WORK A Journal of Prevention, Assessment & Rehabilitation
ELSEVIER
Work 10(1998)21-29
Maintaining work capacity in the aged worker via progressive resistance training: the implications for occupational therapy practitioners Nicholas G. Branch* Sargent College, Boston University, 635 Commonwealth Ave., Boston, MA 02215, USA Received 1 May 1997; accepted 1 July 1997
Abstract Society has an interest in maintaining the work capacity of its aging workers. Fewer and fewer younger workers are entering the workforce to replace older citizens no longer able to perform the worker role. There is a demonstrated relationship between increased strength and work capacity, yet the occupational therapy literature emphasizes generalized exercise programming. This type of programming is ineffective at building strength in the elderly worker. High intensity progressive resistance exercise (PRE) can increase strength in the very old worker, yet the'rapists are hesitant to employ PRE, perhaps due to a potential bias against the use of high intensity PRE with this cohort. Use of PRE may present some difficulties in the clinical situation where continual supervision and resistance training equipment is not available. The adaptive use of functional activities as a resistance training strategy to build strength may be able to overcome the difficulties attendant with the use of PRE while preserving its benefits. Several other implications for occupational therapy practitioners are discussed. © 1998 Elsevier Science Ireland Ltd. Keywords: Therapeutic exercise; Aged worker; Occupational therapy; Strength
1. Introduction It is becoming evident that society has a vested interest in maintaining the work capacity of its
* Corresponding author: 352-R Raymond Hill Rd., Raymond, ME 04071, USA. Tel.: + 1 207 6554645; e-mail: [email protected]
citizens as they become older. MacRae (1991) raises several points in describing the significance of changing demographics in the workforce. As the current working population ages, it will begin to reduce its involvement with paid work. During the same period of time, the supply of younger workers required to replace them will diminish. Therefore, society must find ways to assist the older worker in maintaining his or her capacity
1051-9815/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved. PH S1051-9815(97)00005-5
22
N.G. Branch / Work 10 (J998) 21-29
for work throughout the life span in order to generate an adequate workforce. Maintaining adequate work capacity in the aging workforce may also have a positive impact on the financing of social security and other financial retirement mechanisms. If the aging workforce opts for fulltime retirement rather than a work/retirement mix, the health care/retirement system may be overburdened financially as fewer younger workers struggle to pay for the healthcare of an increasing number of older workers. From an individual perspective, retirement no longer signifies a cessation of all work but rather a redefining of the balance of work, rest and play. Achieving such a balance is often an objective occupational therapists attempt to achieve with their clients. In fact, MacRae (1991, p. 361) suggests 'a balance of play, work and rest is essential for the physical and mental health and well-being of any individual. This paper reviews current research concerning the importance of muscular strength as an essential performance component in maintaining work capacity of the aged worker; and the efficacy of Progressive Resistance Exercise (PRE) for increasing strength in this cohort. PRE is often employed by rehabilitation therapists to increase or maintain muscular strength. The total amount of exercise in PRE is prescribed by specifying a particular frequency, intensity and duration of resistance to the muscle group to be strengthened. Of these three parameters, intensity appears to be receiving the most scrutiny in the current literature. This paper also examines current views of strength/PRE in the occupational therapy literature, then reviews several recent studies of PRE with aged participants performed by other disciplines. The studies investigate the optimal intensity of resistance in progressive resistance exercise required to generate an increase in strength in the elderly worker and what magnitude of strength increase is possible. Limitations to the application of PRE as a broad based intervention and implications for therapists are discussed. Lastly, the utility of employing functional activity as a mechanism for increasing strength is considered.
2. The relationship of strength measures to work capacity Increasing strength in a client has value only insofar as the increase in strength is accompanied by an increase in functional ability. Judge et al. (1996) examined the strength of the association between several measures of strength and the ability to carry out specific instrumental activities. of daily living (IADL). The researchers evaluated data obtained from 2190 participants (mean age = 71) enrolled in a pre-planned meta analysis entitled the Frailty and Injury: Cooperative Studies of Intervention Trails (FICSIT). Measures of strength included hand grip strength, gait velocity and the ability to stand up from a chair. Outcome variables examined included the ability to employ motorized modes of travel, shopping for groceries, doing housework and laundry. The correlations reported were highly significant for each independent variable, ranging from P = 0.007 for hand strength, to P = 0.0004 for gait speed. These correlations were obtained after correcting for several co-variates known to affect IADL independence and persisted across a wide range of physical performance abilities. Guralnik et at. (1995) conducted a similar analysis with 1122 community dwelling men and women aged 71 years or older. These researchers reported that objective measures of lower extremity function were highly predictive of future disability as measured via a valid and reliable disability measure employed in earlier studies. Lower extremity measures employed were walking velocity, rising repeatedly from a chair and climbing stairs. Both studies noted the inability of correlational studies to demonstrate a causal link between evaluated measures. However, based on the strength of the correlational evidence, the researchers speculate that use of strength measures to predict future declines in physical function might enable clinicians to prevent or delay disability rather than attempting to remediate existing deficits. They recommend that randomized clinical trials be conducted to directly investigate these relationships.
