Association Between Sitting, Screen Time, Fitness Domains, and Fundamental Motor Skills in Children Aged 5-16 Years: Cross-Sectional Population Study.

BACKGROUND: To examine the associations between school-age children's sedentary behavior, screen time, and 3 physical activity attributes: muscular strength, cardiorespiratory endurance (CRE), and fundamental movement skills.
METHODS: Cross-sectional survey of 2734 children in years 2 and 4 and 3671 adolescents in years 6, 8, and 10. Total sitting time, 6 screen time behaviors, and physical activity were measured by self-report. Muscular strength was assessed by standing broad jump; CRE by 20-m shuttle run test; and fundamental movement skills by process-oriented checklists. Associations between incremental sitting and screen time (in hours) and meeting the healthy zone of physical activity attributes were examined using logistic regression.
RESULTS: After adjusting for covariates and physical activity, children had lower odds of achieving the healthy zone for muscular strength and CRE for each hour of week (but not weekend) screen time. For adolescents, each hour of screen time per day was associated with lower odds of achieving the healthy fitness zone for CRE, locomotor skills, and overall healthy zone, and each hour of weekend screen time was associated with lower odds of achieving the healthy zone for most attributes and overall healthy zone. The associations were slightly stronger among adolescent girls than boys. The findings were similar for total sitting time.
CONCLUSIONS: Screen time was associated with a lower likelihood to achieve healthy zones of physical activity attributes, and the effect was more consistent and slightly stronger among adolescents than children. This may suggest that the negative effects of screen time are incremental, emerging during adolescence.