Interventions aimed at promoting physical activity behavior have tended to focus on targeting change in motivational determinants (e.g. intentions, attitudes, social norms, beliefs, self-efficacy). However, such interventions tend to lead to large positive changes in the physical activity intentions, and tend to have smaller effects on actual physical activity behavior. A reason for this is a ‘shortfall’ in those acting on their intentions, known as the intention-behavior ‘gap’. These observations have catalyzed research exploring volitional strategies aimed at promoting individuals to act on their physical activity intentions. Based on dual-phase approaches such as the model of action phases, this research has focused on planning strategies, based on the premise that augmenting intentions with plans facilitates behavioral enactment. This chapter briefly reviews the literature on intention-behavior relations in physical activity contexts and outlines the premises of the model of action phases and other dual-phase models of action. It then outlines how cue-to-action plans, especially implementation intentions or ‘if-then’ plans and action plans, have been used to promote behavior change in physical activity contexts. In addition, the conditions under which planning interventions are likely to be most effective, including the type of population, format of the plan, and the format and delivery of the planning intervention, are reviewed. Finally, the chapter outlines priorities for future research on planning interventions in physical activity.