moreover, the cumulative health problems associated with such addictions increase with age. Self-reports from the Toronto Life Assurance study (3% successful smoking withdrawals in the "rst year), from the Staywell programme (6% decrease of smokers relative to controls at year 3), and from Johnson and Johnson (3.5% successful smoking withdrawal in one year, 12% in two years) all support the practical value of employee wellness programmes as a means to encourage a healthy lifestyle (Shephard, 1996). 3.3. Other initiatives to enhance productivity 3.3.1. Retraining of workers The productivity of older employees in technologically advanced work can be sustained by appropriately adapted programmes for the up-grading of skills and the acquisition of new knowledge (Shephard, 1974). Under highly controlled laboratory conditions, task learning proceeds more slowly in older individuals, but it is less certain how far such data can be extrapolated to the worksite, at least through to the normal age of retirement. The learning process may be helped by use of self-paced learning systems rather than requiring individuals to attend classes that are designed primarily for younger workers. Often, the gains from a training programme are greater if active participation is required than if reliance is placed upon formal lectures and instructions that are soon forgotten (Belbin and Down, 1965). Instruction should emphasize continuities with the worker's current knowledge, indicating clearly the relationship between course material and the new demands of employment. 3.3.2. Setting a ceiling age for employment If the physical demands of a task currently do not allow older individuals to match the productivity of younger workers, the options for the employer are (1) to optimize the design of the
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workstation, (2) to maximize the residual abilities of older workers through appropriate wellness programmes, (3) to establish packages that encourage voluntary early retirement or transition to parttime work, (4) to impose retirement at a "xed age, or (5) to set job-related performance standards as a condition of continued employment. 3.3.2.1. Early retirement. In many jobs, workers who are a!ected by ill-health or functional loss are glad to accept the options of early retirement or part-time work, provided that pensions are adequate to meet their foreseeable needs (Gould and Takala, 1993; Huuhtanen and Piispa, 1993; Kilbom et al., 1993). 3.3.2.2. Mandatory retirement. Mandatory retirement is attractive and clear-cut from an administrative point of view, and it avoids making a worker leave a company because he or she has failed some annual test. However, it is unfair to the employee who has conscientiously conserved health throughout a working career (Shephard, 1987). Taking the speci"c example of aerobic power, scores show inter-individual di!erences of at least 20% at any given age. Part of this di!erence is constitutionally determined, but as much as two thirds re#ects the lifestyle of the individual employee, including such items as habitual physical activity, cigarette smoking, and obesity (Jackson et al., 1995; Shephard, 1987). Given that the age-related deterioration in aerobic power averages about 10% per decade, the 20% coe$cient of variation at any given calendar age implies that a person's biological age can vary by as much as $20-yr about the population mean (Sharkey, 1987). In other words, some 65 yr olds will be "tter than the average 25-yr old employee. Plainly, such individuals do not merit dismissal just because they have reached a calendar age of 65 yr. 3.3.2.3. Non-discriminatory employment standards. One alternative to mandatory retirement is to "nd some non-discriminatory measure of performance to identify employees who lack the requisite functional capacity. Unfortunately, it is di$cult to obtain valid and reliable measurements of current functional status. The measurement of maximal oxygen intake might seem a useful objective mea-
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sure of aptitude for heavy physical work. However, even if it is possible to make a direct treadmill measurement, the day-to-day intra-individual variation is at least 4%, and a careful and costly laboratory determination is essential to reach this level of precision. Predictions of maximal oxygen intake that are based upon "eld tests often di!er by as much as 20% from the true value. Moreover, intraindividual di!erences as large as 15}20% can develop due to an intercurrent acute illness (Wright et al., 1978). Thus, employees who have a poor score on a particular day could claim that they were unwell when tested. Finally, oxygen transport is task-speci"c; a person may have well-developed leg muscles and a good treadmill performance, yet experience di$culty in an occupation that requires heavy arm work. The criterion of maximal oxygen intake is thus di$cult to apply and di$cult to defend in practice. Performance tests that mimic "eld demands have greater face validity (Davis and Dotson, 1987). Nevertheless, scores on such items depend heavily upon body size; thus they are open to the objection that they discriminate against women. The optimal method of assessing job performance has yet to be determined. Valid assessments may ultimately be derived from observations made over the course of the normal working day (for example, heart rates, blood lactate levels, and serum enzyme concentrations), but at present, supervisor and peer ratings seem as valid as either laboratory or "eld testing of performance.
4. Ethics of maximizing productivity One "nal issue to consider with an older work force is whether it is still necessary to maximize the industrial output of every worker, regardless of his or her age. How concerned should we be if the 65-yr old worker is a little slower and less productive than a person aged 25? The social need for everincreasing production of consumer goods needs critical re-examination in a world of shrinking non-renewable resources. Automation has given humankind the opportunity to produce an enormous quantity and variety of goods with only limited worker input. It should
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thus be possible to produce all of the goods that society needs, while respecting the dignity of the older person who cannot conform to production `normsa because of ill-health or aging to choose his or her time of withdrawal from the labor force with the dignity appropriate to 40 or 50 yr of loyal service. Acknowledgements Dr. Shephard's studies are supported in part by a research grant from Canadian Tire Acceptance Limited. References Allen, J.G., 1966. Aerobic capacity and physiological "tness of Australian men. Ergonomics 9, 485}494. Aoyagi, Y., McLellan, T., Shephard, R.J., 1997. Interactions of physical training and heat acclimation: the thermophysiology of exercising in a hot climate. Sports Medicine 23, 173}210. As strand, I., 1967. Degree of strain during building work as related to individual aerobic capacity. Ergonomics 10, 293}303. Belbin, E., Down, S., 1965. Interference e!ects from new learning: their relevance to the design of adult training programs. Journal of Gerontology 20, 154}159. Blair, S.N., Piserchia, P.V., Wilbur, C.S., Crowder, J.H., 1986. A public health intervention model for work-site health promotion: impact on exercise and physical "tness in a health promotion plan after 24 months. Journal of the American Medical Association 255, 921}926. Bonjer, F.H., 1968. Relationship between physical working capacity and allowable caloric expenditure. In: Rohmert, W. (Ed.), International Colloquium on Muscular Exercise and Training. Gentner, Darmstadt, Germany, pp. 86}98. Cox, M., Shephard, R.J., Corey, P., 1981. In#uence of an employee "tness programme upon "tness, productivity and absenteeism. Ergonomics 24, 795}806. Danielson, R., Danielson, K., 1982. Exercise Program E!ects on Fire"ghters. Ontario Ministry of Culture and Recreation, Toronto. Davis, P.O., Dotson, C.O., 1987. Job performance testing: an alternative to age discrimination. Medicine and Science in Sports and Exercise 19, 179}185. Droege, R.C., Crambert, A.C., Henkin, J.B., 1963. Relation between GATB aptitude scores and age for adults. Personnel and Guidance Journal 42, 502}508. Godin, G., Shephard, R.J., 1973. Body weight and the energy cost of activity. Archives of Environmental Health 27, 289}293.
