Importance: The beneficial effects of increasing outdoor physical activity time on children's myopia onset and physical well-being are widely acknowledged. However, in countries with competitive educational systems, such as China, parents and school administrators may be relatively reluctant to increase the extracurricular physical activity time for children due to concerns that this action will compromise children's academic performance.
Objective: To investigate whether additional extracurricular physical activity time after school compromises the academic performance of schoolchildren.
Design, setting, and participants: This cluster randomized clinical trial was conducted from October 2020 to June 2021 in Yudu, Jiangxi, China. Eligible children in grades 3 and 4 from 24 elementary schools were randomized to the intervention or control group. Primary analysis was conducted in the full sample using the intention-to-treat principle.
Interventions: The intervention group received 2 hours of after-school physical activity time outdoors on school days. The control group was free to arrange their after-school activity.
Main outcomes and measures: The primary outcome was the between-group mean difference in mathematics test scores at the end of 1 academic year, with a noninferiority margin of -3.3 points. Standardized mathematics tests, physical fitness assessments (in reference to the 2018 National Physical Fitness Survey Monitoring Programme in China), and cycloplegic autorefraction were performed at baseline and the end of 1 academic year. Myopia was defined as a cycloplegic spherical equivalent refraction of -0.5 diopters or less in either eye.
Results: A total of 2032 children (mean [SD] age, 9.22 [0.62] years; 1040 girls [51.2%]) from 24 schools were randomized to the intervention group (12 schools; 1012 children) or control group (12 schools; 1020 children). The mean (SD) mathematics score at the end of 1 academic year was 78.01 (17.56) points in the intervention group and 77.70 (17.29) points in the control group. The adjusted between-group mean difference was 0.65 points (95% CI, -2.85 to 4.15). The adjusted between-group mean difference in physical fitness score was 4.95 points (95% CI, 3.56-6.34; P < .001) and -1.90% (95% CI, -18.72% to 14.91%; P > .99) in myopia incidence.
Conclusions and relevance: Results of this trial indicate that, compared with the control practice of free play after school, adding 2 hours of extracurricular physical activity outdoors after school was noninferior in academic performance and had superior efficacy in improving physical fitness.
Trial registration: ClinicalTrials.gov Identifier: NCT04587765.