Exercise to prevent and treat functional disability

Exercise to prevent and treat functional disability

Clin Geriatr Med 18 (2002) 431 – 462 Exercise to prevent and treat functional disability$ Maria A. Fiatarone Singh, MD, FRACP* School of Exercise and...

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Clin Geriatr Med 18 (2002) 431 – 462

Exercise to prevent and treat functional disability$ Maria A. Fiatarone Singh, MD, FRACP* School of Exercise and Sport Science, University of Sydney, Lidcombe, NSW 2141, Australia Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA Hebrew Rehabilitation Center for Aged, Boston, MA 02131, USA

This article focuses on the complex phenomenon of physical disability, the role of physical activity and exercise in the development of disability, and the therapeutic implications of such a relationship. Epidemiologic and experimental evidence that are important in understanding these interactions will be highlighted. A rational physical activity prescription for the prevention and treatment of disability in old age is then presented, emanating from both a theoretical framework of the pathway to disability as we know it and from the documented physiologic, psychological, and functional adaptations to physical exercise in older adults observed in experimental trials. Although we cannot conclusively state that a single ‘‘exercise prescription’’ for disability prevention or treatment is identifiable at this time or is uniformly useful in all adults, general recommendations, which represent the best synthesis of current knowledge, and guidelines for individualization in clinical practice will be offered.

Inactivity prevalance There has been a gradually growing awareness among policy makers and health care professionals over the past several decades of the centrality of appropriate exercise habits to major public health outcomes. For example, in Healthy People 2010, the goal suggested for physical activity is to ‘‘improve the health, fitness, and quality of life of all Americans through the adoption and maintenance of regular, daily physical activity’’ [1]. Although it has been known $

The contents of this publication do not necessarily reflect the views or policies of the U.S. Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government. * School of Excercise and Sport Science, University of Sydney, Lidcombe, NSW 2141, Australia. E-mail address: [email protected] (M.A. Fiatarone Singh). 0749-0690/02/$ – see front matter D 2002, Elsevier Science (USA). All rights reserved. PII: S 0 7 4 9 - 0 6 9 0 ( 0 2 ) 0 0 0 1 6 - 2

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for many years that physical activity lowers the risk of developing heart disease, recent data suggest that, on average, physically active people outlive those who are inactive [2,3] and that regular physical activity reduces the risk of functional dependency of older adults [4– 12]. The first Surgeon General’s Report on Physical Activity and Health [1], released in July 1996, concluded that regular sustained physical activity can substantially reduce the risk of developing or dying from heart disease, diabetes, colon cancer, and high blood pressure. This hallmark report was meant to provide impetus for Americans to establish an active and fit lifestyle. Unfortunately, as shown in Table 1, relatively few Americans engage in regular physical activity despite the widely reported benefits in both the scientific and popular media. In fact, only about 10% of the US adult population report regular vigorous physical activity three days per week, a small proportion are engaged in muscle strengthening exercise, and about 25% are completely sedentary (engaged in no physical activity). Additionally, disparities exist among population groups in levels of physical activity, which further exaggerate the negative health consequences of a sedentary lifestyle. According to the 1996 Surgeon General’s Report on Physical Activity and Health [1], demographic groups at highest risk for inactivity

Table 1 Prevalence of physical activity among adults in the United States

Type of physical activity Light to moderate sustained physical activity for 30 min at least 5 days per week* Regular vigorous physical activity at least 3 days per week that promotes cardiorespiratory fitnessy Sedentary lifestyle (inactive; most of time spent sitting) Stretching (one time/week) Strengthening exercises (three times/week)

Percentage of adult Americans reporting in 1995

Goal for year 2010 Department of Health and Human Services

23%

30%

16%

25%

23%

15%

27% (1991) 16% (1991)

— —

Data are reported in the draft objectives of Healthy People 2010 (www.HealthyPeople.com) and are drawn from National Health Interview Survey, Centers for Disease Control, and National Center for Health Statistics sources. * Sustained physical activity requires muscular movements and is at least equivalent to brisk walking. In addition to walking, activities may also include swimming, cycling, dancing, gardening and yardwork, and various domestic and occupational activities. y Vigorous physical activities are rhythmic, repetitive physical activities that use large muscle groups at 60% or more of maximum heart rate for age. An exercise heart rate of 60% of maximum heart rate for age is approximately 50% of maximal cardiorespiratory capacity and is sufficient for cardiorespiratory conditioning. Maximum heart rate equals roughly 220 beats/min minus age. Examples of vigorous physical activities include jogging or running, lap swimming, cycling, aerobic dancing, skating, rowing, jumping rope, cross-country skiing, hiking or backpacking, racquet sports, and competitive group sports (eg, soccer, basketball, volleyball).

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are the elderly, women, minorities, those with low income or educational background, and those with disabilities or chronic health conditions. So, for example, in comparison to the figures for all adults shown in Table 1, 43% of adults aged 65 and older were sedentary in 1985, as were 29% in 1991. Women generally report lower than average adult participation levels for strength training (11% vs 16%). In addition, despite the evidence on safety and efficacy in very elderly frail individuals [13 – 15], the prevalence rate for resistive exercise is even lower among the young-old (6% at ages 65 to 74) and is rare among the old-old (4% older than age 75). As expected, these same demographic groups bear a large burden of disability and diseases amenable to prevention and treatment with exercise; however, they often have the least access and opportunity for health promotion efforts related to physical activity. In a random sampling of 2000 Americans compiled after the release of the Surgeon General’s report, awareness of the report and its information linking exercise to chronic disease was lower among the elderly, ethnic minorities, and less-educated adults surveyed [16]. Therefore, health care practitioners should identify and understand barriers to physical activity adoption and adherence faced by vulnerable population groups and should be prepared to develop programs and tools that address these barriers. This recommendation is particularly important for the prevention and treatment of disability, because high-risk individuals are more likely to be non-Caucasian, elderly, female, and from lower socioeconomic backgrounds—the same cohort with the least access to preventive health information and activity programming.

Theoretic relationship among physical activity, exercise, and disability Physical activity can influence the development and expression of disability in old age in many ways. These theoretical relationships are now borne out in many epidemiologic investigations, as outlined below, and provide the rationale for both the experimental studies and exercise recommendations that are found in many recent reviews of this topic [17 – 21]. The most obvious conclusion after reviewing the literature in this area is that a great deal of overlap exists between the identifiable risk factors for disability and the consequences or correlates of habitual inactivity [22 – 26]. These factors are summarized in Table 2. At the most basic level, shared demographic characteristics between those at risk of disability and those more likely to exhibit sedentary behavior include advanced age, female gender, non-Caucasian ethnicity, and lower educational level and income. Psychosocial features common to both cohorts include social isolation, low self-esteem, low self-efficacy, depressive symptoms, and anxiety. Lifestyle choices more prevalent in disabled or inactive adults include smoking and excessive alcohol consumption. Body composition changes associated with both functional decline and inactivity include sarcopenia, obesity, visceral obesity, and osteopenia. Exercise capacity is typically reduced in both conditions in all domains, including aerobic capacity, muscle strength, endurance