Gould, R., Takala, M., 1993. Pension or work- the preferences of older workers. In: Ilmarinen, J. (Ed.), Aging and Work. Institute for Occupational Medicine, Helsinki, pp. 67}73. Griew, S., 1964. Age, information transmission and the positional relationship between signals and responses in the performance of a choice task. Ergonomics 7, 267}277. Hughes, A.L., Goldman, R.F., 1970. Energy cost of hard work. Journal of Applied Physiology 29, 570}572. Hunter, J.E., Hunter, R.F., 1984. Validity and utility of alternative predictors of job performance. Psychological Bulletin 96, 72}98. Huuhtanen, P., Piispa, M., 1993. Attitudes on work and retirement by occupation. In: Ilmarinen, J. (Ed.), Aging and Work. Institute for Occupational Medicine, Helsinki, pp. 152}156. ILO, 1992. The ILO and the Elderly. International Labor Organization, Geneva. Jackson, A.S., Beard, E.F., Wier, L.T., Ross, R.M., Stuteville, J.E., Blair, S.N., 1995. Changes in aerobic power of men ages 25}70 yr. Medicine and Science in Sports and Exercise 27, 113}120. Kilbom, As ., Baltzari, L., Ilmarinen, J., Nygaard, C.-H., NoK rregaard, C., Solem, P.E., Westerholm, P., 1993. Aging and retirement: An international comparison. In: Ilmarinen, J. (Ed.), Aging and Work. Institute for Occupational Medicine, Helsinki, pp. 54}62. Landers, D.M., Petruzello, S.J., 1994. Physical activity, "tness and anxiety. In: Bouchard, C., Shephard, R.J., Stephens, T. (Eds.), Physical Activity, Fitness and Health. Human Kinetics, Champaign, IL, pp. 868}882. LaPorte, W., 1970. La gymnastique de pause dans l'entreprise. Editions de l'administration de l'education physique des sports, Brussels, Belgium. Lavenne, F., Belayew, D., (1966). Exercise tolerance test at room temperature for the purpose of selecting rescue teams for training in a hot climate. Review of the Institute for Hygiene in Mines 21, 48}58. McEvoy, G.M., Cascio, W.F., 1989. Cumulative evidence on the relationship between employee age and job performance. Journal of Applied Psychology 74, 11}17. McPherson, B., 1983. Aging as a Social Process. Butterworth, Toronto. Meier, E., Kerr, E., 1976. Capabilities of middle-aged workers: a survey of the literature. Industrial Gerontology 3, 147}156. Monod, H., 1999. Muscle strength, aging and productivity. International Journal of Industrial Ergonomics, In press. Norman, L.G., 1960. Medical aspects of road safety. Lancet (i), 989}994 & 1039}1045. North, T., McCullagh, P., Tran, Z.V., 1990. E!ect of exercise on depression. Exercise and Sport Science Reviews 18, 379}416. Pandolf, K.B., 1991. Aging and heat tolerance at rest or during work. Experimental Aging Research 17, 189}204. Pandolf, K.B., 1997. Aging and human heat tolerance. Experimental Aging Research 23, 69}105. Pugh, L.G.C.E., Edholm, O.G., Fox, R.H., Harvey, G.R., Hammond, W.H., Tanner, J.M., Whitehouse, R.H., 1960. A physiological study of channel swimming Clinical Science 19, 257}273.
R.J. Shephard / International Journal of Industrial Ergonomics 25 (2000) 535}545 Pyle, R.L., 1979. Performance measures for a corporate "tness program. Human Resource Management 18, 26}30. Rhodes, S.R., 1983. Age-related di!erences in work attitudes and behavior: a review and conceptual analysis. Psychological Bulletin 93, 328}367. Robinson, P.K., Livingston, J., Birren, J., 1985. Aging and Technological Advances. Plenum, New York. Robinson, S., 1963. Temperature regulation in exercise. Pediatrics 32 (Suppl.), 691}703. Rosenfeld, O., Ruskin, H., Halfon, S.T., Tenebaum, G., 1990. The e!ect of physical intervention on industry workers: their needs, habits, and desire for recreational physical activity. In: Kaneko, M. (Ed.), Fitness for the Aged, Disabled and Industrial Worker. Human Kinetics, Champaign, IL, pp. 266}272. Schmidt, F.L., Hunter, J.E., Outerbridge, A.N., 1986. Impact of job experience and ability on job knowledge, work sample performance, and supervisory ratings of job performance. Journal of Applied Psychology 71, 432}439. Schwab, D., Heneman, H., 1977. E!ects of age and experience on productivity. Industrial Gerontology 4, 113}117. Sharkey, B.J., 1987. Functional vs. Chronological age. Medicine and Science in Sports and Exercise 19, 174}178. Shephard, R.J., 1974. Men at work. Thomas, Spring"eld, IL. Shephard, R.J., 1982. The daily workload of the postal carrier. Journal of Human Ergology 11, 157}164. Shephard, R.J., 1986a. Economic Bene"ts of Enhanced Fitness. Human Kinetics, Champaign, IL. Shephard, R.J., 1986b. Fitness and Health in Industry. Karger, Basel. Shephard, R.J., 1987. Human rights and the older worker: changes in work capacity with age. Medicine and Science in Sports and Exercise 19, 168}173. Shephard, R.J., 1988. Sport, leisure and well-being. An ergonomic perspective. Ergonomics 31, 1501}1517. Shephard, R.J., 1990. Assessment of occupational; "tness in the context of human rights legislation. Canadian Journal of Sport Sciences 15, 89}95. Shephard, R.J., 1994. Aerobic Fitness and Health. Human Kinetics, Champaign, IL. Shephard, R.J., 1995. Worksite health promotion and productivity. In: Kaman, R. (Ed.) Worksite Health Promotion Economics: Consensus and Analysis. Human Kinetics, Champaign, IL, pp. 147}174. Shephard, R.J., 1996. Worksite "tness and exercise programs: A review of methodology and health impact. American Journal of Health Promotion 10, 436}452. Shephard, R.J., 1997. Aging, Physical Activity and Health. Human Kinetics, Champaign, IL. Shephard, R.J., 1999. Worksite health promotion and the older worker. International Journal of Industrial Ergonomics, in press.
