Influencing basic behavioral mechanisms of action while targeting daily walking in sedentary adults at risk for cardiovascular disease: randomised factorial design protocol.

Introduction: Cardiovascular disease (CVD) is the leading cause of mortality worldwide, though it may be prevented by increasing physical activity (PA). When behaviour change techniques (BCTs) are bundled together, they increase PA, though which individual BCTs increase PA (and the behavioural mechanism of action (MoA) responsible for said increase) have not been studied. The aim of this study is to conduct a randomised factorial experiment to determine which of four BCTs significantly engage the proposed MoA-self-efficacy for PA-in adults at risk for CVD.

Methods And Analysis: Eight hundred and twenty sedentary adults (18-74 years old) at risk for CVD will be recruited between September 2022 and June 2025 to a fully remote, 24-week randomised BCT intervention. To identify those who might benefit from this intervention, we define self-reported walking <7500 steps per day as 'sedentary'. Following a 4-week run-in period to confirm sedentary behaviour and adherence to the study protocol, 624 eligible participants will be randomised to an 8-week intervention period. A full factorial randomised experiment will be conducted with 16 possible conditions: one will receive no BCTs (no-BCT condition), another will receive all four, and 14 will receive a unique combination of BCTs. During the intervention, participants will receive their randomised daily BCT(s) via text message. Daily steps will be continuously measured using an activity tracker. Self-efficacy for PA will be assessed bi-weekly via the Self-Efficacy for Walking Scale-Duration. Participants will complete a 12-week post-intervention follow-up period where steps will be monitored despite no BCTs being delivered. BCT(s) associated with increased daily step counts and increased self-efficacy for PA between run-in and study completion (week 12 of follow-up) will be determined alongside whether or not self-efficacy for PA mediates the association between each BCT and increased walking.

Ethics And Dissemination: This trial was approved by the Northwell Health Institutional Review Board. The full factorial experimental trial results will be published in a peer-reviewed journal. Data from this clinical trial will be made available on reasonable request.

Trial Registration Number: clinicaltrials.gov; Identifier: NCT05425641, 06/21/2022.