The impact of action plans on habit and intention strength for physical activity in a web-based intervention: is it the thought that counts?

Objective: Action planning is a common approach used in physical activity interventions. The aim of this study was to assess the association of frequency, consistency and content of action planning with physical activity behaviour, intention strength and habit strength.
Methods and Measures: Within a 3-month web-based, computer-tailored physical activity intervention, participants ( N  = 115; 68.7% female, M age =43.9; range = 22-73 years) could create 6 rounds of action plans for 4 activities each (24 total).
Results: Consistency of action planning during the intervention was associated with change in physical activity at 9-months, and intention and habit strength at 3-months and 9-months. Frequency of action planning was negatively associated with intention at 3-months and 9-months. The effect of action planning consistency on physical activity behaviour was no longer significant when accounting for change in intention and habit strength.
Conclusion: Consistency of how, where, when and with whom people plan their physical activity may translate into stronger physical activity habits. Interventions should avoid encouraging making many distinct action plans, but rather encourage stable contexts through consistent action planning.