Mediators of Physical Activity Behavior Change Interventions among Adults: A Systematic Review and Meta-Analysis.

Abstract

Background: An understanding of physical activity through mediators of behaviour change is important to evaluate the efficacy of interventions. The purpose of this review is to update prior reviews with meta-analysis in order to evaluate the state of physical activity interventions that include proposed mediators of behaviour change. Methods: Literature was identified through searching of five key databases. Studies were eligible if they described a published experimental or quasi-experimental trial in English examining the effect of an intervention on physical activity behaviour and mediators in non-clinical adult populations with the necessary statistical information to be included in the meta-analytic structural equation modelling analysis. Results: Fifty-one articles (49 samples) met the eligibility criteria. Small overall effects were identified for mediation paths a (r\u2009=\u2009.16; 95% CI\u2009=\u2009.10 to .22), b (r\u2009=\u2009.21; 95% CI .16 to .27), and c (r\u2009=\u2009.24; 95% CI .12 to .35), c (r\u2009=\u2009.05 to .19) and ab (r\u2009=\u2009.02 to .07) that showed similar findings by theory and construct. Conclusion: The effect sizes seen in physical activity interventions are mediated by our current theories, but the effects are very small and no one construct/theory appears to be a critical driver of the mediated effect compared to any other. Innovation and increased fidelity of interventions is needed.