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Table 2 Relationship of disability and physical activity Risk factor for disability Advanced age Female gender Lower socioeconomic status, educational level, income NonCaucasian racial or ethnic background Smoking Poor social support network Cognitive impairment Depression, anxiety disorders Low self-esteem Low self-efficacy Obesity, visceral obesity Sarcopenia Osteopenia Decreased peak aerobic capacity and submaximal endurance capacity Decreased muscle strength, power, and endurance Decreased flexibility Impaired gait/balance

Associated with sedentary lifestyle

Modifiable with exercise intervention

Yes Yes Yes

No No No

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

No ?* ?* No Yes Yes Yes Yes Yes Yes Yes

Yes Yes Yes

Yes Yes Yes

* Some studies suggest that exercise may improve adherence to other behavioral changes, such as smoking cessation and dietary modification [62] or is associated with a more robust social network [169,170].

and power, flexibility, and balance. Gait instability and slowness and impaired lower extremity function and mobility characterize both disabled and inactive populations. Because most studies have not assessed the full complement of factors known to be associated with disability and because many studies have made observations at a single point in time, it is not possible to say with certainty (1) how all of these complex relationships fit together, (2) which relationships are causal, and (3) which risk factors are independent of each other. In addition to the associations above, chronic diseases associated with inactivity, such as obesity, osteoarthritis, cardiovascular disease, stroke, osteoporosis, type 2 diabetes, hypertension, and depression, are also risk factors for disability. Table 3 presents a summary of the preventive and therapeutic role of exercise in relation to the major disabling diseases in the geriatric population. In some cases, data are available from cross-sectional or prospective cohort studies and experimental trials (eg, diabetes [27 –29], cardiovascular disease [30 –32]), and in other cases from epidemiologic data alone (eg, colon and breast cancer [33,34]). Notable exceptions to these patterns are visual impairment and dementia unrelated to multi-infarct disease, which are not directly linked to inactivity, but are highly significant risk factors for disability in the elderly. This finding does not mean that exercise plays no role when these conditions are present, however. On the contrary, the inability to modify these pathologic contributants to the disability process means that the focus should be on attempting

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Table 3 Role of physical activity in disability-related diseases and syndromes Disease or syndrome

Preventive role of exercise

Therapeutic role of exercise*

Cancer (colon, breast) Cardiovascular disease Chronic lung disease Dementia (other than multi-infarct dementia) Depression, anxiety disorders Diabetes, type 2 Falls Frailty, mobility impairment Hyperlipidemia Hypertension Low back pain Neurodegenerative diseases Obesity Osteoarthritis Osteoporosis Peripheral vascular disease Stroke Visual impairment

Yes Yes No No Yes Yes Yes Yes Yes Yes No No Yes No Yes Yes Yes Noy

No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No

* Exercise shown to have a specific efficacy in treatment of the disease or syndrome, not simply a nonspecific treatment for accompanying disuse. y Visceral adiposity increases the risk for nuclear cataracts [171]; exercise may therefore indirectly decrease risk of visual impairment through this pathway.

to compensate for them by maximizing function in other domains (eg, someone with significant visual impairment from macular degeneration may benefit from strength and balance training to minimize fall risk even more than someone with intact vision). The evidence that physical activity levels are related to the development of disability in older adults is now quite strong [4– 12]. The optimum approach to ‘‘successful aging’’ or to health care in the older population cannot ignore the overlap of these areas. A better understanding of the mechanisms underlying this relationship is critical for optimal health benefits to be realized, however. With this goal in mind, the rationale for integrating a physical activity prescription into disability prevention and treatment may be seen in the context of a theoretical framework supported by four essential concepts: 

Exercise may retard the biologic aging process. Exercise can modify risk factors for disability-related diseases. Exercise can alter the expression or consequences of diseases that are already present.  Exercise can indirectly affect other modifiers of disability, such as psychosocial functioning.  

Each of these constructs is explored briefly below.

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Slowing biologic changes of aging which impair exercise capacity A great similarity exists between the physiologic changes caused by disuse and those which have been typically observed in aging populations. This finding has lead to the speculation that the way in which we age may be modulated with attention to activity levels [22]. Not all changes attributed to the aging process will directly have an impact on exercise capacity and thereby be related to disability, however. Some of the most visible changes we recognize as aging, such as changes in hair color and volume, altered skin texture and elasticity, reductions in height, and even changes in speed of cognitive processing and retention of new information, will have little direct effect on the ability to exercise or to continue to perform ADLs independently in advanced years. In most physiologic systems, the normal aging processes do not result in significant impairment or dysfunction in the absence of pathology and under resting conditions. In response to a stress, however, the age-related reduction in physiologic reserves causes a loss of homeostatic balance or an inability to complete a task requiring near-maximal effort. The most important examples relevant to disability include glucose homeostasis, maximal aerobic capacity, peak strength and power, muscle mass, bone density, and control of balance. Although such changes will be immediately noticeable and disastrous for an elite athlete [35], they may accrue insidiously in nonathletic populations over many years without much effect on daily life. This is because most sedentary individuals rarely call on themselves to exert maximal effort in physical domains. Thus, subtle changes in physical activity patterns over the adult life span allow most people not engaged in athletic pursuits to lose a very large proportion of their physical work capacity before they even notice that something is wrong or find that they have crossed a threshold of disability [36]. Women are particularly susceptible because their initial reserve of muscle mass is so much lower than that of men as a result of gender differences in anabolic hormonal milieu [23,37,38] and as lifestyle factors. In most cases, women will cross this threshold where losses of musculoskeletal capacity impact on functional status at least 10 years before men do [39]. The second consequence of age-related changes in physiologic capacity is the increased perception of effort associated with submaximal work. In middle age, an untrained man or woman may find that walking briskly results in increased blood pressure, heart rate, respiratory rate, and an earlier sense of overall and leg muscle fatigue than in youth [40]. This changing physical capacity has the unfortunate negative side effect of increasing the tendency to avoid stressful activity. This behavioral change compounds the sedentariness caused by changing job requirements or retirement, societal roles and expectations, and other psychosocial influences [41]. Thus a vicious cycle is established: ‘‘usual’’ aging leading to decreasing exercise capacity, resulting in an elevated perception of effort, subsequently causing avoidance of activity, and finally feeding back to exacerbation of the age-related declines, which themselves are secondary to disuse.

