Project Summary Although evidence in favor of physical activity (PA) for reducing age-related cognitive decline continues to grow, critical issues for the viability of PA to promote cognitive health are persistently low PA adoption and adherence in the population. Because PA starts declining at middle-age and neurodegenerative pathologies increasing dementia risk start decades before cognitive impairment, there is a pressing need to understand how and why middle-age adults are successful at adopting and sustaining PA. Theoretical and empirical support have identified self-regulatory capacities as critical for acting on our intentions and plans to be more physically active, however causal evidence testing whether and how strongly self- regulatory capacities affect PA behavior change is absent from the literature. Therefore, our objective is to test the causal role of the self-regulation construct, cognitive control, in PA behavior change among inactive middle-age adults. Based on the Temporal Self-Regulation Theory (TST) for PA behavior change, we hypothesize cognitive training designed to improve cognitive control will increase the success of a PA behavior change program, and that training cognitive control with emotionally valenced stimuli will further increase PA adherence at moderate-to-vigorous intensities. Our predictions are based on research showing the importance of cognitive control in PA adherence and maintenance, evidence that negative affective experiences of PA are common and detrimental to future PA initiation and maintenance, and research supporting the modifiability of cognitive control with adaptive cognitive training. We test our overall hypothesis with three aims, including a developmental R61 phase (Aim 1) to develop and refine a computerized training program targeting aspects of motivation, planning, and cognitive control theorized to promote PA behavior change, followed by an implementation R33 phase (Aim 2) with a lab-based, randomized controlled trial (RCT) to determine the extent that cognitive control for emotionally valenced information is a target mechanism for PA behavior change in inactive middle- age adults. The RCT implemented in Aim 2 will be tested across rural and urban sites to increase diversity and generalizability of our sample, which forms the basis for (Aim 3) determining moderators of intervention efficacy for improving PA behavior change. We predict those with poor cognitive control and high negative affective experiences to moderate intensity PA will benefit most from cognitive control training targeted to an affective domain for PA behavior change. Our results will be significant by determining the causal role of cognitive control and affect in sustainable PA behavior change in the critical period of midlife. Success will culminate in a scalable training program to boost PA adherence, setting the stage for personalized and accessible strategies for midlife adults to change their course towards a more p...