Understanding and Enhancing Human Health and Movement

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