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Many studies suggest that chronic adaptation to physical activity can markedly attenuate decrements in exercise capacity that would otherwise occur with aging, with the exception of peak heart rate. Although peak workload achievable is always lower in aged individuals, the cardiovascular and musculoskeletal adaptations to chronic aerobic exercise [42 – 47] enable trained individuals to sustain higher submaximal workloads with less cardiorespiratory response (ie, heart rate, blood pressure, and dyspnea) and less musculoskeletal and general fatigue. Thus, except for peak athletic performance, the adaptations to cardiovascular training can overcome most of the day-to-day functional limitations, which might otherwise be imposed by the physiologic changes of aging and disuse [48]. Musculoskeletal function (ie, strength, power, muscle endurance) is predicated mainly on the size of the muscle mass that is contracting and to a lessor extent by changes in surrounding connective tissue in the joint (ie, cartilage, tendons and ligaments) and neural recruitment, conduction velocities, and fatigue patterns. Sedentary individuals lose large amounts of muscle mass over the course of adult life (20% to 50%), and this loss plays a major role in the similarly large losses in muscle strength noted in individuals participating in both cross-sectional and longitudinal studies [37,49,50]. Unlike many other changes that impact on exercise capacity, however, muscle mass cannot be maintained into old age even with habitual aerobic activities in either normals [51] or master athletes [52]. Only loading of muscle with weightlifting exercise (resistance training) has been shown to avert losses of muscle mass (and also strength) in older individuals [53]. In this study, elderly men who swam or ran had similar measures of muscle size and strength as their sedentary peers, whereas the muscle of older men who had been weightlifting for 12 to 17 years was almost indistinguishable, and even superior in some aspects, to healthy men 40 to 50 years younger than them. Appropriate progressive resistance training programs of 3 to 6 months in duration can be shown to increase muscle strength by an average of 40% to 150% (depending on the subject characteristics and intensity of the program) and to increase total body muscle mass by several kilograms [14,54 –58]. Thus, even if some of the neural control of muscle and absolute number of motor units remaining is not affected by exercise, the adaptation to muscle loading, even in very old age causes neural, metabolic, and structural changes in muscle which can completely compensate for the strength losses and, to some extent, the atrophy, of aging. Thus, habitual exercise can potentially lessen the impact of biologic aging on two of the major elements of exercise capacity: aerobic fitness and muscle strength. Because the development of disability is associated with decreased reserves in both of these areas [11,59], this is one of the postulated mechanisms by which physical activity may act to prevent disability. Modifying risk factors for disability-related diseases The chronic diseases associated with disability increase with age, and exercise has now been shown to be an independent risk factor for many of the major causes of morbidity and mortality in the developed world, thus providing another

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plausible mechanism for its role in maintaining function in old age. As shown in Table 3, the substantial potential for exercise to act as a primary prevention tool is obvious from the kinds of risk factors and diseases included in this list. From a public health standpoint, minimizing sedentariness or less than optimal participation in physical activities, if possible, would provide more benefit to the health of the population than any other change in behavior [1,60]. This finding is true because 70% to 80% of the adult population in the United States is less than optimally active, and sedentariness is a potent risk factor for these major diseases, doubling risk in many cases. By contrast, smoking behavior, which also doubles the risk of cardiovascular mortality, is only present in 25% of the adult population. Even obesity, at a prevalence of 30% to 40% in adults in the United States, is only half as prevalent as low physical activity levels [61]. Therefore, at this stage, the problem is not in defining the risk of inactivity in relation to chronic disabling diseases, but rather in finding ways to change behavior in sustained ways that will have an impact on subsequent long-term morbidity and mortality [2,62]. At all ages, women are at higher risk for sedentary behavior than men, and as disability, particularly that due to arthritis, increases over the age of 65, this disparity wid-ens even further. Thus, any attempts at risk factor modification must be particularly sensitive to the needs of older women with disabilities. Altering the expression or consequences of diseases that are already present Many older adults have already accumulated many disability-related diseases by the time they present to geriatric health care professionals; however, this does not mean that physical activity is no longer a consideration in the pathway to disability. Traditional medical interventions do not typically address disuse syndromes accompanying chronic disease, which may be responsible for much of their associated disability. Exercise targets syndromes of disuse and may have a significant effect on disability without altering the underlying disease itself in any primary way (eg, Parkinson’s disease [63,64] and chronic obstructive pulmonary disease [65,66]). Exercise may also lower the risk for recurrences of a disease, such as secondary events in patients with cardiovascular disease [31,32]. Third, many pathophysiologic aberrations, which are central to a disease or its treatment, are specifically addressed by exercise, which may therefore serve as an adjunct to standard care. For example, losses of visceral fat achieved through resistive or aerobic training improve insulin resistance and complement dietary and pharmacologic management of type 2 diabetes in older adults with central obesity [67,68]. Likewise, exercises designed to stimulate skeletal muscle hypertrophy in congestive heart failure [69 –71] provide benefit that counteracts the catabolic effects of circulating cytokines in this disease [72] and that cannot be achieved with cardiac medications alone. Examples of this ability of exercise to augment function beyond what is achievable even with optimal pharmacotherapy would include functional improvements in individuals with arthritis [73 – 75] who are given quadriceps exercises or resistance training for patients receiving corticosteroid treatment to counteract the associated proximal myopathy [76].

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Indirect effects on other determinants of disability Although aging, disease, physiologic impairments, and functional limitations may lead to disability, psychological, social, and environmental attributes moderate the extent to which such physical capacities result in disability [24 – 26,77]. Relevant factors include social support systems, personality types, positive and negative psychological constructs, such as happiness, optimism, morale, depression, anxiety, self-esteem, self-efficacy, and vigor. Epidemiologic studies [78,79] and experimental trials [80 – 87] have shown that physical activity is associated with more positive psychological attributes and a lower prevalence of depressive symptoms. Effects are most significant in those with comorbid illness, such as cardiovascular or pulmonary disease [85] or major depression [83,88], thus attesting to the clinical relevance of this mechanism of action of exercise in relation to relief of disability. Depression is an important factor that alters the relationship between performance-based tests of functional limitations and reallife functional status obtained by self-report [89], and even exposing elderly subjects to subliminal negative stereotyped messages about aging has been shown to result in slowing of gait speed [90]. The theoretical model that describes the potential role of physical activity in the development of disability is complex and is not completely understood. Exercise likely exerts it effects through multiple pathways simultaneously, and it is not clear if a single mechanism of action is dominant, even within a given disease paradigm. It is clearly not as simple as impairments leading to functional limitations, and, ultimately, to disability. For example, impairments in strength explain less than 20% of the variance in lower extremity physical performance in the Women’s Health and Aging Study [91]. Depressed individuals may be disabled without any impairment in physical capacity. Conversely, adaptive devices, such as motorized wheelchairs and environmental modifications, may allow completely paralyzed individuals to function without disability. Intervention studies similarly reveal discrepancies in hypothesized relationships between impairment and disability. Many studies exist in which significant improvements in impairments, such as strength or aerobic capacity, are achieved; however, these improvements do not translate into changes in functional limitations or disability level [18,92,93]. On the other hand, sometimes improvements in functional limitations [94], falls [95,96] or disability [75] occur unaccompanied by robust or observable changes in physiology. Thus, predicting the disability outcome response to a change in activity level is not straightforward and will depend on the etiology and extent of the disability, the alterations in impairments, psychosocial factors, and disease status induced by exercise, as well as other variables that have not yet been fully defined.

