Over the past several years, we have examined the relationship between physical activity and cardiovascular fitness as estimated by VO2max in the Baltimore Longitudinal Study of Aging subjects. Physical activity was assessed as the time reported being spent in approximately 100 activities. The time was converted to METS, 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). We estimated 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 examined the impact of national recommendations on leisure time physical activities (LTPA) in healthy men (n=1359) from 1958 to 1998 and in healthy women (n=840) from 1978 to 1998, who were participants of the Baltimore Longitudinal Study of Aging (BLSA). The prevalence of a sedentary lifestyle in each decade was assessed based on compliance with widely publicized recommendations for participation in physical activity. High intensity LTPA, defined as activities >6 METS, showed an increase in median daily values from the 1960s to the 1990s for men with most of the change between the 1960s and 1970s, but did not change between the 1970s and the 1990s in women. Moderate intensity LTPA, defined as 4-5.9 METS, did not change significantly over these periods in either sex. Adjustment for age, education and race did not affect these findings. The percentage of sedentary men, defined as those performing < 40 MET-minutes/day of high intensity LTPA, declined across the four decades whereas for women it did not change significantly. For those over 60 years old, time trends in high intensity LTPA resembled those for the entire sample with a significant increase in men but not in women. Thus, in healthy subjects across a broad age range, national recommendations appear to have made modest progress in decreasing the proportion of sedentary BLSA men whereas women have not changed. The importance of these secular changes can be found when examining whether the level of cardiovascular fitness or physical activity are independent risk factors for mortality. We were able to analyze these effects in BLSA men, but did not have enough deaths to adequately evaluate women. 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. How to increase participation in physical activity has become a major health issue. The answer will lie in offering a variety of programs that allow for individualization. A report is currently in press of an intervention that explored an alternative approach to increase activity in patients with osteoarthritis of the knee. In a pilot study, two groups of subjects were evaluated. The first participated in an educational program while the second had the educational program and in addition were supplied with a pedometer to assess their daily activities. The use of the pedometer was associated with an increase in the amount and speed of walking done by these patients. At present, a project is just beginning where we will take the same strategy and applying it to military reservist who do not meet fitness requirements for a 2 mile run. The goal is to increase their overall activity levels by making them more aware of what they are actually performing, and to set reasonable goals to increase activity during the course of their busy schedules.