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3. Current views of occupational therapy on PRE and strength Occupational therapists consider strength to be an important component in a broad range of functional activities, including work-related activities. Improving strength via exercise is discussed in three· authoritative sources commonly relied upon by occupational therapists. A brief summary of this discussion follows. Lewis (1986) makes numerous references to strength and functional performance in her text entitled Eldercare in Occupational Therapy. In a section entitled Biophysical Realities, she describes the gradual decline of muscle mass and number of muscle fibers occurring after the age of 30. Muscle elasticity and the proportion of type IIA and lIB muscle fibers is altered, reducing the aging muscle's ability to contract. Lewis (1986, p. 78) suggests that medium level isotonic exercise 'is valuable for keeping muscles ... at a good level in late adulthood'. The author cautions against excessive or too violent exercise for fear of damaging tissues and to avoid the slower process of muscle repair common in the elderly. Elsewhere in the work, Lewis (1986, p. 104) suggests that 'proper exercise pursued consistently throughout the lifespan may significantly deter certain bodily functions that are traditionally thought to accompany the aging processes'. Although which body functions she is referring to are not specified, the example which follows refers to training the cardiovascular, not the voluntary muscular system. A basic definition of muscular strength is provided, but the issue of one's ability to improve muscular strength in later life is not discussed. The devel.opment of muscular strength via PRE is listed as a possible component of an exercise program. It is noteworthy that although strength is mentioned as an essential component of functional activity, no specific mention of the mechanism of strength increase is made. Instead, several pages are devoted to how one would establish a cardiovascular exercise program. In a section entitled Modalities and Treatment, Lewis (1986, p. 460) produces a non-inclusive list of 23 occupational therapy modalities for use with an aged population. However, exercise or resis-
23
tance training is not mentioned in the list. 'Gentle' exercise is recommended for elderly clients with arthritis. The American Occupational Therapy Association has published a text for use in its self-paced clinical course entitled, The Role of Occupatio~al Therapy With the Elderly (ROTE) (Davis and Kirkland, 1988). This text also outlines the decline in function typically found as an individual ages, detailing changes in cardiac output, bone mass and a 50% reduction in the number of muscle fibers. The ROTE curriculum notes that some affects of aging may be due to habitual inactivity and that consistent physical activity throughout the lifespan may diminish losses in strength. Page 47 states 'Exercise and activity of the appropriate intensity and duration can be very beneficial to older people'. The text points out that distinguishing between functional decline due to aging and that due to inactivity is essential if a clinician is to properly choose between a compensatory and a biomechanic approach to treatment. If one believes strength declines are due to aging (and therefore inevitable), then the compensatory approach to reduce environmental demands is warranted. On the other hand, if one believes an increase of strength is possible, then the anticipated outcomes of treatment will be far different. In the section on treatment approaches, strength is specifically linked to functional improvement and intervention to increase strength is encouraged, but specifics on how this is to be accomplished are not provided. One might reasonably argue that specific protocols for increasing strength are beyond the scope of comprehensive volume on geriatric occupational therapy. A commonly consulted source for specific protocols in a wide variety of physical disability functions is Occupational Therapy for Physical Dysfunction (Trombly, 1995). Writing in Trombly, Zemke (1995) details a PRE protocol designed to increase strength. PRE is a strategy employed under the biomechanical frame of reference, which seeks to prevent further decline, or restore biomechanical strength enabling an individual to pursue valued daily activities, including work activities. The author describes several strength building protocols. Of those, PRE is
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N.G. Branch /Work 10 (1998) 21-29
recommended for improving strength in muscles with sufficient strength to resist gravity through a full range of motion. Zemke outlines a protocol originally formulated by DeLorme and Watkins (1945) and modified by McGovern and Luscombe (1953) to achieve similar results as the DeLorme technique with fewer lifting repetitions. The techniques are based on a measure of strength called the lO-repetition Maximum (10RM). The 10RM is the maximum amount of resistance a muscle can overcome (lift) 10 times in succession before fatigue results in muscle failure. A warm up of 10 repetitions without resistance is followed by 10 repetitions at the lORM level. Following a 1-min rest, a third 10 repetition set with resistance set at 75% of the 10RM is done. Finally a fourth set of 10 repetitions at the 50% lORM is performed. The resistance training is progressive in that as the 10RM is measured during successive weeks of training, the resistance that can be overcome 10 times will increase. The decreasing level of resistance within a single strength training session was designed to compensate for increased level of fatigue experienced by patients. The study by McGovern and Luscombe was a controlled, nonblinded study of 24 20-30-year-old patients, 12 of whom were in the control group and followed the DeLorme method and the remainder followed the above protocol. The muscle group trained was the knee/hip extensor. There are· many limitations in this particular study, including the generalizablilty of its conclusion due to a small sample, short duration of training and the failure to report gains as a percentage of maximum strength. The essential concern is the use of the 10RM as the maximum amount of resistance provided. 10RM is contrasted with the one repetition maximum (1RM) currently considered the single best measure of strength (Fleck and Kraemer, 1987). For an average individual, the lORM has been empirically found to be approximately 75% of the 1RM (Fleck and Kraemer). For example, if the maximum an individual can lift one time is 100 lbs, she will likely be able to lift 75 lbs 10 times before exhaustion. Note that the number of repetitions accomplished before muscle failure is a measure of strength training intensity.
Several conclusions may be drawn from this review of occupational therapy sources. They are: 1. The link between strength and functional capacity for work is supported within occupational therapy literature. However, PRE is often combined within the broader construct of exercise. In the first two sources reviewed, major attention is devoted to range of motion and cardiovascular components of exercise rather than increasing strength. 2. The tone of these sources is cautionary with respect to exercise. Terms such as 'gentle' and 'appropriate' are often employed, but not defined operationally. Concerns for injury and risks appear to outweigh discussion of specific benefits. 3. ROTE emphasizes the wellness based concept of maintaining strength across the lifespan but fails to discuss the possibility of increasing strength later in life. The assumption that an increase of strength is possible is inherent in the application of the biomechanical frame of reference to this population. The prospect of functional strength increase is also critical from the reimbursement perspective. Medicare, Part B links reimbursement to improvement, not maintenance of function. 4. Use of a maximum resistance intensity of lORM as employed in McGovern and Luscombe (1953) is not typically considered a sufficiently intense training stimulus to maximize strength gains. This next section will survey more recent literature to identify the optimal intensity of increasing strength in an elderly population.
4. Optimal intensity of PRE for strength increase
The three variables for determining the total amount of exercise in PRE are intensity, duration and frequency. Frequencies of between two and five sessions per week have been employed with adequate levels of strength increase (Fleck and Kraemer, 1987). Intensity and duration (the num-
N.G. Branch / Work 10 (1998) 21-29
ber of repetitions of a lift) are somewhat inversely related. For instance, at an intensity of 80% lRM, an individual can complete 6-10 repetitions before muscle failure. At 50% lRM, that same individual will likely be able to complete 12"':'15 repetitions before becoming fatigued. Because intensity can be conveniently expressed as a percentage of one's lRM (maximum strength), intensity has emerged as the key variable in assessing mechanisms of strength increase in the elderly. Although no studies of low intensity PRE could be found, general exercise programs combining low intensity endurance training with stretching or cardiovascular training are commonly employed in nursing homes to maintain strength and functional abilities of residents. Outcome studies reviewed do not support the efficacy of this intervention. Blankfort-Doyle et al. (1989) conducted low intensity endurance training with 15 frail residents of a nursing home for 15 weeks and found no improvement in work capacity (measured by bicycle ergomomentry or observed functional capacity) compared with controls. Molloy et al. (1988) conducted I-h exercise sessions 5 days per week for 12 weeks with 23 geriatric in-patients and found no significant differences in habitual physical activity compared with socialization or control groups. In one of the few studies to examine two different intensities of PRE, Taffe et al. (1995) examined the effect of PRE intensity in a study of 36 65-79-year-old women living in the community. Participants were randomized into three groups and trained for 15 weeks at either 40% lRM or 80% lRM. The researchers reported strength increases of 40 and 36%, respectively, compared with a 4% strength increase in the control group. The difference between high and low intensity PRE training was insignificant. Taffe speculated that the similarity of results may have been due to the total volume of training rather than intensity. No functional outcome measures were provided. Hunter et al. (1995) reported functional improvements with a similar cohort. This study employed PRE training at 50% lRM, adjusting the intensity such that participants could complete two sets of 12 reps three times per week for 16
25
weeks of training. This training regimen resulted in moderate strength increases averaging 52%. The researcher reported an 18% increase in participants' ability to complete the functional tasks of walking with a box of groceries and a more modest decrease in the effort level required to rise from a chair. Although uncontrolled, this study is consistent with Taffe et al. (1995) and demonstrates some functional improvement. It should be noted that the moderate increases in strength demonstrated in these studies of healthy, community dwelling women cannot be generalized to a more frail population more likely to require occupational therapy services. The utility of PRE for a frail popUlation has been examined by Fiatarone et al. (1994) at the Boston site of the Frailty and Injury: Cooperative Studies of Intervention Trails. This controlled, randomized study examined the effect of high intensity PRE with 100 frail nursing home residents. The exclusion criteria for this study was much less strict than the others reviewed here. Eighty-three percent of the participants required a cane, walker, or wheelchair for mobility. Most had fallen within the last year and many suffered from arthritis (50%), pulmonary disease (44%), hypertension (35%) or cancer (24%). Fifty-one percent had mild to moderate cognitive impairment and 38% were depressed. The intervention for the experimental group was 10 weeks of PRE training at 80% lRM with the hip and knee extensor muscle groups. Participants completed three sets every other day. Using a multiple regression model, the researchers reported an average 113% gain in strength compared with a group taking a nutritional supplement and a third group engaging in a combination of walking, calisthenics, board games, crafts and other typical nursing home activities. The study also reported significant functional gains including habitual gait· velocity, stair climbing ability and habitual levels of physical activity. Four participants requiring a walker before the intervention were able to use a cane afterwards. These results were demonstrated independent of other factors such as the level of chronic disease, depression, or functional status at base line.
