title: Head Impact Magnitude in American High School Football.
abstract: To describe determinants of head impact magnitudes between various play aspects in high school football.
  
  
  
  Thirty-two high school American football players wore Head Impact Telemetry System instrumented helmets to capture head impact magnitude (linear acceleration, rotational acceleration, and Head Impact Technology severity profile [HITsp]). We captured and analyzed video from 13 games (n = 3888 viewable head impacts) to determine the following play aspects: quarter, impact cause, play type, closing distance, double head impact, player's stance, player's action, direction of gaze, athletic readiness, level of anticipation, player stationary, ball possession, receiving ball, and snapping ball. We conducted random intercepts general linear mixed models to assess the differences in head impact magnitude between play aspects (α = 0.05).
  
  
  
  The following aspects resulted in greater head impact magnitude: impacts during the second quarter (HITsp: P = .03); contact with another player (linear, rotational, HITsp: P < .001); initial head impact when the head is struck twice (linear, rotational, HITsp: P < .001); longer closing distances, especially when combined with a 3-point stance or when being struck in the head (linear: P = .03); the 2-point stance (linear, rotational, HITsp: P < .001); and offensive linemen not snapping the ball compared with those snapping the ball (rotational: P = .02, HITsp: P = .02).
  
  
  
  Preventing head impacts caused by contact with another player may reduce head impact magnitude in high school football. Rule or coaching changes that reduce collisions after long closing distances, especially when combined with the 3-point stance or when a player is being struck in the head, should be considered.
authors.affiliation: Department of Kinesiology, and Concussion Research Laboratory, University of Georgia, Athens, Georgia; schmidtj@uga.edu.
authors.forename: Julianne D
authors.initials: JD
authors.lastname: Schmidt
authors.affiliation: Matthew A. Gfeller Sport-Related Traumatic Brain Injury Research Center, Department of Exercise and Sport Science, Injury Prevention Research Center.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Guskiewicz
authors.affiliation: Matthew A. Gfeller Sport-Related Traumatic Brain Injury Research Center, Department of Exercise and Sport Science, Injury Prevention Research Center.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Mihalik
authors.affiliation: Department of Exercise and Sport Science, Neuromuscular Research Laboratory, and.
authors.forename: J Troy
authors.initials: JT
authors.lastname: Blackburn
authors.affiliation: MEA Forensic Engineers & Scientists, Richmond, British Columbia, Canada; and School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Gunter P
authors.initials: GP
authors.lastname: Siegmund
authors.affiliation: Injury Prevention Research Center, Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina;
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Marshall
mesh_terms: D000054:Acceleration; D061725:Accelerometry; D000293:Adolescent; D001696:Biomechanical Phenomena; D006259:Craniocerebral Trauma / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control; D005538:Football / Q000293:injuries* / Q000502:physiology*; D006257:Head / Q000502:physiology*; D006260:Head Protective Devices; D006801:Humans; D016014:Linear Models; D008297:Male; D015588:Observer Variation; D015599:Trauma Severity Indices; D014481:United States; D014741:Video Recording