Post by John A. Casler on Jul 31, 2009 6:41:47 GMT -8
This is from Jamie Carruthers as posted to SuperTraining
To visit SUPERTRAINING FORUM
health.groups.yahoo.com/group/Supertraining/?yguid=44276758
The below excerpts may be of interest:
journals.lww.com/acsm-msse/Fulltext/2009/07000/Exercise_and_Physical_Activity_for_Older_Adults.20.aspx#P26
Although no amount of physical activity can stop the biological aging process, there is evidence that regular exercise can minimize the physiological effects of an otherwise sedentary lifestyle and increase active life expectancy by limiting the development and progression of chronic disease and disabling conditions. There is also emerging evidence for significant psychological and cognitive benefits accruing from regular exercise participation by older adults. Ideally, exercise prescription for older adults should include aerobic exercise, muscle strengthening exercises, and flexibility exercises. The evidence reviewed in this Position Stand is generally consistent with prior American College of Sports Medicine statements on the types and amounts of physical activity recommended for older adults as well as the recently published 2008 Physical Activity Guidelines for Americans. All older adults should engage in regular physical activity and avoid an inactive lifestyle.
SECTION 1: NORMAL HUMAN AGING
Back to Top | Article Outline
Structural and functional decline.
With advancing age, structural and functional deterioration occurs in most physiological systems, even in the absence of discernable disease (152). These age-related physiological changes affect a broad range of tissues, organ systems, and functions, which, cumulatively, can impact activities of daily living (ADL) and the preservation of physical independence in older adults. Declines in maximal aerobic capacity (V¢«O2max) and skeletal muscle performance with advancing age are two examples of physiological aging (98). Variation in each of these measures are important determinants of exercise tolerance (245) and functional abilities (16,41) among older adults. Baseline values in middle-aged women and men predict future risks of disability (19,192), chronic disease (18) and death (18,160). Age-related reductions in V¢«O2max and strength also suggest that at any submaximal exercise load, older adults are often required to exert a higher percentage of their maximal capacity (and effort) when compared with younger persons.
Changing body composition is another hallmark of the physiological aging process, which has profound effects on health and physical function among older adults. Specific examples include the gradual accumulation of body fat and its redistribution to central and visceral depots during middle age and the loss of muscle (sarcopenia) during middle and old age, with the attendant metabolic (113,190) and cardiovascular (123,222) disease risks. A summary of these and other examples of physiological aging, the usual time course of these changes, and the potential functional and clinical significance of these changes are provided in Table 2.
Increased chronic disease risk.
The relative risk of developing and ultimately dying from many chronic diseases including cardiovascular disease, type 2 diabetes, obesity, and certain cancers increases with advancing age (137,217,222). Older populations also exhibit the highest prevalence of degenerative musculoskeletal conditions such as osteoporosis, arthritis, and sarcopenia (176,179,217). Thus, age is considered a primary risk factor for the development and progression of most chronic degenerative disease states. However, regular physical activity substantially modifies these risks. This is suggested by studies demonstrating a statistically significant decrease in the relative risk of cardiovascular and all-cause mortality among persons who are classified as highly fit (and/or highly active) compared with those in a similar age range who are classified as moderately fit (and/or normally active) or low fit (and/or sedentary). The largest increment in mortality benefit is seen when comparing sedentary adults with those in the next highest physical activity level (19). Additional evidence suggests that muscular strength and power also predict all-cause and cardiovascular mortality, independent of cardiovascular fitness (69,122). Thus, avoidance of a sedentary lifestyle by engaging in at least some daily physical activity is a prudent recommendation for reducing the risk of developing chronic diseases and postponing premature mortality at any age. Although a detailed breakdown of the impact of physical activity on the reduction in risk of developing and dying from chronic diseases is beyond the scope of this review, the recently published Physical Activity Guidelines Advisory Committee Report (51) by the Department of Health and Human Services (DHHS) provides a comprehensive summary of the evidence linking physical activity with the risk of developing and dying from a variety of different conditions. The report contains information for the general population as well as for older adults in particular.