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Shephard, R.J., Kavanagh, T., 1975. Biochemical changes with marathon running. Observations on post-coronary patients. In: Howald, H., Poortmans, J.R. (Eds.), Metabolic Adaptations to Prolonged Exercise. Birkhauser Verlag, Basel, pp. 245}252. Shephard, R.J., Prien, E., Hughes, G., 1988. Age restrictions on bus driver selection. Journal of Human Ergology 17, 119}138. Shock, N.W., 1967. Physical activity and the &rate of ageing'. Canadian Medical Association Journal 96, 836}842. Simonton, D.K., 1988. Age and outstanding achievement: what do we know after a century of research? Psychological Bulletin 104, 251}267. Slee, D., Peepre, M., 1978. Report to Health and Welfare Committee on Employee Fitness Programmes. Health and Welfare Canada, Ottawa. Smolander, J., Louhevaraa, V., Ilmarinen, J., Korhonen, O., 1992. Feasibility and e!ects of work-site exercise promotion program in a metal company. Poster presentation at International Conference on Physical Activity, Fitness and Health, Toronto, May 1992. Strydom, N.B., Wyndham, C.H., Benade, A.J.S., 1971. The responses of men weighing less than 50kg to standard climatic room acclimatization procedures. Journal of the South African Institute of Mining 72, 101}104. Terborg, J.R., 1995. Computer simulation: a promising technique for the evaluation of health promotion programs at the worksite. In: Kaman, R.L. (Ed) Worksite Health Promotion Economics. Human Kinetics, Champaign, IL, pp. 193-216. Vermeersch, J.A., Feeney, M.J., Wesner, K.M., Dahl, T., 1979. Productivity improvement and job satisfaction among Public Health Nutritionists. Journal of the American Dietetic Association 75, 637}640. Vernon, H.M., Bedford, T., Karner, C.F., 1927. The relationship of atmospheric conditions to the working capacity and the accident rate of miners. Reports of the Industrial Fatigue Research Board, 39. His Majesty's Stationery O$ce, London. Waldman, D.A., Avolio, B.J., 1986. A metanalysis of age di!erences in job performance. Journal of Applied Psychology 71, 33}38. Wright, G.R., Sidney, K.H., Shephard, R.J., 1978. Variance of direct and indirect measurements of aerobic power. Journal of Sports Medicine and Physical Fitness 18, 33}42. Wyndham, C.H., 1974. 1973 Yant Memorial Lecture: Research in the human sciences in the gold mining industry. American Industrial Hygiene Journal 35, 113}136. Yokizomo, Y., 1985. Measurement of ability of older workers. Ergonomics 28, 843}854.
Aging and productivity: some physiological issues Roy J. Shephard * Faculty of Physical Education and Health, Faculty of Medicine, University of Toronto, Canada Department of Public Health Sciences, Faculty of Medicine, University of Toronto, Canada Health Studies Programme, Brock University, St. Catharines, Ontario, Canada
Abstract Aging is associated with progressive decreases in aerobic power, thermoregulation, reaction speed and acuity of the special senses. These changes can reduce productivity, particularly in self-paced activities where the physical or mental input of the individual worker is the rate-limiting step in production. Many potential problems can be corrected by worksite modi"cation, employee wellness programmes and retraining. Given wide interindividual di!erences in the abilities of elderly employees, and the fallibility of most test methods, the setting of appropriate and non-discriminatory standards for recruitment and continued employment of older individuals remains a di$cult challenge for the industrial ergonomist. The social need for ever-increasing production also requires critical examination. Relevance to industry A progressive aging of working populations in the industrial nations poses important practical questions concerning the impact of these changes on productivity. What measures can be taken to extend the span of working life, and what is the best method of determining the age when retirement should occur? 2000 Elsevier Science B.V. All rights reserved. Keywords: Aerobic power; Age ceilings; Employee wellness; Employment standards; Reaction speed; Retirement; Retraining; Sensory deterioration; Thermoregulation
This paper examines the in#uence of aging upon productivity, focusing particularly on the "nal decade of working life, when issues of employee recruitment, continued employment and deteriorations in productivity are most vigorously debated. Speci"c concerns of the industrial ergonomist include appropriate de"nitions of aging and productivity, non-discriminatory methods of setting any necessary ceilings to both recruitment and con-
tinued employment, and the potential to extend productive working life through modi"cations of the working environment, speci"c retraining programmes and the introduction of worksite wellness programmes.
