Targeting self-control as a behavior change mechanism to increase physical activity: Study protocol of a randomized controlled trial.

Despite the highly publicized beneficial effects of physical activity, 51.1% of middle-aged US adults do not achieve the recommended minimum of aerobic physical activity needed to maintain health. A sedentary lifestyle can be attributed in part to a lack of self-control and there is some evidence that self-control strategies can be improved with targeted interventions. The overall aim of this study is to test self-control as a behavior change mechanism for physical activity and to investigate whether a smartphone-based self-control intervention can increase physical activity among sedentary middle-aged adults. This protocol describes the design of a randomized controlled trial with two experimental conditions: The self-control treatment group and the control group. Both groups track their daily physical activity using a Fitbit step counter for eight weeks. Additionally, the self-control intervention group receives a 7-week smartphone-based self-control intervention to learn strategies how to potentiate desirable impulses or weaken undesirable ones. It is expected that the self-control treatment group will show greater increases in physical activity and that changes last longer compared to the control group. All participants will be assessed at pretest (baseline), at the end of each week (weeks 1-7), at posttest (week 8), and at follow-up (week 12). If this self-control intervention proves effective, this digital approach would represent a low-threshold and cost-effective approach to increasing physical activity. Such an intervention could be delivered to a large number of people to improve their health outcomes in the long run. Trial Registration:ClinicalTrials.gov: NCT04522141.