Feel the Move: A Micro-Randomized Trial of a Text-Based Expectation-Setting Intervention to Increase Physical Activity

The Feel the Move study tests the effects of a lightweight text-message based intervention to increase physical activity and affective attitudes towards exercise. The intervention being investigated is text messages that prime expected affective rewards of exercise, sent in advance of a time window during which participants made plans to exercise. At the start of the study, participants will write sentences about feeling good after exercise (which will be used as part of the intervention) and complete baseline questionnaires about their feelings towards exercise. For the next nine weeks, participants will be asked to plan two exercise sessions a week, and will be given a questionnaire after the time window of their planned exercise sessions to assess how it went. At the onset of each time window for their planned exercise session, participants will be micro-randomized to receive one of the following intervention options: no-message; a text message reminding them to fill out the study questionnaires; or a message about the affective rewards of exercise. The messages about affective rewards will be a mix of sentences participants wrote themselves during the baseline assessment and reflective prompts from the research team. At the nine-week mark, participants will again complete the same questionnaires about their feelings towards exercise that they initially completed at baseline. Throughout the study, participants will share data about their activity, including steps and calories burned, with the research team. These data will be automatically collected by the HIPAA-compliant CareEvolution platform from participants' Apple Watches. After the nine weeks of the study participation, a random sample of study participants will be asked to participate in exit interviews to share more details about their experiences with the intervention.

The primary hypothesis is that participants will burn more calories during their planned exercise periods when they receive messages about the affective rewards of exercise vs. when they do not. Researchers will also conduct secondary analyses examining the effects of the intervention on feelings towards exercise and qualitative data from the interviews.

Inclusion criteria

• lives in the US
• 18 years old or older
• desires to increase activity through structured exercise
• has an iPhone that can send/receive text messages and an Apple Watch

Exclusion criteria

• medically advised not to exercise