Arms
Affect (no enhancements) > Intensity
Participants receive affect-based goals for the first 8-weeks, then cross-over to receive intensity-based goals for the second 8-weeks. No enhancements are added to the standard mHealth intervention.
Intensity > Affect (no enhancements)
Participants receive intensity-based goals for the first 8-weeks, then cross-over to receive affect-based goals for the second 8-weeks. No enhancements are added to the standard mHealth intervention.
Affect (+ SAVOR + TYPE/CONTEXT) > Intensity
Participants receive affect-based goals for the first 8-weeks. In addition to the standard mHealth intervention, participants engage in both SAVOR and TYPE/CONTEXT enhancements to augment the treatment effects of the affect-based goals condition. Participants then cross-over to receive intensity-based goals for the second 8-weeks.
Intensity > Affect (+ SAVOR + TYPE/CONTEXT)
Participants receive intensity-based goals for the first 8-weeks, then cross-over to receive affect-based goals for the second 8-weeks. In addition to the standard mHealth intervention, participants engage in both SAVOR and TYPE/CONTEXT enhancements to augment the treatment effects of the affect-based goals condition.
Affect (+SAVOR) > Intensity
Participants receive affect-based goals for the first 8-weeks. In addition to the standard mHealth intervention, participants engage in the SAVOR enhancement to augment the treatment effects of the affect-based goals condition. Participants then cross-over to receive intensity-based goals for the second 8-weeks.
Intensity > Affect (+SAVOR)
Participants receive intensity-based goals for the first 8-weeks, then cross-over to receive affect-based goals for the second 8-weeks. In addition to the standard mHealth intervention, participants engage in the SAVOR enhancement to augment the treatment effects of the affect-based goals condition.
Affect (+TYPE/CONTEXT) > Intensity
Participants receive affect-based goals for the first 8-weeks. In addition to the standard mHealth intervention, participants engage in the TYPE/CONTEXT enhancement to augment the treatment effects of the affect-based goals condition. Participants then cross-over to receive intensity-based goals for the second 8-weeks.
Intensity > Affect (+TYPE/CONTEXT)
Participants receive intensity-based goals for the first 8-weeks, then cross-over to receive affect-based goals for the second 8-weeks. In addition to the standard mHealth intervention, participants engage in the TYPE/CONTEXT enhancement to augment the treatment effects of the affect-based goals condition.
Interventions
Physical Activity Goals mHealth Intervention
On days participants plan to exercise, they engage in two daily goal sessions (morning and evening). Morning sessions provide an activity goal for the day and ask the participant to create a plan, anticipate barriers, and brainstorm solutions for achieving this goal. The affect-based goal condition asks participants to engage in either (1) a type (50% of daily goals) or (2) a context (50% of daily goals) of physical activity that allows them to experience positive affect. Goals focused on context are randomly generated to suggest that the participant performs activity (1) in a place; (2) in a social situation; or (3) while listening to something that makes them feel good. The intensity-based goal condition asks participants to maintain a certain target heart rate range during physical activity. Starting heart rate reflects the approximate age-adjusted heart rate max, with goals progressively increasing from 55% to 70% heart rate max.
TYPE/CONTEXT enhancement
TYPE/CONTEXT augments intervention effects by providing tailored recommendations for activity types and contexts that satisfy personally-important psychological needs as rated by each participant at baseline. Ratings from a crowdsourced panel of adults on Amazon Mechanical Turk will be used to determine the potential for specific activity types and contexts to satisfy psychological needs; our tailoring algorithm will then recommend the corresponding activity type or context while accounting for reported constraints (e.g., ability, access). These details will be incorporated into a tailored recommendation provided to participants each Sunday as they make activity plans for the upcoming week. Specifically, the program will randomly select either type or context (i.e., location, audio, social) recommendations and will rotate every two weeks. For TYPE, participants' top 3 activity types are recommended; for CONTEXT, participants' top 3 activity contexts are recommended.
SAVOR enhancement
SAVOR implements a brief savoring exercise on the smartphone that takes place either after the planned physical activity session or during the evening goal session (after the self-monitoring module). Participants will respond to questions that are intended to enhance and prolong positive experiences during physical activity. To trigger attentional deployment, a common savoring strategy that involves intensifying experiences by focusing on them, participants will answer three open-ended prompts. These prompts are drawn from a prompt pool with slightly varied wording to promote a sense of novelty. Savoring prompts will rotate daily and have a day lag built in every week (i.e., Week 1 Monday Savoring Prompts are Week 2 Tuesday Savoring Prompts).