Are changes in cardiorespiratory fitness resulting from physical activity interventions related to changes in executive function and academic performance in children and adolescents? A systematic review and meta-regression

17 controlled intervention studies reporting pre- and post-intervention cardiorespiratory fitness alongside academic performance and/or executive function

Children and adolescents in school and community physical-activity interventions

Systematic review plus meta-regression of controlled trials, restricted to studies that measured both the putative mediator (cardiorespiratory fitness) and the outcome. This is the design that isolates the causal question the observational fitness-achievement literature cannot answer: does a randomly induced INCREASE in fitness produce an increase in achievement? Graded C because it pools 17 heterogeneous trials of mixed quality and reports estimates after removal of influential studies. Preprint (SportRxiv); no peer-reviewed journal version located.

The mechanism fails at the join. Physical activity interventions reliably raise cardiorespiratory fitness (SMD 0.24, 95% CI 0.09 to 0.40) — so the input works on the input. But the same interventions move academic performance 0.11 (95% CI -0.16 to 0.38) and executive function 0.02 (95% CI -0.09 to 0.13), both indistinguishable from zero. Critically, the meta-regression of fitness CHANGE on outcome CHANGE is uninformative for academic performance (beta = -0.04, 95% CI -1.52 to 1.45) and non-significant for executive function (beta = 0.26, 95% CI -0.18 to 0.70). The authors conclude it is "unlikely improvements in CRF from PA interventions are associated with changes in EF or AP." This is the direct experimental refutation of the fitness-as-input model that the large observational fitness-achievement literature assumes.

The meta-regression uses randomized fitness change, which is the confound-breaking version of the observational fitness-achievement correlation. Given fitness heritability of roughly 55-72%, the contrast between the strong observational association and this null experimental gradient is exactly what passive gene-environment correlation predicts.