Physical activity and the aging process.
Aging is a complex process involving many factors that interact with one another, including primary aging processes, "secondary aging" effects (resulting from chronic disease and lifestyle behaviors), and genetic factors (152,258). The impact of physical activity on primary aging processes is difficult to study in humans because cellular aging processes and disease mechanisms are highly intertwined (137). There are currently no lifestyle interventions, including exercise, which have been shown to reliably extend maximal lifespan in humans (98,175). Rather, regular physical activity increases average life expectancy through its influence on chronic disease development (via reduction of secondary aging effects). Physical activity also limits the impact of secondary aging through restoration of functional capacity in previously sedentary older adults. AET and RET programs can increase aerobic capacity and muscle strength, respectively, by 20%-30% or more in older adults (101,139).
Factors influencing functional decline in aging.
Although the pattern of age-related change for most physiological variables is one of decline, some individuals show little or no change for a given variable, whereas others show some improvement with age (119). There are also individuals for whom physical functioning oscillates, exhibiting variable rates of change over time (120,187,192), possibly reflecting variable levels of physical activity and other cyclical (seasonal) or less predictable (sickness, injuries) influences. However, even after accounting for the effect of different levels of physical activity, there is still substantial between-subject variability (at a given point in time and in rates of change over time) for most physiological measures, and this variability seems to increase with age (231). Individual variation is also apparent in the adaptive responses to a standardized exercise training program; some individuals show dramatic changes for a given variable (responders), whereas others show minimal effects (nonresponders) (24).
Determining the extent to which genetic and lifestyle factors influence age-associated functional declines and the magnitude of the adaptive responses to exercise (i.e., trainability) of both younger and older individuals is an area of active investigation. Exercise training studies involving families and twin pairs report a significant genetic influence on baseline physiological function (explaining ¡30% to 70% of between-subjects variance) and trainability of aerobic fitness (24), skeletal muscle properties (199), and cardiovascular risk factors (24). Although the role of genetic factors in determining changes in function over time and in response to exercise training in older humans is not well understood, it is likely that a combination of lifestyle and genetic factors contribute to the wide interindividual variability seen in older adults.
Exercise and the aging process.
The acute physiological adjustments of healthy sedentary older men and women to submaximal aerobic exercise are qualitatively similar to those of young adults and are adequate in meeting the major regulatory demands of exercise, which include the control of arterial blood pressure and vital organ perfusion, augmentation of oxygen and substrate delivery and utilization within active muscle, maintenance of arterial blood homeostasis, and dissipation of heat (213). The acute cardiovascular and neuromuscular adjustments to resistance exercise (both isometric and dynamic) also seem to be well preserved in healthy older adults (213). Accordingly, the normal age-associated reductions in functional capacity discussed in Section 1 should not limit the ability of healthy older adults to engage in aerobic or resistance exercise. In addition, long-term adaptive or training responses of middle-aged and nonfrail older adults to conventional AET or RET programs (i.e., relative intensity-based, progressive overload) are qualitatively similar to those seen in young adults. Although absolute improvements tend to be less in older versus young people, the relative increases in many variables, including V¢«O2max (100), submaximal metabolic responses (211), and exercise tolerance with AET and limb muscle strength (139), endurance (255), and size (203) in response to RET, are generally similar. Physiological aging alters some of the mechanisms and time course (174,253) by which older men and women adapt to a given training stimulus (i.e., older adults may take longer to reach the same level of improvement), and sex differences are emerging with respect to these mechanisms (16), but the body's adaptive capacity is reasonably well-preserved, at least through the seventh decade (98,217). During the combined demands of large muscle exercise and heat and/or cold stress, however, older individuals do exhibit a greater reduction in exercise tolerance and an increased risk of heat and cold illness/injury, respectively, compared with young adults (126). Age differences in exercise tolerance at higher ambient temperatures may be at least partially due to the lower aerobic fitness levels in older adults (126). Cessation of aerobic training by older adults leads to a rapid loss of cardiovascular (184,210) and metabolic (201) fitness, whereas strength training-induced (neural) adaptations seem more persistent (139), similar to what has been observed in younger populations (44,139).
