PROJECT SUMMARY The US has experienced an unparalleled epidemic of incarceration. More than 9 million Americans are incarcerated in jail (facilities housing individuals awaiting trial and serving short sentences) each year. Of these, about 20% are women. However, the rate of growth for imprisonment among women is twice that of men. Women are entering into institutions designed with little consideration for differences in gender-based health needs that contributes to poor short- and long-term physical and mental health. Women incarcerated have a higher burden of chronic conditions, psychiatric disorders, and drug dependence than men, including conditions found more commonly in men in the general population. Physical activity (PA) can mitigate poor health outcomes and have immediate effects. A single bout of moderate-to-vigorous PA improves anxiety symptoms, decreases blood pressure, and improves sleep on the day it is performed. Despite these benefits, physical inactivity is the single most common cardiovascular risk factor experienced by incarcerated individuals. Jails may provide leisure-time and work-related opportunities to be physically active, but opportunities vary by sex. Depending on policies and practices, jails may provide recreation time, an unstructured time dedicated to leisure-time PA. However, 75% of individuals incarcerated do not attend rec- time, with more women reporting higher rates of non-attendance. There are also disparities in work-related PA opportunities while incarcerated, including disparities in work assignment availability for women and men. However, there is no research about differential access to leisure and work-related PA opportunities in co-ed jails and how PA impacts health during and after incarceration. The scientific objective of the proposed research is to determine gender disparities in PA opportunities in 2 co-ed county jails and examine the impact of these disparities on health while incarcerated and after release. We hypothesize that, compared to men, women will have lower access to PA opportunities in co-ed jails leading to poorer mental and physical health during and after incarceration. We will interview jail staff and individuals incarcerated to determine leisure and work-related PA opportunities and policies in 2 northern Arizona jails. We will construct a 1-year prospective cohort of 500 men and women incarcerated at 2 northern Arizona jails to understand gender-based differences in patterns of time spent in PA and sedentary time while incarcerated and how those patterns impact physical and mental health during and after incarceration. Finally, using data collected from the prospective cohort and the novel parametric g-formula, we will estimate the probable impact of realistic, simulated PA interventions to improve health outcomes. Access to opportunities to increase PA in jails is a health equity issue. The collection of primary, longitudinal data to inform simulated interventions that hold prom...