The Impact of Physical Activity on Internet Addiction among Middle School Students—The Chain Mediating Role of Family Cohesion and Prosocial Behavior

目的：针对青少年网络成瘾率持续升高的现状，探讨体力活动与网络成瘾的关联机制，揭示家庭亲密度与亲社会行为的中介作用。方法：采用横断面研究方法，运用青少年体力活动问卷(APAQ)、中学生网络成瘾量表(IADDS)、家庭环境量表(FACESII-CV)和青少年亲社会行为倾向量表(PTM)对750名中学生进行测评，通过回归分析与中介效应模型验证变量关系。结果：数据表明，体力活动与网络成瘾呈显著负相关(β = −0.23, P Objective: Given the persistent increase in adolescent Internet addiction rates, this study investigates the association between physical activity and Internet addiction, while elucidating the mediating roles of family cohesion and prosocial behavior. Methods: Using a cross-sectional design, we administered standardized scales—Adolescent Physical Activity Questionnaire (APAQ), Internet Addiction Diagnostic Scale (IADDS), Family Adaptability and Cohesion Evaluation System II (FACES II-CV), and Prosocial Tendency Measure (PTM)—to 750 secondary school students. Variable relationships were validated through regression analysis and mediation effect models. Results: Data revealed a significant negative correlation between physical activity and Internet addiction (β = −0.23, P < 0.001). Family cohesion and prosocial behavior formed dual mediation pathways, accounting for 15.7% and 19.9% of total effects respectively, with prosocial behavior demonstrating stronger mediation. Physical activity suppressed Internet addiction development through two mechanisms: enhancing family bonding to strengthen social connections, and reinforcing prosocial behavioral tendencies. Conclusion: The study confirms that adolescents’ physical activity levels directly inhibit Internet addiction risks while indirectly exerting preventive effects through improved family interaction quality and enhanced social adaptive behaviors.