Relations of moderate and vigorous physical activity to fitness and fatness in adolescents

Abstract

It is unclear how moderate and vigorous intensities of physical activity (PA) are associated with cardiovascular fitness (CVF) and percentage of body fat (%BF) in adolescents. We tested the hypothesis that vigorous PA, to a greater degree than moderate PA, would be associated with better CVF and lower %BF. This was a cross-sectional study of 421 black and white high school students (x age: 16 y). PA was measured with 5 d of accelerometry and expressed in min/d of moderate or vigorous PA. CVF was measured with a multistage treadmill test and was expressed as the oxygen consumption at a heart rate of 170 bpm. %BF was measured with dual-energy X-ray absorptiometry. Multiple regressions were used to determine the degree to which variance in CVF and %BF was explained by PA, after control for age, sex, race, and the sex x race interaction. A higher index for CVF was associated with higher amounts of moderate and vigorous PA; more variance was explained by vigorous than by moderate PA. Lower %BF was associated with higher amounts of vigorous PA but not with the amount of moderate PA. Black and white adolescents who engaged in relatively large amounts of free-living vigorous exercise were likely to be relatively fit and lean.