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The goal of this clinical trial is to learn if operant conditioning can reduce spasticity in order to improve walking in stroke patient. The main questions it aims to answer are:

• Can participants self-regulate reflex excitability
• Can participants self-regulate reflex, reduce spasticity and improve walking Participants will undergo surface stimulation to evoke spinal reflexes and will be asked to control these reflexes therefore reducing spasticity.

Researchers will compare result to able bodied participants to see if [insert effects]

The study purpose is to investigate the possibility and later effect of spinal reflex self-regulation in post-stroke stiff-knee gait. The intervention will consist of direct current surface stimulation of the peripheral nerves using electrical stimulation. Stimulation will evoke a motor response that will be collected through surface EMG electrodes and processed to depict a measure of the response as feedback to the participant to complete the loop of operant conditioning. The participant will attempt to modulate their responses over multiple sessions to cause this depiction to either increase or decrease its value depending on an established target.

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Inclusion Criteria:

1. Sign and date consent form
2. At least 3 months since stroke event
3. Over 18 years of age at time of eligibility
4. Ability to stand upright and walk for at least 5 minutes
5. Premorbidly independent
6. Mild to moderate gait impairment
7. Reduced knee flexion during walking relative to the unimpaired side
8. Unilateral hemiparesis of the lower limbs
9. Ability to evoke muscle responses through peripheral nerve stimulation, spinal cord stimulation, and transcranial magnetic stimulation
10. Medically stable
11. Skin intact on hemiparetic leg, abdomen, and scalp
12. Ability to evoke muscle responses and/or reflex responses through peripheral nerve stimulation, spinal cord stimulation, and/or transcranial magnetic stimulation

Exclusion Criteria:

1. Co-existing neurological condition other than prior stroke involving the hemiparetic lower limb (e.g., peripheral nerve injury, PD, SCI, TBI, MS).
2. History of lower limb musculoskeletal injury
3. Functionally relevant osteoarthritis and weight bearing restriction
4. Functionally relevant polyneuropathy resulting in lack of sensation in the lower leg
5. Functionally relevant cognitive impairment
6. Functionally relevant vision impairment
7. Pregnant
8. Botox injection to the ipsilateral leg in the last 12 weeks or taking oral anti-spasticity medications
9. Taking part in physical therapy for any walking-related impairment
10. Cardiac pacemaker or other implanted electronic systems
11. Uncontrolled seizure disorder
12. Use of seizure lowering threshold medications and the discretion of the study physician
13. Deficits in communication that interfere with reasonable study participation
14. Severely impaired cognition and communication
15. Severe lower limb pain