Adherence to physical and mental activity interventions: coping plans as a mediator and prior adherence as a moderator

Objective. Adherence to behavioural intervention programmes is a necessary condition for beneficial outcomes to be achieved. This study tested whether social cognitive variables and coping plans predict adherence. Design and methods. Adherence was examined in a randomized controlled trial with healthy older women (age range: 70–93 years), who were randomized to a physical (N= 86) or a mental (N= 85) activity intervention. Intentions, self‐efficacies, coping plans, and objectively measured adherence levels were assessed. A moderated mediation analysis evaluated the power of coping plans to translate intention into behaviour, depending on levels of prior adherence. Results. Adherence to the physical activity programme (65%) was significantly lower than adherence to the mental activity programme (84%, p < .001). Intentions (β= .22) weakly predicted adherence in the initiation period of the physical activity programme (6 weeks); pre‐action self‐efficacy predicted adherence in the initiation period of the mental activity programme (β= .35). In both groups, coping plans predicted mid‐period adherence (10 weeks) and long‐term adherence (20 weeks), moderated by prior adherence (all ps < .01). Coping plans mediated the relationship between intentions and behaviour only in the exercise condition. Conclusions. Instructing older individuals to generate coping plans facilitated their adherence to physical and mental activity programmes. This effect was larger for participants with lower levels of prior adherence – and may have prevented them from dropping out of the programme.