Locomotion

Spinal cord injury (SCI) often results in partial or complete loss of movement. In the subacute phase (\< 6 months), the central nervous system shows increased potential for neuroplasticity, making it more responsive to rehabilitation and external stimulation. Standard care in rehabilitation centers relies on activity-based therapy (ABT), which uses intensive, task-specific training to promote recovery. Although ABT can improve mobility, its effects are often limited due to the nature of SCI and the indirect activation of neural circuits. Recent findings suggest that adding transcutaneous spinal cord stimulation (tSCS) to ABT in chronic SCI (\> 12 months) can enhance lower-limb motor recovery. This study will evaluate whether combining tSCS with gait training is safe and feasible in individuals with subacute SCI and whether it improves lower-limb motor outcomes compared with gait training alone. The investigators hypothesize that pairing gait training with tSCS early after injury will be safe and feasible and that tSCS delivered during gait training will augment leg muscle activation and lead to greater functional improvements. The study will also assess the feasibility, safety and tolerability of implementing this combined intervention in a intensive functional rehabilitation setting.

The primary purpose of this study is to conduct a clinical trial to test a prototype device for feasibility and not health outcomes. To do this, the investigators will evaluate the performance of commercially available inertial measurement unit sensors incorporated into an existing ankle brace ("sXAB") by TayCo Brace, Inc. We will compare the gait metrics calculated from the sensors incorporated into the brace with gold-standard equipment that is used in research and clinical settings to determine whether the sXAB performs adequately in terms of measurement or technical feasibility prior to further clinical evaluation. The sensors in the ankle brace will be validated in the lab, first on healthy subjects walking in standard tennis shoes/sneakers (protocol 1), and secondarily in the lab on healthy subjects wearing combat boots performing walking, running, jumping, and stair climbing (protocol 2). These movements were selected because they simulate key movements performed during operational activities. Protocol 1 will take place first, then aspects of the sXAB will be evaluated and implemented, then protocol 2 will take place. Participants completing protocol 1 are eligible to complete protocol 2. The study includes two cohorts of participants completing different functional tasks. All participants experience both conditions: with an ankle brace and without an ankle brace. Comparisons are made within-subject between brace and no-brace conditions. It is hypothesized that the sensor-enabled ankle brace will measure gait metrics with a high degree of accuracy (within 5%) when compared against the gold-standard lab equipment (i.e., motion capture and research-grade inertial measurement units).