1. De5nitions 1.1. Aging
* PO Box 521, 41390, Dryden Rd. Brackendale, BC, V0N 1H0, Canada. Tel.: (604)-898-5527; Fax: (604)-898-5724. E-mail address: [email protected] (R.J. Shephard)
Most gerontologists consider that even `younga old age does not begin until the commonly accepted national age of retirement, 65 yr. Nevertheless,
0169-8141/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 9 - 8 1 4 1 ( 9 9 ) 0 0 0 3 6 - 0
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there are concerns because of the growing proportion of employees who have reached late middle age. The average age of the labor force is rising rapidly in many countries, in part because of the decline in birth rate over the past 20}30 yr, and in part because current technology is demanding ever-longer university and community college courses. The ILO has estimated that by the year 2025, the proportion of individuals over the age of 55 yr will be 32% in Europe, 30% in North America, 21% in Asia, and 17% in Latin America (ILO, 1992). In a number of developed nations, there has also been a progressive decrease in the average age of retirement; workers accumulate su$cient wealth to retire early, employers are unwilling to hire older workers, and senior members of the labor force are displace by technical change (McPherson, 1983). Thus, in many countries, participation in the labor market is now quite low among those aged 55}65 yr. However, the growing number of frail elderly is placing an ever-increasing pressure upon national systems of pensions and health care, so that a number of governments now have a strong interest in maximizing the productivity of older workers, and are considering an upward revision of any mandatory retirement age. The peak years of achievement in many professions are often thought to lie in the late 30 s or the early 40 s (Simonton, 1988). Individual studies and meta-analyses have shown surprisingly little relationship between aging and job performance (Hunter and Hunter, 1984; McEvoy and Cascio, 1989; Meier and Kerr, 1976; Schwab and Heneman, 1977; Waldman and Avolio, 1986). Nevertheless, the deterioration of biological function is a relentless life process; it begins in many organs at birth, and a progressive decrease in many biological functions can be detected from early adult life (Shock, 1967). Caution must be shown in extrapolating from laboratory tests to the work-site. However, eight of nine abilities tested by the general aptitudes test battery were found to decline with age (Droege et al., 1963). Moreover, such abilities seem strongly and causally related to job performance (Schmidt et al., 1986). Other papers in this symposium also point to a substantial impact of aging on the Work Ability Index, particularly in heavy physical work.
Population aging has increased the political power of elderly workers, and what previously seemed acceptable age-restrictions upon the recruitment, promotion, and retention of older employees have faced increasing challenge before quasi-legal regulatory agencies such as the Human Rights Commission in Canada and the Equal Employment Opportunities Commission in the United States (Shephard, 1987). The issue of the productivity of the aging worker is thus attracting considerable current attention.
1.2. Productivity Productivity may be considered as the output of goods and/or services per unit investment of human capital. Under conditions where the main production bottleneck is human productivity, the reported "gure thus re#ects the immediate input of human capital, the work-e!ectiveness of the individual employees, any immediate loss of time due to absenteeism, acute or chronic illness, and the long-term loss of human capital due to early retirement or premature death. Biological factors limit productivity less often than some investigators have assumed. Output may be determined simply by the pace of a conveyor belt. In self-paced work, much also depends upon personal initiative (Pyle, 1979; Vermeersch et al., 1979). Productivity varies with occupancy (whether the individual actively seeks work, or passively awaits instructions), on e!ectiveness (selection of an appropriate task), and on e$ciency (adoption of an optimum approach to a task). Performance often re#ects much more than the abilities, motivation, and experience of the individual employee. Output may be limited by absence or lack of cooperation from a key colleague, ine$cient management, union restrictions, a lack of essential equipment or materials, failure to invest in automation, a poor overall quality of the working environment, seasonal factors, or a lack of consumer demand for a product (Shephard, 1986a,b). In many real-life situations, immediate human resources limit neither quantity nor quality of production, and the age of a worker may be irrelevant except to the extent that accumulated experience
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allows older employees to determine some method of circumventing bottlenecks in production. Where the main determinant of productivity is the e!ort contributed by the individual worker, classical concepts have suggested a hyperbolic relationship linking the quality and the quantity of output (Shephard, 1974). More recent investigations have noted the in#uence of both working environment and experience on the quality versus quantity relationship. The younger worker may produce a somewhat larger quantity of the desired end-product in unit time (Droege et al., 1963; Yokizomo, 1985), but against this super"cial attraction, accumulated experience (Schmidt et al., 1986) and a di!ering work ethos (Rhodes, 1983) allow the older worker to produce goods of greater quality, sometimes also in equal amounts. The successful manager seeks to optimize the relationship between the quantity and quality of production for a minimum input of human capital, materials and/or equipment. In our present context, it is worth noting that in many industries today, the in#uence of minor age-related di!erences in physical productivity is far-eclipsed by e!ects from age-linked increases in salaries and fringe bene"ts. Furthermore, large gains in productivity per dollar of labor costs can often be realized through investment in automation or `out-sourcinga of components to countries where wage-rates are low for both young and older workers. Attempts to optimize the hyperbolic relationship between quality and quantity usually assume that both the quantity and quality of industrial output can be monitored accurately. However, it is di$cult to measure either aspect of production in many types of employment. Often, the end-product is the result of team work between good and bad workers, both young and old, so that it becomes almost impossible to assess the individual's contribution. Determinations of the quality of output are particularly di$cult, and indeed output is often expressed simply as a rate of production: the length of "rebreak cut per hour, the average time that an airline clerk takes to answer a telephone call, or the number of policies per hour that are processed by an insurance agent. Such an assessment tends to penalize older employees, since accumulated experience and judgment enhance the quality of their
