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6 Physical Activity and Special Considerations for Older Adults This chapter addresses the aging U.S. population, physiological changes that older people experience as they age, evidence of the bene- fits from physical activity, and the rationale for developing more specific physical activity guidelines targeted toward older Americans. Specific evidence was presented detailing the role of physical activity in the de- velopment of age-associated impairments, functional limitations, physi- cal disability, and cognitive decline. PHYSICAL ACTIVITY AND OLDER ADULTS Presenter: Roger A. Fielding1 This presentation provided background information on demographic changes in the U.S. population and the prevalence of physical inactivity in the elderly. Then Dr. Fielding covered age-related changes in physio- logical function, available evidence for benefits of physical activity, re- search needs, and reasons to develop specific physical activity guidelines for older Americans. 1 Dr. Fielding acknowledged support from U.S. Department of Agriculture 54-K01-01, National Institute of Aging (NIA) AG 18844, NIA AG 25270, and NIA AG 22376. 111
112 PHYSICAL ACTIVITY WORKSHOP Background The U.S. population is aging, with a projected sharp increase in the number of people over age 65 years. The rate of growth in the size of the group that is older than 85 years is even faster than that for persons over age 65 years. The over-85 age group is the fastest growing segment of our population. The prevalence of physical inactivity is highest among the elderly. Data from the Centers for Disease Control and Prevention (CDC, 2005) indicate that close to 40 percent of persons age 70 years or older have no physical activity beyond daily functioning. Similarly, Manson et al. (2004) found that more than 60 percent of persons older than 75 reported no leisure-time physical activity. Age-Related Changes in Physiological Function The disablement pathway originally described by Nagi (1965) and later adapted by Verbrugge and Jette (1994) includes the following steps: 1. Pathology (e.g., type II muscle fiber atrophy) 2. Impairment (e.g., loss of muscle strength) 3. Functional limitation (e.g., loss of mobility) 4. Disability in which the person has a limitation in performing a socially defined role within the social or physical environment. This model has been useful in compartmentalizing the potential ef- fects of physical activity on age-associated functional limitations and disability. Evidence suggests that physical activity by older persons may lead to improvements at the levels of functional limitations and disability by mechanistically improving physiological function at the pathology or impairment level. Functional limitations generally are assessed either by self-report or performance-based measures, while disability usually is assessed with self-reported instruments. Sarcopenia Decline in skeletal muscle mass (sarcopenia) is an obvious change that occurs with aging. Scanning a cross-sectional area of the mid-thigh by computed tomography (CT) or magnetic resonance imaging (MRI)
OLDER ADULTS 113 reveals that even non-obese older women have a smaller amount of mus- cle and more fat than do younger women. The New Mexico Elder Health Survey used dual energy X-ray absoptiometry (DEXA) scans to estimate the prevalence of sarcopenia. Selected data showing the range for men and women appear in Table 6-1. In that survey, sarcopenia was defined as having a DEXA value two standard deviations below normal for young individuals. Decline in voluntary muscle strength occurs along with the decline in skeletal muscle mass and power. Metter et al. (1997) reported that upper extremity strength of persons age 85 and older was about 60 percent that of the 20-year-old group, and upper extremity power was only 40 percent that of the young group. Both strength and power are predictors of func- tion in the elderly; however evidence is accumulating that power may be the stronger predictor of functional limitations and disability. Jette et al. (1981) showed that approximately 20 percent of men and 60 percent of women ages 75â84 years were unable to lift a 4.5 kg (10 lb) weight, which is comparable to the weight of a bag of groceries. Evidence indicates that qualitative changes also occur in muscle. For example, the specific force of single skeletal muscle fibersâboth the slow type I fibers and the fast oxidative type IIA fibersâwas signifi- cantly lower for older men than for younger men (Frontera et al., 2000). Aerobic Capacity Data from a number of studies suggest that aerobic capacity declines about 1 percent per year after the third decade (Astrand, 1960; Fleg et al. 2005). Recent evidence from Fleg and colleagues (2005) suggests that longitudinal declines in aerobic capacity are independent of participation in regular physical activity and that declines in aerobic capacity in late life may be even more precipitous. The change is closely related to the age-associated decline in maximal cardiac output and parallels the
