Background: The effectiveness of interventions to promote physical activity in youths is still developing. To develop a better understanding "what works", researchers are now focusing on constructing an evidence base for mediators of behavior change.
Methods: We reviewed studies that examined the direct effect of physical activity interventions on hypothesized mediators and the relationship between mediators and physical activity in young people (aged 5 to 18 years). Studies were identified via electronic database searches and scanning references against predetermined quality criteria.
Results: We found seven studies that evaluated three mediator groups: cognitive, behavioral and interpersonal mediators. Self-efficacy was the most commonly assessed mediator in youth interventions and there was strong support for its role in mediating the relation between theory-based interventions and physical activity. There was some support for the importance of behavioral strategies as mediators of behavior, but no support for the mediating influence of interpersonal factors.
Conclusions: Despite recognition of the importance of mediation studies, few interventions have assessed mediators of physical activity behavior in youth interventions. The small number of studies examining mediators of behavior and the variability in study design and quality prevent us from forming strong conclusions regarding the most effective mediators of behavior.