This study is to test whether pelvis perturbation training paired with transcutaneous spinal direct current stimulation (tsDCS) will be effective in improving dynamic balance and locomotor function in humans with SCI. One group will receive pelvis perturbation training paired with tsDCS, one group will receive pelvis perturbation training paired with sham, and one group will receive treadmill training only.

A major goal of patients with spinal cord injury (SCI) is to regain walking ability, as limitations in mobility can affect most activities of daily living. In addition, patients with SCI may experience a higher incidence of falls due to impaired balance and gait. Dynamic balance control plays a crucial role during locomotion in human SCI. Thus, improved dynamic balance may facilitate locomotion in this population. Current balance training paradigms can be effective in improving balance during standing, but are less effective in improving dynamic balance during locomotion in humans with SCI. Thus, there is a need to develop new paradigms for improving dynamic balance and locomotor function in patients with SCI. The goal of this study is to test whether pelvis perturbation training paired with transcutaneous spinal direct current stimulation (tsDCS) will be effective in improving dynamic balance and locomotor function in humans with SCI. We postulate that providing a perturbation force to the pelvis during treadmill training will increase the activation of muscles used for maintaining lateral balance while walking. Further, repeated activation of particular sensorimotor pathways may reinforce circuits and synapses used for lateral balance control through a use-dependent neural plasticity mechanism. However, the excitability of spinal cord neural circuitries may be depressed due to the reduced descending drive signals from the upper level control center after SCI, which may reduce the efficacy of neuralplastic changes achieved following rehabilitation. The excitability of neural pathways is crucial for neural reorganization achieved following rehabilitation. Recently studies indicate that tsDCS may modulate the excitability of neural circuitries of the spinal cord in patients with SCI. Thus, we postulate that controlled pelvis perturbation training paired with tsDCS will be more effective than that paired with a sham in improving dynamic balance and locomotor function in humans with SCI. Results obtained from this study will lead to an innovative clinical therapy aimed at improving balance and walking function in humans with SCI. Improvements in balance and walking function may allow for increased participation in community-based ambulation and activities, and significantly improve quality of life in humans with SCI.

Inclusion Criteria:

1. age between 18 and 65 years;
2. medically stable with medical clearance to participate;
3. level of the SCI lesion between C4-T10;
4. passive range of motion of the legs within functional limits of ambulation;
5. ability to walk on a treadmill for more than 20 minutes with partial body weight support as needed and short sitting/standing breaks;
6. ability to ambulate without orthotics or with orthotics that do not cross the knee for more than 10 meters

Exclusion Criteria:

1. the presence of unhealed decubiti, existing infection, severe cardiovascular and pulmonary disease, concomitant central or peripheral neurological injury (e.g. traumatic head injury or peripheral nerve damage in lower limbs);
2. history of recurrent fractures and/or known orthopedic injury to the lower extremities;
3. Botox injection within 6 months of starting the study, and current receiving physical therapy treatment;
4. have metallic implantation in the spinal region underneath where electrodes may be placed.