The Compositional Impacts of 2 Distinct 24-Hour Movement Behavior Change Patterns on Physical Fitness in Chinese Adolescents

Background: The study aimed to examine predicted differences of 2 different behavior change patterns on physical fitness (PF). Methods: Participants were 241 students (51% girls) aged 11-14 years from China. Light physical activity, moderate to vigorous physical activity (MVPA), and sedentary behavior (SB) were objectively measured. Sleep was obtained by subtracting from awake time. According to Chinese National student PF standards, 5 components of PF, including body mass index, cardiorespiratory fitness, speed, muscular explosive power and strength endurance, and flexibility, were assessed. The effects of different time reallocations between 24-hour movement behaviors on PF were estimated based on adjusted compositional multiple linear regression models with isometric log ratios. Results: Compared with MVPA substituting for the remaining behaviors, MVPA replacing SB or light physical activity produced more favorable changes on the comprehensive PF score, cardiorespiratory fitness, explosive power, and speed. MVPA replacing 30 minutes of SB was associated with favorable changes in PF (+1.9 [0.53, 3.18] points), 50-m run (-0.17 [-0.31, -0.04] s), long-distance running (-5.54 s [for girls]/7.25 s [for boys]). and long jump (+0.05 [0.01, 0.09] m). When sleep replaced SB, PF improved. Conclusions: MVPA substituting SB or light physical activity is a strategy with a greater improvement in PF.