Mediating Effects of Fitness and Motor Competence on Children’s Executive Functions: Findings from the Learning to Lead Cluster Randomized Controlled Trial

PURPOSE: The aim of this study was to examine the mediating effects of cardiorespiratory and muscular fitness (the fitness hypothesis) and motor competence (the skill acquisition hypothesis) on executive functions among children participating in the Learning to Lead fundamental movement skills intervention. METHODS: We conducted a two-arm cluster randomized controlled trial in 20 primary schools in New South Wales, Australia ( N = 946). Ten schools were allocated to the intervention condition and ten to the wait-list control condition. Children in the intervention condition participated in 12 × 30-min peer-led fundamental movement skill sessions over a 10-wk period. Cardiorespiratory fitness, muscular fitness, motor competence, inhibition, and cognitive flexibility were assessed at baseline and postintervention. The preregistered mediation analysis was conducted at the individual level within a structural equation modeling framework, using cluster-robust standard errors (SEs), to account for nonindependence of observations at the classroom level. RESULTS: None of the mediation effects were statistically significant. The intervention significantly improved inhibition ( β = 0.125, SE = 0.054, P = 0.021) but not cognitive flexibility ( β = 0.013, SE = 0.068, P = 0.845). The intervention improved cardiorespiratory fitness ( β = 0.14, SE = 0.051, P = 0.007) but not muscular fitness ( β = -0.02, SE = 0.062, P = 0.707) or motor competence ( β = 0.04, SE = 0.076, P = 0.568). Muscular fitness was associated with inhibition ( β = 0.13, SE = 0.035, P < 0.001), and motor competence was associated with inhibition ( β = 0.08, SE = 0.034, P = 0.017) and cognitive flexibility ( β = 0.12, SE = 0.030, P < 0.001) at postintervention. CONCLUSIONS: Changes in fitness and motor competence did not mediate the effect of the intervention on children's executive functions. However, the significant associations between mediators and executive functions offer partial support for both the "fitness" and "skill acquisition" hypotheses, suggesting their potential importance for children's cognitive development.