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4.1 Limitations and conclusions
Viewed collectively, these studies have not identified a consistent relationship between the intensity of resistance employed in PRE and an increase in strength. The variation in results is broad. Blankfort-Doyle (1989) reported no increase in work capacity after endurance training, whereas Fiatarone et a!. (1994) reported a greater than 100% increase in strength in a study employing intensities of 80% lRM in a frail elderly population. Nevertheless, it may be concluded that PRE of some increase in intensity is a more effective mechanism for increasing strength in the elderly worker than the range of motion or calisthenics exercises more commonly employed with this population. The relationship between PRE and increased function is less clear. Studies of general exercise and low intensity endurance training resulted in little functional improvement in participants (Molloy et a!., 1988; Blankfort-Doyle, 1989). Studies evaluating moderate PRE intensity either did not assess functional impacts (Taffe et a!., 1995), or produced only modest functional gains (Hunter et a!., 1995). Fiatarone et a!. (1994) reported a greater magnitude of both strength and functional gains by conducting PRE training at 80% lRM with a functionally impaired population, in contrast to the other studies reviewed that evaluated functionally in tact subjects. It is possible that the superior functional gains demonstrated in Fiatarone et al. (1994) are related to the lower functional level of the subjects at base-line as well as the PRE intensity employed in the study. Collectively, the studies reviewed in this section present some limitations when viewed from the perspective of broad based clinical application. PRE training was conducted with large, expensive variable resistance training equipment such as 'nautilus' type equipment. It is unlikely such equipment is consistently available in most nursing homes, assisted living center or other common treatment settings for this cohort. Secondly, each training session was personally supervised by a rehabilitation professional. One-to-one supervision may not be practical under most current reimbursement guidelines. Adherence to the pre-
scribed exercise regimen is likely to decline dramatically if subjects are initially supervised in the beginning of a PRE program and then asked to proceed with intermittent or no professional supervision (Jette et aI., 1996), thus limiting the benefit derived. 5. Functional activities as a mechanism to improve strength The use of functional activities as a mechanism for increasing strength has potential for overcoming the difficulties encountered in the use of PRE while maintaining its benefits. The use of functional activities in this manner has not been investigated directly, however, there is theoretical support for this strategy in the strength training literature. Fleck and Kraemer (1987) discussed the principal of specificity in PRE. This principal suggests that the greater the similarity of rate, range and associated joint angle during muscular contractions between the resistance training and the functional activity it is designed to enhance, the greater the carryover in training. For example, if a therapist wishes to increase a client's ability to lift groceries from a grocery cart, then a PRE program employing a neutral or fully pronated hand position will be superior to a program using the fully supinated hand position typically used with dumbbells or elastic tubing. PRE employing the neutraljpronated hand position will be superior as this hand position more closely approximates the position typically employed in lifting grocery bags. This principal would appear to provide a rationale to explain the lower magnitude of functional improvement compared to strength improvement in the studies mentioned earlier. The second relevant principal is that of maximum voluntary contraction. This principal suggests that strength is improved by working a muscle at its maximum capacity for a given number of lifts. In other words, if a PRE program requires lifting a weight for a total of 10 repetitions, then the resistance must be set such that the individual will be exerting near maximal effort at the 10th repetition (Fleck and Kraemer, 1987). Applying these principals to both PRE and
N.G. Branch / Work 10 (1998) 21-29
functional activity, we find that PRE cannot easily approximate the biomechanics of functional activity (low specificity), but the strategy is well designed to provide maximal voluntary contractions for the target muscles. On the other hand, if one employs functional activity to increase strength, the question of matching training mode to the target activity does not arise as the training mode and functional activity are one in the same. The challenge in functional activity use arises in applying the maximum voluntary contraction principal. When one typically lifts groceries froin a cart, one does not lift more weight than is usually necessary, nor does one lift several bags in succession until one is totally fatigued. Proponents of PRE and functional activity to increase functional strength must solve two very different problems. PRE advocates must modify PRE programs to simulate the complex biomechanics of functional activities. Advocates of functional activity must find ways of modifying a functional activity such that a client achieves repeated maximum voluntary contractions. Of these two problems, modifying functional tasks may be more feasible than solving the difficult biomechanical challenges of adapting PRE training to mirror functional activities. At least one researcher has advocated for the inclusion of functional activity as a strategy for increasing functional strength. Skelton et al. (1995) conducted 12 weeks of high intensity PRE training with 20 community dwelling women, aged 75 and older, employing elastic tubing or bags of rice as resistance mechanisms. The researcher reported moderate strength increases but few improvements in such measures of functional ability as lifting a bag onto a surface, rising from a chair, or walking in a corridor. She echoed the suggestions of other authors that PRE may be more able to facilitate functional strength gains in a more frail, rather than a less frail populatiOIi. Skelton et al. (1995, p. 1086) also speculated that 'perhaps improving functional ability requires training that includes practice of the functional tasks'. 6. Attitudinal barriers in PRE use The paucity of specific information in the occu-
27
pational therapy literature regarding the mechanism of strength training and the magnitude of improvement in functional strength may be due to low therapist expectations of the cohort's ability to improve. Jones (1974) conducted a literature review concerning the attitudes of occupational therapists towards the aged and concluded that many occupational therapists rightly view some of their patients as functioning within a terminal sick role, but improperly generalize this concept to the larger aging population. Jones (1974, p. 616) stated that the terminal sick role is characterized as a deviant role, emphasizing personal dependence on others with no expectations of future improvement in function. It ' ... allows dependency and excuses the individual from achievement, productivity, responsibility and hard work'. Age bias may be of concern in rehabilitation professionals other .than occupational therapy practitioners. In a blinded study, Barta Kivtek et al. (1986) randomly selected 127 physical therapists into two groups and provided each with a detailed patient history. The history listed the patients age as 78 in one group and 28 in the other. Therapists were asked to develop goals for each hypothetical patient. The author reported that the therapists set significantly less aggressive goals for the older group as measured by a scale of aggressiveness in goal setting (reliability and validity data not reported). A stepwise linear regression analysis demonstrated this reduced aggressiveness in goal setting independent of therapists' knowledge of aging process, experience with geriatric patients, age of therapist, or current caseload. While the conclusions of this study cannot be directly applied to OT practitioners, one must seriously consider the possibility that such bias exists.