114 PHYSICAL ACTIVITY WORKSHOP TABLE 6-1 Range of Prevalencea of Sarcopenia for Older Non-Hispanic White Men and Women ---Percent--- Age group, years Males (n=205) Females (n=173) 70â74 20 33 > 80 53 43 a Prevalence assessed by dual-energy X-ray absorptiometry in the New Mexico Elder Health Survey. SOURCE: Adapted from Baumgartner et al. (1998). decline in skeletal muscle oxidative capacity, as measured by decreased mitochondrial number and function. Because of these declines, even normal activities of daily living may require near maximal effort for many older people. Despite the fact that aerobic capacity does seem to decline with age, older adults who are aerobically fit have maximal ca- pacity for oxygen consumption (VO2max) similar to that of sedentary younger adults. Evidence of Benefits of Physical Activity Many studies have shown that exercise can have beneficial effects by reducing the risk of chronic diseases and mitigating signs and symptoms of disease that are already present in older adults. Strength and Muscle Mass A randomized controlled trial of strength training showed a progres- sive significant increase in muscle strength in the resistance training group throughout the year of the study, and a slight, nonsignificant in- crease in the control group (see Figure 6-1) (Nelson et al., 1994). Muscle mass also increased in the resistance training group. A randomized controlled trial of nursing home residents with a mean age of 85 years found that the group that received exercise alone became stronger than the control group, but there was no improvement in muscle mass (Fiatarone et al., 1994). In contrast, the group that received exercise plus a nutritional supplement benefited in both strength and muscle mass.
OLDER ADULTS 115 34 32 30 28 Strength (kg) 26 24 22 20 Control Exercise 18 16 0 1 2 3 4 5 6 7 8 9 10 11 12 Month of study FIGURE 6-1 Effect of resistance training (lateral pull down) on muscle strength over time, postmenopausal women ages 50â70 years. SOURCE: Morganti et al. (1995). Reprinted, with permission, from Med Sci Sports Exerc. Functional Limitations and Disability In a systematic review of effects of progressive resistance training interventions, Latham et al. (2004) reported on changes in functional limitations and disability among older individuals who were impaired at baseline. In the pooled analysis, improvements in strength were moderate to large, and improvements in functional limitations (gait speed, chair stand, and 6-minute walk) were modest to moderate. No effect of resis- tance training was seen, however, in a physical function subscale or in the measure of activities of daily living. The changes in functional limita- tions were variable and may depend on baseline performance, stimulus intensity, and duration. In a recently released report on the Lifestyle Interventions and Inde- pendence for Elders Pilot (LIFE-P) study (a 1-year program of combined aerobic, strength, and balance training in older men and women with functional limitations at baseline) showed significant and clinically meaningful improvements in the short physical performance battery
116 PHYSICAL ACTIVITY WORKSHOP score compared to a health education control group (The LIFE Investiga- tors, 2006). Another systematic review of the impact of resistance training on the disablement process (Keysor and Jette, 2001) found that 23 of the 26 studies demonstrated improved strength, and over half showed improve- ment in functional tasks such as walking and stair climbing. Only a few studies, however, showed improvement in physical disability, and those improvements were small to modest. Limitations in instruments designed to measure disability may ex- plain, at least in part, why most physical activity studies fail to show an impact on disability. Using a newly developed instrument to assess dis- ability in intervention studies, Dr. Fieldingâs group conducted a 12-week randomized trial of the effect of progressive resistance training on dis- ability in older persons who had experienced a stroke. Strength increased about 16 to 38 percent in the exercise group compared to no change in the attention control group. In addition, data collected using the Late Life Function and Disability Instrument, which was developed and validated by Jette et al. (2002), showed improvements to the advanced lower ex- tremity function domain and two domains of disability (limitation and instrumental role) (Ouellette, 2004). Falls Falls are a precipitating event for fracture. Approximately 50 to 65 percent of all falls occur in or around the home (Cummings et al., 1995). Most occur on the same level, from a standing height, as by tripping while walking rather than falling down stairs. Some evidence indicates that physical activity or a combination of balance and strengthening ac- tivity programs may reduce falls in older individuals. For example, in a randomized trial involving frail older women, Campbell et al. (1997) found that 30 minutes of home-based strength and balance exercises three times per week over 1 year resulted in significant improvements over the control group in chair stand time (the time to stand up from a standard chair five times) and balance measures. In addition, the exercise group had a significant 40 percent decrease in injurious falls.
