Walking Therapy for Recovery After Stroke

Inclusion Criteria: * Sub-acute stroke (1-6 months) * Hemiparesis (Fugl-Meyer \<34) without cerebellar deficits * Ability to ambulate with or without physical assistance over 10 meters but \< 1.0 m/s and assistive devices and below-knee bracing is allowed. * Ability to sit \> 30 seconds without upper-extremity support or physical assistance * Ability to follow 3-step commands * Provision of informed consent and medical clearance from a supervising physician or medical provider to participate * Must have the ability to consent or have a legal health care power of attorney or legally authorized representative to consent for participation on their behalf Exclusion Criteria: * Significant cardiovascular, metabolic, or respiratory disease that limits exercise participation (e.g. previous myocardial infarction \< 3 months prior, uncompensated congestive heart failure, resting blood pressure \> 210/110 mmHg, uncontrolled diabetes, end-stage renal disease, severe infectious or psychiatry disease, or advanced malignancy) * If during the graded-treadmill exercise evaluation, the participant presents with absolute criteria for termination of exercise testing during initial testing (e.g. moderate to severe angina, ST elevation \> 1.0mm without preexisting Q wave secondary to prior MI, signs of poor perfusion, etc). * Any orthopedic or neurological disorders that limited walking to \<50m prior to stroke onset. * Cannot receive physical therapy once baseline testing begins * If patients are prescribed botulinum toxin for their lower extremities will be excluded only if the dosage for any specific muscle is \>50 units in leg muscles above the knee. If doses are \> than 50 units in leg muscles below the knee, the participant will use an ankle-foot orthosis to minimze contributions of those mscles to locomotor function.