We propose to acquire new neuroimaging measures concurrent with muscle measures in 40 adults participating in the Pittsburgh Clinical Center R01AG059416, “Study of Muscle and Mobility in Aging (SOMMA). The goal of SOMMA is to study muscle aging as it relates to disability. The goal of the proposed expanded SOMMA-BRAIN is to identify, for the first time, novel modifiable shared brain-muscle energy characteristics best predicting resilience to fatigue and loss of mobility. By promoting an integrated study of central and peripheral causes of fatigue, this project will provide novel targets for prevention and treatment of fatigue. Additionally, this project would discover modifiable processes in muscle that may influence processes in the brain to, in turn, influence cognitive performance. The data would support a new grant application to NIA to expand the aims of SOMMA, as well as the number of participants and widen the eligibility criteria.