Exercise for Brain Health in the Fight Against Alzheimer's Disease

Inclusion Criteria: * 60 to 80 years old * Fluent in English * Willingness to make the time commitment to participate in the project, including randomization to treatments * Physically inactive (physical activity not more than 2 days per week for the past 6 months) * Physician consent to undergo an exercise stress test and engage in moderate intensity exercise * Determined to be safe for MRI Exclusion Criteria: * Neurological illnesses/conditions such as cerebral palsy, epi¬lepsy, brain tumor, chronic meningitis, multiple scle¬rosis, pernicious anemia, normal-pressure hydrocephalus, HIV infection, Parkinson's disease, and Huntington's disease * Untreated hypertension, glaucoma, and chronic obstructive pul¬monary disease * Untreated severe major depression * Substance abuse or dependence * Current use of psychoactive medications, except selective serotonin/norepinephrine reuptake inhibitor antidepressants * Use of acetylcholinesterase inhibitors (e.g., Aricept) * Unstable or severe cardiovascular disease or asthmatic condition * History of transient ischemic attack, cerebral ischemia, or clinically diagnosed stroke * Diagnosis of mild cognitive impairment or dementia, or objective evidence of cognitive impairment