The investigators want to see how well the intervention of transcutaneous spinal stimulation performs by testing different levels of stimulation pulse rates. Also, transcutaneous spinal stimulation is compared to muscle relaxants such as baclofen and tizanidine, commonly given to people with spinal cord injuries, to reduce muscle stiffness and spasms. By doing this, the investigators hope to discover if transcutaneous spinal stimulation similarly reduces muscle spasms and stiffness or if combining both methods works best. This could help improve treatment options for people with spinal cord injuries in the future. conditions: Spinal Cord Injuries conditions: Spinal Cord Injury conditions: Spinal Cord Injury Cervical conditions: Spinal Cord Injury Thoracic studyType: INTERVENTIONAL phases: EARLY_PHASE1 allocation: NA interventionModel: SEQUENTIAL interventionModelDescription: This study employs a crossover design, wherein each participant is systematically administered a sequence of five distinct interventions randomly. This approach ensures that every participant receives each intervention in a unique sequence. The design facilitates within-subject comparisons by minimizing inter-individual variability, as each participant effectively serves as their own control across the study phases. The random assignment of intervention sequences aims to balance potential carryover effects and period effects. primaryPurpose: OTHER masking: NONE maskingDescription: The participants and assessors are kept unaware of which intervention is being administered. For this, the study drugs are designed to be visually identical for all participants, and the intervention and sham stimulation configuration is set without the assessor being present in the room. count: 16 type: ESTIMATED name: Transcutaneous spinal stimulation at 100 Hz name: Transcutaneous spinal stimulation at 50 Hz name: Transcutaneous spinal stimulation at 50 Hz and single dose of baclofen name: Transcutaneous spinal stimulation at 50 Hz and single dose of tizanidine name: Sham transcutaneous spinal stimulation measure: Change from baseline of posterior root reflexes (PRRs) recruitment curves. measure: Change from baseline of flexion withdrawal reflex (FWR) response amplitude. measure: Change from baseline of stretch reflex (SR) response amplitude. measure: Change from baseline in muscle stiffness as measured by the Modified Ashworth Scale (MAS), measure: Change from baseline in spasms as measured by the Spinal Cord Assessment Tool for Spastic Reflexes (SCATS). measure: Change from baseline of posterior root reflexes (PRRs) recruitment curves. measure: Change from baseline of flexion withdrawal reflex (FWR) response amplitude. measure: Change from baseline of stretch reflex (SR) response amplitude. sex: ALL minimumAge: 18 Years stdAges: ADULT stdAges: OLDER_ADULT facility: Methodist Rehabilitation Center city: Jackson state: Mississippi zip: 39216 country: United States name: Dobrivoje S Stokic, MD, DSc role: CONTACT phone: 601-364-3314 email: dstokic@mmrcrehab.org lat: 32.29876 lon: -90.18481 facility: University of Mississippi Medical Center city: Jackson state: Mississippi zip: 39216 country: United States name: Matthias J Krenn, PhD role: CONTACT phone: 601-364-3413 email: mkrenn@umc.edu lat: 32.29876 lon: -90.18481 hasResults: False