Physical fitness status and associated determinants among Chinese children aged 9–12 years in Shandong province: a population-based cross-sectional study

Children's physical fitness is a critical determinant of lifelong health, yet comprehensive investigations into its multi-level influencing factors remain limited, particularly in developing regions. Guided by the Ecological Model of Health Behavior, this cross-sectional study assessed the physical fitness status and associated determinants among 29,856 children aged 9-12 years in Shandong Province, China. Data were obtained from two primary sources: (1) standardized physical fitness assessments based on the National Physical Fitness Standards for Students of China (Revised 2014), and (2) validated questionnaires capturing individual behaviors, family environments, and lifestyle factors across multiple ecological levels. The physical fitness test qualification rate was adopted as the primary outcome indicator. Multivariable logistic regression analyses revealed that parental support for physical activity (OR = 0.297, 95% CI: 0.266-0.332), moderate-intensity exercise (OR = 0.872, 95% CI: 0.763-0.997), daily breakfast consumption (OR = 0.765, 95% CI: 0.626-0.936), and adequate sleep (6-8 h/day, OR = 0.569, 95% CI: 0.499-0.649) were significant protective factors for physical fitness test qualification. In contrast, daily exposure to secondhand smoke (OR = 1.212, 95% CI: 1.078-1.362), prolonged screen time (> 3 h/day, OR = 1.712, 95% CI: 1.496-1.958), and excessive academic burden (> 3 h/day, OR = 1.294, 95% CI: 1.158-1.447) were associated with increased risks of non-compliance. These findings underscore the multi-layered influences of personal behaviors, family dynamics, and environmental contexts on children's physical fitness, consistent with the socio-ecological framework. This study provides robust empirical evidence for the development of comprehensive, multi-sectoral interventions targeting child health promotion in school-aged populations.