Aim 1: Determine the safety and feasibility of administration of TSCS to children in a clinical setting. Participants will be randomly assigned to experimental (TSCS) or control (sham stimulation) groups. Both groups will receive eight-weeks of individualized gait training. We will measure adverse events, including pain and skin irritation, to determine safety as the primary outcome. Hypothesis 1: Administration of TSCS to children in a clinical setting will be safe based on similar safety outcomes as sham TSCS. Hypothesis 2: TSCS is feasible based on compliance to session interventions and long-term adherence to the protocol. Additionally, we will collect data on effort during sessions of both participant and therapist. We anticipate that the participants will report less effort in the experimental condition, as compared to the control and therapists will report equal effort across conditions.

Aim 2: Determine the neurophysiologic impact of TSCS within a single session. We hypothesize that participants will demonstrate increased volitional muscle activity and strength with TSCS as compared to sham stimulation. This will be assessed by surface EMG and hand-held dynamometry of the dominant-side quadriceps muscle during maximum volitional contraction (MVC), across multiple time points. Changes in EMG activity will indicate change in central excitability in response to stimulation.

Aim 3: Exploratory measurement of TSCS and gait training on walking function. We hypothesize that concurrent TSCS and gait training will augment walking function in children with iSCI, as compared to gait training with sham stimulation. In addition to outcomes defined above, participants will be assessed with clinically relevant outcome measures, to include the Timed Up and Go, 10-Meter Walk Test, Walking Index for Spinal Cord Injury II, and 6-Minute Walk Test. Data collected as part of this aim will elucidate trends in responder qualities and timeline of changes to inform future studies.

Inclusion Criteria:

• Age 3-16
• ≥ 6 months post injury
• Non-progressive SCI
• American Spinal Injury Association Impairment Scale (AIS) Classification C or D AIS C is an incomplete classification where more than half of the key muscles below the neurological level have a muscle grade of 3 or less AIS D is an incomplete classification where more than half of the key muscles below the neurological level have a muscle grade of more than 3
• Neurologic level above T10
• Tolerates upright position for >30 minutes
• Able to advance one lower extremity (LE) when in standing, bracing and assistive device allowed
• Medically stable (no hospitalizations in last 3 mos.)
• Able to comply with The International Standards for neurological and functional Classification of Spinal Cord Injury (ISNCSCI) exam

Exclusion Criteria:

• Progressive Spinal Cord Injury or Disease (SCI/D) (Multiple Sclerosis, Acute Disseminated Encephalomyelitis, etc.)
• Active wounds
• Range of motion limits impacting gait training
• Cardiac pacemaker/defibrillator
• Active cancer diagnosis
• Absent LE reflexes
• Pregnancy