title: Investigating cervical muscle response and head kinematics during right, left, frontal and rear-seated perturbations.
abstract: OBJECTIVE
  Whiplash research has largely focused on rear collisions because they account for the majority of whiplash injuries. The purpose of this study was to evaluate the effects of 4 perturbation directions (anterior, posterior, right, and left) on muscle activity and head kinematics to provide insight into the whiplash mechanism of injury.
  
  
  METHODS
  The effects of 4 perturbation directions induced by a parallel robotic platform, with peak acceleration of 8.50 m/s2, were analyzed on 10 subjects. Surface electromyography (EMG) measures were collected from the sternocleidomastoid (SCM), trapezius, and splenius capitus muscles. Kinematics of the head, thorax, and head relative to thorax were also measured.
  
  
  RESULTS
  We observed stereotypic responses for kinematics and SCM EMG for the various perturbation directions; the trapezius and splenius capitus muscles showed amplitudes that were less than 5 percent maximum voluntary contraction (MVC). Rear perturbations elicited the smallest onset latencies for the SCM (30 ms) and kinematic variables and greatest linear head center of mass (COM) accelerations. Frontal perturbations resulted in an average SCM onset latency of 143 ms and demonstrated the greatest magnitude of head translations and rotations relative to the thorax. Left and right perturbations demonstrated similar kinematics and SCM onset latencies (55 and 65 ms, respectively).
  
  
  CONCLUSIONS
  Compared to frontal, left, and right directions, rear perturbations showed smaller SCM onset latencies, greater SCM amplitudes, and larger head accelerations, relating to a greater potential for injury. We suggest that the greater contact area and stiffness of the seatback, in the posterior direction, compared to restrictions in other directions, led to increased peak head accelerations and shorter SCM onset latencies.
authors.affiliation: University of Guelph, Human Health and Nutritional Sciences, Guelph, Ontario, Canada.
authors.forename: Natalie
authors.initials: N
authors.lastname: Sacher
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Frayne
authors.forename: James P
authors.initials: JP
authors.lastname: Dickey
mesh_terms: D000054:Acceleration; D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006257:Head / Q000502:physiology*; D006801:Humans; D008297:Male; D009334:Neck Muscles / Q000502:physiology*; D014911:Whiplash Injuries / Q000209:etiology* / Q000503:physiopathology; D055815:Young Adult