title: Muscle activity influence on the kinematics of the cervical spine in rear-end sled tests in female volunteers.
abstract: OBJECTIVE
  Although much research has been performed to investigate the cervical spine kinematics during rear-end collisions, our understanding about the exact role of the musculature is limited. The question of the influence of muscle activity on cervical spine kinematics has been discussed.
  
  
  METHODS
  A rear-end collision with a speed change (ΔV) of 6.3 km/h was simulated in a sled test with 8 female subjects to investigate the influence of the ventral and dorsal cervical spine musculature on cervical spine kinematics. A high-speed camera and accelerometers recorded the motion and acceleration data. The activity of the sternocleidomastoid muscles was recorded with surface electrodes. To avoid cross talk, an intramuscular recording of the semispinalis capitis muscles was performed with fine-wire electrodes.
  
  
  RESULTS
  The analysis of the motion and acceleration parameters allowed the definition of 4 phases. The headrest contact began after a median of 84 ms and the sternocleidomastoid muscle force could be detected after a median of 81 ms, with 0 defining the time of the trigger signal. The maximal force of the sternocleidomastoid muscle and the maximal headrest effect began prior to the maximal ventral angular head acceleration and prior to the maximal ventral horizontal head acceleration relative to T1. The start of the semispinalis capitis muscle force was observed after a median of 159 ms and increased until a flexion of 20 to 25° was reached.
  
  
  CONCLUSIONS
  The headrest effect and the sternocleidomastoid muscle force firstly supported the deceleration of the head relative to T1 toward dorsal, which was followed by an accelerating effect toward ventral. The semispinalis capitis muscle force exerted a late decelerating effect on head flexion and ventral translation movement.
authors.affiliation: Department for Trauma, Hand, Plastic and Reconstructive Surgery, University of Ulm, Ulm, Germany. christoph.dehner@uniklinikulm.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Dehner
authors.forename: Sylvia
authors.initials: S
authors.lastname: Schick
authors.forename: Michael
authors.initials: M
authors.lastname: Kraus
authors.forename: Wolfram
authors.initials: W
authors.lastname: Hell
authors.forename: Michael
authors.initials: M
authors.lastname: Kramer
mesh_terms: D000054:Acceleration; D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D000328:Adult; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000502:physiology*; D005260:Female; D006805:Human Experimentation; D006801:Humans; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult