RECOMMENDED AMOUNTS OF PHYSICAL ACTIVITY
PHYSICAL ACTIVITY LEVELS IN OLDER ADULTS
RECOMMENDING PHYSICAL ACTIVITY TO OLDER ADULTS
CONSIDERATIONS IN OLDER ADULTS WITH LOW FITNESS
OSTEOPOROSIS, FALLS, FRACTURES, AND BALANCE TRAINING
THE RISKS OF PHYSICAL ACTIVITY
Physical activity is defined as bodily movement produced by skeletal muscles that expend energy. Exercise is a subset of physical activity that involves a structured program designed to improve one or more components of physical fitness. The primary attributes of physical activity are type (mode), frequency, duration, and intensity. Promoting physical activity is one of the most important and effective preventive and therapeutic interventions in older adults. There is conclusive evidence that regular aerobic activity has large health benefits. Resistance training and balance training also have important health benefits in older adults. Flexibility training is important for maintaining the range of motion required to do physical activities.
Regular physical activity has beneficial effects on most, if not all, organ systems. Consequently, it prevents a large number of diseases. Physical activity reduces the risk of cardiovascular disease, high blood pressure, stroke, some lipid disorders, non-insulin-dependent diabetes mellitus, obesity, osteoporosis, colon cancer, and breast cancer. There is substantial evidence that physical activity also reduces the risk of fall injuries, sarcopenia, depression, and anxiety disorders. There is some evidence that physical activity reduces the risk of sleep problems, cognitive impairment, osteoarthritis, and back pain.
Consistent with its broad physiologic effects, regular physical activity decreases both cardiovascular and noncardiovascular mortality in older adults. The mortality benefit is large. Some studies report that inactive adults have mortality rates that are twice as high as those of active adults.
Observational studies consistently report that regular physical activity substantially delays the onset of functional limitations and loss of independence (disability). For example, an analysis of Established Population for Epidemiologic Studies of the Elderly (EPESE) data showed that inactive, nonsmoking women at age 65 have 12.7 years of active life expectancy, compared with 18.4 years of active life expectancy for highly active women. Higher levels of physical activity are associated with fewer years of disability preceding death.
The health benefits of physical activity accrue independently of other risk factors. For example, sedentary overweight smokers experience health benefits from increasing physical activity, even if they continue to smoke and do not lose weight.
The health benefits of physical activity are generally proportional to the amount of physical activity. When activity is performed above minimum thresholds for frequency, duration, and intensity, health benefit depends mainly upon the volume (energy expenditure) of aerobic activity. The dose-response relationship between physical activity and disease risk varies by disease in a manner that is incompletely understood. Cardiovascular disease risk decreases with volume of aerobic activity over a wide range of volume. Blood pressure shows little dose-response effect, as most of the effect of activity on blood pressure occurs at low levels of activity. The effect of activity on bone density is less related to volume of aerobic activity and more related to resistance training and high-impact activities.
Habitually active adults have lower medical expenditures. One study estimated direct medical expenditures in adults attributable to inactivity as being $330 per person in 1987 ($825 in 2002 dollars). Evidence is growing that medical expenditures decline in sedentary older adults who become more active. In one study comparing older adults who remained sedentary with sedentary older adults who became active 3 or more days each week, the active group was found to have a decline in medical expenditures averaging about $2200 a year. Data on the cost-effectiveness of promoting physical activity in older adults is promising but limited, and it varies by intervention. One study of subsidized exercise classes reported cost savings of around $175 per participant per year.
Physical activity has therapeutic benefits in the management of a wide variety of chronic conditions. Selected clinical guidelines for the use of physical activity in managing common chronic conditions are shown in Table 8.1. In addition, clinical practice guidelines identify a role for physical activity in the management of the following conditions: dementia, persistent pain, heart failure, syncope, reflex sympathetic dystrophy, possible venous thromboembolism, back pain, some sleep disorders, and constipation.