STUDIES OF LONG-TERM PHYSICAL ACTIVITY IN ATHLETES
Aerobic athletes.
Compared to their sedentary, age-matched peers, older athletes exhibit a broad range of physiological and health advantages. These benefits include, but are not limited to the following: 1) a more favorable body composition profile, including less total and abdominal body fat (76,98), a greater relative muscle mass (% of body mass) in the limbs (235), and higher bone mineral density (BMD) at weight bearing sites (78,164); 2) more oxidative and fatigue-resistant limb muscles (98,188,247); 3) a higher capacity to transport and use oxygen (173,189,206); 4) a higher cardiac stroke volume at peak exertion (77,173) and a "younger" pattern of left ventricular filling (increased early-to-late inflow velocity, E/A ratio) (55,98); 5) less cardiovascular (83) and metabolic (38,206,211,212) stress during exercise at any given submaximal work intensity; 6) a significantly reduced coronary risk profile (lower blood pressure, increased HR variability, better endothelial reactivity, lower systemic inflammatory markers, better insulin sensitivity and glucose homeostasis, lower triglycerides, LDL, and total cholesterol, higher HDL, and smaller waist circumference) (264); 7) faster nerve conduction velocity (253); and 8) slower development of disability in old age (257).
Resistance-trained athletes.
The number of laboratory-based physiological comparisons of resistance-trained athletes at various ages is small by comparison to the literature on aging aerobic athletes. Nevertheless, older RET athletes tend to have a higher muscle mass (131), are generally leaner (217), and are ∼30%-50% stronger (131) than their sedentary peers. Compared to age-matched AET athletes, RET athletes have more total muscle mass (131), higher bone mineral densities (236), and maintain higher muscle strength and power (131).
Metabolic and endocrine effects.
The effects of short- and long-term RET programs on basal metabolic rate (BMR) in older adults are not clear. Some investigations have reported increases of 7%-9% in BMR after 12-26 wk of exercise (33,105,139,249), whereas other studies of similar duration have not demonstrated changes (158,237). RET programs can enhance older adults' use of fat as a fuel, as indicated by increased lipid oxidation and decreased carbohydrate and amino acid oxidation at rest (105,249). Serum cholesterol and triglycerides are also influenced by RET, and reports suggest that training can increase HDL cholesterol by 8%-21%, decrease LDL cholesterol by 13%-23%, and reduce triglyceride levels by 11%-18% (62,86,114).
Resting testosterone is lower in older adults, and acute responses of total and free testosterone to weight lifting are blunted in seniors after RET. Neither short- (10-12 wk) (45,112,135) nor longer-term (21-24 wk) (22,87) RET increases resting concentrations of total or free testosterone. A decrease in resting cortisol (15%-25%) (112,133), however, has previously been observed, which may create a favorable environment for muscle hypertrophy. Peptide hormones, including growth hormone and insulin-like growth factor 1 (IGF-1) also have important anabolic action. Circulating growth hormone stimulates synthesis of IGF-1 in the liver, and circulating IGF-1 promotes differentiation of satellite cells into myotubes (95). Another IGF, mechanogrowth factor, is synthesized locally in muscle and signals the proliferation of satellite cells (94). Although one report suggests that RET may increase circulating IGF-1 in participants with low baseline serum IGF-1 levels (178), most investigations suggest that RET does not alter circulating IGF-1 (8,15,22,89). RET also seems to have no effect on free IGF-1 (15) and does not decrease IGF-1 binding proteins (22,178).
