Inclusion Criteria:  Age 65-80 yrs (inclusive at time of consent). Conversant English speaking and reading ability. Medical clearance by a health care provider. Reliable means of transportation. Telephone Interview of Cognitive Status score > 25 and adjudication of normal cognition based on cognitive test data by a study medical monitor.  Exclusion Criteria:  Intention to move out of the area or travel for more than 4 weeks in the next year. Use of an assistive device for ambulation. Joint pain severe enough to prevent taking walks in community, lifting objects over your head due to pain or restriction of movement, or that is worsened by increasing physical activity. Any MRI contraindications or refusal to attempt MRI. Treatment for alcohol or substance abuse in the last 2 years. Treatment for cancer (other than non-metastatic, localized cancer) in the last 2 years. Currently taking insulin. Diagnosis of heart disease, heart failure, heart attack, or heart surgery or chest pain with effort in the last 2 years. Untreated atrial fibrillation, valve replacements, angioplasty or stent placement in the last 2 years regardless of physician clearance. History of major psychiatric illness including schizophrenia (not including general anxiety disorder or depression), MS, Parkinson's, Dementia, MCI, brain injury (traumatic or clinically evident Stroke), or similar, likely to negatively impact cognitive testing. Head injury with loss of consciousness for more than a few minutes. Change in blood pressure medication in the last 2 months. Considered "Active" or engaging in a progressive resistance training 2 or more times a week.