Psychological mechanisms in a digital intervention to improve physical activity: A multicentre randomized controlled trial.

Although the intervention produced overall improvements in physical activity, the time-by-treatment interaction emerged only for women. The mechanism included a sequence leading from motivation via planning, self-monitoring, and habit strength towards physical activity. Statement of contribution What is already known on this subject? Digital lifestyle interventions can be effective in terms of physical activity performance gains. Men are on average more physically active than women. Long-term adherence rates to digital interventions are usually low. What does this study add? Giving users of an online platform more interactive options did not make a difference. Women gained more than men from adaptive, dynamic online platform content. Individual characteristics (motivation, planning, self-monitoring, habit) were more important than online treatment features.