CONCLUSIONS
Although no amount of physical activity can stop the biological aging process, there is evidence that regular exercise can minimize the physiological effects of an otherwise sedentary lifestyle and increase active life expectancy by limiting the development and progression of chronic disease and disabling conditions. There is also emerging evidence for psychological and cognitive benefits accruing from regular exercise participation by older adults (Table 4). It is not yet possible to describe in detail exercise programs that will optimize physical functioning and health in all groups of older adults. New evidence also suggests that some of the adaptive responses to exercise training are genotype-sensitive, at least in animal studies (14). Nevertheless, several evidence-based conclusions can be drawn relative to exercise and physical activity in the older adult population: 1) A combination of AET and RET activities seems to be more effective than either form of training alone in counteracting the detrimental effects of a sedentary lifestyle on the health and functioning of the cardiovascular system and skeletal muscles. 2) Although there are clear fitness, metabolic, and performance benefits associated with higher-intensity exercise training programs in healthy older adults, it is now evident that such programs do not need to be of high intensity to reduce the risks of developing chronic cardiovascular and metabolic disease. However, the outcome of treatment of some established diseases and geriatric syndromes is more effective with higher-intensity exercise (e.g., type 2 diabetes, clinical depression, osteopenia, sarcopenia, muscle weakness). 3) The acute effects of a single session of aerobic exercise are relatively short-lived, and the chronic adaptations to repeated sessions of exercise are quickly lost upon cessation of training, even in regularly active older adults. 4) The onset and patterns of physiological decline with aging vary across physiological systems and between sexes, and some adaptive responses to training are age- and sex-dependent. Thus, the extent to which exercise can reverse age-associated physiological deterioration may depend, in part, on the hormonal status and age at which a specific intervention is initiated. 5) Ideally, exercise prescription for older adults should include aerobic exercise, muscle strengthening exercises, and flexibility exercises. In addition, individuals who are at risk for falling or mobility impairment should also perform specific exercises to improve balance in addition to the other components of health-related physical fitness. The conclusions of this Position Stand are highly consistent with the recently published 2008 Physical Activity Guidelines for Americans, which state that regular physical activity is essential for healthy aging. Adults aged 65 yr and older gain substantial health benefits from regular physical activity, and these benefits continue to occur throughout their lives. Promoting physical activity for older adults is especially important because this population is the least physically active of any age group (50).
To visit SUPERTRAINING FORUM
health.groups.yahoo.com/group/Supertraining/?yguid=44276758
The below excerpts may be of interest:
journals.lww.com/acsm-msse/Fulltext/2009/07000/Exercise_and_Physical_Activity_for_Older_Adults.20.aspx#P26
Although no amount of physical activity can stop the biological aging process, there is evidence that regular exercise can minimize the physiological effects of an otherwise sedentary lifestyle and increase active life expectancy by limiting the development and progression of chronic disease and disabling conditions. There is also emerging evidence for significant psychological and cognitive benefits accruing from regular exercise participation by older adults. Ideally, exercise prescription for older adults should include aerobic exercise, muscle strengthening exercises, and flexibility exercises. The evidence reviewed in this Position Stand is generally consistent with prior American College of Sports Medicine statements on the types and amounts of physical activity recommended for older adults as well as the recently published 2008 Physical Activity Guidelines for Americans. All older adults should engage in regular physical activity and avoid an inactive lifestyle.
SECTION 1: NORMAL HUMAN AGING
Back to Top | Article Outline
Structural and functional decline.
With advancing age, structural and functional deterioration occurs in most physiological systems, even in the absence of discernable disease (152). These age-related physiological changes affect a broad range of tissues, organ systems, and functions, which, cumulatively, can impact activities of daily living (ADL) and the preservation of physical independence in older adults. Declines in maximal aerobic capacity (V¢«O2max) and skeletal muscle performance with advancing age are two examples of physiological aging (98). Variation in each of these measures are important determinants of exercise tolerance (245) and functional abilities (16,41) among older adults. Baseline values in middle-aged women and men predict future risks of disability (19,192), chronic disease (18) and death (18,160). Age-related reductions in V¢«O2max and strength also suggest that at any submaximal exercise load, older adults are often required to exert a higher percentage of their maximal capacity (and effort) when compared with younger persons.
