Physical inactivity and low physical fitness are important causes of morbidity and mortality in the US and in other industrialized countries. Population attributable risk calculations provide estimates of 35% of coronary heart disease, 32% of colon cancer, and 35% of adult-onset diabetes mellitus attributable to sedentary habits.1 In addition, inactivity also may contribute to high rates of prostate and breast cancer, hypertension, obesity, and mood disorders.2 The effect of physical inactivity on all-cause and cardiovascular disease mortality is observed in all adult age-groups, including individuals more than 70 years of age.3, 4 Presumption of a causal relation between inactivity and mortality is strengthened by recent reports showing substantial reductions in death rates in men who converted from a sedentary or unfit way of life to being active and fit, and this benefit was seen in all age groups.5, 6 In these reports, improving low activity or fitness was associated with as great a reduction in death rates as did smoking cessation. The risk of death associated with functional limitation is high in older adult populations. In a representative sample of noninstitutionalized older adults, risk of dying was 2.5 times higher in persons aged 70 to 79 who were functionally limited (limited in at least one activity of daily living) when compared with those who had no limitations.7 There are numerous causes of functional limitation: stroke, emphysema, arthritis, senile dementia, and other chronic diseases and conditions that may lead to loss of independence. It is, however, becoming evident that decades of sedentary living leading to low physical fitness also take their toll on functional limitations. Sedentary older men and women participating in the Longitudinal Supplement of Aging of the National Health Interview Survey had higher rates of disability during a 2-year follow-up than did their more active peers.8 More recently, the 1994 National Health Interview Survey found that 38% of persons aged 65 and older had at least one functional limitation.7 See also pp 489 and 498 The public health impact of such a large percentage of functionally limited older adults will grow as the number of older adults increases during the coming decades. We can expect to see a greater demand for home-care programs, adult day care programs, and, ultimately, long-term care facilities. Effective yet inexpensive community-based programs that promote retention of strength, balance, and overall physical functioning are needed to reduce rates of functional limitation and subsequent dependency in older adults. There are at least three separate components of physical fitness that appear to be important for preservation of function: muscular strength, aerobic power, and balance. These fitness components can be improved by physical training in older individuals. Preliminary analyses in the Aerobics Center Longitudinal Study (ACLS) suggest that low levels of both aerobic power9 and musculoskeletal fitness10 are associated with higher rates of self-reported limitations when compared with active and fit individuals. Fiatrone and colleagues show that muscular strength is doubled with high-intensity resistance strength training as late as the tenth decade of life.11 Substantial increases in aerobic power are seen in older men and women who change from being inactive to participating in even moderate amounts and intensities of physical activity.12, 13 There are fewer training studies in older individuals for balance than there are for aerobic power and strength, but it also appears that this fitness component responds to appropriate interventions.14 Most of the training studies to improve muscular strength, aerobic power, and balance in older men and women have been conducted in controlled laboratory settings. These interventions usually required expensive and technically sophisticated equipment and highly qualified staff. Thus, the question of broad generalizability of these interventions must be raised. If specialized equipment and staff are required for physical training of older persons, it is unlikely that the majority of those who might benefit will be served. The studies by Wolf et al. and Wolfson et al. in this issue provide hope that relatively simple community-based interventions might improve or maintain function in older men and women.15, 16 These two reports are characterized by excellent methods. Both were randomized controlled trials, data collection staff were blinded to study group assignment of participants, and standardized tests and assessments were used. Both studies used computer-assisted balance training and Tai Chi exercise either as a primary15 or maintenance16 intervention. The principal advantage of Tai Chi exercise is that it is a low technology approach to conditioning that can be implemented at relatively low cost in widely distributed facilities throughout the community. Convenience can be maximized and costs for staff and equipment minimized. The results of the Atlanta and Connecticut studies add to the growing body of evidence regarding the efficacy of Tai Chi interventions in improving or maintaining function in older individuals. The design and methods of these two studies address weaknesses of some earlier reports, thus increasing confidence in the benefits of Tai Chi intervention. The main findings are that Tai Chi can help maintain strength and balance gains achieved by more intensive laboratory training16 and reduce the risk of multiple falls.15 Thus, Tai Chi appears to influence favorably two important physical fitness traits: balance and strength. It is unfortunate that neither study had an adequate measure of aerobic power, but other reports suggest that Tai Chi also affects this important fitness component.17 Several recent pronouncements from groups such as the American Heart Association,18 the American College of Sports Medicine/Centers for Disease Control and Prevention,19 World Health Organization,20 World Forum on Physical Activity,21 and the National Institutes of Health22 emphasize the public health importance of high levels of physical inactivity and low levels of physical fitness. Most of these reports focus on aerobic exercise and chronic diseases such as hypertension, coronary heart disease, adult-onset diabetes mellitus, and colon cancer. The accumulating evidence on activity, fitness, and function in older men and women, as exemplified by the Wolf et al. and Wolfson et al. reports, suggests that consensus conferences and statements addressing these important issues are needed.
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Blair et al. (1996) studied this question.