Background: Evidence has indicated the health importance of fundamental movement skills (FMS) and physical activity (PA) in children and their relationships seems bidirectional. However, their bidirectional relationship has not yet been fully answered in the literature. Aim: This study sought to determine bidirectional relationship between FMS and PA in children using cross-lagged study design. Methods: A total of 183 second-level students (8.8 ± 1.1 years old) from three primary schools in Henan Province, China were selected as subjects. The average number of steps per school day was used as the amount of PA in the school environment; the third edition of the test of gross motor development was used for FMS testing. The baseline data (T1) and tracking data (T2) were collected at the beginning and end of the fall semester, respectively. The two tests were separated by 3 months (11 weeks), and a cross-lag model analysis was performed. Based on the hypothetical model, we tested the cross-lag effect of children’s PA and FMS. Results: The model fit index was χ2/df = 2.861 (p < 0.001, n = 183); goodness of fit index GFI = 0.900; NFI = 0.909; CFI = 0.931 and the 95%CI was between 0.071−0.192. The RMSEA = 0.063, and the standardized residual root mean square SRMR = 0.029. The T1 FMS can be used to predict the number of steps in the T2 teaching days with statistical significance (β = 0.22, 95% CI: 0.07−0.38, p = 0.003). However, the T1 steps cannot be used to predict the T2 FMS (β = 0.05, 95% CI: 0.07−0.13, p = 0.475). Further analysis shows that the main contributor to these relationships are ball skills in the FMS. Conclusions: The relationship between children’s fundamental movement skills and PA is not two-way. Students with higher FMS are expected to reach higher levels of PA after undergoing school PA in a teaching cycle. The PA of the students can be improved by improving their motor skills, which further improves their physical and mental health.
Keywords: children; cross-lag model; fundamental movement skills; physical activity; quasi-experimentation design; test of gross motor development.