Dr. Laura Talbot, Associate Professor of Nursing, Texas Christian University and now at Johns Hopkins University has worked with us to examine what contribution physical activity has on cardiovascular fitness as estimated by VO2max. Based on currently accepted estimates of oxygen utilization for specific physical activities, the time BLSA 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). Univariate analysis found that 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 there 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. The Physical Functioning Inventory (PFI) was developed by the laboratory to assesses self-reported functioning in 5 areas: Activities of Daily Living, Instrumental Activities of Daily Living, Mobility, and Moderate and Strenuous Activity. The goal was to develop an instrument that would be sensitive to early functional changes across the life span, and would detect how individuals modify how they do activities as they age. The questionnaire has been used to study inactive BLSA participants, and to compare them to the active population. Functional changes are found to begin by age 50 in many of our participants. The early changes are not disabling, but require modifications in how some activities are accomplished. In all 5 areas, partially active BLSA participants have higher levels of difficulty than fully active participants, but the difference increases with age, particularly after age 75. The largest differences were observed in the IADL and ADL categories. Women report relatively more difficulty, especially in activities dependent on upper body strength. Studies are underway to examine the relationship of physical activity to physical functioning (PFI) and mortality. The goal is to define, where possible, the levels of physical activity required to minimize functional limitations and maximize longevity.
