Mediation analysis of fundamental movement skills, physical activity, fitness, and BMI in primary school children

Abstract This study aims to investigate the relationship between fundamental movement skills (FMS) and moderate-to-vigorous physical activity (MVPA) in children, with physical fitness (PF) and body mass index (BMI) as potential mediating factors. The sample included 1014 Portuguese children (540 girls) aged 6–10 years from the REACT project. MVPA was measured using wrist-worn accelerometers over 7 days. BMI z-scores were calculated. PF assessment included: standing long jump, handgrip strength, shuttle-run, 50-yard dash, and pacer; all test scores were standardized and summed to generate an overall PF score. The Meu Educativo platform was used to assess five object control FMS. FMS were factor analyzed and derived factor scores were standardized to generate an overall FMS score. A serial mediation model was tested. Showed a significant total effect of FMS on MVPA (b = 10.574, SE = 1.059, p < 0.001). PF was the principal specific mediator of the FMS-MVPA relationship (b = 2.748, SE = 0.559, p < 0.001). BMI did not mediate this association independently (b=-0.181, SE = 0.139, p > 0.05). However, the serial pathway through PF followed by BMI (FMS -> PF -> BMI -> MVPA) was statistically significant, though smaller in magnitude (b = 0.395, SE = 0.134, p < 0.05). Together, PF and BMI mediated 28.0% of the FMS-MVPA relationship. FMS was associated with MVPA directly and indirectly, primarily through PF, with BMI playing a role only within the sequential PF-to-BMI pathway.