Temporary Inactivation of Strong Muscle Sensation to Improve Rehabilitation Interventions in SCI

The investigators are conducting a research study to try to improve rehabilitation interventions for individuals with spinal cord injury (SCI). In this study, the aim is to determine if temporarily numbing non-paralyzed arm muscles with an over-the-counter numbing cream while exercising paralyzed muscles, can improve the strength, function, and sensation of paralyzed muscles after a spinal cord injury.

Inclusion Criteria: SCI Patients: * Provision of signed and dated informed consent form * Stated willingness to comply with all study procedures and availability for the duration of the study * Male or female, aged between 18 and 75 years old * Have physician diagnosed cervical incomplete spinal cord injury or lesion (iSCI) * Classified by the American Spinal Cord Association (AIS) impairment scale as AIS C or D * iSCI occurred at least 18 months ago * Level of injury or lesion is between C2 and T1 * Bicep strength must be classified as ≥ 3 muscle grade as defined by the medical research council scale * Tricep strength must be at least an MRC grade of 2 and bet at least 1 muscle grade lower than the bicep * Both the biceps and triceps will be required to elicit an active motor evoked potential \>200 uV with transcranial magnetic stimulation * Must maintain current medication regime * Must present with a weaker side of the body, as indicated by a Upper extremity motor score difference between the left and right side * UEMS \< 40 (50 max score) * Must be able to perform reaching movement training task Healthy Controls: * Provision of signed and dated informed consent form * Stated willingness to comply with all study procedures and availability for the duration of the study * Male or female, aged between 18 and 75 years old * Must be right-handed * Must be able to perform hand exercises Exclusion Criteria: SCI Patients: * Pacemaker or another implanted device * Metal in the skull * History of seizures * Pregnancy * First-degree relative with medication-resistant epilepsy * Current participation in upper limb rehabilitation therapies * Current use of illicit drugs, abusing alcohol, or have withdrawn from alcohol in the last 6 months * Other neurological impairment or condition * Pressure ulcers * Significant lower motor neuron loss at C7 as noted by a nerve conduction velocity \