6.1 Concern for injuries during PRE Many expressions of concern for injury were found in the occupational therapy literature. Studies of injury during PRE have yielded conflicting results. Pollock (1991) compared injury rates of 70-79-year-old men and women exercising in either PRE or a walk/jog exercise program. Pollock reported that 19.3% of the PRE
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group sustained an injury during the initial 1RM assessment to determine baseline strength. Two of 28 participants sustained injuries during the 26 weeks training protocol itself. The training injury rate was less than that sustained in the walk/jog treatment condition and may be similar to injury rates in a more general population. Injuries during PRE were often exacerbations of old injuries. Alternatively, Shaw et al. (1995) conducted 1RM testing in a similar cohort and found a 2.4% injury rate. Like Pollock et al. (1991), both injuries were exacerbations of earlier injuries. Shaw et al. (1995) limited their intervention to 1RM testing and did not consider injuries while training at submaximal levels. The discrepancy in results can perhaps be explained by different operational definitions of 'injury'. Although not specifically designed to address the issue, Fiatarone et al. (1995) reported no injuries during the training of her subjects. 7. Conclusions While the occupational therapy literature reviewed is supportive of the concept of PRE as a mechanism for increasing strength in the older worker, specific information on how this is to be accomplished is either outdated or lacking. This generalized concept of exercise has led to the practice of offering multi-faceted exercise combining light resistive exercise, ROM, cardiovascular and other components. Non-specific exercise may not be effective in increasing work capacity when functional decline is secondary to diminished strength. Rehabilitation professionals must be made aware of the possiblity that they harbor a bias against intensity in exercise. Therapists should be made aware that even their frailest patients can maintain a worker role and have the capacity to increase their work capacity even late in life and despite complicating medical factors. Moreover, the potential for functional gains may be greater for impaired clients than for similarly aged workers without functional deficits. Properly supervised high intensity progressive resistance training is a safe and effective method of increasing strength in the elderly worker and
results in a significant increase in several functional activities underlying work capacity. In prescribing PRE, therapists should be aware of the need to choose PRE training which is biomechanically related to the functional activity they wish to improve. Therapists must also take steps to insure adequate compliance with the PRE program, especially if it is to be accomplished with intermittent supervision. For those concerned with injury potential, use of the 1RM max may be· eliminated in favor of monitoring the increase in resistance required to reach a voluntary maximal contraction for any given number of repetitions. Can the principals underlying effective PRE also be applied to progressive assistive exercise (PAE) for clients with muscles unable to resist gravity? If so, can high intensity PAE be conducted safely with a weaker client? Modifying functional activities for use as a therapeutic mechanism for increased muscle strength, rather than as an outcome measure should be investigated. This strategy has some advantages over PRE especially in settings where strength training equipment is unavailable, or one-to-one supervision is impractical. Given the relative safety of functional activities and the significant potential benefit of increased work capacity, therapists can ethicaUy begin to prescribe functional activities for strength gain in the absence of formal studies demonstrating the efficacy of this procedure. In light of the potential for functional activity as a mechanism for strength increase, the current occupational therapy practice of environmental adaptation to reduce work demands may be counter productive. For instance, if routine climbing of stairs provides knee/hip extensor muscles with high intensity resistance, then an environmental modification to minimize that functional activity may result in further decline in mobility and a concomitant loss in independence and increased safety hazard. Safety hazards inherent in stair. climbing must be balanced against the loss in function which may result in the elimination of this activity. The prospect of functional improvement in the elderly is corisistent with the expectations contained in the HCFA guidelines for Medicare, Part
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B. According to (Lewis, 1989, p. 239) these guidelines link reimbursement to 'significant practical improvement in patient's/client's functional level within a reasonable time period'. Such improvement would seem within the reach of a large percentage of elderly workers. Perhaps these conclusions may seem more intuitive if elderly workers are viewed not from the perspective of how they differ from younger workers, but how they are the same. References Barta Kivitek SD, Shaver BJ, Blood H, Shepard KF. Age bias: Physical Therapists and older patients. J Gerontol 1986;41(6):706-709. Blankfort-Doyle W, Waxman H, Coughey K, Naso F, Carner EA, Fox E. An exercise program for nursing home residents. In: Ostrow AC, editor. Aging and motor behavior. Indianapolis, IN: Benchmark Press, 1989. Davis U, Kirkland M, editors. The role of occupational therapy with the elderly. RockviIle, MD: The American Occupational Therapy Association, 1988. DeLorme TL, Watkins AL Technics of progressive resistance exercise. Arch Phys Med 1946;27(10):263-273. Fiatarone MA, O'NeiII EF, Ryan ND et aI. Exercise training and nutritional supplementation for physical fraility in very elderly people. N Eng) J Med 1994;330(25):1769-1775. Fleck SJ, Kraemer WJ. Designing resistance training programs. Champaign, IL: Human Kinetics Books, 1987. Guralnik JM, Ferrucci L, Simonsick EM, Salive ME, Wallace RB. Lower-extremity function in persons over the age of 70 years as a predictor of subsequent disability. N Eng) J Med 1995;332(9):556-561. Hunter GR, Treuth MS, Weinsier RL et al. The effects of strength conditioning on older women's ability to perform daily tasks. J Am Geriatr Soc 1995;43(7):756-760.
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Jette AM, Harris BA, Sleeper L et al. A home-based exercise program for nondisabled older adults. J Am Geriatr Soc 1996;44(6):644-649. Jones NA. Occupational therapy and the aged. Am J Occup , Ther 1974;28(10):615-618. Judge JO, Schechtman K, Cress E, the FICSIT Group. The relationship between physical performance measures and independence in instrumental activities of daily living. J Am Geriatr Soc 1996;44(11):1332-1341. Lewis CS. Elder care in occupational therapy. Thorofare, NJ: Slack, 1989. MacRae N. The older worker. In: Jacobs K, editor. Occupational therapy: work related programs and assesssments. 2nd ed. Boston: Little, Brown, 1991. Molloy DW, Richardson DL. The effects of a three-month exercise programme on neurophychological function in elderly institutionalized women: a randomized controlled trial. Age Ageing 1988;17:303-310. McGovern RE, Luscombe HB. Useful modifications of progressive resistive exercise technique. Arch Phys Med Rehabil 1953;34:475-477. Pollock ML, Carroll JF, Graves JE et al. Injuries and adherence to walk/jog and resistance training programs in the elderly. Med Sci Sports Exercise 1991;23(10):1194-1120. Shaw CE, McCully KK, Posner JD. Injuries during one repetition maximum assessment in the elderly. J Cardiopulm Rehabil 1995;15(4):283-287. Skelton DA, Young A, Greig CA, Malbut KE. Effects of resistance training on strength, power, and selected functional abilities of women aged 75 and older. J Am Geriatr Soc 1995;43(10):1081-1087. Taffe DR, Pruitt L, Reim J, Butterfield G, Marcus R. Effect of sustained resistance training on basal metabolic rate in older women. JAm Geriatr Soc 1995;43(5):465-471. Zemke R. Remediating biomechanical and physiological impairments of motor performance. In: Trombly CA, editor. Occupational' therapy for physical dysfunction. 4th ed. Baltimore: Williams and Wilkins, 1995:405-422.
