The promotion of physical activity (PA) is paramount to public health, yet interventions in the social cognitive tradition have yielded negligible improvements. Two reasons for these results may be the over reliance on intention as the proximal determinant of behaviour and a lack of consideration of implicit/automatic determinants of PA. The purpose of this study was to apply Multi-Process Action Control (M-PAC), a framework centered on PA intention-translation and the gradual building of habit to examine PA change using a two-arm parallel design, randomized controlled trial.