After being informed about the purpose, study timeline, and procedures, all participants giving written informed consent will undergo repeated baseline measurements throughout four weeks, followed by intensive exercise therapy for six weeks.~Next, participants will receive (1) closed-loop stimulation and (2) open-loop stimulation treatment for Aim 1 Section of the study. Stimulation will be delivered non-invasively using skin electrodes on the back of the neck. Each treatment arm will last six weeks. The investigators will determine the order of the treatment arms randomly. For closed-loop stimulation, The investigators will place a sensor on the arm muscles over the skin. This sensor will detect the movement and start the stimulation accordingly.~For Aim 2 Section, intervention arms will consist of (1) transcutaneous stimulation, followed by (2) spasticity-reducing stimulation treatment arms.~There will be a 6-week waiting period between two stimulation arms where participants will not receive any stimulation or exercise therapy. Treatments will last 90 minutes per session, three sessions per week. Overall participation in the study will last ten months: Four weeks baseline + three treatment periods (each will last six weeks) + six weeks waiting period between stimulation treatments + 12 weeks follow-up.
The purpose of this study is to assess the efficacy of non-invasive (transcutaneous) closed-loop electrical spinal cord stimulation for recovery of upper limb function (Aim 1) and spasticity (Aim 2) following spinal cord injury.