Participants. The study investigators will recruit 40 sedentary (exercise <1 hour/week) participants who are 45-65 years of age, have impaired fasting glucose and are cognitively normal (based on the comprehensive ADRC battery). The cohort has received detailed annual medical and cognitive evaluation since enrolling in the Wisconsin ADRC. The cohort is well-characterized for health status and medication use, has undergone genotyping AD-related risk genes, and has banked fluid samples and DNA. Importantly, participants are characterized on metabolic risk, with slightly more than half meeting criteria for central obesity and/or elevated fasting glucose. Exclusion criteria are: active lifestyle (exercise >1 hour/wk); body mass index > 40; MRI contraindications; history of neurological disease, prior neurosurgery; diagnosed and/or treated type 1 or 2 diabetes; pregnancy; acute or subacute active cardiac disease (ongoing chest pain or myocardial infarction < 3 months); significant orthopedic or musculoskeletal condition that limits weight bearing.