The interrelationship among physical activity, smartphone addiction, loneliness, and sport motivation in Chinese college students: a cross-sectional network analysis.

Background: The rapid digital transformation in China has posed significant challenges to the lifestyles of youth, most notably characterized by physical inactivity and heightened mental health risks among university students. Clarifying the systemic interaction mechanisms between smartphone addiction, loneliness, and sport motivation is essential for developing effective behavioral intervention frameworks in the digital age. Objective: Drawing on Psychological Network Analysis (PNA), this study explores the topological interaction structures and cross-domain association pathways among physical activity, smartphone addiction, loneliness, and sport motivation in Chinese university students. Methods: A cross-sectional design was employed, involving a large-scale sample of 10,676 full-time Chinese university students. A 15-dimensional psychological network was constructed using a LASSO-regularized Gaussian Graphical Model (GGM). Centrality metrics were utilized to identify core hubs, while bridge centrality was applied to detect cross-domain spillover effects. Additionally, the Network Comparison Test (NCT) was conducted to evaluate topological robustness and heterogeneity across genders. Results: The network topology revealed that Stimulation Orientation and Achievement Orientation within the sport motivation domain occupied the system's core, demonstrating high strength centrality. Regarding cross-system associations, Amotivation yielded highest in both bridge strength and two-step expected influence, serving as the pivotal functional link between the sport motivation cluster and the smartphone addiction community. Loneliness emerged as another critical bridge node, significantly associated with both addictive symptoms and the depletion of autonomous motivation. Local edge analysis indicated a significant negative correlation between smartphone-related loss of control and exercise duration. While global network strength was consistent across genders ( Conclusion: This study elucidates the central role of sport motivation and the cross-domain hub function of amotivation, reflecting an integrated framework of Self-Determination Theory (SDT) and the I-PACE model. The identified key topological sites provide systemic evidence for developing targeted, gender-sensitive intervention strategies that focus on "bridge variables" within the Chinese cultural context.