Physical activity, sedentary behaviour and physical self-perceptions in adolescent girls: A mediation analysis

Objective: Few studies have examined the relationship between sedentary behaviour (SB) and mental well-being. This study assessed whether SB is associated with physical self-perceptions, independent of participation in moderate-to-vigorous physical activity (MVPA). Previous studies in this area simultaneously entered measures of SB and MVPA as predictors in regression models. In a novel approach, this study used mediation analyses to avoid problems of collinearity between SB and MVPA. Design: Cross-sectional. Setting: School-based. Method: Adolescent females (N = 238) used validated instruments to self-report time spent in SB and MVPA on the previous day, and to provide ratings for physical self-perceptions. Where a self-perception variable was associated with SB, Baron and Kenny's method was used to test if the relationship was mediated by MVPA. Results: There were small direct associations between SB and two self-perceptions, which were not mediated by MVPA: 'sports competence' (-.022) and 'physical conditioning' (-.023). There was also a negative association between SB and perceived 'physical strength', which, by contrast, was mediated by MVPA. Conclusion: Results for selected self-perceptions indicate that SB may be important to aspects of mental well-being independent of MVPA engagement. Future studies should use longitudinal and prospective designs to (a) assess the causality and direction of associations between SB and self-perceptions; (b) explore how individual SBs relate to self-perceptions; and (c) establish if the magnitude of these associations is clinically relevant.