Sex-specific associations of moderate and vigorous physical activity with physical fitness in adolescents

The present study examined the sex-specific associations of moderate and vigorous physical activity (VPA) with physical fitness in 300 Japanese adolescents aged 12-14 years. Participants were asked to wear an accelerometer to evaluate physical activity (PA) levels of various intensities (i.e. moderate PA (MPA), 3-5.9 metabolic equivalents (METs); VPA, 6 METs; moderate to vigorous PA (MVPA), 3 METs). Eight fitness items were assessed (grip strength, bent-leg sit-up, sit-and-reach, side step, 50m sprint, standing long jump, handball throw, and distance running) as part of the Japanese standardised fitness test. A fitness composite score was calculated using Japanese fitness norms, and participants were categorised according to their score from category A (most fit) to category E (least fit), with participants in categories D and E defined as having low fitness. It was found that for boys, accumulating more than 80.7min/day of MVPA may reduce the probability of low fitness (odds ratio (ORs) [95% confidence interval (CI)]=0.17 [0.06-0.47], p=.001). For girls, accumulating only 8.4min of VPA could reduce the likelihood of exhibiting low fitness (ORs [95% CI]=0.23 [0.05-0.89], p=.032). These results reveal that there are sex-specific differences in the relationship between PA and physical fitness in adolescents, suggesting that sex-specific PA recommendation may be needed to improve physical fitness in adolescents.