STUDY OF PHYSICAL ACTIVITIES IN THE BLSA

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Over the past year, we have reported the relationship between physical activity and cardiovascular fitness as estimated by VO2max. Based on currently accepted estimates of oxygen utilization for specific physical activities, the time Baltimore Longitudinal Study of Aging subjects spent doing 100 activities was converted to METS*minutes. METS is a standard way to express oxygen utilization that adjusts for body size. The 100 activities were then divided into three categories: low level activity (<4 METS), moderate level activity (4-6 METS), and high level activity (>6 METS). Cardiovascular fitness was significantly correlated with high level activity (r=.32), moderate level activity (r=.15), body size (BMI) (r=-.32), and age (r=-.58). In multivariate analysis with these variables, physical activity independently explained 1.6% of the variance in VO2max while sharing about 10% of the variance with age and BMI. Using the regression models, we estimate that for an average individual to increase their VO2max 10% requires 35-40 minutes a day of high level activity and 150 minutes a day of moderate level activity. These calculations support the general concept of the recent Surgeon General recommendations for daily physical activity. We have examined whether the level of cardivascular fitness or physical activity are independent risk factors for mortality in men. Cardiovascular fitness, as assesse by VO2max, is a strong independent contributor to both all cause and cardiac mortality. Physical activity is important, not to the same degree as fitness. Of interest, high intensity physical activity was an independent risk factor in older men (>60 years) but not younger men, while cardiovascular fitness was important at all ages. If physical activity is important for survival and fitness, should we judge the levels of activity based on an absolute scale, or on an age-adjusted scale. We have explored this question in the BLSA, and found that by using an absolute scale, there is an age-associated decrement in the levels of physical activity. Using an age-adjusted scale, the level of physical activity increases with increasing age. While relative scales may be of value in examining the relationships between activity and well being, they lead to the wrong conclusions regarding the physical capacity of the elderly.