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contribution relative to that of a younger person, but may slow the speed of response. Alternative bases of assessment include in some applications a self-rating of productivity, a consideration of supervisor ratings of performance, a history of commendations or merit pay awards, a scoring of `errors,a and the computer monitoring of an employee's speed and rhythm of working. This last technique is widely criticized as an invasion of privacy, and it usually leads to a deterioration in worker/supervisor relationships. 2. Functional changes and productivity 2.1. General considerations As aging progresses, various decreases in peak functional capacity may limit an employee's potential to engage in strenuous physical work. If a person's physical capabilities have become marginal, the quantity of production will diminish in self-paced work, and in machine-paced tasks excessive fatigue may lead to poor quality output, industrial disputes, accidents, injuries, absenteeism, a high employee turnover rate and demands for early retirement. Particularly in self-paced work, age-related decreases in muscular strength and endurance, anaerobic power and anaerobic capacity may threaten the productivity of older individuals (Monod, 1999). This paper will focus on other potential constraints that can limit the occupational performance of the older person, including a decrease in aerobic power, an impairment of thermoregulation, a slowing of reactions and a deterioration in the acuity of the special senses. If the rate of working is truly limited by some aspect of an employee's functional capacity, there is opportunity for the industrial ergonomist to address these physiological problems by modi"cation of the workplace, employee wellness programmes and retraining of the older worker. 2.2. Decreases in aerobic power Aerobic power declines progressively over working life, from around 50 ml/[kg ) min] in a young man and 40 ml/[kg ) min] in a young woman, to 25}30 ml/[kg ) min] in 65-yr-olds of either sex
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(Shephard, 1994). A corresponding decrease of productivity might thus be anticipated in tasks with a high aerobic demand. In self-paced heavy work, the average individual maintains an energy expenditure where there is little accumulation of lactate over an eight-hour working day; the critical intensity of e!ort is typically 40% of maximal oxygen intake (Hughes and Goldman, 1970); however, the 40% ceiling is situational. Values decrease from 50% under very favorable working conditions to around 35% if the environment is di$cult, rest periods are not practicable, and/or the task demands adoption of an awkward posture, the use of small muscle groups and intermittent peaks of more intensive physical activity (As strand, 1967); even lower percentages are usual in lifting tasks. With any pattern of activity, much also depends on the individual's motivation; substantially higher percentages of aerobic power are developed both during an occupational emergency and in an athletic competition such as an ultra-marathon run (Shephard and Kavanagh, 1975) than during normal daily work. Finally, although this point has yet to be tested, the ceiling may be somewhat higher in an old person, since the resting metabolism then accounts for a larger fraction of the 40% standard. The energy cost of individual work-site tasks can be estimated by devices such as a Kofranyi} Michaelis respirometer or an Oxylog recorder, but unfortunately employees may tend to accelerate their work-pace while their energy expenditure is measured. Further, on a normal work-day, the `heavya components of work described by such devices occupy only a fraction of an 8 h shift, although both management and unions may be reluctant to admit the extent of time lost through relaxation breaks, machinery failures and other causes. Analysis is further complicated by interindividual di!erences in both the energy cost of speci"c tasks and the work structure of a typical day (Shephard, 1974). In older employees, an agerelated increase in body mass tends to increase the cost of tasks where body mass must be displaced (Godin and Shephard, 1973), but this disadvantage is o!set by accumulated experience and resulting improvements in mechanical e$ciency in the older employee. Moreover, seniority rules may allow
older employees to choose physically easier subtasks within a given job category. In machine-paced tasks, the standard rate of working is commonly set at a pace which demands four-"fths of the 40% e!ort tolerance of the average employee, that is 32% of the presumed average maximal oxygen intake for the population (Shephard, 1974). However, this pace may have been agreed with unions when the average worker was male and aged 40 yr or younger. Let us assume that such a standard is indeed appropriate for a typical 40 yr-old male who is engaged in hard physical work for much of an eight-hour day. If employment continues through to the age of 65 yr, with a 10% loss of aerobic power per decade, and a 30}40% di!erence of aerobic power between men and women, then an average 65 yr old man will be working at 105% rather than the intended 80% of his 8-hr aerobic capacity. Likewise, a 65-yr-old female will be operating at over 140% of this standard, in other words at 56% of her peak aerobic power. There are a few occupations where aerobic demand remains high; examples include the infantry soldier (Hughes and Goldman, 1970) and the postal carrier (Shephard, 1982), both of whom may be required to walk long distances while carrying heavy loads. But in practice, there is only a weak relationship between aerobic power and job performance, and complaints of fatigue are relatively infrequent, even among older women who are engaged in such work. This is because: (i) The 80% standard was usually reached by union negotiation, and is less than the true, physiological 8-h ceiling for the average worker. (ii) Employees often choose heavy occupations or continue in such work if their initial physique gives an above average physical working capacity. (iii) In many physically demanding tasks, a substantial fraction of the energy cost is attributable to the displacement of body mass (Godin and Shephard, 1973). Performance thus depends on the relative rather than the absolute working capacity. This reduces the disadvantage of female employees relative to their male counterparts. (iv) Experience increases mechanical e$ciency. The energy cost of many occupational tasks is thus smaller in older employees who have