ELSEVIER
Work 10(1998)21-29
Maintaining work capacity in the aged worker via progressive resistance training: the implications for occupational therapy practitioners Nicholas G. Branch* Sargent College, Boston University, 635 Commonwealth Ave., Boston, MA 02215, USA Received 1 May 1997; accepted 1 July 1997
Abstract Society has an interest in maintaining the work capacity of its aging workers. Fewer and fewer younger workers are entering the workforce to replace older citizens no longer able to perform the worker role. There is a demonstrated relationship between increased strength and work capacity, yet the occupational therapy literature emphasizes generalized exercise programming. This type of programming is ineffective at building strength in the elderly worker. High intensity progressive resistance exercise (PRE) can increase strength in the very old worker, yet the'rapists are hesitant to employ PRE, perhaps due to a potential bias against the use of high intensity PRE with this cohort. Use of PRE may present some difficulties in the clinical situation where continual supervision and resistance training equipment is not available. The adaptive use of functional activities as a resistance training strategy to build strength may be able to overcome the difficulties attendant with the use of PRE while preserving its benefits. Several other implications for occupational therapy practitioners are discussed. © 1998 Elsevier Science Ireland Ltd. Keywords: Therapeutic exercise; Aged worker; Occupational therapy; Strength
1. Introduction It is becoming evident that society has a vested interest in maintaining the work capacity of its
* Corresponding author: 352-R Raymond Hill Rd., Raymond, ME 04071, USA. Tel.: + 1 207 6554645; e-mail: [email protected]
citizens as they become older. MacRae (1991) raises several points in describing the significance of changing demographics in the workforce. As the current working population ages, it will begin to reduce its involvement with paid work. During the same period of time, the supply of younger workers required to replace them will diminish. Therefore, society must find ways to assist the older worker in maintaining his or her capacity
1051-9815/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved. PH S1051-9815(97)00005-5
22
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for work throughout the life span in order to generate an adequate workforce. Maintaining adequate work capacity in the aging workforce may also have a positive impact on the financing of social security and other financial retirement mechanisms. If the aging workforce opts for fulltime retirement rather than a work/retirement mix, the health care/retirement system may be overburdened financially as fewer younger workers struggle to pay for the healthcare of an increasing number of older workers. From an individual perspective, retirement no longer signifies a cessation of all work but rather a redefining of the balance of work, rest and play. Achieving such a balance is often an objective occupational therapists attempt to achieve with their clients. In fact, MacRae (1991, p. 361) suggests 'a balance of play, work and rest is essential for the physical and mental health and well-being of any individual. This paper reviews current research concerning the importance of muscular strength as an essential performance component in maintaining work capacity of the aged worker; and the efficacy of Progressive Resistance Exercise (PRE) for increasing strength in this cohort. PRE is often employed by rehabilitation therapists to increase or maintain muscular strength. The total amount of exercise in PRE is prescribed by specifying a particular frequency, intensity and duration of resistance to the muscle group to be strengthened. Of these three parameters, intensity appears to be receiving the most scrutiny in the current literature. This paper also examines current views of strength/PRE in the occupational therapy literature, then reviews several recent studies of PRE with aged participants performed by other disciplines. The studies investigate the optimal intensity of resistance in progressive resistance exercise required to generate an increase in strength in the elderly worker and what magnitude of strength increase is possible. Limitations to the application of PRE as a broad based intervention and implications for therapists are discussed. Lastly, the utility of employing functional activity as a mechanism for increasing strength is considered.
2. The relationship of strength measures to work capacity Increasing strength in a client has value only insofar as the increase in strength is accompanied by an increase in functional ability. Judge et al. (1996) examined the strength of the association between several measures of strength and the ability to carry out specific instrumental activities. of daily living (IADL). The researchers evaluated data obtained from 2190 participants (mean age = 71) enrolled in a pre-planned meta analysis entitled the Frailty and Injury: Cooperative Studies of Intervention Trails (FICSIT). Measures of strength included hand grip strength, gait velocity and the ability to stand up from a chair. Outcome variables examined included the ability to employ motorized modes of travel, shopping for groceries, doing housework and laundry. The correlations reported were highly significant for each independent variable, ranging from P = 0.007 for hand strength, to P = 0.0004 for gait speed. These correlations were obtained after correcting for several co-variates known to affect IADL independence and persisted across a wide range of physical performance abilities. Guralnik et at. (1995) conducted a similar analysis with 1122 community dwelling men and women aged 71 years or older. These researchers reported that objective measures of lower extremity function were highly predictive of future disability as measured via a valid and reliable disability measure employed in earlier studies. Lower extremity measures employed were walking velocity, rising repeatedly from a chair and climbing stairs. Both studies noted the inability of correlational studies to demonstrate a causal link between evaluated measures. However, based on the strength of the correlational evidence, the researchers speculate that use of strength measures to predict future declines in physical function might enable clinicians to prevent or delay disability rather than attempting to remediate existing deficits. They recommend that randomized clinical trials be conducted to directly investigate these relationships.
