title: Changes of postural control and muscle activation pattern in response to external perturbations after neck flexor fatigue in young subjects with and without chronic neck pain.
abstract: OBJECTIVE
  Previous studies have identified sensorimotor disturbances and greater fatigability of neck muscles in patients with neck pain. The purpose of this study was to investigate the effect of neck pain and neck flexor fatigue on standing balance following postural perturbations.
  
  
  METHODS
  Twenty patients with chronic neck pain (CNP) (24.7±3.6 year-old) and 20 age-matched asymptomatic subjects (22.1±2.2 year-old) were recruited. Subjects stood barefoot on a force plate and experienced backward perturbations before and after neck flexor fatigue. Center of pressure, electromyography of cervical and lumbar muscles, and head/trunk accelerations were recorded. Two-way ANOVA (pain×fatigue) was used for statistical analysis.
  
  
  RESULTS
  CNP group showed larger body sway during quiet standing but not during perturbed standing compared with asymptomatic adults. In both groups, neck flexor fatigue resulted in greater body sway during the quiet standing but smaller body sway during perturbed standing, increased neck muscle activations and decreased lumbar muscle activations, as well as increased time to maximal head acceleration.
  
  
  CONCLUSIONS
  Disturbed balance control was observed in CNP patients during the quiet standing. However, a rigid strategy was used to minimize the postural sway and to protect the head against backward perturbations in both CNP and asymptomatic young adults after neck flexor fatigue. The results facilitate the understanding of how the subjects with chronic neck pain and with neck muscle fatigue deal with the challenging condition. Further studies are needed to verify if such phenomenon could be changed after the intervention of specific flexor muscle retraining and balance control exercises.
authors.affiliation: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan, ROC.
authors.forename: Chih-Hsiu
authors.initials: CH
authors.lastname: Cheng
authors.affiliation: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan, ROC; Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Andy
authors.initials: A
authors.lastname: Chien
authors.affiliation: School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Wei-Li
authors.initials: WL
authors.lastname: Hsu
authors.affiliation: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan, ROC.
authors.forename: Ling-Wei
authors.initials: LW
authors.lastname: Yen
authors.affiliation: Department of Physical Therapy and Graduate Institute of Rehabilitation Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan, ROC.
authors.forename: Yang-Hua
authors.initials: YH
authors.lastname: Lin
authors.affiliation: Graduate Institute of Early Intervention, College of Medicine, Chang Gung University, Taoyuan, Taiwan, ROC. Electronic address: kcheng@mail.cgu.edu.tw.
authors.forename: Hsin-Yi Kathy
authors.initials: HY
authors.lastname: Cheng
mesh_terms: D000328:Adult; D002908:Chronic Disease; D004576:Electromyography / Q000379:methods; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D009334:Neck Muscles / Q000503:physiopathology*; D019547:Neck Pain / