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