Discussion
MYOPIA
In this cluster RCT, children who received an additional 2-hour extracurricular physical activity after school showed noninferior academic performance compared with those who were free to arrange their after-school time over 1 academic year. Children who received extracurricular physical activity had significantly higher physical fitness scores than the control group.Existing RCTs regarding the effect of increasing physical activity on academic performance are limited and have substantial heterogeneity in sample size, participant characteristics, and study duration. A meta-analysis reported that physical activity could improve mathematics scores by 1.12 points (95% CI, 0.56-1.67) compared with controls, but 3 of the 4 included RCTs had a follow-up time shorter than 2 months.The findings from this trial showed that participation in after-school extracurricular physical activity for 1 academic year did not compromise academic performance. Success in academic performance was reported to be associated with well-being and the cognitive functions that contribute to the processes of memory, perception, intellect, and action.Consistent with previous research, 2-hour extracurricular physical activity after school was noted to be beneficial for physical fitness in this study. Data from the 2014 National Survey on Students’ Constitution and Health suggested that children who engaged in more than 1 hour of physical activity per day had a 0.41-fold higher passing rate on the composite physical fitness test than those with less than 1 hour of physical activity.The effect of time outdoors on myopia prevention has been well-established in existing studies.A common parental concern is that more physical activity time leads to reduced studying time. Results of this trial largely alleviate this concern by providing evidence that time spent on after-school studying or reading was not significantly different between the intervention and control groups. In addition, mathematics scores did not differ significantly between children with more than 2 hours vs children with less than 1 hour of studying or reading after school. The proportion of children with screen time of more than 30 minutes per day increased more in the control group than the intervention group, suggesting that more after-school outdoor physical activity may provide extra benefits in reducing screen time.