Grant Number:	1R01CA303696-01A1 Interpret this number
Primary Investigator:	Dunton, Genevieve
Organization:	University Of Southern California
Project Title:	Using Real-Time Data Capture to Examine Affective Mechanisms as Mediators of Physical Activity Maintenance in Interventions
Fiscal Year:	2026

PROJECT SUMMARY Cancer remains a leading cause of mortality in the United States. Approximately 42% of new cancer cases are considered preventable through modifiable behaviors such as physical activity. While behavioral interventions have shown success in promoting the short-term adoption of physical activity, they have been less effective in sustaining long-term behavior maintenance. One reason for this challenge may be that many interventions focus on changing cognitive beliefs but overlook the affective (i.e., emotional) experiences that accompany physical activity, which may be key to sustaining long-term behavior change. While some individuals experience pleasure during physical activity, others find it unpleasant. Our team has employed an experimental medicine approach to early-stage intervention development, demonstrating that digital affect-based treatments can improve affective responses (e.g., feeling good or bad during activity) and affectively-charged motivations (e.g., wanting or dread- ing future activity). However, variation in changes in affective mechanisms may signal a need for personalized booster interventions, as behavior maintenance likely depends on sustained shifts in underlying mechanisms. This Phase 1 trial will use a Sequential Multiple Assignment Randomized Trial (SMART) design to test whether individual differences in long-term responses to a randomized digital physical activity adoption intervention (R01CA272933) should guide the content and dose of a subsequent booster intervention targeting affective mechanisms to promote maintenance. Six months after the adoption intervention, adults (N=200) at elevated cancer risk (overweight/obese and inactive) will begin a 6-month digital booster intervention (delivered via daily SMS). Participants will be re-randomized to booster treatment content and dose based on their long-term mechanistic (i.e. change in affective mechanisms) and behavioral (i.e., change in physical activity) responses to the adoption intervention at the 6-month follow-up. Mechanistic non-responders will be randomized to enhanced affect (e.g., savoring affect) vs core affect (e.g., affect goals) content, and mechanistic responders will be randomized to core affect vs no affect (e.g., planning only) content. Behavioral non-responders and re- sponders will receive a full (100% of days) or micro (25% of days) dose, respectively. Real-time mobile data capture (i.e., ecological momentary assessment and accelerometry) will assess affective mechanisms and phys- ical activity continuously during the booster intervention. Physical activity will also be assessed during the 6- month periods after the adoption (n=100) and booster (n=100) interventions. The study aims are: (1) evaluate the effects of booster treatment content on affective mechanisms and physical activity maintenance, (2) examine whether changes in affective mechanisms during the adoption and booster interventions are prospectively as- sociated with subsequent 6-month physical activity maintenance, and (3) explore the effects of booster treatment dose on affective mechanisms and physical activity maintenance. This study is impactful because it addresses the need to identify and optimize intervention strategies that promote physical activity maintenance. Dr. Delfien Van Dyck is a Professor in the Department of Movement and Sports Sciences in the School of Medicine and Health Sciences at Ghent University in Belgium. Her research is primarily focused on theory-based interventions through eHealth and mHealth to promote an active lifestyle in adults. Her work uses ecological momentary assessment (EMA) to identify the dynamic determinants of physical activity and sedentary behavior. Dr. Van Dyck was a key collaborator on the MyDayPlan daily self-regulation intervention, which provides the basic format for the daily behavior change strategies proposed in the current study. Thus, she will advise of the adaption of the intervention to incorporate affect-based daily goals and strategies. She will provide expert consultation on the design, implementation, iterative improvements, and testing of these daily intervention strategies for physical activity promotion in the target population. She will be available via email or telephone on an as-needed basis, and will attend monthly research meetings by teleconference or video. She will also contribute to the dissemination of findings in peer-reviewed publications





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