Upper Limb Rehabilitation Using Non-invasive Spinal Cord Stimulation

The goal of this RCT study is to evaluate if combining activity-based therapy (ABT) with transcutaneous spinal cord stimulation (tSCS) can improve recovery of arm and hand movement in people with cervical spinal cord injury (SCI). As secondary aims, the study will also investigate at how this combination approach affects the cortical changes in the somatosensory and motor areas of the brain, as well as in the spinal cord and whether it helps participants use their arms more in daily life. The main questions relevant to this study are: 1. Can the combination of ABT + tSCS improve motor and sensory functions of the arms and hands more than ABT alone during the sub-acute stage after SCI? 2. Does ABT + tSCS induce neuroplasticity, that is, changes in the brain and spinal cord activity linked to motor and sensory functions? 3. Do participants who receive ABT + tSCS report greater use of their arms in daily activities compared to those who receive ABT only? In this study, participants will: * Receive either ABT + tSCS or ABT + sham stimulation (a low-intensity current that does not facilitate the movements) * Take part in 20 training sessions over 6-8 weeks (3 times per week, 45 min of active training each). During this, they will perform strengthening, task-based training, and motor control strengthening exercises with a therapist. * Complete clinical tests and neurophysiological assessments (transspinal electrical stimulation, electroencephalography and transcranial magnetic stimulation) at three time points-- at the start, after training, and one month later to measure recovery and brain activity changes. Researchers will compare the assessment outcomes across the three time points.