title: In vivo study of head impacts in football: a comparison of National Collegiate Athletic Association Division I versus high school impacts.
abstract: OBJECTIVE
  To compare the frequency and magnitude of head impacts between National Collegiate Athletic Association Division I and American high school football players. The long-term goal is to correlate impact forces with injury patterns, leading to improvements in protective headgear.
  
  
  METHODS
  The helmets of football players at the University of Oklahoma (n = 40) and Casady High School (n = 16) were instrumented with the Head Impact Telemetry System (Simbex, Lebanon, NH). Data were collected for practices and games for the 2005 football season and were analyzed by player position and school. Player positions were separated into two groups (skill and line) for analysis. Two case studies of athletes who sustained a concussion are also presented.
  
  
  RESULTS
  A total of 54,154 impacts were recorded at the University of Oklahoma and 8326 at Casady High School. College players sustained high-level impacts greater than 98 g more frequently than high school players. The mean linear accelerations for the top 1, 2, and 5% of all impacts were also higher for college players (P < 0.02). Skill position players received 24.6% of all impacts and sustained an impact greater than 98 g once every 70 impacts. In contrast, linemen sustained the highest number of impacts, but most were relatively low-magnitude (20-30 g). Linemen sustained an impact greater than 98 g once every 125 impacts.
  
  
  CONCLUSIONS
  Differences in the frequency and magnitude of head acceleration after impact exist between a Division I college team and a high school team. Compared with linemen, skill position players typically sustain the highest-level impacts. Additional data collection and analysis are required to correlate concussion diagnosis with acceleration magnitude and impact location.
authors.affiliation: Department of Orthopedics, University of Oklahoma, Norman, Oklahoma, USA. bschnebel@mcbrideclinic.com
authors.forename: Brock
authors.initials: B
authors.lastname: Schnebel
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Gwin
authors.forename: Scott
authors.initials: S
authors.lastname: Anderson
authors.forename: Ron
authors.initials: R
authors.lastname: Gatlin
mesh_terms: D000054:Acceleration; D000293:Adolescent; D000328:Adult; D001924:Brain Concussion / Q000503:physiopathology*; D005538:Football / Q000502:physiology*; D016489:Head Injuries, Closed / Q000503:physiopathology*; D019416:Head Movements; D006801:Humans; D008297:Male; D010812:Physical Stimulation; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013334:Students / Q000145:classification / Q000706:statistics & numerical data*