Cognitive mediation of intervention effects on physical exercise: Causal models for the adoption and maintenance stage

Objective: To investigate how the effects of a group-based intervention program (MoVo-LISA) on exercise behaviour were mediated by cognitive variables. Different causal models mapping the short-term (adoption) and long-term (maintenance) intervention effects were tested using path analyses. Design: N = 220 in-patients of a rehabilitation clinic were assigned to an usual care or intervention group (quasi-experimental design). Questionnaire-based assessment was conducted at baseline; discharge; and at six weeks, six months and 12 months post discharge. Measures: The potential mediator variables were outcome expectations, self-efficacy, strength of goal intention (intention strength), self-concordance, action planning and barrier management. Results: Observed intervention effects on exercise behaviour (p textless 0.05) were mediated by intention strength at the adoption and maintenance stages, by action planning only at the adoption, and by barrier management only at the maintenance stage. Self-efficacy and outcome expectations were only indirectly involved in these mediations by affecting intention strength and self-concordance. Conclusion: This is the first study to track the cognitive mediation processes of intervention effects on exercise behaviour over a long time-period by differentiating the adoption and maintenance stages of behaviour change. The findings emphasise the importance of deconstructing intervention effects (modifiability vs. predictive power of a mediator) to develop more effective interventions.