It is possible that physical activity will assume a prominent role in the management of mental health conditions in older adults. There is substantial evidence that both aerobic activity and resistance training improve symptoms of depression. Physical activity should be considered as an adjunct to medication and psychotherapy for older adults with depressive illness, pending more studies clarifying which patients can be prescribed activity as a substitute for medication and psychotherapy. Cognitive ability is positively correlated with higher levels of physical activity and fitness. Ongoing research is testing if, and how much, physical activity can improve cognitive function.
The therapeutic use of exercise to reverse low fitness, physical functional limitations, and disability has been carefully studied over the past 20 years. Randomized trials of exercise in sedentary older adults show that aerobic capacity, muscle strength, flexibility, and balance can be improved by appropriate forms of exercise. Several evidence-based reviews conclude that exercise has a beneficial effect on functional limitations (restrictions in basic physical actions such as walking). Although some exercise studies report only small improvements in functional limitations, most randomized trials prescribe just 3 or 4 days of exercise each week, for only 3 to 12 months. Generally, the benefits of exercise are most demonstrable in older adults with low fitness and clinically significant functional limitations. However, a study of relatively healthy older adults, using a highly sensitive physical performance measure of functional limitations, found that 6 months of aerobic exercise and strength training caused a 14% improvement in functional limitations. These results suggest that relatively healthy adults experience some functional gains with exercise. Other studies suggest that, after an initial boost in function due to exercise, exercisers show a decline in function, but have a slower rate of loss than nonexercisers. There are too few studies to determine whether physical activity in sedentary older adults has a beneficial effect on disability (ability to do activities of daily life such as personal care and work).
An adult can achieve recommended levels of aerobic activity by doing either vigorous or moderate activity. The vigorous-intensity recommendation, developed in the 1980s, is to engage in at least 20 minutes of vigorous physical activity on 3 or more days each week. The moderate-intensity recommendation, published in 1995 by the Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM), is that “every US adult should accumulate thirty minutes or more of moderate intensity physical activity on most, preferably all, days of the week.” An alternative statement of the recommendation, which better communicates the meanings of some of its terms, is this: Adults should engage in a brisk walk, or an equivalently intense aerobic activity, for at least 10 minutes at a time, for a total of at least 30 minutes a day, on at least 5 days a week.
Several comments help to clarify these two recommendations. First, moderate-intensity physical activity is defined as aerobic activities that expend 3.0 to 6.0 METS (metabolic equivalents; ie, 4 to 7 kcal/min). The standard example of a moderate-intensity activity is brisk walking at 3 to 4 miles per hour. Vigorous activities, such as running, expend more than 6.0 METS. Many activities allow a broad range of intensity of effort, so they can be performed as either moderate or vigorous activities, including cycling, swimming, backpacking, skiing, stair climbing, and volleyball. Second, only activity bouts of at least 10 minutes in duration count toward meeting either recommendation. Third, any physical activity, not just exercise, can count toward meeting the recommendations, including occupational activity, leisure-time activity, domestic activity such as gardening, and transportation activity. Fourth, daily physical activity is preferable, in part because there are beneficial acute effects of physical activity such as reduction in blood pressure. Daily activity is also recommended on the basis of the philosophy that the body is designed to be active every day. Finally, greater amounts of physical activity produce greater health benefits. It is inappropriate to cite the recommendations as meaning that “a person only needs 30 minutes a day.”
Despite some evidence that vigorous activity has greater health benefit and some evidence that even low-intensity activities have benefit, the recommendations reflect consensus that moderate intensity is the minimum threshold for substantial health benefits. Despite the fact “more is better” and that a minimum of 60 minutes of moderate activity has been suggested, the recommendations reflect consensus that substantial health benefits accrue from 30 to 60 minutes of moderate activity.
Adults should perform resistance training activities of the major muscle groups on 2 or 3 days each week, with at least 48 hours of rest in between. For all adults, ACSM recommends resistance training of moderate intensity that is sufficient to develop and maintain muscular fitness and fat-free mass. Selected adults may prefer high-intensity training instead. Dynamic resistance training (as opposed to static training) is recommended for most adults.