Evidence from cross-sectional and longitudinal epidemiologic studies Over the past decades, many studies have emerged that identify relationships between measures of physical activity or physical fitness and prevalence or risk

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of disability. Although there are numerous cross-sectional studies, they provide less insight into the relationships than longitudinal studies because they can only determine association of factors not causality. For example, Laukkanen et al [97] reported that in 291 80-year-olds residing in the community in Finland, difficulty with ADL functioning was partly explained by muscle strength, balance, and upper extremity flexibility, but not aerobic capacity. Cross-sectional data from the ongoing Women’s Health and Aging Study (WHAS) [10] indicates that in 1002 disabled community-dwelling women older than age 65, an inverse relationship exists between disability and physical activity levels and knee extension and handgrip strength at baseline, and these factors contribute independently to the severity of the disability. These authors have proposed a spiraling deterioration process in which motor disability (contributed to by age, chronic disease and knee pain) leads to a reduction in physical activity, which in turn causes muscle strength to decrease, causing more disability. In another cross-sectional study, 1097 participants from the EPESE study sites who were not disabled at baseline were analyzed for factors related to disability-free survival until death in old age [6]. Physically active adults were more likely to survive to age 80 or beyond and had approximately half the risk of dying with disability compared with their sedentary peers. Because few studies have examined a variety of physiologic factors and activity in the same cohort, it has been difficult to attribute differential risk to various impairments. Foldvari et al [98] measured muscle strength, endurance, and power; aerobic capacity; physical activity level; psychological status; and health conditions in 80 disabled community-dwelling women. Although upper and lower body strength and power, aerobic capacity, physical activity level were all related to functional dependency in univariate analyses (as well as selfefficacy, depression, and burden of disease), only leg extension power and physical activity level were independently predictive of disability in a multiple regression model, explaining fully 40% of the variance. The findings of a modest contribution of aerobic capacity to disability in the elderly have been reported by Morey et al [99] and Posner et al [100] as well, although muscle power and strength measures were not assessed in these studies. In contrast to these studies, cross-sectional data from 753 participants in the Framingham Heart Study aged 72 to 98 years [101] showed that grip strength, muscle mass (using dual-energy x-ray absorptiometry scans), and physical activity level were not related to disability, whereas high levels of body fat were associated with increased disability. It is possible that upper extremity strength is not as important as lower extremity strength for many activities requiring mobility or that the advanced age of these subjects reduced the variability of physical activity levels. The authors suggest that muscle mass may be less important than strength as a determinant of function, despite the often shown direct correlation between these two measurements. Longitudinal studies are better able to determine the putative causal role of sedentariness and impairments to disability. An extensive systematic review of

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the literature in community-dwelling elderly was reported by Stuck et al in 1999 [5]. In the 78 longitudinal studies included, low levels of physical activity and impairments of upper and lower body strength or function were rated as among the strongest predictors of future disability in these cohorts. Two longitudinal studies have been published using data from the Cooper Clinic cohort, which relate physical fitness and physical activity to functional status after 5 years. Brill et al [59] reported that higher strength (ie, upper, lower, and trunk) was independently associated with functional disability in 3658 men and women at follow-up, reducing the risk by almost half. Aerobic capacity independently reduced risk by another 10%, which is consistent with other findings regarding the relative weight of these two components of fitness as regards functional abilities when both are measured in the same sample. In the other study from this cohort, Huang et al [11] reported physical fitness and activity levels in 4670 middle-aged subjects over a 5-year follow-up period. A steep gradient of risk was noted across categories of fitness and activity, with a 70% reduction in disability at the highest tertile of aerobic fitness, compared with the lowest in both men and women. Similar trends were observed for physical activity (50% and 30% reductions in risk at the highest tertile in men and women, respectively). These associations were both independent of other known risk factors for disability, such as smoking, body mass index, or disease history. These studies are unique in expanding the relationships observed in older and disabled populations to healthy, middle-aged persons and suggest a strong role for physical activity in preventing disability from middle-age onward. Recent longitudinal studies have strengthened the hypothesized causal relationship among sedentariness, functional limitations, and disability in older adults. Miller et al [4] have reported results from 5151 participants in the Longitudinal Study of Aging and have shown that physical activity results in a slower progression of functional limitations and thereby slower progression from ADL/ independent to ADL disability. Specifically, older adults who walked a mile at least one time per week were significantly less likely to progress to functional limitations or disability than their sedentary counterparts over the 6 years of follow-up. In another prospective study from Finland, Hirvensalo et al [12] found that physical activity lowered the risk of subsequent disability and mortality among 1109 community dwelling older adults, counteracting the negative effect of mobility impairment.

Clinical trials of exercise interventions with disability as an outcome Over the past few years, many studies have examined the potential of exercise to modify functional limitations in the elderly, in addition to proximate physiologic outcomes, such as strength, aerobic capacity, and balance. Although functional limitations bear a relationship to future disability, institutionalization, and death [102,103], these studies of exercise and functional limitations,

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reviewed elsewhere [18], do not definitively address the potential of exercise to prevent or change disability itself. General population studies Primary prevention of disability through exercise has been examined by some investigators. Kerschan et al [104] reported results from 124 initially nondisabled postmenopausal women who were nonrandomly assigned to home-based exercise or control groups during a visit to an outpatient medical clinic. After 7.7 years of follow-up, no differences were noted between the groups in any measures of physiology or disability. The exercise program, which included elements of balance, flexibility, strengthening, postural control, and walking prescribed three days per week, was carried out by 36% of the exercise group at follow-up, but was likely not robust enough to induce physiologic or functional changes. An 8-week randomized controlled trial of supervised low-intensity resistance training with elastic bands in 62 healthy older women was reported by Damush et al [105]. Although small increases in strength were observed in the exercisers, no group differences in physical, social or mental functioning were found, as both groups improved slightly, possibly because of the social interaction of the experimental and control condition classes. The short duration of the study, low intensity of exercise, and nondisabled status of the participants may have also precluded an effect on disability. Secondary prevention of disability in adults with impairments or functional limitations has been studied somewhat more extensively, but with mixed results. Mihalko et al [106] reported on 58 men and women aged 71 to 100 who were residents of senior citizen or nursing homes and were randomly assigned to an 8-week moderate-intensity, supervised upper body resistance training program using dumbbells or an upper body stretching control condition. Exercisers increased muscle strength by more than 50% compared with no changes in the controls. Difficulty in performing ADLs was significantly improved in exercisers and worsened in controls over the course of the intervention, as rated by primary caregivers. Strength gains were significantly related to final ADL status, explaining 10.3% of the variance. This study is unique in that isolated upper extremity training used, in contrast to the typical lower extremity focus of most exercise-disability trials. In a sample of 215 community-dwelling older adults with self-reported functional limitations, 6 months of home-based strength training with elastic bands increased strength, gait stability, and measures of social role functioning compared with untreated controls [107]. Physical disability was not altered by this intervention, however, and the modest strength changes observed (17% exercisers vs. 7% controls) suggest that other mechanisms may explain the functional outcomes of this trial. In another study of more significantly disabled elders living alone [108], 86 subjects (mean, 82 years of age) were randomized to a home-based strengthening exercise group (stretching plus elastic bands), mobility exercise group (stretching only), or health education control group. No group differences in functional limitations, morale, or ADL

