Temporal trends in physical fitness among Chinese children and adolescents from 2000 to 2019 and analysis of social-ecological factors.

This study aimed to estimate temporal trends in physical fitness (PF) by regions, age groups and nutritional status among Chinese children and adolescents and to longitudinally examine PF determinants based on social-ecological model. Participants (n = 68,265) aged 7-18 were from five successive national surveys (2000 to 2019). Six tested items of PF were calculated as PF indicator (PFI), which was used to divide participants into two categories: low vs. moderate/high. One-way analysis of variance was used to compare difference and change trend of PFI. Linear regression evaluated relationship between PFI and body mass index (BMI), and logistic regression assessed association between PFI and factors of behaviours and lifestyles on individual-, family- and school-level based on the social-ecological model. PFI declined sharply from 2000 to 2010, increased slightly from 2010 to 2014 and then edged down in 2019. Students with moderate BMI and students in urban areas tended to have higher PFI, and larger increase of PFI was found in students aged 7-9 and 13-15 after 2010. Several determinants on individual-, family- and school-level related to PFI. Efforts to develop PF mainly include increasing PA and reducing sedentary behaviours by facilitating home-school collaboration and emphasizing age-, region- and BMI-specific actions.