A Structural Analysis of the Relationships among Adolescents’ Moderate-to-Vigorous Physical Activity, Optimism, and Quality of Life Based on a Triaxial Accelerometer: A Multi-Group Analysis by Gender

Background Adolescents’ quality of life(QoL) has received increasing attention. Previous studies have shown that moderate-to-vigorous physical activity (MVPA) is closely associated with optimism and QoL. However, the underlying mechanisms remain unclear. This study aimed to examine the relationship between MVPA and QoL, as well as optimism’s mediating role, among adolescents. Methods Overall, 350 students aged 12–18 years (167 boys and 183 girls) from Seoul and Daegu were included. Physical activity was objectively measured over eight days using a triaxial accelerometer, while related variables were assessed using standardized QoL and optimism scales. The collected data were analyzed using SPSS 29 and AMOS 28. Results First, MVPA positively predicted both optimism and QoL, whereas optimism positively predicted QoL. Second, MVPA exerted both a direct effect on QoL and an indirect effect through optimism. Third, MVPA’s effect on optimism was stronger among girls, whereas MVPA’s direct effect on QoL was stronger among boys. Furthermore, a partial mediation effect was observed among boys, whereas among girls, the indirect pathway through optimism served as the primary mechanism. Conclusions This study identified gender differences in the mechanism through which MVPA influences QoL via optimism. Collectively, these findings highlight that gender-specific intervention strategies should be considered when developing policies to promote physical activity among adolescents.