Understanding and Enhancing Human Health and Movement

By doing this study, investigators hope to learn how electrical stimulation can improve human movement, biomechanics, and function and to gather information on the safety and effectiveness of an implanted electrical stimulation system after paralysis from spinal cord injury, stroke, multiple sclerosis, and traumatic brain injury.

Inclusion Criteria: * Skeletal maturity and ability to sign informed consent (\>18 years) * Non-ventilator dependent paralysis resulting from injuries such as: mid cervical/thoracic (C4 or below) spinal cord injuries, poststroke hemiparesis, TBI, or MS, affecting the trunk and/or lower limbs * Innervated and excitable lower extremity and trunk musculature * Adequate social support and stability * Willingness to comply with follow-up procedures * Time post injury greater than six months * Appropriate body habitus (height and weight within acceptable limits as determined by study physician) * Neurologically stable as determined by a physician Exclusion Criteria: * Non-English speaking * Females who are pregnant * Current pressure injuries that would be exacerbated by study activities * Severe contractures or uncontrolled spasticity of any major joint of the upper or lower extremities that results in a fixed deformity that would interfere with study activities * History of spontaneous fractures or other evidence of excessively low bone density * History of vestibular dysfunction, balance problems, or spontaneous falls * Acute and or/untreated orthopedic problems that would prevent a participant from weight bearing or exercising such as a dislocation or fracture. * Acute and/or chronic problems left untreated or not controlled that would put a participant at risk by using stimulation such as cardiac abnormalities, immunological/pulmonary/renal/circulatory compromise, diabetes or hypertension * Presence of a demand pacemaker or cardiac defibrillator * Any other medical or psychological condition that would be a contraindication * Current pressure ulcers * Significant range of motion limitations that would compromise study activities * Body habitus that would compromise study activities