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3. Current views of occupational therapy on PRE and strength Occupational therapists consider strength to be an important component in a broad range of functional activities, including work-related activities. Improving strength via exercise is discussed in three· authoritative sources commonly relied upon by occupational therapists. A brief summary of this discussion follows. Lewis (1986) makes numerous references to strength and functional performance in her text entitled Eldercare in Occupational Therapy. In a section entitled Biophysical Realities, she describes the gradual decline of muscle mass and number of muscle fibers occurring after the age of 30. Muscle elasticity and the proportion of type IIA and lIB muscle fibers is altered, reducing the aging muscle's ability to contract. Lewis (1986, p. 78) suggests that medium level isotonic exercise 'is valuable for keeping muscles ... at a good level in late adulthood'. The author cautions against excessive or too violent exercise for fear of damaging tissues and to avoid the slower process of muscle repair common in the elderly. Elsewhere in the work, Lewis (1986, p. 104) suggests that 'proper exercise pursued consistently throughout the lifespan may significantly deter certain bodily functions that are traditionally thought to accompany the aging processes'. Although which body functions she is referring to are not specified, the example which follows refers to training the cardiovascular, not the voluntary muscular system. A basic definition of muscular strength is provided, but the issue of one's ability to improve muscular strength in later life is not discussed. The devel.opment of muscular strength via PRE is listed as a possible component of an exercise program. It is noteworthy that although strength is mentioned as an essential component of functional activity, no specific mention of the mechanism of strength increase is made. Instead, several pages are devoted to how one would establish a cardiovascular exercise program. In a section entitled Modalities and Treatment, Lewis (1986, p. 460) produces a non-inclusive list of 23 occupational therapy modalities for use with an aged population. However, exercise or resis-
23
tance training is not mentioned in the list. 'Gentle' exercise is recommended for elderly clients with arthritis. The American Occupational Therapy Association has published a text for use in its self-paced clinical course entitled, The Role of Occupatio~al Therapy With the Elderly (ROTE) (Davis and Kirkland, 1988). This text also outlines the decline in function typically found as an individual ages, detailing changes in cardiac output, bone mass and a 50% reduction in the number of muscle fibers. The ROTE curriculum notes that some affects of aging may be due to habitual inactivity and that consistent physical activity throughout the lifespan may diminish losses in strength. Page 47 states 'Exercise and activity of the appropriate intensity and duration can be very beneficial to older people'. The text points out that distinguishing between functional decline due to aging and that due to inactivity is essential if a clinician is to properly choose between a compensatory and a biomechanic approach to treatment. If one believes strength declines are due to aging (and therefore inevitable), then the compensatory approach to reduce environmental demands is warranted. On the other hand, if one believes an increase of strength is possible, then the anticipated outcomes of treatment will be far different. In the section on treatment approaches, strength is specifically linked to functional improvement and intervention to increase strength is encouraged, but specifics on how this is to be accomplished are not provided. One might reasonably argue that specific protocols for increasing strength are beyond the scope of comprehensive volume on geriatric occupational therapy. A commonly consulted source for specific protocols in a wide variety of physical disability functions is Occupational Therapy for Physical Dysfunction (Trombly, 1995). Writing in Trombly, Zemke (1995) details a PRE protocol designed to increase strength. PRE is a strategy employed under the biomechanical frame of reference, which seeks to prevent further decline, or restore biomechanical strength enabling an individual to pursue valued daily activities, including work activities. The author describes several strength building protocols. Of those, PRE is
24
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recommended for improving strength in muscles with sufficient strength to resist gravity through a full range of motion. Zemke outlines a protocol originally formulated by DeLorme and Watkins (1945) and modified by McGovern and Luscombe (1953) to achieve similar results as the DeLorme technique with fewer lifting repetitions. The techniques are based on a measure of strength called the lO-repetition Maximum (10RM). The 10RM is the maximum amount of resistance a muscle can overcome (lift) 10 times in succession before fatigue results in muscle failure. A warm up of 10 repetitions without resistance is followed by 10 repetitions at the lORM level. Following a 1-min rest, a third 10 repetition set with resistance set at 75% of the 10RM is done. Finally a fourth set of 10 repetitions at the 50% lORM is performed. The resistance training is progressive in that as the 10RM is measured during successive weeks of training, the resistance that can be overcome 10 times will increase. The decreasing level of resistance within a single strength training session was designed to compensate for increased level of fatigue experienced by patients. The study by McGovern and Luscombe was a controlled, nonblinded study of 24 20-30-year-old patients, 12 of whom were in the control group and followed the DeLorme method and the remainder followed the above protocol. The muscle group trained was the knee/hip extensor. There are· many limitations in this particular study, including the generalizablilty of its conclusion due to a small sample, short duration of training and the failure to report gains as a percentage of maximum strength. The essential concern is the use of the 10RM as the maximum amount of resistance provided. 10RM is contrasted with the one repetition maximum (1RM) currently considered the single best measure of strength (Fleck and Kraemer, 1987). For an average individual, the lORM has been empirically found to be approximately 75% of the 1RM (Fleck and Kraemer). For example, if the maximum an individual can lift one time is 100 lbs, she will likely be able to lift 75 lbs 10 times before exhaustion. Note that the number of repetitions accomplished before muscle failure is a measure of strength training intensity.
Several conclusions may be drawn from this review of occupational therapy sources. They are: 1. The link between strength and functional capacity for work is supported within occupational therapy literature. However, PRE is often combined within the broader construct of exercise. In the first two sources reviewed, major attention is devoted to range of motion and cardiovascular components of exercise rather than increasing strength. 2. The tone of these sources is cautionary with respect to exercise. Terms such as 'gentle' and 'appropriate' are often employed, but not defined operationally. Concerns for injury and risks appear to outweigh discussion of specific benefits. 3. ROTE emphasizes the wellness based concept of maintaining strength across the lifespan but fails to discuss the possibility of increasing strength later in life. The assumption that an increase of strength is possible is inherent in the application of the biomechanical frame of reference to this population. The prospect of functional strength increase is also critical from the reimbursement perspective. Medicare, Part B links reimbursement to improvement, not maintenance of function. 4. Use of a maximum resistance intensity of lORM as employed in McGovern and Luscombe (1953) is not typically considered a sufficiently intense training stimulus to maximize strength gains. This next section will survey more recent literature to identify the optimal intensity of increasing strength in an elderly population.
4. Optimal intensity of PRE for strength increase
The three variables for determining the total amount of exercise in PRE are intensity, duration and frequency. Frequencies of between two and five sessions per week have been employed with adequate levels of strength increase (Fleck and Kraemer, 1987). Intensity and duration (the num-
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ber of repetitions of a lift) are somewhat inversely related. For instance, at an intensity of 80% lRM, an individual can complete 6-10 repetitions before muscle failure. At 50% lRM, that same individual will likely be able to complete 12"':'15 repetitions before becoming fatigued. Because intensity can be conveniently expressed as a percentage of one's lRM (maximum strength), intensity has emerged as the key variable in assessing mechanisms of strength increase in the elderly. Although no studies of low intensity PRE could be found, general exercise programs combining low intensity endurance training with stretching or cardiovascular training are commonly employed in nursing homes to maintain strength and functional abilities of residents. Outcome studies reviewed do not support the efficacy of this intervention. Blankfort-Doyle et al. (1989) conducted low intensity endurance training with 15 frail residents of a nursing home for 15 weeks and found no improvement in work capacity (measured by bicycle ergomomentry or observed functional capacity) compared with controls. Molloy et al. (1988) conducted I-h exercise sessions 5 days per week for 12 weeks with 23 geriatric in-patients and found no significant differences in habitual physical activity compared with socialization or control groups. In one of the few studies to examine two different intensities of PRE, Taffe et al. (1995) examined the effect of PRE intensity in a study of 36 65-79-year-old women living in the community. Participants were randomized into three groups and trained for 15 weeks at either 40% lRM or 80% lRM. The researchers reported strength increases of 40 and 36%, respectively, compared with a 4% strength increase in the control group. The difference between high and low intensity PRE training was insignificant. Taffe speculated that the similarity of results may have been due to the total volume of training rather than intensity. No functional outcome measures were provided. Hunter et al. (1995) reported functional improvements with a similar cohort. This study employed PRE training at 50% lRM, adjusting the intensity such that participants could complete two sets of 12 reps three times per week for 16
25
weeks of training. This training regimen resulted in moderate strength increases averaging 52%. The researcher reported an 18% increase in participants' ability to complete the functional tasks of walking with a box of groceries and a more modest decrease in the effort level required to rise from a chair. Although uncontrolled, this study is consistent with Taffe et al. (1995) and demonstrates some functional improvement. It should be noted that the moderate increases in strength demonstrated in these studies of healthy, community dwelling women cannot be generalized to a more frail population more likely to require occupational therapy services. The utility of PRE for a frail popUlation has been examined by Fiatarone et al. (1994) at the Boston site of the Frailty and Injury: Cooperative Studies of Intervention Trails. This controlled, randomized study examined the effect of high intensity PRE with 100 frail nursing home residents. The exclusion criteria for this study was much less strict than the others reviewed here. Eighty-three percent of the participants required a cane, walker, or wheelchair for mobility. Most had fallen within the last year and many suffered from arthritis (50%), pulmonary disease (44%), hypertension (35%) or cancer (24%). Fifty-one percent had mild to moderate cognitive impairment and 38% were depressed. The intervention for the experimental group was 10 weeks of PRE training at 80% lRM with the hip and knee extensor muscle groups. Participants completed three sets every other day. Using a multiple regression model, the researchers reported an average 113% gain in strength compared with a group taking a nutritional supplement and a third group engaging in a combination of walking, calisthenics, board games, crafts and other typical nursing home activities. The study also reported significant functional gains including habitual gait· velocity, stair climbing ability and habitual levels of physical activity. Four participants requiring a walker before the intervention were able to use a cane afterwards. These results were demonstrated independent of other factors such as the level of chronic disease, depression, or functional status at base line.
