title: The influence of cervical muscle characteristics on head impact biomechanics in football.
abstract: BACKGROUND
  An athlete is thought to reduce head acceleration after impact by contracting the cervical musculature, which increases the effective mass of the head.
  
  
  OBJECTIVE
  To compare the odds of sustaining higher magnitude in-season head impacts between athletes with higher and lower preseason performance on cervical muscle characteristics.
  
  
  METHODS
  Cohort study; Level of evidence, 2.
  
  
  METHODS
  Forty-nine high school and collegiate American football players completed a preseason cervical testing protocol that included measures of cervical isometric strength, muscle size, and response to cervical perturbation. Head impact biomechanics were captured for each player using the Head Impact Telemetry System. A median split was used to categorize players as either high or low performers for each of the following outcome measures: isometric strength (peak torque, rate of torque development), muscle size (cross-sectional area), and response to cervical perturbation (stiffness, angular displacement, muscle onset latency). The odds of sustaining moderate and severe head impacts were computed against the reference odds of sustaining mild head impacts across cervical characteristic categorizations.
  
  
  RESULTS
  Linemen with stronger lateral flexors and composite cervical strength had about 1.75 times' increased odds of sustaining moderate linear head impacts rather than mild impacts compared with weaker linemen. Players who developed extensor torque more quickly had 2 times the increased odds of sustaining severe linear head impacts (odds ratio [OR], 2.10; 95% CI, 1.08-4.05) rather than mild head impacts. However, players with greater cervical stiffness had reduced odds of sustaining both moderate (OR, 0.77; 95% CI, 0.61-0.96) and severe (OR, 0.64; 95% CI, 0.46-0.89) head impacts compared with players with less cervical stiffness.
  
  
  CONCLUSIONS
  The study findings showed that greater cervical stiffness and less angular displacement after perturbation reduced the odds of sustaining higher magnitude head impacts; however, the findings did not show that players with stronger and larger neck muscles mitigate head impact severity.
authors.affiliation: Department of Kinesiology, University of Georgia, Athens, Georgia, USA schmidtj@uga.edu.
authors.forename: Julianne D
authors.initials: JD
authors.lastname: Schmidt
authors.affiliation: Matthew A. Gfeller Sport-Related Traumatic Brain Injury Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Injury Prevention Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Guskiewicz
authors.affiliation: Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Neuromuscular Research Laboratory, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: J Troy
authors.initials: JT
authors.lastname: Blackburn
authors.affiliation: Matthew A. Gfeller Sport-Related Traumatic Brain Injury Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Injury Prevention Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Mihalik
authors.affiliation: MEA Forensic Engineers & Scientists, Richmond, British Columbia, Canada School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Gunter P
authors.initials: GP
authors.lastname: Siegmund
authors.affiliation: Injury Prevention Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Marshall
mesh_terms: D000054:Acceleration; D000293:Adolescent; D001696:Biomechanical Phenomena; D006259:Craniocerebral Trauma / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004576:Electromyography; D005538:Football / Q000293:injuries / Q000502:physiology*; D006260:Head Protective Devices; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D009334:Neck Muscles / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D012307:Risk Factors; D013686:Telemetry; D019415:Torque; D014463:Ultrasonography; D055815:Young Adult
keywords: concussion; mild traumatic brain injury; neck musculature; neck stiffness; neck strength