Participants will undergo baseline visits and follow-up visits to include neurocognitive testing, VO2 max testing (graded exercise test), blood draws, and retinal scans. Potential subjects must pass an exercise stress test with 12-lead ECG, and training sessions (exercise protocol). Standardized neurocognitive tests assessing functions such as memory and attention will be administered and retinal scans will be conducted. The at-home exercise intervention will be supervised via the Polar beat/flow applications by study personnel. Subjects will engage in cardiovascular exercise with heart rate monitoring on 4 days per week for a total of 10 weeks.

Participants will exercise 4 days/week for 10 weeks using the High Intensity Interval Training (HIIT) protocol. Sessions can be conducted at home or at a gym with access to a cycle ergometer. Participants will undergo 2 supervised training sessions to learn the HIIT protocol. To record heart rate, session duration, and time at each exercise intensity, participants will be provided with an H10 Polar TM heart rate chest strap monitor and a Polar Beat/Polar Flow account. Participants will download the Polar Beat/Flow smart phone application to record exercise sessions and allow the researcher to conduct remote data monitoring. Research staff will contact participants twice per week to provide feedback.

This test will measure participants' maximal oxygen utilization and will be done once before and once after exercise intervention. The investigator will use a graded exercise test on a stationary cycle. The test will continue to maximum, and expired gases will be collected (via a spirometer) throughout the test to monitor oxygen consumption and carbon dioxide expiration. The investigator defines maximum or test termination as either voluntary exhaustion by the participant, or by two of three physiologic criteria: 1) heart rate = 220 minus age; 2) respiratory exchange ratio > 1.15; 3) Stabilization of oxygen consumption with increasing workload. The participant's effort is monitored at each test stage via the standard 6-20 rating of a perceived exertion scale. Lactate levels will also be collected by finger prick to help determine maximum.

Standardized Optical Coherence Tomography Angiography (OCT-A) scans will occur twice before and once after exercise intervention to measure retinal microvascular density changes. A fractal analysis will be used to uniquely analyze the retinal microvascular network so that global changes of the vascular system can be quantified.

Standardized neuropsychological tests will be completed twice before and once after exercise intervention. These are designed to assess global functions of processing speed, memory, attention, and executive function, which have been shown to be sensitive to diffuse effects of cardiogenic, cerebral hypoperfusion. All tests have published, aged-adjusted norms. Specific tests include: Trail making A & B, Digit Span; Rey Complex Figure (RCFT); Digit Symbol; Controlled Oral Word Association (verbal fluency); Hopkins Verbal Learning Test (HVLT); Boston Naming Test; Center for Epidemiologic Studies-Depression Scale (CES-D), and the Brief Visual Memory Test (BVMT). At each time point, the Z scores for all measures will be aggregated and divided by 9 to arrive at the total cognitive Z-score. In addition, we will calculate composite scores for separate cognitive domains using the same approach and compare each time point to measure total cognitive changes.