1. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
2. University of North Carolina Injury Prevention Research Center, Chapel Hill, North Carolina, USA.
3. Department of Exercise and Sport Science, College of Arts and Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
4. Department of Orthopaedics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.