Accelerometer based independent and combined associations of physical activity and sedentary time on physical fitness in preschool children: a cross-sectional study

To investigate the independent and combined associations between total physical activity (TPA) and sedentary time (ST) using accelerometer on physical fitness in preschool children. A cross-sectional study involving 375 participants (211 boys, and 164 girls) was conducted. Participants were classified as low- or high-active according to the PA guidelines of 180 min/day of TPA and low- or high-sedentary based on the median ST per day. Low active/high sedentary, low active/low sedentary, high active/high sedentary, and high active/low sedentary groups were created. The physical fitness composite Z-score (fitness score) was created from the 20 m shuttle run, musculoskeletal fitness (handgrip and standing long jump), and 2 x 10 m shuttle run tests. Data shown TPA was positively related to the 20 m shuttle run, musculoskeletal fitness, and the fitness score (P < 0.05). Regression of TPA on the fitness score was weak (beta, 0.01; 95% CI, 0.00, 0.01). The high active/low sedentary Group had the highest odds of higher handgrip strength, musculoskeletal fitness, and fitness score. Classification as high active/low sedentary increased the probability of a high fitness score by 30% (beta, 0.30; 95% CI, 0.07, 0.54). Both increasing TPA and reducing ST is essential for promoting physical fitness in this population. The trial registration number is ChiCTR-OOC-15,007,439, and the date of registration is 10/27/2015.