Inclusion Criteria- Cognition sufficiently intact to give valid informed consent to participate.
- Sufficient endurance to participate in rehabilitation sessions.
- Ability to follow 2 stage commands.
- Medically stable
- Age > 21 years
- Impaired ambulation as follows: inability to flex the knee and ankle in the sagittal plane, in a normal manner so the foot clears the floor; inability to control normal knee angle during single limb weight bearing during stance phase.
- Trace contraction of hip, knee, and ankle flexors and extensors.
- Passive range of motion (ROM) at hip, knee, ankle greater than or equal to normal gait kinematics.
- Reported comfort of surface FES at a stimulus level producing a visible or palpable muscle contraction of ankle dorsiflexors.
- Greater than 3 weeks post-stroke.
- Living in the community and able to travel to training and assessment sites.
- Approval of participation by primary care physician
Exclusion Criteria- Acute or progressive cardiac, renal, respiratory, neurological disorders or malignancy.
- Active psychiatric diagnosis or psychological condition, or active drug/alcohol abuse.
- Lower motor neuron damage or radiculopathy.
- More than one stroke.
- Cerebellar dysfunction.
- Fugl-Meyer lower limb motor sub-score greater than 32.
- Severe obesity (body mass index > 35)
- For the chronic group: current participation in physical therapy or cardiopulmonary rehabilitation.
- Significant visual impairment affecting capability to gauge movement accuracy.
- Current enrollment in any clinical trial
- Planning to relocate out of the greater Gainesville, FL area during the study period
- Unable to communicate sufficiently with study personnel
- Clinical judgement regarding safety or non-compliance