Activities that develop and maintain musculoskeletal flexibility and that are performed a minimum of twice a week are recommended. Unlike aerobic activities and resistance training, flexibility training by itself does not have substantial health benefits. It is recommended because regular physical activity requires an adequate range of motion, and flexibility training permits and facilitates the types of physical activity that have health benefit.
Unlike aerobic activity, resistance training, and flexibility training, balance training is not recommended for all adults. Balance training is currently recommended only for adults at increased risk of falls, as explained below.
Older adults are the least active age group. In 2001, 11% of adults aged 65 and over reported strength training activities at least twice a week, and only 6% met both strength training and aerobic recommendations. However, trend data show increasing levels of physical activity in older adults over time. In 1990, 30% of adults aged 75 and over met either the strength training or aerobic recommendation, compared with 35% in 2000. In 1988, 41% of adults aged 70 and over were sedentary (reported no leisure-time physical activity), compared with 30% in 2002.
The vast majority of sedentary and insufficiently active older adults should gradually increase moderate aerobic activity, especially walking, so as to meet the recommendation for moderate intensity. Moderate exercise is associated with lower cardiovascular risk, lower risk of musculoskeletal injury, and, in comparison with vigorous exercise, a higher adherence to training. Most older adults prefer moderate-intensity activities. A target between 30 and 60 minutes of moderate activity on 5 to 7 days each week is appropriate for most older adults.
The traditional emphasis on walking for older adults is appropriate. The obvious advantages of walking are that it requires no special skills, equipment, or facilities. The risk of injury is relatively low. One study has reported that higher amounts of walking are not associated with a higher injury risk. Walking is the most common physical activity reported by older adults.
Age-related decreases in skeletal muscle mass and quality, termed sarcopenia, contribute to functional limitations and dependence in older adults. Sarcopenia is more than just disuse atrophy, as even highly trained athletes lose muscle mass with age. The biologic mechanisms for sarcopenia are incompletely understood. Neurogenic mechanisms may involve the loss of neurons for a variety of reasons, such as exposure to heavy metals, loss of blood supply, and mechanical damage. Denervated muscle fibers can be reinnervated by axonal sprouting of remaining motor neurons, but the process appears to be incomplete, so that cycles of denervation and reinnervation result in net loss of fibers. Myogenic mechanisms include the possibility that repair processes for contraction-induced muscle damage are impaired with aging. General mechanisms of cell damage may involve skeletal muscle, including damage of skeletal muscle mitochondria by free radicals.
Epidemiologic studies report that regular physical activity reduces age-related loss of muscle mass. Randomized controlled trials have demonstrated that resistance training increases muscle mass and thereby counteracts sarcopenia. Early studies of resistance training prescribed vigorous training similar to that prescribed for young adults. Subsequently, it has been demonstrated that less training has both physiologic effects on muscle function and health benefits. Larger gains in strength are typically reported by studies using weight machines. For older adults with good fitness, weight machines are usually the most feasible and safest training method. Randomized trails have also tested resistance training programs that use body weight or free weights, such as weight cuffs or dumbbells. These programs are more appropriate for adults with lower fitness levels, where lower amounts of weight provide adequate exercise stimulus. In theory, resistance in a home-based program can be adjusted on the basis of the progressive overload principle, and, given sufficient repetitions, strength should increase steadily. In practice, these programs typically report smaller gains in strength.
With older adults, there is more emphasis on doing the minimum amount of all recommended types of activity: aerobic activities, resistance training, flexibility training, and (if at increased risk of falling) balance training. It is appropriate to encourage older adults to join exercise classes that mix aerobic, resistance, and flexibility training.
The traditional guidance to increase level of physical activity gradually over time is highly appropriate for older adults. Injury risk is minimized, and the experience is more pleasant. Focus group studies report that older adults view increasing physical activity as an extremely difficult task. It is appropriate to break this task up into stages, with intermediate goals. Adults with lower fitness should be permitted more time to adapt to each stage.
Older adults should be strongly encouraged to reduce sedentary behavior and get some activity each week, even if less than the minimum recommended. Illustrative of the dose-response relationship of activity and health, many studies show that levels of activity below minimum recommendations have health benefits in older adults.
