Eligibility CriteriaInclusion Criteria: Chronic Stroke
1. age 18-70
2. at least six month post-stroke
3. residual paresis in the lower extremity (Fugl-Meyer LE motor score <34)
4. ability to sit unsupported for ≥ 30 sec
5. ability to walk at least 10 ft.
6. self-selected 10 meter gait speed < 0.8 m/s
7. provision of informed consent.
Exclusion Criteria: Acute Stroke
1. Unable to ambulate at least 150 feet prior to stroke, or experienced intermittent claudication while walking < 200 meters
2. history of congestive heart failure, unstable cardiac arrhythmias, hypertrophic cardiomyopathy, severe aortic stenosis, angina or dyspnea at rest or during activities of daily living
3. History of COPD or oxygen dependence
4. Preexisting neurological disorders, dementia or previous stroke
5. History of major head trauma
6. Legal blindness or severe visual impairment
7. history of significant psychiatric illness
8. Life expectancy <1 yr
9. Severe arthritis or orthopedic problems that limit passive ROM
10. post-stroke depression (PHQ-9 ≥10)
11. History of DVT or pulmonary embolism within 6 months
12. Uncontrolled diabetes with recent weight loss, diabetic coma, or frequent insulin reactions
13. Severe hypertension with systolic >200 mmHg and diastolic >110 mmHg at rest
14. presence of cerebellar stroke.