title: Influence of Cervical Muscle Fatigue on Musculo-Tendinous Stiffness of the Head-Neck Segment during Cervical Flexion.
abstract: OBJECTIVE
  The aim of this study is to determine if the fatigue of cervical muscles has a significant influence on the head-neck segment musculo-tendinous stiffness.
  
  
  METHODS
  Ten men (aged 21.2 ± 1.9 years) performed four quick-release trials of flexion at 30 and 50% MVC before and after the induction of muscular fatigue on cervical flexors. Electromyographic activity was recorded on the sternocleidomastoids (SCM) and spinal erectors (SE), bilaterally. Musculo-tendinous stiffness was calculated through the quick-release method adapted to the head-neck segment.
  
  
  RESULTS
  We noticed a significant linear increase of the head-neck segment musculo-tendinous stiffness with the increase of exertion level both before (P < 0.0001) and after the fatigue procedure (P < 0.0001). However, this linear relationship was not different before and after the fatigue procedure. EMG analysis revealed a significant increase of the root mean square for the right SCM (P = 0.0002), the left SCM (P < 0.0001), the right SE (P < 0.0001), and the left SE (P < 0.0001) and a significant decrease of the median power frequency only for the right (P = 0.0006) and the left (P = 0.0003) SCM with muscular fatigue.
  
  
  CONCLUSIONS
  We did not find significant changes in the head-neck segment musculo-tendinous stiffness with fatigue of cervical muscles. We found a significant increase in EMG activity in the SCM and the SE after the induction of fatigue of the SCM. Our findings suggest that with fatigue of cervical flexors, neck muscle activity is modulated in order to maintain the musculo-tendinous stiffness at a steady state.
authors.affiliation: Département d'Automatique, GIPSA Lab, UMR CNRS 5216, Université Joseph Fourier, Grenoble, France; Service de Rééducation Neuro-Orthopédique, Hôpital Rothschild (AP-HP), Paris, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Portero
authors.affiliation: Département d'Automatique, GIPSA Lab, UMR CNRS 5216, Université Joseph Fourier, Grenoble, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Quaine
authors.affiliation: Département d'Automatique, GIPSA Lab, UMR CNRS 5216, Université Joseph Fourier, Grenoble, France.
authors.forename: Violaine
authors.initials: V
authors.lastname: Cahouet
authors.affiliation: Département d'Automatique, GIPSA Lab, UMR CNRS 5216, Université Joseph Fourier, Grenoble, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Léouffre
authors.affiliation: Département d'Automatique, GIPSA Lab, UMR CNRS 5216, Université Joseph Fourier, Grenoble, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Servière
authors.affiliation: Bioingénierie, Tissus et Neuroplasticité, EA 7377, Université Paris-Est, UPEC, Créteil, France; Service de Rééducation Neuro-Orthopédique, Hôpital Rothschild (AP-HP), Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Portero
mesh_terms: D000465:Algorithms; D004576:Electromyography; D006257:Head; D006801:Humans; D008297:Male; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D009129:Muscle Tonus / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009333:Neck; D009334:Neck Muscles / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D013710:Tendons / Q000502:physiology*; D055815:Young Adult