Brain Blood Flow Responses During Exercise

Inclusion Criteria: * Healthy men or women between the ages of 55-69 years * Demonstrate an exercise history of engaging in aerobic physical activity at least 3 times per week for a minimum of 30 continuous minutes * Have experience using cardiovascular exercise equipment (e.g., treadmill, elliptical, upright or recumbent bicycle, stair-stepper) Exclusion Criteria: * Outside of specified age range * Do not have experience using cardiovascular exercise equipment * Do not meet the physical activity criteria * Present with a history or evidence of hepatic, renal, hematological disease, cardiovascular disease including uncontrolled hypertension, peripheral vascular disease, stroke/neurovascular disease, and diabetes * have a body mass index ≥35 kg/m2 * are ≥ 71 inches (180 cm) in height * have any contraindications to MRI * currently use or have a history of use of tobacco or illegal substances * have current and/or a history of depression or other mood related disorders (those with mild depression and/or anxiety that is controlled with medication and/or therapy will not be excluded) * vulnerable populations (e.g., pregnant women, prisoners, individuals lacking capacity to consent) * if the desired moderate/vigorous exercise intensity corresponds to \> 350 watts on the stepper device