PROJECT SUMMARY/ABSTRACT Novel intervention strategies to increase physical activity need to reduce barriers to exercise and increase adherence to achieve optimal brain health benefits. Despite considerable physical and brain health benefits associated with exercise, most adults fail to adhere to recommended physical activity guidelines. Barriers, including lack of time and low enjoyment of exercise, can lead to reduced adherence. Dual-system neural models of behavior theorize two systems that drive behavior and can be engaged in interventions. The reward brain system responds to and evaluates the rewarding properties of stimuli in the environment and drives behaviors. The regulation brain system downregulates responses to rewarding stimuli and promotes healthy behaviors by helping individuals adhere to and achieve their goals. Our long-term goal is to develop enhancements to health behavior interventions that engage the reward and regulation mechanisms related to increase adherence and promote optimal brain health. The rationale for the proposed study is based on previous studies showing relationships between regulation, positive affect, and exercise and our preliminary data that show targeting the regulation and reward systems increases healthy choices and positive affect. we will apply the NIH Stage Model to develop guided imagery to target reward AND regulation brain systems and assess the impact on exercise adherence. First, we will test a brief guided imagery approach to engage regulation and reward brain systems and the acceptability of HIIT in mid-life adults (R61). We will use guided imagery that includes PAI to increase positive associations with exercise and/or EFT to increase focus on one's healthy, physically active, future self and increase regulation. We will dynamically refine the HIIT exercise intervention to increase acceptability. Systematically testing the independent effects of engaging reward or regulation on changes in reward and regulation indices and refining the HIIT protocol will help us develop the optimal behavioral and exercise intervention approach. Next, we will test this approach and the impact on exercise adherence and physical activity in a 6-week HIIT exercise intervention (R33). This innovative study fills a gap in the current literature by examining the impact of EFT and positive affect guided imagery among mid-life adults and will inform future interventions to improve health decision-making, promote healthy behaviors and brain health, and reduce the risk of developing Alzheimer's disease.