Changing body composition is another hallmark of the physiological aging process, which has profound effects on health and physical function among older adults. Specific examples include the gradual accumulation of body fat and its redistribution to central and visceral depots during middle age and the loss of muscle (sarcopenia) during middle and old age, with the attendant metabolic (113,190) and cardiovascular (123,222) disease risks. A summary of these and other examples of physiological aging, the usual time course of these changes, and the potential functional and clinical significance of these changes are provided in Table 2.
Increased chronic disease risk.
The relative risk of developing and ultimately dying from many chronic diseases including cardiovascular disease, type 2 diabetes, obesity, and certain cancers increases with advancing age (137,217,222). Older populations also exhibit the highest prevalence of degenerative musculoskeletal conditions such as osteoporosis, arthritis, and sarcopenia (176,179,217). Thus, age is considered a primary risk factor for the development and progression of most chronic degenerative disease states. However, regular physical activity substantially modifies these risks. This is suggested by studies demonstrating a statistically significant decrease in the relative risk of cardiovascular and all-cause mortality among persons who are classified as highly fit (and/or highly active) compared with those in a similar age range who are classified as moderately fit (and/or normally active) or low fit (and/or sedentary). The largest increment in mortality benefit is seen when comparing sedentary adults with those in the next highest physical activity level (19). Additional evidence suggests that muscular strength and power also predict all-cause and cardiovascular mortality, independent of cardiovascular fitness (69,122). Thus, avoidance of a sedentary lifestyle by engaging in at least some daily physical activity is a prudent recommendation for reducing the risk of developing chronic diseases and postponing premature mortality at any age. Although a detailed breakdown of the impact of physical activity on the reduction in risk of developing and dying from chronic diseases is beyond the scope of this review, the recently published Physical Activity Guidelines Advisory Committee Report (51) by the Department of Health and Human Services (DHHS) provides a comprehensive summary of the evidence linking physical activity with the risk of developing and dying from a variety of different conditions. The report contains information for the general population as well as for older adults in particular.
Physical activity and the aging process.
Aging is a complex process involving many factors that interact with one another, including primary aging processes, "secondary aging" effects (resulting from chronic disease and lifestyle behaviors), and genetic factors (152,258). The impact of physical activity on primary aging processes is difficult to study in humans because cellular aging processes and disease mechanisms are highly intertwined (137). There are currently no lifestyle interventions, including exercise, which have been shown to reliably extend maximal lifespan in humans (98,175). Rather, regular physical activity increases average life expectancy through its influence on chronic disease development (via reduction of secondary aging effects). Physical activity also limits the impact of secondary aging through restoration of functional capacity in previously sedentary older adults. AET and RET programs can increase aerobic capacity and muscle strength, respectively, by 20%-30% or more in older adults (101,139).
Factors influencing functional decline in aging.
Although the pattern of age-related change for most physiological variables is one of decline, some individuals show little or no change for a given variable, whereas others show some improvement with age (119). There are also individuals for whom physical functioning oscillates, exhibiting variable rates of change over time (120,187,192), possibly reflecting variable levels of physical activity and other cyclical (seasonal) or less predictable (sickness, injuries) influences. However, even after accounting for the effect of different levels of physical activity, there is still substantial between-subject variability (at a given point in time and in rates of change over time) for most physiological measures, and this variability seems to increase with age (231). Individual variation is also apparent in the adaptive responses to a standardized exercise training program; some individuals show dramatic changes for a given variable (responders), whereas others show minimal effects (nonresponders) (24).
Determining the extent to which genetic and lifestyle factors influence age-associated functional declines and the magnitude of the adaptive responses to exercise (i.e., trainability) of both younger and older individuals is an area of active investigation. Exercise training studies involving families and twin pairs report a significant genetic influence on baseline physiological function (explaining ¡30% to 70% of between-subjects variance) and trainability of aerobic fitness (24), skeletal muscle properties (199), and cardiovascular risk factors (24). Although the role of genetic factors in determining changes in function over time and in response to exercise training in older humans is not well understood, it is likely that a combination of lifestyle and genetic factors contribute to the wide interindividual variability seen in older adults.
