Increasing Physical Activity Through Principles of Habit Formation in New Gym Members: a Randomized Controlled Trial

The promotion of physical activity (PA) is paramount to public health, yet interventions in the social cognitive tradition have yielded negligible improvements. The limited progression may be due to an overreliance on intention as the proximal determinant of behavior and a lack of consideration of implicit/automatic processes. The purpose of this study was to examine the impact of a habit formation intervention on PA over 8 weeks in a two-arm parallel design, randomized controlled trial. Participants (n = 94) were new gym members with the intention to engage in PA but below international PA guidelines at baseline, who were randomized into a control or habit experimental group. The experimental group attended a workshop (at baseline) and received a follow-up booster phone call at week 4. The primary outcome of the study was minutes of moderate-vigorous intensity PA (MVPA) at week 8. The secondary outcome was a manipulation check to determine if the experimental group effectively incorporated habit-building constructs (cues and practice consistency). The experimental group showed a significant increase in MVPA after 8 weeks in both accelerometry (d = 0.39, p = .04) and self-report (d = 0.53, p = .01) compared with the control group. The experimental group also showed an increase in use of cues (d = 0.56, p < .001) and practice consistency (d = 0.40, p = .01) at week 8. The results contribute to the initial validity of increasing PA through a focus on preparation cues and practice consistency. Future research should replicate these findings and extend the duration of assessment to evaluate whether PA changes are sustained. Registered Trial Number NCT02785107.