PROJECT SUMMARY/ABSTRACT Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of morbidity and mortality in the United States (US). Regular physical activity has been demonstrated to reduce the risk of ASCVD and is associated with a number of other health benefits. Yet, less than 50% of adults in the US achieve enough physical activity to actually obtain these benefits. This level of inactivity in the US has been mostly unchanged for the past decade; innovative and scalable approaches that achieve sustained increases in physical activity are needed. Insights from behavioral economics have been shown to both better reflect the `predictable irrationality' of humans and to be effective in designing interventions that achieve sustained improvements in health behavior. Our prior work has demonstrated that interventions using financial incentives and gamification can leverage principles from behavioral economics to increase physical activity during 3-month interventions and sustain effects in 3-month follow-up periods. These findings warrant further investigation of longer-term effects. In this study, we propose to conduct a four-arm randomized, controlled trial with a 12-month intervention and then a 6- month follow-up period to address the following aims: Aim 1: To evaluate the effectiveness of gamification, financial incentives, or both approaches combined on increasing physical activity relative to control during a 12-month intervention among individuals at elevated risk for atherosclerotic cardiovascular events. Aim 2: To evaluate the sustainability of the three interventions (gamification, financial incentives, or both combined) in increasing physical activity during a 6-month follow-up period. Aim 3: To compare the cost-effectiveness of using each of the intervention approaches relative to control in increasing physical activity. We will test a scalable intervention by using wearable devices to monitor physical activity levels and an automated research technology platform to deliver interventions remotely.