For many older adults, exercise has a therapeutic role in one or more chronic conditions, as well as its traditional preventive role. Most commonly, integrating preventive and therapeutic recommendations involves essentially following public health recommendations, with specific preferences for modes of activity. For example, aquatic exercise classes are chosen for adults with arthritis, weight-bearing exercise is chosen for adults with osteoporosis, and rotation of exercise modes is chosen for adults with obesity to minimize risk of orthopedic injury. As chronic conditions become more severe, therapeutic considerations typically are the main determinants of the activity recommendation, such as pulmonary rehabilitation for adults with moderate to severe lung disease.
For aerobic activities, a different definition of intensity is necessary for adults with low fitness. Intensity is defined, not as absolute energy expenditure in METS, but relative to the person’s level of fitness, as judged by the heart-rate response to exercise. Moderate-intensity activity has a heart-rate response in the range of 55% to 69% of maximal heart rate (220 – age for men; 220 – [0.6 × age] for women), and vigorous intensity is the range greater than 69% of maximal heart rate. With this definition of intensity, unfit older adults need not do a brisk walk or equivalently intense activity to meet the moderate recommendation. Rather, the person should walk at a speed that causes a heart rate response in the range of moderate intensity.
Physical activity should be increased very gradually in adults with low fitness. Initially, short bouts of activity are appropriate. Activity bouts less than 10 minutes are acceptable. It is not necessary to specify a minimum heart rate.
Older adults in community-based long-term-care programs and residents of long-term-care facilities benefit from physical activity. Supervised classes of a few months’ duration cause improvements in fitness and functional limitations, even in older adults who are physically frail or who have incontinence or mild dementia. Physical activity may improve sleep and decrease agitation. Exercise programs for nursing-home residents may include strength training, even high-intensity training. Randomized trials show strength training to be safe, increase strength, improve functional limitations, and increase amount of spontaneous activity.
The obesity epidemic has placed a great deal of attention on the role of physical activity in maintaining a healthy body weight. Public health recommendations advise that weight loss should be achieved by both reducing caloric intake and increasing energy expenditure. Possibly, regular physical activity during weight loss may be more important for older adults. Obesity increases the risk of many chronic diseases and of functional limitations in older adults, but it also has the beneficial effects of increasing bone and muscle mass. Weight loss is accompanied by loss of bone and muscle mass. Exercise during weight loss, particularly resistance training, should theoretically reduce loss of bone and muscle mass. For older adults advised to lose weight, a reasonable approach is to meet the moderate recommendations for 30 minutes or more and to limit caloric intake. Physical activity level then can be gradually increased as necessary to achieve and maintain a healthy weight.
Regular physical activity by older adults has a modest effect in slowing age-related loss of bone mass. Evidence indicates that resistance and high-impact exercises are most beneficial. Weight-bearing aerobic activities can also provide the mechanical loading that maintains bone mass.
In older adults at increased risk for falling, randomized trials demonstrate that falls can be prevented by multicomponent interventions targeting factors such as sedative use, environmental hazards, and poor balance. Increasing physical activity is regarded as an effective component of falls prevention programs. Solid evidence of the effectiveness of exercise in falls prevention comes from a meta-analysis of a series of exercise studies in New Zealand, which reported that exercise reduces both falls and fall injuries by 35% to 45%. One meta-analysis of randomized trials reported that aerobic activity, resistance training, and balance training are all associated with reduced risk of falling. Balance training is specifically recommended in clinical practice guidelines for falls prevention in adults at increased risk. There is no experimental evidence that exercise reduces either total fractures or hip fractures. However, a meta-analysis of epidemiologic studies reported that physical activity reduces the risk of hip fracture by up to 50%.
A variety of balance training interventions have been studied. Some exercises focus on maintaining balance over a narrow base of support, such as a tandem stand or one-leg stand. Other exercises train dynamic balance, such as ability to do a tandem walk. Some programs have separate balance exercises. Others propose that some stretching and strengthening exercises be done in a manner that also improves balance. An example of the latter is the program described in the books Exercise: A Guide from the National Institute on Aging (http://www.niapublications.org/exercisebook/index.asp) and Exercise: Getting Fit for Life (http:www.niapublications.org/engagepages/exercise.asp).
