Background: Existing evidence regarding how time spent on various types of sedentary behavior (SB) in relation to physical fitness (PF) and academic performance (AP) in children and adolescents is limited. This cross-sectional study aimed to explore the associations of SB types with PF and AP among 8-19-year-old Chinese students. Methods: A total of 1164 students were recruited from five schools in Zhejiang province, China. Children's SB was assessed by a valid questionnaire and AP was represented by scores on four courses. PF was measured by Chinese National Student PF Standard battery. The associations were assessed using linear mixed-effects models adjusted for age, school, grade, and class. Results: Students' screen-based SB was observed to be negatively associated with PF in girls (p < 0.05). Screen-based SB was inversely associated with AP in both girls and boys (p < 0.001). The significant interaction between weekdays and weekends, and SB on AP was observed in girls (p < 0.001). On weekends, screen-based SB ≥ 6 h/day (<3 h/day as reference group) was significantly and negatively associated with AP (p < 0.01 for both sex). Conclusions: Longer screen-based SB, especially on weekends, was related to poorer AP in 8-19-year-old Chinese students. Our findings suggest that restrictions on any type of screen-based SB for leisure on weekends are beneficial to AP in Chinese students.
Keywords: academic achievement; cardiorespiratory fitness; children; screen time; sedentary lifestyle.