Inclusion Criteria1. age between 21 and 75 years;
2. history of unilateral, supratentorial, ischemic or hemorrhagic stroke;
3. no prior stroke;
4. demonstration of impaired walking function (self-selected walking speed ≤ 0.80 m/s);
5. able to stand and walk (>10 meters) without physical assistance.
Exclusion Criteria1. significant cardiorespiratory/metabolic disease;
2. other neurological or orthopedic injury that impairs locomotion;
3. scores on the Mini Mental Status examination < 24;
4. stroke of the brainstem or cerebellar lesions;
5. uncontrolled hypertension (systolic > 200 mm Hg, diastolic > 110 mm Hg);
6. botox injection within 6 months of starting the study.