ABSTRACT/PROJECT SUMMARY Maintaining physical activity (PA) is critical for older adults with cardiovascular disease (CVD) who complete cardiac rehabilitation (CR) because it prevents adverse secondary cardiac events, declining functional status, and poor quality of life. CR is an evidence-based, exercise-based program prescribed after cardiac events (e.g., myocardial infarction, revascularization) to improve overall physical, mental, and social functioning. However, the majority (50-85%) of individuals report no exercise 6 months after completing CR, leaving them vulnerable to rapid clinical, functional, and cognitive decline. The objective of this 6-month randomized controlled trial (n=143 per arm) is to test the efficacy of a virtual coaching and social support intervention to improve PA, psychosocial, social cognitive, and clinical outcomes as well as understand the mechanisms that affect change in outcomes for older adults (age ≥ 60) exiting CR and living in urban and rural areas. Virtual coaching includes: 1) education, 2) personalized feedback, and 3) motivation; social support includes social networking in groups of 4-6. The rationale for our approach is that CR is typically only 12 weeks or less but older adults desire and require extended support to reap the numerous benefits of sustained PA. The specific aims are: 1) Determine the effect of a virtual coaching and social support intervention on adherence to PA (measured by objective step counts) in the intervention vs. control groups; secondary measures will be sedentary time, functional fitness, and self-reported exercise. 2) Determine the effect of the virtual coaching and social support on psychosocial and social cognitive factors (self-efficacy, self-regulation, perceived social support) in the intervention vs. control groups; and 2a) Evaluate the extent to which psychosocial and social cognitive factors mediate the effect of the intervention on PA adherence. 3) Examine differences in clinical outcomes including CVD risk factors (hypertension, hyperlipidemia, diabetes, obesity) between groups. We will also record and explore group differences in cardiac events/rehospitalization. This study is innovative because we will: 1) provide a virtual social network to mimic the social support received in CR; 2) include an optional leader board/buddy system/badges to increase engagement; 3) intentionally recruit diverse, under-represented groups (rural, women, racial/ethnic minorities) and deliver the intervention in Spanish; and 4) be the first clinical trial to address loneliness in patients with CVD. Significance: We address key NIH priorities to improve adherence to healthy behaviors and reduce burden of chronic conditions as well as promote a program in older adults to maintain maximum PA/functional fitness. Impact: While leveraging digital health innovations, we will test a novel and pragmatic solution to maintain PA after CR completion that may lead to an efficacious evidence-based inte...