[1] Datalys Ctr Sports Injury Res & Prevent Inc, Indianapolis, IN 46202 USA
[2] Univ N Carolina, Dept Exercise & Sport Sci, Chapel Hill, NC USA
[3] Univ N Carolina, Matthew A Gfeller Sport Related Traumat Brain Inj, Dept Exercise & Sport Sci, Chapel Hill, NC USA
[4] Univ N Carolina, Ctr Study Retired Athletes, Dept Exercise & Sport Sci, Chapel Hill, NC USA
[5] Univ N Carolina, Injury Prevent Res Ctr, Chapel Hill, NC USA
[6] Univ N Carolina, Dept Epidemiol, Chapel Hill, NC USA
[7] Univ Washington, Dept Pediat, Seattle, WA 98195 USA
[8] Harvard Univ, Harvard Interfac Initiat Hlth Policy, Cambridge, MA 02138 USA
[9] Boston Childrens Hosp, Div Sports Med, Boston, MA USA
[10] Univ N Carolina, Chapel Hill, NC USA