Predictors of low physical fitness in a cohort of active-duty US Air Force members

Background: Each branch of the U.S. armed forces has standards for physical fitness as well as programs for ensuring compliance with these standards. In the U.S. Air Force (USAF), physical fitness is assessed using submaximal cycle ergometry to estimate maximal oxygen uptake (VO2max). The purpose of this study was to identify the independent effects of demographic and behavioral factors on risk of failure to meet USAF fitness standards (hereafter called low fitness). Methods: A retrospective cohort study (N=38,837) was conducted using self-reported health risk assessment data and cycle ergometry data from active-duty Air Force (ADAF) members. Poisson regression techniques were used to estimate the associations between the factors studied and low fitness. Results: The factors studied had different effects depending on whether members passed or failed fitness testing in the previous year. All predictors had weaker effects among those with previous failure. Among those with a previous pass, demographic groups at increased risk were toward the upper end of the ADAF age distribution, senior enlisted men, and blacks. Overweight/obesity was the behavioral factor with the largest effect among men, with aerobic exercise frequency ranked second; among women, the order of these two factors was reversed. Cigarette smoking only had an adverse effect among men. For a hypothetical ADAF man who was sedentary, obese, and smoked, the results suggested that aggressive behavioral risk factor modification would produce a 77% relative decrease in risk of low fitness. Conclusions: Among ADAF members, both demographic and behavioral factors play important roles in physical fitness. Behavioral risk factors are prevalent and potentially modifiable. These data suggest that, depending on a member's risk factor profile, behavioral risk factor modification may produce impressive reductions in risk of low fitness among ADAF personnel.