Spinal cord injury leads to long-lasting impairment, and currently, there is no cure for paralysis. Although transcutaneous spinal cord stimulation has shown promising results in recovering lost movements, its poor selectivity in muscle recruitment compared to invasive approaches limits the type of rehabilitation exercises that can be practiced. This project studies how spatial, frequency, and amplitude control of stimulation can be used to selectively target different neural pathways and muscle groups.

Spinal cord injury (SCI) is a life-altering event that leads to long-lasting motor impairment. Currently, there is no cure for paralysis. Transcutaneous spinal cord stimulation (tSCS) combined with exercise training can restore posture control, voluntary walking, and arm/hand function in people with SCI. However, its low selectivity in activating specific muscles compared to invasive approaches limits the rehabilitation exercises that can be practiced and help with recovery. This project will generate evidence-based knowledge of the neural mechanisms underlying spatial, frequency, and amplitude control of tSCS in generating different types of leg movements. Participants with SCI will perform leg movements using different stimulation parameter configurations in non-invasive tSCS. We will quantify changes in muscle recruitment, torque generation, and pain enabled by the different stimulation parameters. A clear understanding of the mechanisms by which these different parameters in non-invasive tSCS can be used to selectively target different muscle groups will promote the development of personalized therapies that directly target only those muscles that need assistance while respecting individuals' residual motor function.

Inclusion Criteria:

1. Age between 16 and 65 years.
2. Have a spinal cord injury (neurological level C3-T12) that occurred ≥1 year (chronic stage) prior to enrollment.
3. American Spinal Injury Association (ASIA) Impairment Scale (AIS) classification C or D
4. Able to voluntarily contract (motor score ≥ 1) at least two leg muscles (visual or palpable contraction).
5. Use of prescription medication(s) for control of spasticity has not changed in the last 2 weeks
6. Able to provide consent
7. Ability to follow multiple instructions and communicate pain or discomfort

Exclusion Criteria:

1. Progressive spinal lesions, including degenerative disorders of the spinal cord
2. Pregnant, planning to become pregnant, or currently breastfeeding
3. History of cardiopulmonary disease or cardiac symptoms
4. Implanted stimulators of any type (baclofen pump, epidural spinal stimulator, cardiac defibrillator, pace-maker, etc.)
5. Presence of orthopedic conditions that would negatively affect participation in leg exercise
6. History of autonomic dysreflexia that is severe, unstable, and/or uncontrolled
7. Unstable or significant medical conditions that can interfere with exercise or neurophysiological evaluations, such as severe neuropathic pain, depression, mood disorders, or other cognitive disorders
8. Spasms that limit the ability to participate in leg exercise activity
9. Breakdown in skin area that will be in contact with electrodes

De-identified and anonymized individual participant data including kinematic measures, EMG torque, stimulation parameters, nociception/pain measures, and associated session/task metadata. Processed datasets and summary statistics used for publications will be shared. Identifiable video recordings will not be shared.

IPD and supporting information will be made available no later than the time of publication of the primary results and/or at the end of the study performance period, whichever occurs first. Data will remain available for at least 5 years following the end of the study, subject to repository policies and continued availability of the hosting platforms.

Access will be provided to qualified researchers for non-commercial scientific purposes. Shared datasets will be de-identified/anonymized and will not include direct identifiers or any information that could reasonably be used to re-identify participants. Data will be accessed via public repositories when available (e.g., Open Data Commons for Spinal Cord Injury) and/or through controlled-access request mechanisms (e.g., NICHD DASH) as applicable.