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4.1 Limitations and conclusions
Viewed collectively, these studies have not identified a consistent relationship between the intensity of resistance employed in PRE and an increase in strength. The variation in results is broad. Blankfort-Doyle (1989) reported no increase in work capacity after endurance training, whereas Fiatarone et a!. (1994) reported a greater than 100% increase in strength in a study employing intensities of 80% lRM in a frail elderly population. Nevertheless, it may be concluded that PRE of some increase in intensity is a more effective mechanism for increasing strength in the elderly worker than the range of motion or calisthenics exercises more commonly employed with this population. The relationship between PRE and increased function is less clear. Studies of general exercise and low intensity endurance training resulted in little functional improvement in participants (Molloy et a!., 1988; Blankfort-Doyle, 1989). Studies evaluating moderate PRE intensity either did not assess functional impacts (Taffe et a!., 1995), or produced only modest functional gains (Hunter et a!., 1995). Fiatarone et a!. (1994) reported a greater magnitude of both strength and functional gains by conducting PRE training at 80% lRM with a functionally impaired population, in contrast to the other studies reviewed that evaluated functionally in tact subjects. It is possible that the superior functional gains demonstrated in Fiatarone et al. (1994) are related to the lower functional level of the subjects at base-line as well as the PRE intensity employed in the study. Collectively, the studies reviewed in this section present some limitations when viewed from the perspective of broad based clinical application. PRE training was conducted with large, expensive variable resistance training equipment such as 'nautilus' type equipment. It is unlikely such equipment is consistently available in most nursing homes, assisted living center or other common treatment settings for this cohort. Secondly, each training session was personally supervised by a rehabilitation professional. One-to-one supervision may not be practical under most current reimbursement guidelines. Adherence to the pre-
scribed exercise regimen is likely to decline dramatically if subjects are initially supervised in the beginning of a PRE program and then asked to proceed with intermittent or no professional supervision (Jette et aI., 1996), thus limiting the benefit derived. 5. Functional activities as a mechanism to improve strength The use of functional activities as a mechanism for increasing strength has potential for overcoming the difficulties encountered in the use of PRE while maintaining its benefits. The use of functional activities in this manner has not been investigated directly, however, there is theoretical support for this strategy in the strength training literature. Fleck and Kraemer (1987) discussed the principal of specificity in PRE. This principal suggests that the greater the similarity of rate, range and associated joint angle during muscular contractions between the resistance training and the functional activity it is designed to enhance, the greater the carryover in training. For example, if a therapist wishes to increase a client's ability to lift groceries from a grocery cart, then a PRE program employing a neutral or fully pronated hand position will be superior to a program using the fully supinated hand position typically used with dumbbells or elastic tubing. PRE employing the neutraljpronated hand position will be superior as this hand position more closely approximates the position typically employed in lifting grocery bags. This principal would appear to provide a rationale to explain the lower magnitude of functional improvement compared to strength improvement in the studies mentioned earlier. The second relevant principal is that of maximum voluntary contraction. This principal suggests that strength is improved by working a muscle at its maximum capacity for a given number of lifts. In other words, if a PRE program requires lifting a weight for a total of 10 repetitions, then the resistance must be set such that the individual will be exerting near maximal effort at the 10th repetition (Fleck and Kraemer, 1987). Applying these principals to both PRE and
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functional activity, we find that PRE cannot easily approximate the biomechanics of functional activity (low specificity), but the strategy is well designed to provide maximal voluntary contractions for the target muscles. On the other hand, if one employs functional activity to increase strength, the question of matching training mode to the target activity does not arise as the training mode and functional activity are one in the same. The challenge in functional activity use arises in applying the maximum voluntary contraction principal. When one typically lifts groceries froin a cart, one does not lift more weight than is usually necessary, nor does one lift several bags in succession until one is totally fatigued. Proponents of PRE and functional activity to increase functional strength must solve two very different problems. PRE advocates must modify PRE programs to simulate the complex biomechanics of functional activities. Advocates of functional activity must find ways of modifying a functional activity such that a client achieves repeated maximum voluntary contractions. Of these two problems, modifying functional tasks may be more feasible than solving the difficult biomechanical challenges of adapting PRE training to mirror functional activities. At least one researcher has advocated for the inclusion of functional activity as a strategy for increasing functional strength. Skelton et al. (1995) conducted 12 weeks of high intensity PRE training with 20 community dwelling women, aged 75 and older, employing elastic tubing or bags of rice as resistance mechanisms. The researcher reported moderate strength increases but few improvements in such measures of functional ability as lifting a bag onto a surface, rising from a chair, or walking in a corridor. She echoed the suggestions of other authors that PRE may be more able to facilitate functional strength gains in a more frail, rather than a less frail populatiOIi. Skelton et al. (1995, p. 1086) also speculated that 'perhaps improving functional ability requires training that includes practice of the functional tasks'. 6. Attitudinal barriers in PRE use The paucity of specific information in the occu-
27
pational therapy literature regarding the mechanism of strength training and the magnitude of improvement in functional strength may be due to low therapist expectations of the cohort's ability to improve. Jones (1974) conducted a literature review concerning the attitudes of occupational therapists towards the aged and concluded that many occupational therapists rightly view some of their patients as functioning within a terminal sick role, but improperly generalize this concept to the larger aging population. Jones (1974, p. 616) stated that the terminal sick role is characterized as a deviant role, emphasizing personal dependence on others with no expectations of future improvement in function. It ' ... allows dependency and excuses the individual from achievement, productivity, responsibility and hard work'. Age bias may be of concern in rehabilitation professionals other .than occupational therapy practitioners. In a blinded study, Barta Kivtek et al. (1986) randomly selected 127 physical therapists into two groups and provided each with a detailed patient history. The history listed the patients age as 78 in one group and 28 in the other. Therapists were asked to develop goals for each hypothetical patient. The author reported that the therapists set significantly less aggressive goals for the older group as measured by a scale of aggressiveness in goal setting (reliability and validity data not reported). A stepwise linear regression analysis demonstrated this reduced aggressiveness in goal setting independent of therapists' knowledge of aging process, experience with geriatric patients, age of therapist, or current caseload. While the conclusions of this study cannot be directly applied to OT practitioners, one must seriously consider the possibility that such bias exists.
