Effects of school-based physical activity interventions on cardiorespiratory fitness and body composition in children and adolescents: A systematic review and meta-analysis using the RE-AIM framework.

School-based physical activity interventions had a significant positive effect on cardiorespiratory fitness in children and adolescents.

• SMD = 0.28, 95% CI = 0.19 to 0.38
• Substantial heterogeneity was observed (I2 = 75%)
• 43 studies with a total of 27,626 participants were included in the meta-analysis
• Eligible participants were healthy children and adolescents aged 5-17 years
• Studies were randomized or non-randomized controlled trials identified from five databases (PubMed, Embase, Web of Science, EBSCO, and Cochrane Library) published from January 1, 2000, to July 10, 2024

School-based physical activity interventions did not produce a statistically significant effect on percentage of body fat.

• SMD = -0.05, 95% CI = -0.10 to 0.00
• Low heterogeneity was observed for this outcome (I2 = 28%)
• Only studies that reported CRF or body composition with PA or exercise as the sole intervention were included
• The confidence interval just touched zero, indicating a borderline non-significant result

The total proportion of RE-AIM framework dimensions reported across included studies was 48.1%.

• Effectiveness was the most frequently reported dimension at 72.7%
• Reach was reported in 53.1% of studies
• Adoption was reported in 52.3% of studies
• Implementation was reported in 42.4% of studies
• Maintenance was the least frequently reported dimension at only 4.7%

Internal validity indicators (Reach and Effectiveness) were reported more often than external validity components (Adoption, Implementation, and Maintenance) in the included studies.

• Reach (53.1%) and Effectiveness (72.7%) represent the internal validity dimensions of the RE-AIM framework
• Adoption (52.3%), Implementation (42.4%), and Maintenance (4.7%) represent the external validity dimensions
• Maintenance was by far the least reported dimension across all included studies at 4.7%
• The RE-AIM framework was used to evaluate both internal and external validity of the included studies