Funding for this research was provided by:
Centers for Disease Control and Prevention (R49/CE002106-01, R49/CE000674-01)
National Operating Committee on Standards for Athletic Equipment
National Federation of State High School Associations
Children's Memorial Research Center
Children's Memorial Office of Child Advocacy
Received: 13 March 2018
Accepted: 30 May 2018
First Online: 16 July 2018
Ethics approval and consent to participate
: The Colorado Multiple Institutional Review Board and the Children’s Memorial Hospital Institutional Review Board approved this study.
: The authors declare that they have no competing interests.