Table 1.

Inclusion and exclusion criteria.

Inclusion criteria

Exclusion criteria

•Age 65–80 yrs. •Ambulatory without pain or the use of assisted walking devices •Able to speak and read English •Medical clearance by primary care physician (PCP) •Living in community for duration of the study •Reliable means of transportation •No diagnosis of a neurological disease •Telephone Interview of Cognitive Status score > 25 •Cognitive adjudication decision of cognitively normal

•Current diagnosis of an Axis I or II disorder including Major Depression •History of major psychiatric illness including schizophrenia (not including general anxiety disorder or depression (Geriatric Depression Scale [GDS] ≥9) •Current treatment for cancer – except non-melanoma skin cancer •Neurological condition (MS, Parkinson's, Dementia) or brain injury (Stroke) •Type I Diabetes, Insulin-dependent Type II Diabetes, uncontrolled Type II diabetes (defined as an HbA1c level > 10) •Current alcohol or substance abuse or treatment for abuse in the past 5 years •Current treatment for congestive heart failure, angina, uncontrolled arrhythmia, deep vein thrombosis (DVT) or another cardiovascular event •Myocardial infarction, coronary artery bypass grafting, angioplasty or other cardiac condition in the past year •Claustrophobia or inability to complete the MRI scan due to metal implants (pacemaker, stents) that are MR ineligible •Color Blindness •Engaging in >20 min of moderate intensity physical activity per day for 3 days or more per week •Not local or able to travel 3 times per week to the exercise facility •Traveling consecutively for 3 weeks or more during the study •Unwillingness to be randomized to one of the three groups •Current participation in an ongoing trial likely to influence exercise ability or cognitive function (e.g., mindfulness training).