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accumulated many years of experience in a given occupation. (v) Heavy work may occasionally help to sustain aerobic "tness as a person becomes older, although the intensity of e!ort required in most occupations is insu$cient to have any marked training e!ect (Allen, 1966). (vi) Categorizations of jobs are crude. Promotion or seniority rules may thus allow those who are still classed as `heavy workersa to select less demanding types of employment as they become older. (vii) Those whose physical abilities no longer match task demands often seek lighter employment, part-time work or early retirement. 2.3. Thermoregulation In general, the literature suggests that individuals aged 46}65 have a poorer heat tolerance than younger adults, and su!er more physiological strain during heat acclimation (Pandolf, 1991, 1997). One adverse in#uence of aging is that the rate of sweating seems to be reduced for any given thermal load and vasodilatation is less well coordinated (Robinson, 1963). More importantly, when work is performed in a hot environment, the rise in core body temperature depends upon the relative rather than the absolute intensity of e!ort. Elderly employees are thus handicapped because their maximal oxygen intakes are low (Lavenne and Belayew, 1966; Strydom et al., 1971). In many older individuals, problems of heat dissipation are further exacerbated by chronic disease or because the average skinfold thickness increases by 4}5 mm over the course of working life; indeed (Pandolf, 1991,1997) has argued that in those over the age of 65 who are free of chronic disease and have maintained personal "tness, heat tolerance is unimpaired. Hot conditions a!ect productivity mainly by causing discomfort. Work becomes progressively more di$cult as the rectal temperature rises above 383C (Wyndham, 1974). The quality of output is reduced, and there is an increased likelihood of both industrial disputes and accidents (Vernon et al., 1927). Muscle blood #ow is reduced, in part because of the #uid lost in sweating, and in part because a substantial fraction of the available blood #ow is diverted from the working muscles to
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the skin. One consequence of these circulatory changes is that the worker can no longer operate at 40% of maximal oxygen intake throughout an 8-h day without developing severe fatigue. In some tasks such as deep mining, physical demands can also push core body temperatures to dangerously high levels where there are risks of heat collapse and heat stroke (Wyndham, 1974). Older workers are on average less productive and more vulnerable to heat stroke than their younger peers if working conditions are hot (Strydom et al., 1971). However, the handicap of the older employee depends on how far physical condition has been allowed to deteriorate. Lavenne and Belayew (1966) concluded that a peak oxygen intake of 40 ml/ [kg ) min] provided a useful dividing line between those who were able to tolerate a high temperature and those who were adversely a!ected by it. The e!ect of hot conditions on productivity can be examined using some calculations of Pugh et al. (1960); they evaluated the rate of heat exchange in cross-channel swimmers. Since the water was cold, their subjects were fully vasoconstricted. Given an energy expenditure of 10 metabolic equivalents (METS), Pugh et al. (1960) argued that the application of a 1 mm layer of grease external to the skin (an increase in thickness of the layer of super"cial fat from 10 to 11 mm) would augment the core-toskin temperature gradient by 10%, or 1.673C. Vasodilatation greatly reduces the initial thermal gradient from the core to the skin surface when a person is working in a hot environment. At an energy expenditure typical of a heavy worker (5 METS), the total thermal gradient is unlikely to exceed 23C. If aging leads to a 4 mm increase in skinfold thickness (a 2 mm increase in super"cial fat relative to the usual initial value of 6 mm in a young man), then this should increase the steady state core-to-surface temperature gradient by one third, or 0.73C. If environmental conditions are such that even young workers reach the safe limiting core temperature of 39.23C during the working day (Wyndham, 1974), then older workers who carry an extra 2 mm of super"cial fat will need to reduce their gross rate of energy expenditure by 33% (1.7 METs) in order to maintain thermal equilibrium. The corresponding decrease in net external energy expenditure is a substantial 42%.
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2.4. Reaction speed and special senses Age-related decreases in reaction speed and the acuity of the special senses are well-documented (Shephard, 1997). There are certain special categories of employment in which a deterioration of vision or hearing can substantially limit employment prospects * for example, a loss of near vision in a watchmaker, or a decrease of auditory acuity in a person who is using their hearing to check the performance of vacuum cleaner motors (Shephard, 1974). However, the magnitude of such problems is progressively being reduced by modern technology. It is now often cheaper to replace than to repair a watch mechanism, and the sound patterns associated with malfunction of a motor can be displayed on a VDT, rather than relying upon an acute sense of hearing in the diagnostician. Concern is often expressed regarding the impact of changes in reaction speed and sensory acuity upon an employee's susceptibility to accidents. Although overall injury rates for any given type of employment show little change with aging, Griew (1964) has argued that accident rates for a number of speci"c trades within an occupational category increase in older employees; the disability resulting from a given injury may also take longer to resolve in an older worker. There has been particular anxiety about the ability of older employees to operate public service vehicles such as buses safely. However, available statistics (Norman, 1960; Shephard et al., 1988) show that the number of accidents per vehicle per kilometer are fewer for 60}64 yr old drivers than for other age categories, even after control of the data for years of bus driving experience. The greater judgment and patience of the older worker, plus the progressive selecting out of `accident pronea personnel seem more than enough to compensate for any adverse e!ects from a slowing of reaction speed or a deterioration in vision. Detailed task analysis suggests that problems are more likely to arise from decreases in muscle strength. A loss of strength may prove a handicap when making fast turns in a bus that is not equipped with power steering, when loading wheelchair patients into vehicles that are only partially adapted for special populations, and when
carrying the fare-box back to the manager's o$ce (Shephard et al., 1988). In some types of o$ce work such as VDT data entry, the average employee may have a less than optimal productivity because the job is boring and arousal decreases over the course of the workday. Problems of this sort could be less likely in an older person, for two reasons. Any reduction of ability because of declining senses and out-dated skills makes a given task more challenging for the older person. This can increase stress in demanding employment, but in a boring job it helps to sustain arousal. Progressive job selection tends to match the individual's ability and task demands over the course of a working career, but this bene"t of aging is increasingly o!set by problems of redundancy and the need of displaced workers to accept any type of employment, irrespective of its demands. Many causes of occupational stress are environmental: excessive task di$culty, a lack of perceived control over operations, unclear job requirements, lack of social interactions, personality con#icts or inadequate feedback of performance (Shephard, 1988). Some of the items that cause such stress are relatively independent of age, but problems can be greater for older employees because of declining physical and mental abilities and an out-dating of skills by a rapidly changing technology (Robinson et al., 1985).
