Exploring the effect of an eHealth intervention on women's physical activity: Design and rationale for a randomized controlled trial

Objective This manuscript reports on the protocol for a three-arm randomized controlled trial aiming to assess the effect a self-determination theory-based eHealth intervention on physical activity among insufficiently active women who are overweight or obese. Methods The intervention-of-interest provided (A) six weekly behavioural support emails, (B) a wearable activity tracker, and (C) a copy and verbal explanation of the Canadian physical activity guidelines, and was compared to an intervention that provided (B + C) and another that provided (C). Women from a local community were invited to participate in this study. Participants were recruited between September 2018 and March 2019. Data were collected using self-report and direct measures three times: at baseline (week 0), post-intervention (week 7), and at follow-up (week 21). The primary outcome was self-reported total metabolic equivalent minutes of physical activity per week (MET-m/week); exploratory outcomes included number of days of strength training per week, self-determination theory constructs (i.e. motivational regulations, basic psychological needs satisfaction and thwarting), and well-being indicators (i.e. affect, vitality, depression). Conclusion Findings will provide insight into which combination of intervention components may be more effective at promoting physical activity among insufficiently active women who are overweight or obese, and thus inform the design of future interventions aiming to promote physical activity.