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CHAPTER 14 EXERCISE

CHAPTER 14 EXERCISE
Practice of Geriatrics
CHAPTER 14 EXERCISE
Julie Chandler, Ph.D., P.T., and Stephanie Studenski, M.D., M.P.H.
Strength Training Programs in the Elderly
Aerobic Exercise Training in the Elderly
Balance Training in the Elderly
Combined Exercise Programs
Discussion
Choice of Exercise Program
Regular exercise offers an attractive approach to preventing decline and restoring function in older adults. While the effects of exercise are known and formal guidelines exist for younger adults,1 less is known about exercise later in life, especially in people with multiple illnesses or existing functional limitations. Programs for such special populations have been the subject of intense study in recent years. Can exercise be used to improve health status in the frail person with limited mobility, muscle weakness, poor balance, and poor endurance? The evidence, though incomplete, is encouraging. Some limitations in frail elders may be the result of deconditioning due to inactivity, which is often a final common pathway entered from a classic geriatric vicious cycle of illness and complications.2,3 Some impairments due to disuse and deconditioning (such as strength, balance, and endurance) can be modified with exercise, just as they are in younger, healthier adults.4,5 Whether a reversal of impairments such as weakness translates into improved function and mobility is less clear, but the initial findings hold promise. The purpose of this chapter is to review exercise programs intended to increase strength, aerobic conditioning, and balance in older adults and to make recommendations for clinical practice.
The conceptual basis for exercise intervention in frail older adults rests on a model of disability that describes disability as the result of a mix of organ system–based impairments. Muscle weakness, limited joint mobility, poor aerobic capacity, and poor balance are all potentially reversible impairments that have been associated with mobility problems (walking, climbing stairs, rising from a chair),6,7,8 and 9 routine activities (showering, housekeeping, shopping),10,11 and falls.12,13 and 14 In a deconditioned older person, walking, showering, or rising from a chair can represent up to 80% of maximum oxygen uptake (VO2 max).5 Poor joint mobility has been associated with difficulty in using public transportation.7 The accumulation of multiple impairments may be an especially stressful burden for a frail elderly person; multiple deficits in strength, range of motion, central processing, and sensation predict poor endurance and poor performance in tasks such as walking, reaching, and climbing stairs, better than any single impairment or disease.15 These observations from cross-sectional data have led to the hypothesis that treatment of reversible physiologic deficits may lead to improved function.
STRENGTH TRAINING PROGRAMS IN THE ELDERLY
High-Intensity Strengthening
Numerous studies have convincingly shown that gains in strength are achievable with high-intensity strength training even in nursing home residents in their nineties16,17,18,19,20,21,22,23 and 24 (Table 14-1 and Table 14-2). Programs consist of progressive resistive training in which the participant lifts 70% to 90% of a one-repetition maximum (the amount of weight that can be lifted fully through the range of motion one time only) three times per week for at least 8 to 10 weeks. The load is increased weekly to maintain the intensity of the stimulus. Usually two to three sets of 10 are repeated per muscle group per exercise session. Strength gains of up to 200% have been reported using these exercise programs.

