Effectiveness of Exercise Snacks in Mitigating Adolescent Problematic Smartphone Use: A Four‐Wave Cluster Randomized Controlled Trial

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.