The joint associations of physical activity, sedentary time, and sleep on V{dot}O2max in trained and untrained children and adolescents: A novel five-part compositional analysis

The benefits of physical activity (PA) and the negative impacts of sedentary time (SED) on both short- and long-term health in youth are well established. However, uncertainty remains about how PA and SED jointly influence maximal oxygen uptake (VO2max). Therefore, the aim of this study was to determine the joint influence of PA and SED on peak VO2 using compositional analyses. 176 adolescents (84 girls, 13.8 {+/-} 1.8 years) completed an incremental ramp test, and supramaximal validation bout, on cycle ergometer with PA and SED recorded for seven consecutive days on the right hip using a ActiGraph GT3X accelerometer. Time spent in sleep, SED, light, moderate and vigorous PA was analysed using a compositional linear regression model. Compositions with 10 minutes more time in vigorous PA (> 27.5 mins{middle dot}day-1) compared to the average 17.5 mins{middle dot}day-1 were associated with a + 2.9% - 11.1% higher absolute and allometrically scaled peak VO2. Whereas compositions with less (> -10 mins{middle dot}day-1) VPA were associated with a reduced absolute and allometrically scaled VO2max (-4.6% - 24.4%). All associations were irrespective of sex, maturity, and training status. The proportion of time spent sedentary had little impact on absolute and scaled peak VO2 (0.01 - 1.98%). These findings therefore highlight that intensity of PA may be of greater importance for increases in VO2max than reductions in SED and should be incorporated into future intervention designs.