TABLE 14-1 STRENGTHENING INTERVENTIONS IN HEALTHY ELDERLYa

TABLE 14-2 STRENGTHENING INTERVENTIONS IN IMPAIRED ELDERSa

The impact of high-intensity resistance training on physical performance has been more variable than its impact on strength. Significant increases in habitual gait speed, maximum gait speed, tandem gait speed and stair-climbing power have been reported in some studies16,17,22 but not others.21 The magnitude of benefit in physical performance may be directly related to the initial performance level of patients. More impaired participants who have initial habitual gait speeds of 0.7 meter per second or less tend to gain more after resistance training17 than those with initial gait speeds of over 1 meter per second.21 On the other hand, healthier individuals with initial gait speeds of over 1 meter per second may show increased maximum (fastest) gait velocity after strength training.22 These findings suggest that improvement in habitual gait speed is likely to occur with strength training especially in more impaired individuals, while in healthier elders strength training affects mostly the elements of physiologic reserve such as maximum gait speed.
Low-Intensity Strengthening
Lower-intensity resistance training has also been used successfully to increase strength, although the magnitude of strength gain is not as marked.25 In older persons with osteoarthritis, resistance training that includes both isotonic (lifting a weight through the range of motion) and isometric (static) contractions (three to five repetitions each) at an intensity of 50% of a maximum effort, three times a week for 16 weeks, has been shown to increase strength (35%), muscle endurance (35%), and speed of limb movement (50%).25 With use of a similar program in nursing home residents, strength improved by 15%, endurance by 35%, and speed of limb movement by 35%.26 Another study showed only modest gains (5% to 10%) in strength in deconditioned nursing home patients after a three day per week, 12-week program of resistance training at 40% to 60% of a one-repetition maximum.27 A supervised in-home progressive resistive exercise program using graded elastic bands in frail older men and women showed gains of 10% to 15% in lower extremity strength after 10 to 12 weeks of three times per week exercise.28 In healthier community-dwelling older women, a 25-week program of light resistance exercise increased shoulder strength by about 20% and lower extremity strength modestly (10%).29
In patients who have conditions that make it difficult to exercise, lower-intensity training is an acceptable alternative method for achieving modest increases in strength. Can lower-intensity strength training achieve the same effects on gait and function as high-intensity strengthening? The few studies that have looked specifically at measures of performance after low-intensity strength training have shown mixed results. Osteoarthritis patients showed improvement in the functional status index with decreases in dependency, difficulty, and pain.25 Nursing home residents showed some evidence of increased spontaneous activity in one study and improvement in mobility in another.26 An in-home supervised exercise program that increased lower extremity strength in frail elderly men and women showed no improvement in measures of gait or mobility.28 Because there are many other determinants of mobility performance besides strength, such as the presence of co-morbid conditions, depression, and cognition, it is unclear who is likely to benefit from low-intensity exercise and how much strength gain is required to enhance performance. Integrated treatment approaches that incorporate low-intensity strength exercise with interventions for other impairments may be more successful in improving function than strength training alone.
AEROBIC EXERCISE TRAINING IN THE ELDERLY
High-Intensity Endurance Training
Aerobic exercise programs in healthy older adults improve aerobic capacity as measured by maximum oxygen uptake (VO2 max) and resting heart rate (Table 14-3 and Table 14-4). Aerobic activities are those that require continuous exercise of large muscle groups to raise the heart rate above the resting level for a sustained period of time. Examples of aerobic activity are walking, biking, running, and swimming. Guidelines for aerobic exercise prescription for healthy adults recommend an intensity of 60% to 75% of maximum heart rate (as measured by an exercise stress test), three days per week for at least 6 weeks.1 Appropriate adaptations for impaired older persons with mobility limitations have not been clearly established.

TABLE 14-3 AEROBIC EXERCISE IN HEALTHY ELDERSa

TABLE 14-4 AEROBIC CONDITIONING IN IMPAIRED ELDERSa

In healthy men and women over the age of 64, supervised high-intensity aerobic training at 70% of maximum heart rate for 30 minutes, three times per week for 16 weeks, results in increased VO2 max and a significantly decreased incidence of new cardiac conditions.30 In healthy men and women in their 70s, Hagberg and colleagues showed that high-intensity aerobic exercise (35 to 45 minutes at 75% to 85% of maximum heart rate, three times per week for 6 months) results in significantly greater gains in VO2 max than high-intensity strength training.31
Low-Intensity Exercise Training
Like high-intensity aerobic exercise, low-intensity aerobic exercise (30% to 45% of maximum heart rate for 25 minutes, three times per week) can significantly increase VO2 max in healthy men and women over the age of 60.32,33 The magnitude of effect on VO2 max is related to both the intensity and the duration of exercise. The higher the intensity and the longer the duration of exercise, the greater the effect on aerobic capacity. These findings, though made in healthy older adults, have important implications for more impaired persons who cannot tolerate high-intensity exercise. Studies of aerobic conditioning programs in frail populations suggest that low-intensity training three days per week can lead to small but significant training effects.34 Concurrent illnesses that prevent continuous training are common in this population and may dampen the potential effect of such a program on cardiovascular outcomes. Sidney and Shephard advocate frequent repetition of a low-intensity (30% to 40% of maximum heart rate) program in the very deconditioned older person to achieve the desired increase in aerobic capacity and avoid undue stress.35 In addition to physiologic benefits, aerobic exercise has a positive impact on depression and other markers of psychological well-being in elderly men and women.36,37
BALANCE TRAINING IN THE ELDERLY
Specific balance training programs have been advocated as a means of improving postural reactions and reducing falls in older persons. The impact of static and dynamic balance training on measures of gait and balance in healthy and impaired older persons has been reported in a few studies21,38,39 (Table 14-5).

