Brain blood flow will be measured during exercise using magnetic resonance imaging.

Over 6 million Americans are living with Alzheimer's disease and related dementias and this number is expected to reach over 13 million by 2060. Thus, there is an urgent need for interventions to prevent the development and progression of Alzheimer's disease and related dementias. Regular exercise is currently the most promising strategy as it is repeatedly shown to have neuroprotective benefits. Evidence suggests that the neuroprotective effects of exercise is the result of improved health of blood vessels. Despite the vast amount of evidence on the benefit of exercise on the peripheral vasculature, there is little information regarding brain vascular responses during exercise. This study will investigate the impact of exercise at varying intensities on brain blood flow during exercise, and will also examine the influence of age and sex.

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