Balance training is typically designed so that exercises are graduated in difficulty, and adults progress to more difficult exercise as training improves balance. For example, a tandem walk is easiest when holding on to a table and becomes progressively harder with arms in any position, arms close to the body, and arms close to the body while holding a weight.
Tai Chi Chuan is often mentioned as a form of exercise that improves balance and prevents falls. Although the original study of Tai Chi reported almost a 50% reduction in falls, a follow-up study reported a (nonsignificant) 25% reduction. A reasonable summary of the evidence is that Tai Chi remains a promising intervention that is popular, fun, and social, and it is appropriate for the balance training component of a falls prevention program.
Although the benefits of physical activity far outweigh the risks, promoting physical activity should include strategies for minimizing risk. The main risk of physical activity is musculoskeletal injury. Several factors affecting musculoskeletal injury risk are modifiable and offer opportunities for risk management. The risk of injury is higher with vigorous exercise, with higher volume of exercise, and with obesity. The risk of injury is less with higher fitness, supervision, protective equipment such as bike helmets, and in well-designed exercise environments. The principle that physical activity should be increased gradually over time is widely regarded as critical for reducing risk of injury. Vigorous activity, such as running and participation in vigorous sports, should be recommended only to older adults who are accustomed to these activities or who have sufficient fitness, experience, and knowledge to perform vigorous activities and prevent injuries associated with them. ACSM recommends that older adults begin resistance training with one set of 10 to 15 repetitions of each exercise, rather than the 8 to 12 repetitions for younger adults. To complete more repetitions, training must begin with less resistance (relative to maximal strength), which should reduce injury risk.
The risk of both exercise-related myocardial infarction and sudden death is greatest in individuals who are the least active. Sedentary adults should avoid isolated bouts of vigorous activity and should increase activity gradually over time.
A general clinical approach to promoting physical activity is shown in Figure 8.1. Healthy People 2010 recommends that clinicians counsel physically inactive adults to increase their physical activity level. However, the U.S. Preventive Services Task Force regards the efficacy data on counseling as difficult to interpret. A wide variety of interventions have been studied, and the results are mixed. The U.S. Preventive Services Task Force has recommended high-intensity counseling about diet and exercise, together with behavioral interventions, for obese adults with a body mass index of 30 or greater.
One clinical approach to promoting physical activity is to adopt the 5-A framework (assess, advise, agree, assist, and arrange), which has been used in behavioral interventions such as smoking cessation. Because of the importance of physical activity, the clinician assesses an older patient’s level of physical activity at least once a year and provides a specific recommendation about physical activity. The clinician and patient collaboratively agree on goals for physical activity. The clinician provides assistance. Counseling is one option; other options include self-help materials, referral to community programs, and referral to medically supervised programs.
Older adults typically feel overwhelmed by recommendations calling for substantial and immediate life-style changes. A stepwise approach is often appropriate. It allows the person to take small steps toward a tangible goal and feel rewarded upon meeting it, before moving on to the next, more ambitious goal.
Pedometers have become popular in promoting walking. Pedometers can be useful in providing feedback and monitoring progress toward physical activity goals. However, it is not appropriate to prescribe a universal step goal, such as 10,000 steps a day. Recommendations specify a minimum bout of 10 minutes, so many of the steps recorded by a pedometer do not count toward physical activity recommendations. Further, pedometers can miscount steps in older adults with slower gaits. However, some adults find step counters to be helpful in tracking activity levels and use them appropriately to ensure that every day includes an adequate amount of brisk walking. Some weight-management approaches use bouts of activity less than 10 minutes or low-intensity activity, or both, to increase caloric expenditure. Pedometers can be useful in tracking progress to caloric expenditure goals.
