PROJECT ABSTRACT/SUMMARY Although heart disease is the number one cause of death among women, prevention efforts in women have lagged. Additionally, in most studies to date, research on heart disease has focused on older women, but there is a growing burden of myocardial infarction among women under 60 years of age. Recent studies point to stress as playing a more important role in the manifestation of cardiovascular disease risk factors in younger women compared to younger men. Women experience increased emotional and physical symptoms as a result of stress. Psychological stress and autonomic physiological (i.e., heart rate variability) are associated with physical inactivity. Physical inactivity is a major risk factor for cardiovascular diseases and death. Therefore, more research is needed to investigate the role of physical inactivity as a unique risk factor for cardiovascular diseases amongst young women. We will leverage data from the NHLBI-funded study: Mental Stress and Myocardial Ischemia After MI: Sex Differences, Mechanisms and Prognosis (MIMS3) (2 R01 HL109413) in order to investigate the role of stress and physical activity in a group of post-MI women and men. In AIM 1, we will compare physical activity levels between young post-MI women and men. In AIM 2, we will investigate whether daily reports of psychological stress are temporally associated with physical activity levels in post-MI individuals and examine for interaction by sex. And in AIM 3, we will examine whether autonomic physiology (i.e., heart rate variability) is temporally associated with physical activity levels in post-MI individuals and examine for interaction by sex. We hypothesize that there will be differences in physical activity between women and men who are post-MI. We also hypothesize that there will be a bi-directional, temporal relationship between both physiological and autonomic physiology and physical activity. This research project will be important in generating the impetus for future studies regarding risk factors for cardiovascular diseases in young, post-MI individuals, especially with regards to stress reduction as a lever for increasing physical activity. We hope that this research aids in decisions made by public health practitioners, clinicians, and policy-makers in the design of interventions for post-MI populations that could help narrow the gap in and reduce the risk factors for negative cardiovascular outcomes by sex.