1. Department of Health, Human Performance and Recreation/Office for Sport Concussion Research, University of Arkansas , Fayetteville, AR 72703 , USA
2. Inova Sports Medicine Concussion Program , Inova Hospital, Fairfax, VA 22031 , USA
3. UPMC Sports Medicine Concussion Program - Department of Orthopaedic Surgery, University of Pittsburgh , Pittsburgh, PA 15203 , USA