TABLE 14-5 BALANCE INTERVENTIONS IN HEALTHY ELDERSa

Static balance training involving balance recovery activities on the balance platform has been compared with dynamic balance training involving a set of slow, smooth, and rhythmical movements found in the ancient Chinese martial art form of Tai Chi.39 Persons who participated in the 15-week (one to two times per week) Tai Chi program had a lower incidence of falling than persons in the static balance training group. Tai Chi also was effective in lowering the fear of falling among participants. Training in neither group significantly affected strength, joint range of motion, or cardiovascular endurance.
In healthy women over the age of 75, balance training included three 45-minute sessions of training on a computerized balance platform and floor-based exercises such as standing on one leg, standing on foam, tandem walking forward and backward, walking on a narrow beam, and sitting on a rubber ball.21,38 This balance intervention significantly improved performance on all balance measures tested including loss of balance on the sensory organization test, single leg stance time, and functional base of support, but it was not associated with an increase in walking velocity or with improvement in chair rise time. Interestingly, balance training was actually associated with a decrease in gait speed.
These recent results suggest that an integrated dynamic movement approach to balance training may be an effective approach to reducing falls in active community-dwelling elderly men and women. The success of balance interventions in more impaired populations such as nursing home residents has not been reported.
COMBINED EXERCISE PROGRAMS
The principle of specificity of exercise dictates that the physiologic effects of training will be limited to the physiologic systems stressed most by the exercise intervention. Aerobic conditioning programs have marked effects on VO2 max but little or no effect on muscle strength.31,40 In healthy persons, high-intensity strength training significantly increases muscle strength but has little effect on aerobic capacity,18,31 although recent studies suggest that in sedentary older persons, strength training alone may lead to a modest improvement in walking endurance.23 Balance interventions have little effect on either strength or endurance.38,39 Because of limited cross-training ability, a single mode of exercise is not likely to maximize the rehabilitation potential of the deconditioned older person with multiple impairments. In healthy older men and women, studies that have combined aerobic and strengthening interventions have demonstrated their anticipated beneficial effects on physiologic outcomes of strength and aerobic capacity and possibly on some markers of static balance38,41 (Table 14-6). For the most part, combined exercise programs in healthy elderly persons have not shown gains in gait or other markers of mobility. Because high-functioning elderly people may perform at or near a perfect score at baseline on many common mobility tests, there may be no room in which to detect improvement—a ceiling effect.

TABLE 14-6 COMBINED EXERCISE PROGRAMS IN HEALTHY ELDERSa

A low-intensity program of progressive resistive plus aerobic conditioning exercise delivered to male nursing home residents three times per week for 12 weeks produced modest physiologic changes in strength and aerobic capacity and significant changes in the Tinetti mobility score and gait velocity27 (Table 14-7 and Table 14-8). An individualized physical therapy program stressing low-intensity progressive resistive exercise, range of motion, balance, and mobility training delivered to very frail nursing home residents failed to improve measures of strength, balance, and joint range of motion but did have a modest effect on physical mobility.42

