1. Department of Epidemiology, Gillings School of Global Public Health, University of Chapel Hill at North Carolina , Chapel Hill, NC 27516, USA
2. Injury Prevention Research Center, University of Chapel Hill at North Carolina , Chapel Hill, NC 27516, USA
3. John A. Feagin Sports Medicine Fellowship, Keller Army Hospital, United States Military Academy , West Point, NY 10996, USA
4. Department of Physical Medicine and Rehabilitation, Uniformed Services University of the Health Sciences , Bethesda, MD 20814, USA