OLDER ADULTS 117 Cognitive Function In a review, Kramer et al. (2006) reported that observational studies suggest an association between physical activity in persons with normal cognitive decline and the development of Alzheimerâs disease and other dementias. However, the studies generally covered a short period of evaluation (2 to 8 years). Intervention studies suggest that exercise train- ing has a positive effect on executive control processes. These processes include planning, scheduling, working memory, and multitasking. Mean differences in baseline cognitive function scores showed a sig- nificant value for trend by quartile of walking for four of five tests of cognitive function (Weuve et al., 2004). Two meta-analyses have been conducted of intervention trials that address physical activity and cogni- tive function (Colcombe and Kramer, 2003; Heyn et al., 2004). In non- demented older adults, the estimated effect size was 0.48; and in demented elderly patients, the effect size was similar (0.57). Dr. Fielding highlighted the need to conduct more basic studies to identify the areas of the brain that are activated by exercise and the mechanisms of action by which exercise exerts its effects. Concluding Remarks In closing, Dr. Fielding provided his perspective on information needs and on reasons for specific physical activity guidelines for older Americans. Research Needs Among the research needs relating to physical activity in older adults are the following: â¢ A definitive randomized trial of physical activity on disability outcomes â¢ Evidence of the ability of older individuals with functional limi- tations to adhere to physical activity recommendations â¢ Better understanding of appropriate physical activities to im- prove balance â¢ Definitive studies on exercise and cognition
118 PHYSICAL ACTIVITY WORKSHOP Rationale for Developing Specific Physical Activity Guidelines for Older Americans Specificity is needed to address the unique changes in physiological reserve that occur with aging. This is especially important if guidelines will be developed to apply to older individuals with several comorbid- ities and functional limitations, as well as to older healthy persons. Older persons have more medical conditions and comorbidities than do younger persons, and they are at increased risk of injury. In addition, long-term adherence to physical participation can be an issue, especially for older adults with functional limitations. In the LIFE-P study (The LIFE Investigators, 2006), over the course of 1 year, about half the sub- jects had to suspend participation in moderate physical activity for a pe- riod because of a health problem. Thus effective strategies that can help older adults resume physical activity following these common health transitions merit consideration when developing physical activity guide- lines for this population. DISCUSSION Physical Activity Guidelines for Older Adults Discussant: Anne B. Newman Background In contrast with common perception, the rates of disability for activi- ties of daily living (defined as difficulty with self-care) are rather low (about 1 to 2 percent) in older persons. Rates of loss of mobility, how- ever, are much higher. After age 70, the rate of incident mobility diffi- culty is 10 percent per year, and about one-third of the affected individuals have severe mobility disability (Penninx et al., 2004). Chal- lenges to oneâs ability to remain physically active with older age include risk of hip fracture, pneumonia, and congestive heart failure. The acute declines and limited recovery from such intermittent health events may further accelerate functional decline and ultimately lead to disability. As mentioned earlier in this session by Dr. Fielding, longitudinal data show a decline in maximal oxygen consumption with aging. Al- though those who are active maintain higher oxygen consumption, the
OLDER ADULTS 119 rate of the decline is not prevented by physical activity (Fleg et al., 2005; Metter et al., 1999). Metter et al. (1999) observed age-associated de- creases in leg isometric strength and muscle mass, and Goodpaster et al. (2006) showed that loss of strength is proportionately much greater than loss of muscle mass in men and women ages 70 to 79 years. Reasons for Developing Guidelines for Older Adults Dr. Newman agreed with Dr. Fielding on the need for developing physical activity guidelines for older adults and highlighted the following reasons: â¢ Older adults are at risk for or may have multiple chronic condi- tions. Thus physical activity may interfere with or retard both disease pathways and age-related decline in the pathway to disability. â¢ Old age is a heterogeneous period of development, during which the dynamics of weight change need to be considered. Weight tends to fluctuate and decline after about age 70 years (Roberts and Williamson, 