TABLE 14-7 COMBINED EXERCISE PROGRAMS IN IMPAIRED ELDERSa

TABLE 14-8 DEFINITIONS PERTAINING TO TABLE 14-1, TABLE 14-2, TABLE 14-3, TABLE 14-4, TABLE 14-5, TABLE 14-6 AND TABLE 14-7

DISCUSSION
Exercise interventions in older adults in general produce positive physiologic effects in persons of all ages and levels of impairment. Musculoskeletal and cardiovascular systems respond to both resistance and aerobic training as measured by impairment level outcomes such as strength and maximum oxygen uptake. The magnitude of the physiologic effect may be dampened in frailer individuals in response to lower exercise stimuli. Nevertheless, there is promising evidence that even low-intensity aerobic and strengthening programs result in physiologic gains in moderately frail individuals. In the most impaired elders, exercise may not lead to substantial gains but may help to forestall further declines in physiologic reserve.42
The extent to which exercise programs enhance performance and reduce disability is less clear. High-intensity interventions are most likely to improve physiologic reserve in relatively healthy elders. Low-intensity interventions may or may not produce enough effect to truly influence function. Interpretations of these programs are confounded by the limitations of our current measures of function, which may have ceiling effects or be insensitive to change.
The impact of specific balance training on function is unclear at this time. Variability in the measures used to assess balance as well as variability in the exercise programs delivered makes it difficult to evaluate the impact of balance training alone. Programs such as Tai Chi are promising as an effective means of reducing the risk of falls in community-dwelling elderly. Their impact on frailer individuals and on other aspects of performance has not been reported.
Studies of exercise interventions of all types have largely targeted healthy community-dwelling elderly because exercise programs are often delivered in group settings and require sufficient function to travel and perhaps walk some distance to an exercise site. Group exercise has many benefits in addition to the training effects; it may have a positive influence on psychological and social factors. However, frailer community-dwelling individuals may have difficulty in accessing group exercise sessions and have not been extensively studied. Low-intensity home exercise programs may be an alternative means of providing an exercise stimulus to the more frail community-dwelling elders.
CHOICE OF EXERCISE PROGRAM
The data currently available suggest that high-intensity strength (80% of a one-repetition maximum) and aerobic training (60% to 75% of maximum heart rate) programs given three times per week for at least 6 weeks can lead to substantial gains in physiologic function. Low-intensity strength (light resistance, body weight) and endurance training (30% to 45% of VO2 max) programs carried out over longer periods of time (at least 9 weeks) can also lead to significant gains in physiologic function.
The intensity, duration, and content of exercise prescription for the geriatric patient should be based on individual need. The higher functioning older adult can tolerate high-intensity training in one or more systems (strength, endurance, balance). Such an older adult might be prescribed a program of aerobic activity such as walking, swimming, or bicycling at least three times a week and a strength training program using weights two to three times a week. More impaired individuals are likely to demonstrate deficits in more than one system and thus would probably benefit from a low-intensity program of longer duration of combined strength, aerobic, and balance training. The program may have to be supervised if the patient is unstable during movement. Otherwise, the choice of group or individual exercise can be left to personal preference. Since the risk of musculoskeletal injury is increased with poor weight-lifting technique, older adults should be encouraged to learn good form under supervision as they begin weight training. For all persons, exercise should be carried out at a level that is challenging but sustainable. For example, during aerobic exercise, the patient should have the breath to talk and keep up a conversation. During strength training, the individual should be able to complete a set of lifts in good form. All exercise programs should include warm-up and cool-down periods and flexibility exercises to avoid cardiovascular and musculoskeletal injury. Cardiac stress testing prior to a high-intensity exercise program is indicated for individuals with multiple cardiac risk factors, and thus probably for many older adults. There is no clear evidence of the need to undergo stress testing prior to a more moderate program.
Geriatric rehabilitation is based on the assumption that an improvement in modifiable impairments provides the resources to compensate for fixed deficits. Even individuals with several reversible impairments may have the potential for functional gain if the aggregate burden is reduced. Exercise training is a potential avenue for reducing the burden of impairments to pave the road toward improved function.
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