1. Department of Physical Medicine and Rehabilitation (PM&R), Virginia Commonwealth University, Richmond, Virginia, USA
2. Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
3. Division of Epidemiology, Department of Internal Medicine, University of Utah Hospital, Salt Lake City, Utah, USA
4. Department of Kinesiology, University of Virginia, Charlottesville, Virginia, USA
5. Ben Taub Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Houston, Texas, USA
6. National Intrepid Center of Excellence, Walter Reed National Military Medical Center, Bethesda, Maryland, USA