title: Kinematics of head movement in simulated low velocity rear-end impacts.
abstract: OBJECTIVE
  To evaluate kinematics of head movement related to impact velocity, gender and awareness in simulated low velocity rear-end impacts.
  
  
  METHODS
  Thirty individuals were subjected in random order to three rear-end impacts: two unexpected impacts causing chair acceleration of 4.5m/s2 (slow) and 10.0m/s2 (fast) and one 10.0m/s2 expected impact. Rearward head displacement, and linear and angular head accelerations were recorded.
  
  
  RESULTS
  Angular head displacement was almost two times higher for the fast than the slow unexpected-impacts (P=0.04). Rearward and forward angular head accelerations increased two to three times with increased impact magnitude (P<0.05). Rearward and forward linear head accelerations were two and a half to three and a half times higher for the fast than for the slow unexpected impacts (P<0.05). Males presented two times higher upward linear head acceleration than females in the unexpected fast impact. No significant magnitude differences were identified for impact awareness in kinematics of head movement (P>0.05). Rearward angular head acceleration reached the peak between 62 and 84 ms later than the rearward linear head acceleration (P<0.05) in all impacts. No significant differences were identified for timing of kinematics of head movement (P>0.05) with increased impact magnitude; however, statistical powers were low.
  
  
  CONCLUSIONS
  Kinematics of head movement increases with increased impact magnitude. Gender differences exist for vertical linear head acceleration only. Temporal and amplitude awareness do not change the magnitude in kinematics of head movement. There are temporal differences between angular and linear head accelerations.
authors.affiliation: Faculty of Medicine and Dentistry, Department of Dentistry, University of Alberta, Room 4051b, Dentistry/Pharmacy Centre, Edmonton, AB, Canada T6G 2N8.
authors.forename: Ivonne A
authors.initials: IA
authors.lastname: Hernández
authors.forename: Ken R
authors.initials: KR
authors.lastname: Fyfe
authors.forename: Giseon
authors.initials: G
authors.lastname: Heo
authors.forename: Paul W
authors.initials: PW
authors.lastname: Major
mesh_terms: D000054:Acceleration; D000063:Accidents, Traffic; D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena / Q000379:methods; D003198:Computer Simulation; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D010812:Physical Stimulation / Q000009:adverse effects / Q000379:methods*; D014911:Whiplash Injuries / Q000209:etiology / Q000503:physiopathology*