Introduction: School sports leagues foster students’ physical activity and social participation; however, recruitment and sustained engagement remain challenging. This study compared the effects of three gamification models (individual competition, team competition, and social reward) versus usual information on students’ enrollment and sustained participation.

Methods: This four-arm cluster-randomized trial recruited 480 secondary-school students across 32 classes in eight schools in Khorramabad using multistage cluster sampling. Classes were randomly allocated to control, individual competition, team competition, and social reward arms. The recruitment phase lasted 14 days, followed by a six-week league. Primary outcomes included valid enrollment (by day 14) and sustained participation (valid enrollment plus attendance at

5 of 6 sessions and the final session). Analyses followed the intention-to-treat (ITT) principle using logistic regression with cluster-robust standard errors and Holm correction.

Results: Enrollment rates for control, individual competition, team competition, and social reward were 30.8%, 50.0%, 45.0%, and 43.3%, respectively; all interventions significantly increased enrollment compared to control, with the highest point estimate in individual competition. Sustained participation rates were 16.7%, 30.8%, 38.3%, and 30.0%, respectively, with team competition demonstrating the largest point estimate.

Conclusion: Gamification significantly improves enrollment and sustained participation compared with usual information. However, intervention efficacy depends on design: individual competition is optimal for initial recruitment, whereas team competition is more effective for sustaining long-term participation.