3. Maintaining productivity in an aging workforce Much can be done to sustain the productivity of an aging workforce through redesign of the workplace, the introduction of employee wellness programmes and speci"c retraining of individual employees. 3.1. Workplace redesign Mechanization and automation can reduce the energy demands of most tasks to the point that the age-related decrease in aerobic power is no longer an issue. If mechanization is still di$cult to organize, other options include the extension of workbreaks and the arrangement of job-sharing or part-time work for older employees; the usable
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fraction of peak oxygen intake increases progressively as the length of the working day is shortened (Bonjer, 1968). The average rate of energy expenditure can often be reduced to an acceptable level by a simple rearrangement of duties. For example, a shipping clerk may spend a part of each hour labelling rather than lifting boxes (Shephard, 1974), or a postal carrier may structure a mail delivery route so that the mailbag is heaviest while he or she is descending any hills on the route (Shephard, 1982). An excessive accumulation of body heat can be avoided by improvements in the design of protective clothing, by the installation of more powerful air-conditioning systems, or simply by a reduction in the standard rate of working. Likewise, if a task is proving stressful, the mental demands can be reduced by simpli"cation of the work-station and the development of clearer organizational guidelines. 3.2. Employee wellness programs The bene"ts of employee wellness programmes are discussed in an accompanying paper (Shephard, 1999), but certain salient points that are relevant to productivity will be underlined here. Corporate motivation for such programmes may re#ect either a belief that enhanced productivity will increase pro"ts, or an altruistic desire of a key executive to maintain employee health (Shephard, 1986a, b). The development of such programmes also serves to demonstrate to the Equal Employment Opportunity Commission that everything possible has been done to accommodate and sustain the e!ectiveness of older employees (Shephard, 1990). 3.2.1. Aerobic power A well-designed laboratory endurance training programme can enhance aerobic power by around 20%. Moreover, in percentage terms, the response of a 65-yr old is similar to that of a young adult (Shephard, 1997). A recent review has summarized the functional gains that result from worksite exercise programmes (Shephard, 1996). The early studies of Slee and Peepre (1978) and Cox et al. (1981) remain fairly typical of the work-site response. Both research teams found that a useful 13% in-
541
crease of predicted aerobic power developed within a few months of initiating the programme. This was equivalent to a 13 yr reduction in biological age, but unfortunately gains were restricted to frequent programme participants, about 10% of the total work-force. Thus, when averaged across the entire company, there was only a 1.3% gain of maximal oxygen intake. Slee and Peepre (1978) and Cox et al. (1981) both examined o$ce workers, a group where aerobic power was unlikely to have limited job performance. But even if the work had been physically demanding, and the aerobic power of the oldest third of the labor force had initially been inadequate to meet task demands, the programmeinduced gain in oxygen transport would only have boosted productivity by 0.4% (1.3;0.33%) (Shephard, 1995). Blair et al. (1986) claimed that the average employee showed a 10.5% gain in aerobic power two years after inception of Johnson and Johnson's `Live for Lifea worksite wellness programme. However, gains were estimated from submaximal cycle ergometer tests, and control subjects who received only a health screening also showed a 4.7% increase of score. The net programme impact was thus a 5.8% increase in aerobic power. Moreover, the need to boost oxygen transport is greatest in those over 45 yr of age, and in this critical group the di!erence between experimental and control subjects was only 0.9%. Nevertheless, empirical data suggest that gains of work performance can be substantial, particularly under arduous conditions. Danielson and Danielson (1982) assessed productivity from the speed with which forestry workers cut a "re-break. On average, aerobically trained crews cut a 62% greater length per day than control crews. After covariance adjustment for age and experience, performance was signi"cantly correlated with the individual's maximal oxygen intake. Under hot summer conditions, the trained group had a 101% advantage of cutting speed over their untrained peers. 3.2.2. Thermoregulation There is some interaction between aerobic training and heat acclimatization. Worksite exercise programmes could thus enhance tolerance of hot
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conditions, especially in older employees whose tolerance of heat stress has become marginal. Acclimatization is maximized if subjects are exposed to a combination of heat and regular endurance exercise. Strydom et al. (1971) have used this technique to prepare recruits for deep gold mining in South Africa. It is less clear whether enhanced "tness increases the comfort of workers who are exposed to more moderate heat. Fit individuals sweat more readily, and this may actually increase discomfort under conditions where it is di$cult for sweat to evaporate (Aoyagi et al., 1997). In such situations, comfort may be as important to productivity as is overall thermal balance. 3.2.3. Self-ezcacy and mood-state Fitness programmes have a positive in#uence upon feelings of self-e$cacy, reducing both anxiety and depression (North et al., 1990; Landers and Petruzello, 1994). The response depends in part upon the initial disturbance of mood-state, and since depression is more common in older individuals, exercise programmes may be particularly helpful in boosting the mood-state of older employees. Given the subjective nature of occupational fatigue, an increased sense of self-e$cacy and/or an elevation of mood-state may in turn allow the completion of demanding tasks without complaints of tiredness. Early uncontrolled but objective studies suggested that "tness programmes decreased error scores in both manual telegraph operation and the inspection of textiles (LaPorte, 1970). A study of pharmaceutical workers found decreased self-perceptions of work load and fatigue and enhanced job satisfaction among exercise participants relative to social group controls (Rosenfeld et al., 1990; Shephard, 1995). Cox et al. (1981) compared work-times to previously established standards for a variety of o$ce tasks; 6 months after inception of a work-site wellness programme, there was a 7.0% gain of productivity at the experimental company, but * perhaps because of a Hawthorne e!ect * there was also a 4.3% gain at the control company. Likewise, Smolander et al. (1992) noted a 5.5% gain in performance of exercised subjects at a metal company, although there was also a 2.5% improvement in the performance of controls.
