The goal of this study is to evaluate if non-invasive electrical spinal stimulation can help people with paralysis caused by SCI improve strength and function of their arms, legs, hands or feet. The study will involve therapy sessions involving exercises done at the same time as electrical stimulation therapy. This study has multiple parts to evaluate the effectiveness and safety of "smart" electrical stimulation of the spinal cord, which involves stimulating the spinal cord at precise locations and times to improve movement and function.

This trial is investigating the use of transcutaneous spinal cord stimulation, where the electrical stimulation is delivered non-invasively via surface electrodes placed on the skin along the spine. The trial will have two phases: open-loop transcutaneous spinal cord stimulation (SCS) phase (where stimulation parameters are selected and subsequently fixed for each stimulation sessions) and closed-loop transcutaneous SCS phase, (where stimulation parameters are continuously revised in real-time during each session based upon the exact movement state of the person as captured by wearable kinematic and electromyographic sensors). For both open-loop and closed-loop phases, the transcutaneous spinal cord stimulation will be incorporated into Functional Task Practice (FTP) sessions guided closely by a team of trained technicians and occupational and physical therapists.

Upon enrollment, participants will complete a baseline assessment of outcome measures validated for spinal cord injury rehabilitation. They will also undergo mapping with sensors of their movements without stimulation to simply characterize their unique "motor signature". Then they will undergo the same mapping with open-loop transcutaneous SCS applied to determine if and how stimulation at a variety of settings can modify their unique "motor signature". They will then participate in the open-loop phase - 15 open-loop SCS+FTP sessions - after which they will repeat the outcome measures (interim assessment). They will then proceed to the closed-loop phase - 15 closed-loop SCS+FTP sessions - after which they will repeat the outcome measures a final time (endpoint assessment).

Inclusion Criteria:

• Has a non-progressive or central cord spinal cord injury from C2-T10 inclusive
• Has American Spinal Injury Association (ASIA) Impairment Scale (AIS) classification B, C, or D
• Can participate in physical and occupational therapy rehabilitation programs
• Is at minimum 12 months post- spinal cord injury
• Can provide informed consent
• Has adequate caregiver support to facilitate participation in study

Exclusion Criteria:

• Has uncontrolled cardiopulmonary disease or cardiac symptoms (as determined by the Investigator)
• Has diffuse lower motor neuron injury rendering majority of muscles not excitable
• Has any unstable or significant medical condition that is likely to interfere with study procedures or likely to confound study endpoint evaluations like severe neuropathic pain, depression, mood disorders or other cognitive disorders
• Has autonomic dysreflexia that is severe, unstable, and uncontrolled or uncontrolled orthostatic hypotension that may interfere with rehabilitation.
• Requires ventilator support
• Has an autoimmune etiology of spinal cord dysfunction/injury
• Has spasms that limit the ability to participate in the study training (as determined by the Investigator)
• Has skin breakdown in area(s) that will come into contact with electrodes
• Has any active implanted medical device
• Is pregnant, planning to become pregnant or currently breastfeeding
• Has concurrent participation in another drug or device trial that may interfere with this study
• Has other traumatic injuries such as peripheral nerve injuries, severe musculoskeletal injuries (e.g., shattered pelvis, long bone fractures), that prevent evaluation of response to or participation in rehabilitation.
• Is deemed ineligible because the investigators believe the study would not be safe or appropriate for the individual