1. Spinal Cord Injury and Disorders Center, Richmond VA Medical Center, Richmond, VA 23249, USA
2. Physical Therapy Program, Department of Physical Medicine and Rehabilitation, University of Colorado School of Medicine, Aurora, CO 80045, USA
3. Department of Medicine, University of Udine, 33100 Udine, Italy
4. Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Palo Alto, CA 94304, USA
5. Department of Physical Medicine and Rehabilitation, Virginia Commonwealth University, Richmond, VA 23284, USA
6. Physical Medicine and Rehabilitation, Richmond VA Medical Center, Richmond, VA 23249, USA