People living with stroke have very low aerobic fitness, which can negatively impact brain health. Identifying the best exercise which includes exercise stimulus type (interval, continuous) or intensity, how hard to exercise (moderate, high) that benefit aerobic fitness, vascular health, and the brain's main blood vessels after stroke are unknown. This study is designed to determine the preliminary efficacy of high-volume HIIT to moderate intensity exercise using a seated stepper exercise device that allows the arms and legs to move back and forth.

People with stroke often experience physical decline and aerobic fitness that can be reversed through exercise. Evidence has shown that participating in exercise benefits aerobic fitness and vascular health while less is known about brain health. However, the optimal exercise dose such as intensity and exercise type (continuous, interval) are not yet known.

The long-term goal of this project is to develop and test strategies to be implemented in larger clinical trials to improve health in people living with stroke. For this preliminary efficacy trial, the Investigator will enroll 50 participants with chronic stroke, age 20-85 years, into a 4-week exercise program. Participants will be allocated to one of the following groups using minimization, a type of randomization based on the lower extremity Fugl-Meyer score: 1) moderate intensity continuous training (MICT), that serves as the control, or 2) high-intensity interval training (HIIT). Exercise will be performed on a recumbent stepper. The Investigator will: Assess the preliminary efficacy of HIIT on aerobic fitness (Aim 1), cerebrovascular hemodynamics (Aim 2), and vascular function (Aim 3).

Current exercise recommendations for stroke use general exercise prescription principles for older adults and are not grounded on data generated from large, well-designed, randomized controlled trials in stroke. If aerobic exercise could be proven to reduce the number of "years of life lived with disability," it would offer a key strategy for: 1) minimizing dependence on caregiver support, 2) reducing overall healthcare costs, and 3) extending quality of life for individuals after stroke. This proposed trial will address an important gap in knowledge for both the scientific and clinical communities and provide essential data that will contribute to future exercise prescription recommendations focused on stroke.

Inclusion Criteria:

• Both sexes between the age of 20-85 years at time of consent
• Chronic ischemic or hemorrhagic stroke 6 months to 15 years at consent. People with stroke and newly diagnosed cardiovascular complications had >50% prevalence of recurrent stroke at 5 years. Index stroke or recurrent stroke on same side as index stroke will be allowed.
• Ability to walk over ground with assistive devices and no continuous physical assistance from another person to perform tests for gait speed and six-minute walk test
• Exercise continuously for minimum of 30 watts for 3 minutes on the recumbent stepper to demonstrate ability to perform the exercise test.
• No aerobic exercise contraindications or other safety/physical concerns during the submaximal exercise test.
• Able to communicate with investigators, follow 2-step command & correctly answer consent comprehension questions
• Currently participating in less than 150 minutes of physical activity/week assessed by the Rapid Assessment of Physical Activity
• Stable blood pressure & statin medication doses for 30 days prior to enrollment due to effects on vascular health/hemodynamics

Exclusion Criteria:

• Hospitalization for cardiac or pulmonary disease within past 3 months
• Implanted pacemaker or defibrillator limiting exercise performance
• Reported pain that limits or interferes with activities of daily living and physical activity/exercise
• Severe LE spasticity (Ashworth >2) due to inability to exercise
• Recent history (<3 months) of illicit drug or alcohol abuse or diagnosis of significant mental illness
• Major post-stroke depression (Patient Health Questionnaire, PHQ-9 ≥ 1084)
• Currently participating in physical therapy targeting lower extremity function or another interventional study that may influence study outcomes
• Other significant neurologic, orthopedic or peripheral vascular conditions that would limit exercise participation
• Oxygen-dependent chronic obstructive pulmonary disease
• Diagnosis of other neurological disease (Multiple Sclerosis, Alzheimer's disease, Parkinson's disease)
• Self report pregnancy

Outcome assessors will be blinded to the participant's intervention group. Participants will not be given detailed information about the exercise groups.