Influence of a Planning Intervention on Physical Activity Behavior: the Moderating Role of Intentions and Executive Functions in a Randomized Controlled Trial

Background Planning and executive functions (EFs; inhibition, updating, shifting) are self-regulatory variables that help people to become and stay physically active. The aim of this study was to examine how and for whom a planning intervention affects physical activity (PA) behavior in the short term. Therefore, the mediating role of planning and the moderating role of intentions and EFs for the planning–behavior link were examined. Method In a randomized control trial with two treatment groups (planning group vs. control group) and two points of measurement (t1 and t2, 1 week apart), n = 200 students participated in both measurements. At t1, participants filled in standardized questionnaires assessing PA behavior, intention, and planning. Computer-based tests assessed the following EFs: inhibition, updating, and shifting. At t2, planning and PA behavior were measured again. Moderated mediation analyses were conducted. Results A significant increase in PA between t1 and t2 was found for the planning group compared with the control group. Furthermore, planning cognitions significantly mediated the effect of the planning group on behavior and intention, as well as the EF updating moderated the association between planning and behavior. Forming plans was particularly beneficial for participants with high intentions and lower updating performance. Conclusion Planning enhances PA behavior, particularly when PA intention is high. Poor performance in updating can be compensated by planning since encouraging people to generate plans might facilitate automatic enactment of the behavior.