Effectiveness of Exercise Snacks in Mitigating Adolescent Problematic Smartphone Use: A Four-Wave Cluster Randomized...

Prolonged sedentary behavior and physical inactivity are important concerns in secondary-school settings. This 6-month, four-wave cluster randomized controlled trial evaluated whether integrating high-intensity exercise snacks into the school schedule could reduce adolescent problematic smartphone use. A total of 386 adolescents from 12 classes were randomized at the class level to an intervention group, which performed four daily 2-minute bouts of vigorous physical activity during scheduled school breaks, or a wait-list control group that maintained standard routines. Primary outcomes were smartphone addiction severity and device-derived daily screen time. Secondary outcomes included psychological measures and device-derived physical activity. Outcomes were assessed at baseline and months two, four, and six. The intervention group showed lower mean SAS-SV scores and daily screen time at month four than at baseline, alongside increases in daily steps and improvements in several psychological measures. The unadjusted between-group differences in change from baseline to month four were -6.356 SAS-SV points and -46.829 min/day of screen time. The pooled model-adjusted between-group differences in change from baseline to month four were -6.55 SAS-SV points (95% CI, -7.38 to -5.71) and -52.22 min/day of screen time (95% CI, -67.21 to -37.23). During the 2-month unguided follow-up, some improvements attenuated. These findings suggest that school-based exercise snacks may help reduce problematic smartphone use. The psychological mechanisms and clinical importance of the observed changes require further investigation.