- Must be medically stable with medical clearance to participate, with absence of concurrent severe medical illness including: unhealed decubiti, existing infection, significant cardiovascular or metabolic disease which limits exercise participation, significant osteoporosis (as indicated by history of fractures following injury), active heterotrophic ossification in the lower extremities, known history of peripheral nerve injury in lower legs, history of known traumatic head injury, mental illness, history of pre-existing QT interval prolongation, congenital long QT syndrome, and history of pulmonary complications, including significant obstructive and/or restrictive lung diseases