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function were seen after 6 months. Again, the low-intensity of exercise used, limited supervision (one visit per month), and emphasis on stretching may explain the lack of efficacy. A similar exercise program carried out earlier by these investigators in frail institutionalized elders did provide some functional benefits, perhaps because of improved compliance and supervision in this setting [109,110]. Unlike many reported studies, Westhoff et al [111] found that 10 weeks of strength training (two thirds of /3 sessions were supervised), using a combination of isometric contractions and dynamic exercises with elastic bands for the knee extensors, improved strength by 54%, and lower-extremityrelated ADL score by 12% in 21 older adults with lower extremity weakness living in sheltered housing for the elderly. These changes were significantly different than in control subjects and were preserved at 6 months of follow-up after the intervention ended. In the largest reported randomized controlled trial of exercise and disability to date, Morris et al [15] randomly allocated 468 residents of six different nursing homes into resistive exercise (using dumbbells and ankle weights), nursing rehabilitation, or control conditions. After 10 months, residents in both intervention arms had significantly less decline in ADL functioning than those in control homes, and 6-minute walk time was better maintained in the exercise home subjects compared with the other two groups of residents. In this intention-to-treat analysis, exercise was effective despite participation of only about 35% to 40% of the residents in exercise homes [112], suggesting that increased penetration of the intervention by modifications in delivery and targeting of nonambulatory residents might provide even more functional benefits. Disease-specific population studies Studies targeting disability in disease-specific populations, such as depression, cardiovascular disease, stroke, chronic lung disease, provide evidence that exercise is beneficial in all of these conditions as a primary or ancillary treatment. The largest body of data exists for older adults with osteoarthritis, which is the most common condition related to disability [73]. Five of the 11 randomized controlled trials reported up to 1999 showed improvements in disability scores relative to controls in trials from 4 weeks to 18 months in duration. Weight-bearing functional exercises, walking, and resistance training were used in various combinations in these studies, and there is no clear indication of the superiority of one modality over another in reducing pain and disability from osteoarthritis. The largest trial (by Ettinger et al [75] in 1997) found that 439 patients randomized to aerobic exercise or resistance training for 18 months had less pain and disability at follow-up compared with controls, who declined over this period. Physiologic improvements in strength or aerobic capacity were not observed in this trial, and compliance was only 50% at 18 months, suggesting that other mechanisms may have been operative in the benefits observed. O’Reilly et al [113] similarly found that 6 months of daily isometric quadriceps strengthening and stepping in a home-based protocol

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improved strength, pain, and disability in a randomized trial of 191 men and women (aged 40 to 79) with knee pain compared with no-treatment controls. The small ( < 5%) but significant gains in strength in the exercisers appear unlikely, however, to explain the functional results, and interpretation is hampered by nonblinded assessors and the Hawthorne effect. In contrast, Maurer et al [114] found that 8 weeks of isokinetic quadriceps strengthening resulted in only slightly more benefits in pain and disability compared with health education and disease self-management classes in 113 patients randomized to the two treatments. The minimal effects on functional status in this study may be attributed to the training of only the more affected limb rather than both knees and to the use of a nonprogressive, isokinetic training regimen as opposed to progressive resistance training. In summary, particularly in arthritis patients, many pathways are available by which interventions—exercise or nonexercise—may affect pain, mobility, function, and quality of life. Factors, such as likelihood of compliance, cost, patient preference, access to exercise trainers and equipment, and presence of other comorbid conditions, may dictate the type of exercise or educational programs offered to this cohort, rather than clearly superior efficacy of one approach. Some form of quadriceps strengthening and weight-bearing exercises appear to comprise the core of effective exercise treatment for osteoarthritis of the knee.

Exercise prescription for disability prevention and treatment Exercise used to prevent disability As outlined above, the risk of disability is related to both a lower level of physical activity and reduced physical capacity (strength, aerobic capacity, balance, flexibility). In addition, certain diseases that are implicated in the development of disability are more prevalent in sedentary individuals. Therefore, the exercise prescription for the prevention of disability should focus on four goals: 

changing sedentary behavior to a more active lifestyle; modifying risk factors for disability and disability-related diseases (eg, visceral obesity, sarcopenia, hypertension, dyslipidemia, insulin resistance);  maintaining or improving exercise capacity in all domains (strength, aerobic capacity, balance, flexibility); and  enhancing psychosocial functioning. 

Because a physically active lifestyle appears to offer protection independently of its association with higher fitness levels, it may be unnecessary for prevention of disability to promote only those activities that would substantially modify physical capacity. Walking during daily life, use of stairs, shifting toward more active recreational pursuits, and less reliance on automated devices will decrease

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sedentariness and should thus confer benefit. It is possible to change habitual physical activity levels even in older, sedentary adults for up to 2 years in both supervised and home-based settings [115,116]. Although modification of risk factors for disability-related diseases is generally associated with higher levels or intensities of aerobic activities, this result may be caused by the much higher prevalence of aerobic activities in general populations rather than a lack of efficacy of other modes of exercise. For example, the prevalence of type 2 diabetes is markedly reduced by increased frequency and intensity of walking and other cardiovascular forms of exercise [28,117,118]. The effects of resistance training on insulin sensitivity and glucose homeostasis are at least as great [119 – 121]; however, too few individuals practice this form of exercise to have been studied epidemiologically. Finally, many of the ‘‘age-related’’ physiologic changes described in crosssectional and longitudinal studies that are related to the prevalence or incidence of disability are modifiable by exercise, even in the oldest old [38,122]. These changes include decreased aerobic capacity [123,124], muscle strength [13,14, 58,110,125], muscle mass [13], and balance [126]. Therefore, preservation of exercise capacity and optimal body composition is an important goal of disability prevention recommendations and will require more specific ‘‘prescriptive’’ elements, such as those outlined below. Functional aerobic activities (eg, walking) and those activities that promote muscle mass and strength maintenance should be prioritized in the prescription. Static balance as assessed by tandem stand time is one component of the Short Physical Performance Battery, which is predictive of self-reported disability, institutionalization, and mortality in older adults [102,103]. Balance training appears to be a useful component of falls prevention programs and therefore may also prevent disability indirectly by reducing the rate of injurious falls and fear of falling [95,96,115,126]. Flexibility is associated with a more active lifestyle, which may explain its association with functional status in some epidemiologic studies [97,127]. Flexibility training has not been shown, however, to be an effective intervention by itself—either for the prevention of diseases or disability— and it often serves as the control or ‘‘sham exercise’’ condition in randomized exercise trials with functional outcomes. Therefore, based on current evidence, no specific recommendation can be made for isolated stretching exercise as a means to prevent disability. Instead, gains in flexibility associated with other forms of exercise may be expected [128,129] and will perhaps contribute to overall functional benefits. A ‘‘lifestyle’’ approach to health promotion with exercise has been recently advocated in an attempt to improve the penetration of public health messages about exercise [62]. It is not clear that such an approach is superior to a structured exercise prescription or that it would work for elderly individuals who may have less opportunity to integrate physical activity into work or leisure-time activities, however. Therefore, it may be prudent to offer both structured exercise recommendations (Table 4) and suggestions on incorporating these elements into everyday activities to maximize compliance with the