Research highlights the importance of the physical and social environment in promoting physical activity. Studies report that people with access to recreational facilities are twice as likely to get recommended levels of physical activity. People are more likely to commute to work by bicycle or by walking if they live in a city center with a variety of destinations, such as grocery stores and restaurants, and have good access to public transportation. The medical care system should work in tandem with the community to promote environments that encourage physical activity. Clinicians should be aware that there are effective community-level interventions to promote physical activity. The Guide to Community Preventive Services identifies six recommended or strongly recommended community-level interventions proven effective in increasing physical activity. These are community-wide campaigns, prompts to increase usage of stairs, individually adapted behavior change programs implemented in groups of adults, school-based physical education, interventions that increase nonfamily social support such as programs that arrange walking groups, and enhanced access to recreational facilities (eg, parks and trails) combined with outreach to promote awareness of facilities.
■ Balfour JL, Kaplan GA. Neighborhood environment and loss of physical function in older adults: evidence from the Alameda County Study. Am J Epidemiol. 2002;155(6):507–515.
The main focus of this report was to provide evidence that environmental factors influence functional limitations in older adults. The study found that six neighborhood problems (traffic, noise, crime, trash and litter, lighting, and public transportation) were associated with higher risk of loss of physical function over 1 year. More neighborhood problems were also associated with lower physical activity levels. Like other cohort studies, the study also found that higher levels of physical activity were associated with lower risk of disability. The study suggests the neighborhood environment affects the risk of loss of physical function in older adults, and one mechanism by which the environment affects function is by influencing physical activity levels.
■ Nelson ME, Layne JE, Bernstein MJ, et al. The effects of multidimensional home-based exercise on functional performance in elderly people. J Gerontol A Biol Sci Med Sci. 2004;59(2);154–160.
A genre of community exercise programs for older adults has become popular over the past decade. These programs include strength training using body weight, cuff weights or dumbbells or both, balance training, aerobic activities that do not involve expensive equipment, and stretching exercises. As these programs do not require a gym or fitness facility, they can be done at home or in settings like senior centers. This randomized trial of one such program, in 72 adults aged 70 years and over, illustrates that these programs can have beneficial effects. The study found that 6 months of home-based exercise improves dynamic balance and functional performance, as measured by the Physical Performance Test and the Established Population for Epidemiologic Studies of the Elderly (EPESE) short physical performance battery.
■ Penninx BW, Messier SP, Rejeski WJ, et al. Physical exercise and the prevention of disability in activities of daily living in older persons with osteoarthritis. Arch Intern Med. 2001;161(19):2309–2316.
This report from the Fitness Arthritis and Seniors Trial (FAST) appears to provide the first data from a randomized trial that exercise by sedentary older adults reduces the incidence of disability. The study recruited adults aged 60 and over with knee osteoarthritis and free of activities of daily living (ADL) disability; it randomized participants to 18 months of aerobic exercise, resistance exercise, or attention control. Risk of incident disability during follow-up was reduced by both aerobic exercise (relative risk = .60) and by resistance training (relative risk = .53). Lowest risk of ADL disability was associated with the highest adherence to exercise. These data support the value and importance of both aerobic training and strength training in older adults.
■ Tanasescu M, Leitzmann MF, Rimm EB, et al. Exercise type and intensity in relation to coronary heart disease in men. JAMA. 2002;288(16);1994–2000.
This report from the Health Professionals’ Follow-up Study analyzed the relationship between physical activity and risk of coronary heart disease (CHD) in 44452 U.S. men aged 40 through 75 at the start of the study. After 12 years of follow-up, the study reported that total physical activity, running, weight training, and walking are each associated with reduced risk of CHD. The results illustrate some themes of physical activity and health. First, moderate-intensity walking has health benefits. Second, both moderate and vigorous aerobic activities have health benefits, though vigorous aerobic activity has greater benefit. Third, there is increasing evidence for the benefit of resistance training on CHD risk. Fourth, the beneficial effects of physical activity on health are independent of other risk factors. In particular in this study, effects were found to be independent of body mass index. Finally, cardiovascular disease risk decreases with volume of aerobic activity over a wide range of volume.
David M. Buchner, MD, MPH