6.1 Concern for injuries during PRE Many expressions of concern for injury were found in the occupational therapy literature. Studies of injury during PRE have yielded conflicting results. Pollock (1991) compared injury rates of 70-79-year-old men and women exercising in either PRE or a walk/jog exercise program. Pollock reported that 19.3% of the PRE
28
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group sustained an injury during the initial 1RM assessment to determine baseline strength. Two of 28 participants sustained injuries during the 26 weeks training protocol itself. The training injury rate was less than that sustained in the walk/jog treatment condition and may be similar to injury rates in a more general population. Injuries during PRE were often exacerbations of old injuries. Alternatively, Shaw et al. (1995) conducted 1RM testing in a similar cohort and found a 2.4% injury rate. Like Pollock et al. (1991), both injuries were exacerbations of earlier injuries. Shaw et al. (1995) limited their intervention to 1RM testing and did not consider injuries while training at submaximal levels. The discrepancy in results can perhaps be explained by different operational definitions of 'injury'. Although not specifically designed to address the issue, Fiatarone et al. (1995) reported no injuries during the training of her subjects. 7. Conclusions While the occupational therapy literature reviewed is supportive of the concept of PRE as a mechanism for increasing strength in the older worker, specific information on how this is to be accomplished is either outdated or lacking. This generalized concept of exercise has led to the practice of offering multi-faceted exercise combining light resistive exercise, ROM, cardiovascular and other components. Non-specific exercise may not be effective in increasing work capacity when functional decline is secondary to diminished strength. Rehabilitation professionals must be made aware of the possiblity that they harbor a bias against intensity in exercise. Therapists should be made aware that even their frailest patients can maintain a worker role and have the capacity to increase their work capacity even late in life and despite complicating medical factors. Moreover, the potential for functional gains may be greater for impaired clients than for similarly aged workers without functional deficits. Properly supervised high intensity progressive resistance training is a safe and effective method of increasing strength in the elderly worker and
results in a significant increase in several functional activities underlying work capacity. In prescribing PRE, therapists should be aware of the need to choose PRE training which is biomechanically related to the functional activity they wish to improve. Therapists must also take steps to insure adequate compliance with the PRE program, especially if it is to be accomplished with intermittent supervision. For those concerned with injury potential, use of the 1RM max may be· eliminated in favor of monitoring the increase in resistance required to reach a voluntary maximal contraction for any given number of repetitions. Can the principals underlying effective PRE also be applied to progressive assistive exercise (PAE) for clients with muscles unable to resist gravity? If so, can high intensity PAE be conducted safely with a weaker client? Modifying functional activities for use as a therapeutic mechanism for increased muscle strength, rather than as an outcome measure should be investigated. This strategy has some advantages over PRE especially in settings where strength training equipment is unavailable, or one-to-one supervision is impractical. Given the relative safety of functional activities and the significant potential benefit of increased work capacity, therapists can ethicaUy begin to prescribe functional activities for strength gain in the absence of formal studies demonstrating the efficacy of this procedure. In light of the potential for functional activity as a mechanism for strength increase, the current occupational therapy practice of environmental adaptation to reduce work demands may be counter productive. For instance, if routine climbing of stairs provides knee/hip extensor muscles with high intensity resistance, then an environmental modification to minimize that functional activity may result in further decline in mobility and a concomitant loss in independence and increased safety hazard. Safety hazards inherent in stair. climbing must be balanced against the loss in function which may result in the elimination of this activity. The prospect of functional improvement in the elderly is corisistent with the expectations contained in the HCFA guidelines for Medicare, Part
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B. According to (Lewis, 1989, p. 239) these guidelines link reimbursement to 'significant practical improvement in patient's/client's functional level within a reasonable time period'. Such improvement would seem within the reach of a large percentage of elderly workers. Perhaps these conclusions may seem more intuitive if elderly workers are viewed not from the perspective of how they differ from younger workers, but how they are the same. References Barta Kivitek SD, Shaver BJ, Blood H, Shepard KF. Age bias: Physical Therapists and older patients. J Gerontol 1986;41(6):706-709. Blankfort-Doyle W, Waxman H, Coughey K, Naso F, Carner EA, Fox E. An exercise program for nursing home residents. In: Ostrow AC, editor. Aging and motor behavior. Indianapolis, IN: Benchmark Press, 1989. Davis U, Kirkland M, editors. The role of occupational therapy with the elderly. RockviIle, MD: The American Occupational Therapy Association, 1988. DeLorme TL, Watkins AL Technics of progressive resistance exercise. Arch Phys Med 1946;27(10):263-273. Fiatarone MA, O'NeiII EF, Ryan ND et aI. Exercise training and nutritional supplementation for physical fraility in very elderly people. N Eng) J Med 1994;330(25):1769-1775. Fleck SJ, Kraemer WJ. Designing resistance training programs. Champaign, IL: Human Kinetics Books, 1987. Guralnik JM, Ferrucci L, Simonsick EM, Salive ME, Wallace RB. Lower-extremity function in persons over the age of 70 years as a predictor of subsequent disability. N Eng) J Med 1995;332(9):556-561. Hunter GR, Treuth MS, Weinsier RL et al. The effects of strength conditioning on older women's ability to perform daily tasks. J Am Geriatr Soc 1995;43(7):756-760.
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Jette AM, Harris BA, Sleeper L et al. A home-based exercise program for nondisabled older adults. J Am Geriatr Soc 1996;44(6):644-649. Jones NA. Occupational therapy and the aged. Am J Occup , Ther 1974;28(10):615-618. Judge JO, Schechtman K, Cress E, the FICSIT Group. The relationship between physical performance measures and independence in instrumental activities of daily living. J Am Geriatr Soc 1996;44(11):1332-1341. Lewis CS. Elder care in occupational therapy. Thorofare, NJ: Slack, 1989. MacRae N. The older worker. In: Jacobs K, editor. Occupational therapy: work related programs and assesssments. 2nd ed. Boston: Little, Brown, 1991. Molloy DW, Richardson DL. The effects of a three-month exercise programme on neurophychological function in elderly institutionalized women: a randomized controlled trial. Age Ageing 1988;17:303-310. McGovern RE, Luscombe HB. Useful modifications of progressive resistive exercise technique. Arch Phys Med Rehabil 1953;34:475-477. Pollock ML, Carroll JF, Graves JE et al. Injuries and adherence to walk/jog and resistance training programs in the elderly. Med Sci Sports Exercise 1991;23(10):1194-1120. Shaw CE, McCully KK, Posner JD. Injuries during one repetition maximum assessment in the elderly. J Cardiopulm Rehabil 1995;15(4):283-287. Skelton DA, Young A, Greig CA, Malbut KE. Effects of resistance training on strength, power, and selected functional abilities of women aged 75 and older. J Am Geriatr Soc 1995;43(10):1081-1087. Taffe DR, Pruitt L, Reim J, Butterfield G, Marcus R. Effect of sustained resistance training on basal metabolic rate in older women. JAm Geriatr Soc 1995;43(5):465-471. Zemke R. Remediating biomechanical and physiological impairments of motor performance. In: Trombly CA, editor. Occupational' therapy for physical dysfunction. 4th ed. Baltimore: Williams and Wilkins, 1995:405-422.
