High-Intensity Exercise Snacks for Reducing Mobile Phone Addiction in Adolescents

Background and Rationale: Adolescents face increasing risks of mobile phone addiction, which is associated with sedentary behavior. "Exercise Snacks"-isolated bouts of vigorous exercise performed periodically throughout the day-offer a time-efficient solution. This study applies the COMB model and Self-Determination Theory to a long-term, semester-based intervention. Study Design: This is a single-blind, randomized controlled trial conducted over a 6-month period (5 months of intervention + 1 month of follow-up). Intervention Protocol: The intervention group follows a progressive "Exercise Snacks" program: Adaptation Phase (Month 1 / Weeks 1-4): Focus on habit formation. Participants perform "Sprint Snacks" (e.g., stair climbing) 3 times daily and "Strength Snacks" (e.g., squats) 2 times weekly. Intensity is monitored to ensure safety and correct posture. Enhancement Phase (Months 2-3 / Weeks 5-12): Focus on physiological adaptation. Frequency increases to 4 daily Sprint Snacks and 3 weekly Strength Snacks. A weekly collective High-Intensity Interval Training (HIIT) session is introduced to maximize cardiorespiratory benefits. Consolidation Phase (Months 4-5 / Weeks 13-20): Focus on psychological integration. Daily snacks continue. Collective HIIT sessions increase to twice weekly. A cognitive-behavioral guidance component is added (bi-weekly) to help students identify phone use triggers and internalize healthy behaviors. Follow-up Phase (Month 6 / Weeks 21-24): The structured intervention ceases. Participants are encouraged to maintain self-guided exercise. Final assessments are conducted at the end of Month 6 to evaluate the retention of intervention effects and any "rebound" in mobile phone addiction. Outcome Measures: The primary outcome is Mobile Phone Addiction (SAS-SV), assessed at baseline, Month 3, Month 5 (post-intervention), and Month 6 (follow-up). Secondary outcomes include physical activity levels (PARS-3 and wearables), self-control (BSCS), resilience (RSCA), and mental health status.