High vs Low-frequency of High-intensity Training in Chronic Stroke

Inclusion Criteria: * Unilateral deficits following stroke \> 6 months prior; however individuals \> 4 months post-stroke are eligible for consenting, but final eligibility and potential enrollment will not occur until \> 6 months * Age 18-85 * Weight \< 350 pounds * Able to follow 3-step commands * Able to ambulate with self-selected gait speeds between 0.10-1.0 m/s without physical assistance, but with below knee bracing and/or assistive device as needed * Lower extremity Fugl-Meyer \< 34 * Medical clearance to participate Exclusion Criteria: * Evidence of cerebellar ataxia * Uncontrolled cardiopulmonary or metabolic disease that limits exercise participation, active heterotopic ossification, recurrent history of lower extremity fractures, previous orthopedic or other peripheral or central neurologic injury that may impair locomotor activities such that, in the judgement of the PI, could compromise the safety of the participant, limit the ability to complete the study, or compromise the objectives of the study. * Currently participating in other physical therapy * \>50 units of Botox in the lower extremity OR in the lower extremity, but above the knee if the participant wears an ankle-foot-orthosis (AFO) within the past three months