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Table 4 Exercise recommendations for disability prevention and treatment Modality Dose Frequency Volume

Intensity

Requirements for safety Maximal efficacy

Resistance training

Cardiovascular endurance training

2 – 3 days/wk 1 – 3 sets of 8 – 12 repetitions, 8 – 10 major muscle groups

3 – 7 days/wk 20 – 60 min

15 – 18 on Borg Scale (80% one repetition maximum), 10 sec/repetition Slow speed; no ballistic movements; day of rest between sessions Good form; no substitution of muscles; no breath holding; Valsalva manuever; increase weight progressively to maintain relative intensity

11 – 14 on Borg Scale (45% – 80% maximal heart rate reserve) Low impact activity

Weight-bearing if possible, include standing/walking; increase workload progressively to maintain relative intensity

Balance training 1 – 7 days/wk 1 – 2 sets of 4 – 10 different exercises emphasizing dynamic postures* Progressive difficulty as toleratedy Safe environment or monitoring Dynamic rather than static modes; Gradually increase difficulty as competence is shown

* Examples of balance-enhancing activities include T’ai Chi movements, standing yoga or ballet movements, tandem walking, standing on one leg, stepping over objects, climbing up and down steps slowly, turning, standing on heels and toes, walking on compliant surface, such as foam mattresses, and maintaining balance on moving vehicle, such as bus or train. y Intensity is increased by decreasing the base of support (eg, progressing from standing on two feet while holding onto the back of a chair to standing on one foot with no hand support); by decreasing other sensory input (eg, closing eyes or standing on a foam pillow); or by perturbing the center of mass (eg, holding a heavy object out to one side while maintaining balance, standing on one leg while lifting other leg out behind body, or leaning forward as far as possible without falling or moving feet).

prescription. The recommended exercise modalities are described briefly in the section that follows; more extensive instructions are available in standard textbooks [130 –132]. Progressive resistance training Progressive resistance training (PRT) is the process of challenging the skeletal muscle with an unaccustomed stimulus, or load, such that neural and muscle tissue adaptations occur, leading ultimately to increased muscle force producing capacity (strength) and muscle mass. In this kind of exercise, the muscle is contracted slowly just a few times in each session against a relatively heavy load (60% to 80% of maximal capacity). Equipment may range from only body weight to technologically sophisticated pneumatic or hydraulic resistance training machines. Although PRT is usually conceptualized as a discreet ‘‘exercise’’ activity, there are in fact ways to incorporate elements of PRT into daily life in the same way

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that aerobic activities are integrated into daily life. The guiding principles underlying such incorporation are: 1.

2. 3.

4.

Use the smallest possible muscle mass to accomplish a given task (eg, lift a heavy container with one hand instead of two or get up from a chair without using arms) Resist gravity rather than relying on it to make tasks easier (eg, sit down slowly) Avoid use of momentum and strive for optimal development of force instead to move an object or body weight through space (eg, do not rock to get out of a low chair) Perform static muscle contractions periodically during ‘‘resting’’ periods or other activities

Cardiovascular endurance training Cardiovascular endurance training refers to exercise in which large muscle groups contract many times (thousands of times at a single session) against little or no resistance other than that imposed by gravity. The purpose of this type of training is to increase the maximal amount of aerobic work that can be carried out and to decrease the physiologic response and perceived difficulty of submaximal aerobic workloads. Extensive adaptations in the cardiopulmonary system, peripheral skeletal muscle, circulation, and metabolism are responsible for these changes in exercise capacity and tolerance. Many different kinds of exercise are included in this category, including walking and its derivatives (ie, hiking, running, dancing, stair climbing, biking, swimming, and ball sports). Balancing the skeletal need for weight-bearing or loading and the safety requirements of the joints and connective tissues for low impact, one would favor exercises, such as walking, dancing, hiking, or stair climbing over running, step aerobics or jumping rope in older adults, particularly those with underlying arthritis. Healthy younger adults may safely perform high-impact activities as long as muscle and ligament strength and joint structure is normal. Overall, walking and its derivations are the most widely studied, feasible, safe, accessible, and economic modes of aerobic training for adults of most ages and states of health. Walking bears a natural relationship to ordinary ADLs, making it easier to integrate into lifestyle and functional tasks than any other mode of exercise, and it is the most commonly reported activity in epidemiologic studies relating physical activity to disability risk. Among all the modalities of exercise, cardiovascular exercise is perhaps the easiest to integrate into daily activities. It simply requires a few behavioral choices to be made that can be adhered to with reasonable success. For example, decisions could be made to: 1. 2.

Never use an escalator or elevator when stairs are available Never take the car for errands that can be accomplished by a 10 minute walk or less

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3. 4. 5.

Avoid using use remote control devices Substitute manual devices (lawn mowers, electric mixers, brooms) for mechanical devices whenever possible Park in the most remote corner of the parking lot whenever shopping.

Balance training Balance training is probably the least well standardized of the various exercise modalities. Any activity that increases one’s ability to maintain balance in the face of stressors may be considered a balance-enhancing activity. Stressors include decreased base of support; perturbation of the ground support; decrease in proprioception, vision, or vestibular system input; increased compliance of the support surface; or movement of the center of mass of the body. In real life, stressors may also include things, such as environmental hazards to traverse, postural hypotension, and drugs that affect central nervous system function. Balance-enhancing activities have an impact on the central nervous system control of balance and coordination of movement and augment the peripheral neuromuscular system response to signals that balance is threatened. The general approach to the enhancement of balance should rely on theoretic principles that are designed to elicit adaptations in the central neurologic control of posture and equilibrium. The basic idea is to progressively challenge the system with stressors of increasing difficulty in three different domains: 1. 2. 3.

Narrowing the base of support for the center of mass of the body Displacing the center of mass to the limits of tolerance Removing visual, vestibular, and proprioceptive inputs to balance

Some forms of exercise, such as yoga and T’ai chi, are intrinsically balanceenhancing, although they may also have other benefits. Many activities in daily life can also be turned into a balance-enhancing movement or position with a little creativity, making balance training one of the easiest modalities of exercise to integrate. Some examples of how this can be accomplished are listed below: 

   

While standing in line, cooking, or doing other functional tasks, stand on one leg if possible during the task (or with feet in tandem position); alternate legs every 15 to 30 seconds. When crossing a room or other short distance, tandem, heel, toe, crossover, or sideways walk for 10 to 20 feet instead of normal walking. Carry small items (books, cartons of milk) by holding them out at arm’s length while walking (without bending the spine). Stand on one leg or close eyes while standing on a moving bus or train (hold onto a bar for support lightly). Stand up and sit down using only one leg, without using hand support and with eyes closed if possible.

