Predicting Engagement and Retention During an Online Theory-Based Intervention to Promote Physical Activity Among Inactive Parent-Child Dyads.

Insufficient physical activity is a widespread health concern, necessitating the broad implementation of evidence-based behavior change interventions. Such evidence commonly derives from randomized controlled trials, but questions arise about who is willing to enroll and actively engage in such trials. This study investigated factors predicting engagement and retention in an online physical activity intervention for inactive parent-child dyads. Participants were recruited from the general Finnish population and assigned to either an intervention or wait-list control group. The intervention consisted of online materials, SMS prompts, and four online sessions. Partial least squares regression models were used to analyze autonomous motivation, parent and child gender, parental education, employment status, and recruitment source as predictors of intervention retention and engagement. Results showed that intervention retention was predicted by higher autonomous motivation, being a mother, social media recruitment, and university education. Session attendance was higher for autonomously motivated parents, fathers, parents of daughters, and university-educated parents. These findings highlight the importance of autonomous motivation and demographic factors in intervention engagement. However, the higher engagement of already motivated participants demonstrates challenges for reaching and intervening on those who might benefit most from such programs. Future research should explore strategies to engage and retain less motivated individuals and investigate reasons behind non-compliance to improve the effectiveness of physical activity interventions for inactive families.