Abstract
BACKGROUND: In the global context of promoting active health, the issue of insufficient exercise adherence among women is increasingly prominent. As digital health intervention tools, the efficacy of fitness apps hinges on their ability to provide "need support" that satisfies users' deep psychological needs. However, the internal psychological mechanism from need support to long-term behavioral adherence, particularly the serial mediation pathway for female users, requires further exploration. METHODS: Grounded in Self-Determination Theory and Social Cognitive Theory, this study examined a sequential mediation model in which self-efficacy and health locus of control functioned as mediators. A cross-sectional questionnaire survey was administered to 721 female fitness app users recruited from 12 cities across 9 provinces in eastern, central, and western China. Data analyses were conducted using SPSS 27.0 and the PROCESS 4.0. Pearson correlation analyses and multiple linear regression were employed to test the associations and direct effects among variables, while mediation effects were examined using bootstrap procedures with 5,000 resamples and bias-corrected 95% confidence intervals. Indirect effects were considered statistically significant when the confidence intervals did not include zero. RESULTS: (1) Fitness app need support significantly and positively predicted women's exercise adherence behavior (total effect = 0.341, 95% CI [0.281, 0.400]). (2) Self-efficacy and perceived health control both played significant mediating roles, with mediation effect values of 0.098 and 0.079, respectively. (3) Self-efficacy and perceived health control formed a significant serial mediation pathway (effect value = 0.023). The total indirect effect, comprising this serial path and the two independent mediation paths, was 0.200, accounting for 58.65% of the total effect. CONCLUSION: Need support from fitness apps can directly promote women's exercise adherence. It also indirectly fosters long-term behavioral persistence by sequentially enhancing users' self-efficacy and perceived health control. This internal psychological sequence provides evidence of a chain mechanism for understanding the psychological "black box" of how digital health technologies influence behavior. The findings offer crucial theoretical and practical implications for the future design and optimization of fitness apps oriented toward women's deep psychological needs.