Effects of the FITKids Randomized Controlled Trial on Executive Control and Brain Function

221 children aged 7-9, individually randomized to a 9-month afterschool physical activity programme or wait-list control

Preadolescent US children aged 7-9

Individually randomized 9-month afterschool programme (FITKids). Outcomes were laboratory executive-control tasks (flanker inhibition, task-switching cognitive flexibility) and P3 event-related potential amplitude, plus VO2max. CRITICAL SCOPING POINT: there is no academic-achievement outcome in this trial. Every reported cognitive effect is a laboratory task, i.e. near-to-far transfer, not an education outcome. The comparator is a wait-list, not an active control, so expectancy and adult-contact time are not held constant — precisely the moderator whose adjustment shrank the pooled exercise-cognition effect fourfold in Ciria et al. 2023.

The most-cited RCT supporting exercise-cognition transfer in children, and its effects are small, on lab tasks, against a passive control. Fitness rose 1.3 mL/kg/min (d=0.34). Inhibition accuracy improved 3.2% (95% CI 0.0 to 6.5; d=0.27) and cognitive flexibility 4.8% (95% CI 1.1 to 8.4; d=0.35); the lower bound on the inhibition CI is exactly zero. P3 amplitude rose only in the intervention group. The dose-response evidence is correlational within-arm (attendance correlated r=0.22-0.24 with gains), which is a self-selection contrast, not a randomized dose comparison. Taken at face value the effects sit in the range Ciria 2023 shows disappears under active-control adjustment and bias correction.

Individual randomization removes genetic confounding of the treatment contrast. The within-arm attendance-gain correlations do NOT — children who attend more differ in conscientiousness and family circumstance, both heritable, so those r values carry no causal weight.