title: Frequency, magnitude, and distribution of head impacts in Pop Warner football: the cumulative burden.
abstract: BACKGROUND
  A growing body of research suggests that subconcussive head impacts or repetitive mild Traumatic Brain Injury (mTBI) can have cumulative and deleterious effects. Several studies have investigated head impacts in football at the professional, collegiate, and high school levels, in an attempt to elucidate the biomechanics of head impacts among football players. Youth football players, generally from 7 to 14 years of age, constitute 70% of all football players, yet burden of, and susceptibility to, head injury in this population is not well known.
  
  
  METHODS
  A novel impact sensor utilizing binary force switches (Shockbox(®)) was used to follow an entire Pop Warner football team consisting of twenty-two players for six games and five practices. The impact sensor was designed to record impacts with linear accelerations over 30g. In addition, video recording of games and practices were used to further characterize the head impacts by type of position (skilled versus unskilled), field location of impact (open field versus line of scrimmage), type of hit (tackling, tackled, or hold/push), and whether the impact was a head-to-head impact or not.
  
  
  RESULTS
  We recorded a total of 480 head impacts. An average of 21.8 head impacts occurred per practice, while 61.8 occurred per game. Players had an average of 3.7 head impacts per game and 1.5 impacts per practice (p<0.001). The number of high magnitude head impacts (>80g) was 11. Two concussions were diagnosed over the course of the season. However, due to technical reasons the biomechanics of those hits resulting in concussions were not captured.
  
  
  CONCLUSIONS
  Despite smaller players and slower play when compared to high school, collegiate or professional players, those involved in youth football sustain a moderate number of head impacts per season with several high magnitude impacts. Our results suggest that players involved in open-field, tackling plays that have head-to-head contact sustain impacts with the highest linear accelerations. Our data supports previously published data that suggests changes to the rules of play during practice can reduce the burden of hits.
authors: Section of Neurosurgery, University of Chicago, 5841 S. Maryland Avenue MC3026, Chicago 60637, USA. Electronic address: wong.ricky@gmail.com.
authors: Ricky H
authors: RH
authors: Wong
authors: Department of Neurosurgery, North Shore University Health System, 2650 Ridge Avenue, Evanston 60201, USA.
authors: Andrew K
authors: AK
authors: Wong
authors: Department of Neurosurgery, North Shore University Health System, 2650 Ridge Avenue, Evanston 60201, USA.
authors: Julian E
authors: JE
authors: Bailes
mesh_terms: D000054:Acceleration; D000293:Adolescent; D001696:Biomechanical Phenomena; D001835:Body Weight; D001924:Brain Concussion / Q000453:epidemiology; D001930:Brain Injuries / Q000150:complications / Q000453:epidemiology; D002648:Child; D017281:Cost of Illness; D006259:Craniocerebral Trauma / Q000150:complications / Q000453:epidemiology*; D005538:Football / Q000293:injuries*; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D012008:Recurrence; D014741:Video Recording
keywords: Chronic traumatic encephalopathy; Head impact; Pop Warner football; Traumatic brain injury; Youth football