Automaticity mediates the association between action planning and physical activity, especially when autonomous motivation is high.

Objectives: Action planning promotes physical activity (PA). However, mechanisms underlying this association are poorly understood, as are the variables that moderate this link remain unexplored. To fill these gaps, we investigated whether automaticity mediated the association between action planning and PA, and whether autonomous motivation moderated this mediation.

Methods and measures: PA was measured by accelerometry over seven days among a sample of 124 adults. Action planning, automaticity, and autonomous motivation were assessed by questionnaires.

Results: Structural equation models revealed that automaticity mediated the association between action planning and PA (total effect, β = .29, p < .001) - action planning was associated with automaticity (a path, β = .47, p < .001), which in turn related to PA (b path, β = .33, p = .003). Autonomous motivation moderated the a path (β = .16, p = .035) - action planning was more strongly associated with automaticity when autonomous motivation was high (+1 standard-deviation [SD]) (unstandardized b = 0.77, p < .001) versus low (-1 SD) (b = 0.35, p = .023).

Conclusion: These findings not only support that action planning favors an automatic behavioral regulation, but also highlight that a high autonomous motivation toward PA may reinforce this mechanism.