Exercise and the aging process.
The acute physiological adjustments of healthy sedentary older men and women to submaximal aerobic exercise are qualitatively similar to those of young adults and are adequate in meeting the major regulatory demands of exercise, which include the control of arterial blood pressure and vital organ perfusion, augmentation of oxygen and substrate delivery and utilization within active muscle, maintenance of arterial blood homeostasis, and dissipation of heat (213). The acute cardiovascular and neuromuscular adjustments to resistance exercise (both isometric and dynamic) also seem to be well preserved in healthy older adults (213). Accordingly, the normal age-associated reductions in functional capacity discussed in Section 1 should not limit the ability of healthy older adults to engage in aerobic or resistance exercise. In addition, long-term adaptive or training responses of middle-aged and nonfrail older adults to conventional AET or RET programs (i.e., relative intensity-based, progressive overload) are qualitatively similar to those seen in young adults. Although absolute improvements tend to be less in older versus young people, the relative increases in many variables, including V¢«O2max (100), submaximal metabolic responses (211), and exercise tolerance with AET and limb muscle strength (139), endurance (255), and size (203) in response to RET, are generally similar. Physiological aging alters some of the mechanisms and time course (174,253) by which older men and women adapt to a given training stimulus (i.e., older adults may take longer to reach the same level of improvement), and sex differences are emerging with respect to these mechanisms (16), but the body's adaptive capacity is reasonably well-preserved, at least through the seventh decade (98,217). During the combined demands of large muscle exercise and heat and/or cold stress, however, older individuals do exhibit a greater reduction in exercise tolerance and an increased risk of heat and cold illness/injury, respectively, compared with young adults (126). Age differences in exercise tolerance at higher ambient temperatures may be at least partially due to the lower aerobic fitness levels in older adults (126). Cessation of aerobic training by older adults leads to a rapid loss of cardiovascular (184,210) and metabolic (201) fitness, whereas strength training-induced (neural) adaptations seem more persistent (139), similar to what has been observed in younger populations (44,139).
STUDIES OF LONG-TERM PHYSICAL ACTIVITY IN ATHLETES
Aerobic athletes.
Compared to their sedentary, age-matched peers, older athletes exhibit a broad range of physiological and health advantages. These benefits include, but are not limited to the following: 1) a more favorable body composition profile, including less total and abdominal body fat (76,98), a greater relative muscle mass (% of body mass) in the limbs (235), and higher bone mineral density (BMD) at weight bearing sites (78,164); 2) more oxidative and fatigue-resistant limb muscles (98,188,247); 3) a higher capacity to transport and use oxygen (173,189,206); 4) a higher cardiac stroke volume at peak exertion (77,173) and a "younger" pattern of left ventricular filling (increased early-to-late inflow velocity, E/A ratio) (55,98); 5) less cardiovascular (83) and metabolic (38,206,211,212) stress during exercise at any given submaximal work intensity; 6) a significantly reduced coronary risk profile (lower blood pressure, increased HR variability, better endothelial reactivity, lower systemic inflammatory markers, better insulin sensitivity and glucose homeostasis, lower triglycerides, LDL, and total cholesterol, higher HDL, and smaller waist circumference) (264); 7) faster nerve conduction velocity (253); and 8) slower development of disability in old age (257).
Resistance-trained athletes.
The number of laboratory-based physiological comparisons of resistance-trained athletes at various ages is small by comparison to the literature on aging aerobic athletes. Nevertheless, older RET athletes tend to have a higher muscle mass (131), are generally leaner (217), and are ∼30%-50% stronger (131) than their sedentary peers. Compared to age-matched AET athletes, RET athletes have more total muscle mass (131), higher bone mineral densities (236), and maintain higher muscle strength and power (131).
Metabolic and endocrine effects.
