title: Biomechanical investigation of head impacts in football.
abstract: OBJECTIVE
  This study sought to measure the head accelerations induced from upper extremity to head and head to head impact during the game of football and relate this to the risk of mild traumatic brain injury using the Head Impact Power (HIP) index. Furthermore, measurement of upper neck forces and torques will indicate the potential for serious neck injury. More stringent rules or punitive sanctions may be warranted for intentional impact by the upper extremity or head during game play.
  
  
  METHODS
  Game video of 62 cases of head impact (38% caused by the upper extremity and 30% by the head of the opposing player) was provided by F-MARC. Video analysis revealed the typical impact configurations and representative impact speeds. Upper extremity impacts of elbow strike and lateral hand strike were re-enacted in the laboratory by five volunteer football players striking an instrumented Hybrid III pedestrian model crash test manikin. Head to head impacts were re-enacted using two instrumented test manikins.
  
  
  RESULTS
  Elbow to head impacts (1.7-4.6 m/s) and lateral hand strikes (5.2-9.3 m/s) resulted in low risk of concussion (<5%) and severe neck injury (<5%). Head to head impacts (1.5-3.0 m/s) resulted in high concussion risk (up to 67%) but low risk of severe neck injury (<5%).
  
  
  CONCLUSIONS
  The laboratory simulations suggest little risk of concussion based on head accelerations and maximum HIP. There is no biomechanical justification for harsher penalties in this regard. However, deliberate use of the head to impact another player's head poses a high risk of concussion, and justifies a harsher position by regulatory bodies. In either case the risk of serious neck injury is very low.
authors.affiliation: Biokinetics and Associates Ltd, Ontario, Canada. withnall@biokinetics.com
authors.forename: C
authors.initials: C
authors.lastname: Withnall
authors.forename: N
authors.initials: N
authors.lastname: Shewchenko
authors.forename: R
authors.initials: R
authors.lastname: Gittens
authors.forename: J
authors.initials: J
authors.lastname: Dvorak
mesh_terms: D000054:Acceleration / Q000009:adverse effects; D000328:Adult; D001696:Biomechanical Phenomena / Q000379:methods; D001924:Brain Concussion / Q000209:etiology; D004550:Elbow; D005542:Forearm; D006225:Hand; D016489:Head Injuries, Closed / Q000209:etiology*; D019416:Head Movements / Q000502:physiology; D006801:Humans; D019838:Neck Injuries / Q000209:etiology*; D012307:Risk Factors; D012916:Soccer / Q000293:injuries*; D014741:Video Recording; D014953:Wrist