Ankle Robotics After Stroke

Inclusion Criteria: * Ages 18 and older * In the subacute phase of stroke recovery (\>6 weeks to \<6 months post-stroke) with residual hemiparesis of the lower extremity that includes symptoms of foot-drop. - or - In the chronic phase of stroke recovery (\>6 months post-stroke) with residual hemiparesis of the lower extremity that includes symptoms of foot-drop. * Clear indications of hemiparetic gait by clinical observation Exclusion Criteria: * Cardiac history of (a) unstable angina, (b) recent (less than 3 months) myocardial infarction, congestive heart failure (NYHA category II); (c) hemodynamically significant valvular dysfunction * Hypertension that is a contraindication for routine physical therapy (greater than 160/100 on two assessments). * Medical History: (a) recent hospitalization (less than 3 months) for severe medical disease, (b) symptomatic peripheral arterial occlusive disease, (c) orthopedic or chronic pain conditions that significantly alter gait function, (d) pulmonary or renal failure (e) active cancer * History of non-stroke neuromuscular disorder restricting gait. * Aphasia or cognitive functioning that confounds participation, defined as unable to follow 2 step commands or judgment of the medical officer or therapist.