The effects of short- and long-term RET programs on basal metabolic rate (BMR) in older adults are not clear. Some investigations have reported increases of 7%-9% in BMR after 12-26 wk of exercise (33,105,139,249), whereas other studies of similar duration have not demonstrated changes (158,237). RET programs can enhance older adults' use of fat as a fuel, as indicated by increased lipid oxidation and decreased carbohydrate and amino acid oxidation at rest (105,249). Serum cholesterol and triglycerides are also influenced by RET, and reports suggest that training can increase HDL cholesterol by 8%-21%, decrease LDL cholesterol by 13%-23%, and reduce triglyceride levels by 11%-18% (62,86,114).
Resting testosterone is lower in older adults, and acute responses of total and free testosterone to weight lifting are blunted in seniors after RET. Neither short- (10-12 wk) (45,112,135) nor longer-term (21-24 wk) (22,87) RET increases resting concentrations of total or free testosterone. A decrease in resting cortisol (15%-25%) (112,133), however, has previously been observed, which may create a favorable environment for muscle hypertrophy. Peptide hormones, including growth hormone and insulin-like growth factor 1 (IGF-1) also have important anabolic action. Circulating growth hormone stimulates synthesis of IGF-1 in the liver, and circulating IGF-1 promotes differentiation of satellite cells into myotubes (95). Another IGF, mechanogrowth factor, is synthesized locally in muscle and signals the proliferation of satellite cells (94). Although one report suggests that RET may increase circulating IGF-1 in participants with low baseline serum IGF-1 levels (178), most investigations suggest that RET does not alter circulating IGF-1 (8,15,22,89). RET also seems to have no effect on free IGF-1 (15) and does not decrease IGF-1 binding proteins (22,178).
CONCLUSIONS
Although no amount of physical activity can stop the biological aging process, there is evidence that regular exercise can minimize the physiological effects of an otherwise sedentary lifestyle and increase active life expectancy by limiting the development and progression of chronic disease and disabling conditions. There is also emerging evidence for psychological and cognitive benefits accruing from regular exercise participation by older adults (Table 4). It is not yet possible to describe in detail exercise programs that will optimize physical functioning and health in all groups of older adults. New evidence also suggests that some of the adaptive responses to exercise training are genotype-sensitive, at least in animal studies (14). Nevertheless, several evidence-based conclusions can be drawn relative to exercise and physical activity in the older adult population: 1) A combination of AET and RET activities seems to be more effective than either form of training alone in counteracting the detrimental effects of a sedentary lifestyle on the health and functioning of the cardiovascular system and skeletal muscles. 2) Although there are clear fitness, metabolic, and performance benefits associated with higher-intensity exercise training programs in healthy older adults, it is now evident that such programs do not need to be of high intensity to reduce the risks of developing chronic cardiovascular and metabolic disease. However, the outcome of treatment of some established diseases and geriatric syndromes is more effective with higher-intensity exercise (e.g., type 2 diabetes, clinical depression, osteopenia, sarcopenia, muscle weakness). 3) The acute effects of a single session of aerobic exercise are relatively short-lived, and the chronic adaptations to repeated sessions of exercise are quickly lost upon cessation of training, even in regularly active older adults. 4) The onset and patterns of physiological decline with aging vary across physiological systems and between sexes, and some adaptive responses to training are age- and sex-dependent. Thus, the extent to which exercise can reverse age-associated physiological deterioration may depend, in part, on the hormonal status and age at which a specific intervention is initiated. 5) Ideally, exercise prescription for older adults should include aerobic exercise, muscle strengthening exercises, and flexibility exercises. In addition, individuals who are at risk for falling or mobility impairment should also perform specific exercises to improve balance in addition to the other components of health-related physical fitness. The conclusions of this Position Stand are highly consistent with the recently published 2008 Physical Activity Guidelines for Americans, which state that regular physical activity is essential for healthy aging. Adults aged 65 yr and older gain substantial health benefits from regular physical activity, and these benefits continue to occur throughout their lives. Promoting physical activity for older adults is especially important because this population is the least physically active of any age group (50).