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To be safely performed, these balance-enhancing activities should only be progressed when a given level is mastered and in a setting where near-falls can be observed and averted. Exercise used to treat impairments, functional limitations, and disability General principles The rationale for the prevention of disability with exercise is slightly different than that used to treat disability or its precursors—impairment and functional limitation. The difference lies in the specificity of the prescriptive elements and the intensity of the physiologic or psychological change desired. For example, prevention of disability may require only generalized advice to maintain an active lifestyle. Once mobility is lost because of a stroke or other disabling condition, however, specific therapeutic exercises to correct the motor weakness and impairment of gait and balance may limit disability, but advice to simply ‘‘walk as much as possible’’ might be unrealistic or unhelpful. An analogy may be drawn to the pharmacologic treatment of cardiovascular disease. Aspirin may reduce the risk of developing overt cardiovascular ischemic disease in healthy individuals. Once atherosclerosis is established and symptomatic, however, aspirin alone may not suffice, and other pharmacological regimens must be invoked for maximal benefit. Thus, activities identified in epidemiologic studies as lowering the risk of disability, such as low-moderate intensity walking, may not be the best approach to treat the established disability. A substantial body of scientific data provides reassurance of the safety of exercise in the oldest old [23] and provides evidence of efficacy. The wideranging benefits include physiologic, metabolic, psychological, and functional adaptations to physical activity that can substantially contribute to quality of life in older individuals with disabilities. Goals of exercise appropriate to younger adults [133], such as prevention of cardiovascular disease, cancer, or diabetes, or increases in longevity itself [134], are replaced in the disabled elderly with a new set of goals, which include slowing biologic changes of aging [122]; reversing disuse syndromes [135]; contributing to the control of chronic diseases [136 –138]; maximizing psychological health [139,140], mobility, and function [14,141]; and assisting with rehabilitation from acute and chronic illnesses. A targeted exercise prescription offers benefit for many of the geriatric syndromes commonly present in this vulnerable population that cannot be achieved with any other therapeutic modality. Resistance training The problems of mobility impairment, falls, arthritis, osteoporotic fractures, and functional status are partly related to muscle strength and mass [21,98], and thus strengthening activities, while important for all age groups, are particularly important for disabled older adults. Age-related loss of strength, muscle mass, and bone density, which are most dramatic in women, may be attenuated by

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strengthening exercises [132,138] and may be regained even long afterwards with appropriate resistance training [142]. Resistance training in frail elders results in a range of clinical adaptations that are relevant to the target of disability, which is almost always a multifactorial phenomenon. Gains in strength after resistance training in the frail elderly may be accompanied by improvements in other physiologic impairments (balance [138], aerobic capacity [143,144], flexibility [128,129]), and performance-based tests of functional limitations, such as gait velocity, ability to rise from a chair, and stair climbing power [13,14,125,142,145,146]. Although self-reported disability has been assessed far less frequently, it has been seen to improve, particularly in specific populations, such as those with osteoarthritis of the knee [74,75]. Psychological responses to resistance training include improved morale, depressive symptoms, and self-efficacy [82,88,147 – 149], and these factors have strong independent effects on functional status as well [97], which should not be ignored as a mechanism of action of this mode of exercise. Low-moderate intensity resistance training programs have been increasingly advocated for the elderly (particularly the frail or disabled elderly) as a way to increase the practical dissemination and acceptability of this modality of training. Most programs use free weights, such as dumbbells and ankle cuff weights or elastic bands and body weight, as the means of resistance. Although it is possible to show significant strength gains with such interventions, in fact most programs do not change strength substantially when it is objectively measured [15,146]. This does not mean that this type of exercise is not beneficial, however, because it has been shown to reduce disability [15], improve gait stability [94], reduce injurious fall rates [95,96,115] and reduce arthritis pain and disability [75]. Aerobic exercise High-intensity aerobic training interventions have not been described in frail elderly populations. Low to moderate intensity aerobic activities, such as walking, standing, and stationary cycling at 60% of maximal predicted heart rate, have been associated with modest improvements in cardiovascular efficiency [123,124] and mobility tasks [150] (walking, standing from a chair). The energy cost of activities for frail elders with assistive devices, such as walkers and wheelchairs, joint deformities, and gait disorders may be significantly higher, however, than standard equations would predict, leaving unclear the exact magnitude of the physiologic benefits of aerobic training. Aerobic training in disabled adults should be delayed until balance and strength have been addressed with specific exercise prescriptions. If this is not done, mobility will be severely limited by the impairments of neuromuscular function, and aerobic training will be difficult or even hazardous to prescribe in any case. Although a meta-analysis of the various exercise studies in the FICSIT trials indicates a small protective effect of exercise on fall risk, the interventions, which included only aerobic training (walking), were not protective [151]. This finding is in agreement with other walking studies in the elderly that in general do not show a balance-enhancing effect. A simple rule is to watch the person rise

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from a chair, stand with eyes closed, open eyes, and then walk across the room. If standing from the chair is difficult or if it requires use of the arms, strengthening exercises should be prescribed first. If standing balance is impaired, balance exercises are also indicated. If these first two tests are performed easily, the aerobic training may be the first or only mode of exercise prescribed. Balance training Exercise programs that include balance training or resistive exercises have been shown to improve clinical testing of balance in elders selected for mobility disorders or functional impairment. In the healthy elderly, T’ai Chi has been shown to reduce fall rates [152], and a multicomponent intervention, which included low intensity lower extremity resistive exercises and balance training, also significantly reduced falls [153]. Although a combination of balance and strengthening exercises in the home setting has been shown to reduce falls and injuries, particularly in women over the age of 80 [95,96,115], the independent contribution of balance exercises to this outcome is not known. Resistance training alone can improve dynamic balance in older women [138]; however, other studies using computerized assessments of static and dynamic balance have not reported such crossover effects [154]. Balance training has not been shown, as an isolated intervention in the frail elderly, to have a direct impact on functional status, although it may improve the balance impairment [154]. Much debate still exists about the exact nature of the stimulus or dose of balance training required to best enhance balance and ultimately reduce falls [155]; although most programs described use some combination of the techniques outlined in Table 4. Flexibility exercise Flexibility declines markedly with aging and is associated with disability [97,127,156,157]; however, no specific studies have been done to test responsiveness to standard proprioceptive neural facilitation or other techniques in this population [158]. Increases in active range of motion involving trained muscle groups have been observed after high-intensity progressive resistance training in the frail elderly [14], depressed elders [128] and cardiac rehabilitation patients [129], but not after low-intensity resistance training [128] or aerobic interventions. Bony deformity and muscle weakness, tendon shortening, and tissue inelasticity from disuse may contribute to the problem, thus indicating more than one approach may be needed for its resolution. No evidence exists that training for flexibility or physical therapy programs concentrating on range of motion and stretching alone have a significant impact on disability [159]. Because of misconceptions about the efficacy and safety of other modes of exercise, however, stretching is often the only exercise prescribed for disabled or frail elders. The data reviewed above on the safety and efficacy of resistance training and balance training in particular would argue for the substitution of these exercise modalities whenever possible as an alternative to some of the ‘‘movement programs’’ offered in aged care facilities and other