2002). Many older persons will lose weight at a low level of food intake and a very low level of energy expendi- ture (Newman et al., 2005). â¢ Older adults may not know what they can do or should do for physical activity. In the Dynamics of Health, Aging and Body Composition Study (Health ABC), only three-quarters of older adults who reported no difficulty walking a quarter of a mile could actually do so at examination (Newman et al., 2006) There is a need for a message about goals that address ability and capacity. Need for a Consistent Message Dr. Newman highlighted the importance of developing a consistent message that addresses the type of activity to choose for a particular benefit: â¢ Aerobic and/or strength training for function â¢ Weight-bearing and strength training activities for bone health
120 PHYSICAL ACTIVITY WORKSHOP â¢ Neurologically stimulating activities for balance and speeded tasks Potentially beneficial activities not mentioned earlier include tâai chi (Wolf et al., 1996) and dance (Verghese, 2006). There is a need for a message about goals that address ability and for methods to measure ability. A majority of adults older than 70 years have difficulty with treadmill testing, and many cannot provide a useful self- report of their ability to walk a distance (Sayers et al., 2004). Notably, Newman et al. (2006) showed that rates of disability are inversely related to the ability to walk one-quarter mile. Concluding Remarks In closing, Dr. Newman underscored that older adults do benefit from physical activity. Comprehensive messages need to be developed, and the recommendations need to be individualized to the developmental period in the life course. Finally, objective assessment of the functional capacity of older adults needs to be incorporated into clinical practice for appropriate goal setting. Group Discussion Moderator: Miriam Nelson Among the points raised during the discussion were the following: â¢ The rate of loss of aerobic capacity with age may be accelerated in older age groups. In the Baltimore Longitudinal Study of Ag- ing, the rate of loss for persons in their seventies and eighties was approximately 20 to 30 percent per decade. Since the rate of loss is about the same for persons at different levels of fitness, it becomes even more important for inactive persons to increase their level of aerobic capacity through physical activity. Focus- ing efforts on prevention could help raise fitness levels above the threshold for disability, thus helping prevent disability. â¢ Evidence suggests that physical activity of moderate intensity may have quite robust health effects for older adults. A fair
OLDER ADULTS 121 amount of evidence from randomized controlled trials indicates health benefits at levels of physical activity that are lower than currently recommended. â¢ Physical activity programs for older persons can be safe and ef- fective in community settings. â¢ Clinically meaningful outcome measurements are needed to as- sess the effectiveness of physical activity interventions in the field. â¢ Large randomized controlled trials are needed to determine the extent to which physical activity can reduce disability over the long term. Observational studies have serious limitations. â¢ The examination of adiposityâin addition to muscle mass and qualityâis important in investigations of physical activity and functional limitations in disability. Carrying excess weight is an independent factor in predicting disability. â¢ The International Consensus Conference on DoseâResponse covered a large percentage of persons older than 65 years and reported a well-documented doseâresponse effect. In particular, greater amounts of physical activity reduced mortality rates. REFERENCES Astrand I. 1960. Aerobic work capacity in men and women with special refer- ence to age. J Appl Physiol 49(169):1â92. Baumgartner RN, Koehler KM, Gallagher D, Romero L, Heymsfield SB, Ross RR, Garry PJ, Lindeman RD. 1998. Epidemiology of sarcopenia among the elderly in New Mexico. Am J Epidemiol 147(8):755â763. Campbell AJ, Robertson MC, Gardner MM, Norton RN, Tilyard MW, Buchner DM. 1997. Randomised controlled trial of a general practice programme of home based exercise to prevent falls in elderly women. BMJ 315(7115):1065â 1069. CDC (Centers for Disease Control and Prevention). 2005. Trends in leisure-time physical inactivity by age, sex, and race/ethnicityâUnited States, 1994â2004. MMWR 54(39):991â994. Colcombe S, Kramer AF. 2003. Fitness effects on the cognitive function of older adults: A meta-analytic study. Psychol Sci 14(2):125â130. Cummings SR, Nevitt MC, Browner WS, Stone K, Fox KM, Ensrud KE, Cauley J, Black D, Vogt TM. 1995. Risk factors for hip fracture in white women. Study of Osteoporotic Fractures Research Group. N Engl J Med 332(12): 767â773.
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