Inclusion criteria
1. All participants must be able to provide a provision of a signed and dated informed consent form.
2. Stated willingness to comply with all study procedures and availability for the duration of the study.
3. Male or female, aged 22-75 years old.
4. Documentation from the participant's primary treating physician confirming a stable medical condition.
5. Inability to maintain standing independently without external support due to SCI AIS A-C.
6. Ability to tolerate at least 15 minutes in an upright (supported) position.
7. Able to self-transfer from the wheelchair and demonstrate active range of motion of bilateral upper extremities in gravity dependent plane.
8. Able to passively range bilateral lower extremities within normal mobility parameters including:
1. greater than 90 degrees of hip flexion and 165 degrees of hip extension;
2. greater than 90 degrees of knee flexion and reach neutral knee extension of 180 degrees;
3. neutral ankle position reaching a minimum of 90 degrees of dorsiflexion.
9. Participants should be on a stable intrathecal baclofen or oral anti-spasticity regimen/dose for the period of the study unless advised otherwise by their physician.
10. 1 to 30 years post spinal cord injury.
11. Non-progressive spinal cord injury.
12. Neurological level of injury below C4 and above T12 (excluding conus injury and/or indications of lower motor neuron injury).
13. Eligible for fMRI per safety questionnaire.
14. Women of childbearing potential must agree to the use of an effective means of avoiding pregnancy for the duration of the study.
15. Able to commit to the full study.
Exclusion Criteria:
1. Ability to maintain standing independently without external support.
2. Currently involved in another rehabilitation training of the lower extremities.
3. Active pressure sores, unhealed bone fractures, peripheral neuropathies, or painful musculoskeletal dysfunction (including but not limited to contractures in the upper and lower extremities).
4. Any ongoing medical condition which would preclude participant from regular physical activity (including but not limited to: cardiopulmonary disease, uncontrollable autonomic dysreflexia or orthostatic hypotension, active urinary tract infections, pregnant or nursing).
5. Intrathecal baclofen pump therapy for spasticity not compatible with 3T MRI.
6. Must not have received Botox injections to primary lower extremity and trunk musculature within the past 3 months, resulting in absence of muscle tone and precluding response to electrical stimulation therapy.
7. Current or history of neuromuscular conditions (including but not limited to: unhealed ligament of muscular tears in the upper or lower extremities, pain in weight bearing positions for upper and lower extremities).
8. Clinically significant depression, psychiatric disorders, or ongoing drug abuse, including heavy alcohol use.
9. Any reason the PI or treating physician may deem as harmful to the participant to enroll or continue in the study.
10. Body Mass Index (BMI) over 30.
11. Pregnancy.
12. Use a ventilator or diaphragmatic pacer.
13. Participants with the following conditions will be excluded from TMS, but may take part in the overall study:
- Personal or first-degree family history of seizures or epilepsy.
- Metal in the head, except mouth implants.
- History of suicide attempts.
- History of intracranial lesions, increased intracranial pressure, or stroke.
- Current use of tricyclic anti-depressants, selective serotonin reuptake inhibitors (SSRIs), serotonin nor-epinephrine reuptake inhibitors (SNRIs), buproprion (Wellbutrin), or tramadol.