3.2.4. Healthy lifestyle A healthy lifestyle may be another important dividend of a worksite wellness programme. Terborg (1995) estimated that smoking was associated with a 1.8% loss of productivity, and alcoholism with a 30% loss. Moreover, the cumulative health problems associated with such addictions increase with age. Self-reports from the Toronto Life Assurance study (3% successful smoking withdrawals in the "rst year), from the Staywell programme (6% decrease of smokers relative to controls at year 3), and from Johnson and Johnson (3.5% successful smoking withdrawal in one year, 12% in two years) all support the practical value of employee wellness programmes as a means to encourage a healthy lifestyle (Shephard, 1996). 3.3. Other initiatives to enhance productivity 3.3.1. Retraining of workers The productivity of older employees in technologically advanced work can be sustained by appropriately adapted programmes for the up-grading of skills and the acquisition of new knowledge (Shephard, 1974). Under highly controlled laboratory conditions, task learning proceeds more slowly in older individuals, but it is less certain how far such data can be extrapolated to the worksite, at least through to the normal age of retirement. The learning process may be helped by use of self-paced learning systems rather than requiring individuals to attend classes that are designed primarily for younger workers. Often, the gains from a training programme are greater if active participation is required than if reliance is placed upon formal lectures and instructions that are soon forgotten (Belbin and Down, 1965). Instruction should emphasize continuities with the worker's current knowledge, indicating clearly the relationship between course material and the new demands of employment. 3.3.2. Setting a ceiling age for employment If the physical demands of a task currently do not allow older individuals to match the productivity of younger workers, the options for the employer are (1) to optimize the design of the
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workstation, (2) to maximize the residual abilities of older workers through appropriate wellness programmes, (3) to establish packages that encourage voluntary early retirement or transition to parttime work, (4) to impose retirement at a "xed age, or (5) to set job-related performance standards as a condition of continued employment. 3.3.2.1. Early retirement. In many jobs, workers who are a!ected by ill-health or functional loss are glad to accept the options of early retirement or part-time work, provided that pensions are adequate to meet their foreseeable needs (Gould and Takala, 1993; Huuhtanen and Piispa, 1993; Kilbom et al., 1993). 3.3.2.2. Mandatory retirement. Mandatory retirement is attractive and clear-cut from an administrative point of view, and it avoids making a worker leave a company because he or she has failed some annual test. However, it is unfair to the employee who has conscientiously conserved health throughout a working career (Shephard, 1987). Taking the speci"c example of aerobic power, scores show inter-individual di!erences of at least 20% at any given age. Part of this di!erence is constitutionally determined, but as much as two thirds re#ects the lifestyle of the individual employee, including such items as habitual physical activity, cigarette smoking, and obesity (Jackson et al., 1995; Shephard, 1987). Given that the age-related deterioration in aerobic power averages about 10% per decade, the 20% coe$cient of variation at any given calendar age implies that a person's biological age can vary by as much as $20-yr about the population mean (Sharkey, 1987). In other words, some 65 yr olds will be "tter than the average 25-yr old employee. Plainly, such individuals do not merit dismissal just because they have reached a calendar age of 65 yr. 3.3.2.3. Non-discriminatory employment standards. One alternative to mandatory retirement is to "nd some non-discriminatory measure of performance to identify employees who lack the requisite functional capacity. Unfortunately, it is di$cult to obtain valid and reliable measurements of current functional status. The measurement of maximal oxygen intake might seem a useful objective mea-
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sure of aptitude for heavy physical work. However, even if it is possible to make a direct treadmill measurement, the day-to-day intra-individual variation is at least 4%, and a careful and costly laboratory determination is essential to reach this level of precision. Predictions of maximal oxygen intake that are based upon "eld tests often di!er by as much as 20% from the true value. Moreover, intraindividual di!erences as large as 15}20% can develop due to an intercurrent acute illness (Wright et al., 1978). Thus, employees who have a poor score on a particular day could claim that they were unwell when tested. Finally, oxygen transport is task-speci"c; a person may have well-developed leg muscles and a good treadmill performance, yet experience di$culty in an occupation that requires heavy arm work. The criterion of maximal oxygen intake is thus di$cult to apply and di$cult to defend in practice. Performance tests that mimic "eld demands have greater face validity (Davis and Dotson, 1987). Nevertheless, scores on such items depend heavily upon body size; thus they are open to the objection that they discriminate against women. The optimal method of assessing job performance has yet to be determined. Valid assessments may ultimately be derived from observations made over the course of the normal working day (for example, heart rates, blood lactate levels, and serum enzyme concentrations), but at present, supervisor and peer ratings seem as valid as either laboratory or "eld testing of performance.
4. Ethics of maximizing productivity One "nal issue to consider with an older work force is whether it is still necessary to maximize the industrial output of every worker, regardless of his or her age. How concerned should we be if the 65-yr old worker is a little slower and less productive than a person aged 25? The social need for everincreasing production of consumer goods needs critical re-examination in a world of shrinking non-renewable resources. Automation has given humankind the opportunity to produce an enormous quantity and variety of goods with only limited worker input. It should
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thus be possible to produce all of the goods that society needs, while respecting the dignity of the older person who cannot conform to production `normsa because of ill-health or aging to choose his or her time of withdrawal from the labor force with the dignity appropriate to 40 or 50 yr of loyal service. Acknowledgements Dr. Shephard's studies are supported in part by a research grant from Canadian Tire Acceptance Limited. References Allen, J.G., 1966. Aerobic capacity and physiological "tness of Australian men. Ergonomics 9, 485}494. Aoyagi, Y., McLellan, T., Shephard, R.J., 1997. Interactions of physical training and heat acclimation: the thermophysiology of exercising in a hot climate. Sports Medicine 23, 173}210. As strand, I., 1967. Degree of strain during building work as related to individual aerobic capacity. Ergonomics 10, 293}303. Belbin, E., Down, S., 1965. Interference e!ects from new learning: their relevance to the design of adult training programs. Journal of Gerontology 20, 154}159. Blair, S.N., Piserchia, P.V., Wilbur, C.S., Crowder, J.H., 1986. A public health intervention model for work-site health promotion: impact on exercise and physical "tness in a health promotion plan after 24 months. Journal of the American Medical Association 255, 921}926. Bonjer, F.H., 1968. Relationship between physical working capacity and allowable caloric expenditure. In: Rohmert, W. (Ed.), International Colloquium on Muscular Exercise and Training. Gentner, Darmstadt, Germany, pp. 86}98. Cox, M., Shephard, R.J., Corey, P., 1981. In#uence of an employee "tness programme upon "tness, productivity and absenteeism. Ergonomics 24, 795}806. Danielson, R., Danielson, K., 1982. Exercise Program E!ects on Fire"ghters. Ontario Ministry of Culture and Recreation, Toronto. Davis, P.O., Dotson, C.O., 1987. Job performance testing: an alternative to age discrimination. Medicine and Science in Sports and Exercise 19, 179}185. Droege, R.C., Crambert, A.C., Henkin, J.B., 1963. Relation between GATB aptitude scores and age for adults. Personnel and Guidance Journal 42, 502}508. Godin, G., Shephard, R.J., 1973. Body weight and the energy cost of activity. Archives of Environmental Health 27, 289}293.
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