How does MobileMums work? Mediators of a physical activity intervention.

To establish which Social Cognitive Theory constructs mediated effects of the MobileMums (MMP) program on increased duration and frequency of moderate-vigorous physical activity (MVPA) in women with young children (<5 years). This secondary data analysis is from a community-based randomised controlled trial. Over 12 weeks, intervention participants received a minimum of 52 individually tailored text messages, one face-to-face and one telephone-delivered session with a trained behavioural counsellor. Participants identified a support person who also received 12 weeks of individually tailored text messages. Control participants received minimal intervention contact. Data were collected pre- and post-program. Five potential mediators were assessed: barrier self-efficacy, goal setting skills, outcome expectancies, perceived environmental opportunity for physical activity and social support for physical activity. Improvements in MVPA frequency were mediated by improvements in barrier self-efficacy, goal setting skills, outcome expectancies and perceived social support. Improvements in MVPA duration resulting from the MMP were mediated by improvements in women's barrier self-efficacy and goal setting skills. MMP improved targeted theoretical constructs and this led to changes in women's MVPA. These findings are valuable for refinement and translation of the MMP and for further research to create theory- and evidence-based physical activity behaviour change programs for women with young children.