Self-control treatment group
The treatment group used the MindHike coaching application, which supports and guides people who would like to train their self-control with the help of a digital coach. The app delivered the same dialogs to all participant in the treatment group. There was no bi-directional communication, but participants clicked on predesignated responses to advance the chatbot dialog. The original MindHike coaching app targets self-control without focusing on the domain of physical activity (Participants were contacted by the app twice each day for 8 weeks (one baseline week and seven intervention weeks). During the baseline week, the first daily message was a push notification which reminded them to wear their Fitbit at customized times in the morning. The second daily push notification reminded participants to sync their step data and charge the Fitbit at customized times in the evening. During the seven intervention weeks, participants received an additional short daily chatbot-based self-control coaching input.As part of the self-control intervention, participants set their own physical activity goal because physical activity interventions are more effective when individuals can choose their preferred activities (