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settings. Time and availability of trained personnel to perform exercise programming for frail adults are significant barriers to implementation. Therefore, any prescriptive elements should be soundly based on scientific evidence where it is available. In light of this, strength, balance, and endurance training should receive a higher priority than flexibility training when the goal is a reduction in disability. Safety of exercise in frail adults The contraindications to exercise in this population are not different than those applicable to younger healthier adults [131]. In general, although frailty or extreme age is not a contraindication to exercise, the specific modalities may be altered to accommodate individual disabilities [124]. Acute illnesses, particularly febrile illnesses, undiagnosed or unstable chest pain, uncontrolled diabetes, hypertension, asthma, congestive heart failure, or new or undiagnosed musculoskeletal pain, weight loss, or falling episodes, warrant investigation, regardless of exercise status, but certainly before a new regimen is begun. Temporary avoidance of certain kinds of exercise is sometimes required during treatment of hernias, cataracts, retinal bleeding, or joint injuries. A small number of untreatable or serious conditions are more permanent exclusions for vigorous exercise, including an inoperable enlarging aortic aneurysm, known cerebral hemorrhage or aneurysm, malignant ventricular arrhythmia, critical aortic stenosis, end-stage congestive heart failure or other rapidly terminal illness, or severe behavioral agitation in response to participation in exercise secondary to dementia, alcoholism, or neuropsychological illness. The mere presence of cardiovascular disease, diabetes, stroke, osteoporosis, depression, dementia, chronic pulmonary disease, chronic renal failure, peripheral vascular disease, or arthritis is not by itself, however, a contraindication to exercise. In fact, for many of these conditions, exercise will offer benefit not achievable through medication alone. The intolerance to many medication side effects in the very old makes the search for alternative nonpharmacologic therapies, such as exercise, very attractive in this cohort. The literature on exercise training in the frail elderly (between the ages of 80 and 100) in nursing homes does not include any reports to date of serious cardiovascular incidents, sudden death, myocardial infarction, exacerbation of metabolic control of diabetes, or hypertension [13 – 15,110,124,125,145,150,159 – 167]. No serious adverse events related to resistance training in small groups with free weights have been reported in a large randomized controlled trial of nursing home residents exercising over a 12-month period [15] or in several large trials of homebased training with free weights in older adults at risk of falls for up to 2 years [95,96,115]; patients with osteoarthritis of 6 to 18 months in duration [74,75]; or in the year after hip fracture [168]. Prioritizing the elements of the exercise prescription The first step is to assess the overall level of habitual activity in daily life, including recreational and household activities, noting areas where improve-

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ments are possible. Second, an evaluation of exercise capacity in the domains of endurance, power, strength, balance, and flexibility is needed to identify areas where the greatest impairments exist. Table 5 presents simple tests to assess these domains in lieu of laboratory measurements. Third, identification of factors that are potentially contributing to the disability is needed, including disease states, such as arthritis or depression, sarcopenia, obesity, or cognitive impairment. Table 1 includes most of the important elements to consider. Fourth, a specific exercise prescription should be provided, which is tailored to the risk factors and impairments in the individual and is robust enough to cause adaptations that can potentially modify function. Often, many risk factors and impairments will be identified, making prioritization difficult. A general rule would be to target remediable deficits that are most closely related to the observed functional limitations and disability. For example, a patient may present with independent ADL difficulties for tasks requiring mobility outside the home and on evaluation may be found to have lower extremity weakness and wasting, peripheral neuropathy, ataxia from prior alcohol abuse, and early macular degeneration. Assessment of functional limitations reveals difficulties

Table 5 Clinical tests of physical impairments and associated functional limitations Domain Aerobic capacity

Muscle strength and power

Laboratory test of impairment

Clinical tests of impairment

Associated functional limitations

Maximal oxygen consumption (VO2 peak) Dynamic measurements of specific muscles for peak torque and power

6-minute walk distance

Walking endurance

Isometric strength measurements with dynamometer; heel rise (plantar flexors); pushups (chest and triceps); situps (abdominal muscles) Static balance Standing times with narrowed base of support; reduced visual input Functional reach test Dynamic balance Tandem walking, forward and backwards Back reach; touching toes; Sit and reach test

Multiple chair rise time; Stair climbing time; power* lifting objects up or onto a shelf

Balance

Computerized balance platform measures of static balance with perturbation, visual, and vestibular alterations

Flexibility

Inclinometer or goniometer measurements of active and passive range of motion

Negotiating obstacles, steps, transferring between bed and chair; turning in a circle

Putting on a jacket; picking up object from the floor

* Power (W) is body weight (N) x vertical height climbed (m)/ascent time (sec).

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Table 6 Prioritizing the elements of the exercise prescription

Targeted condition Muscle weakness Impaired balance Impaired aerobic capacity Impaired range of motion Depression Obesity Sarcopenia Osteopenia, osteoporosis Peripheral vascular disease Stroke Falls Osteoarthritis Chronic obstructive pulmonary disease Congestive heart failure Cardiovascular disease General frailty Diabetes

Aerobic training recommended

Resistance training recommended

Balance training recommended

Combination training and functional task training recommended

— — Yes — Yes Yes — Yes Yes Yes — Yes Yes

Yes Yes — Yes Yes Yes Yes Yes — Yes Yes Yes Yes

— Yes — — — — — Yes — Yes Yes — —

— — — Yes — — — — — Yes — — —

Yes Yes Yes Yes

Yes Yes Yes Yes

— — Yes —

— — Yes —

rising from a chair and climbing stairs. Although vision, balance, proprioception, and muscle power are all impaired, the deficit clearly responsive to an exercise prescription would be muscle strength and power. Improvements in balance may be limited because of the irreversible nature of the neuropathy and cerebellar dysfunction; however, strengthening ankle muscles may improve balance despite the neurological abnormalities. Therefore, resistance training for strength and power should be prescribed to address the impairments, functional limitations, and disability described. Periodic reassessment of impairments, limitations, disability, and behavioral changes in exercise and other activities will determine if and when other elements of the exercise prescription should be added. Table 6 provides a summary of the benefits of different exercise modalities for treating diseases, impairments, and psychological factors that may be contributing to disability.

Conclusions Recognition of the role of exercise and physical activity in the prevention and treatment of disability in the elderly is vital to optimal management of this problem. Exercise has direct effects on disability by virtue of its relationship to the attainment of peak physiologic capacity in young adulthood and on the

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prevention and treatment of disuse atrophy caused by aging, sedentariness, and diseases. The most important physical capacities include muscle strength and power, and control of balance; although aerobic capacity and flexibility also contribute to the syndrome of disability. Exercise may also work through the pathway of risk factor modification, disease prevention, and adjunctive treatment of established diseases. The primary examples of this pathway include hypertension, insulin resistance, osteoarthritis, osteoporosis, type 2 diabetes mellitus, cardiovascular disease, stroke, depression, and obesity. In addition, physical activity patterns that may indirectly influence the expression of disability include effects on dietary intake, positive and negative psychological states, stress hormones, smoking and other behaviors, social support network strength, self-efficacy, self-esteem, level of participation in other social activities or work, and the need for multiple medications with potential side effects that may impair function. The wealth of epidemiologic data linking physical activity or physical fitness to disability is not yet matched by experimental evidence of benefit from randomized controlled clinical trials. Although many studies in general populations have documented changes in impairments or limitations after exercise, only a few studies have shown improvements in long-term disability as well.

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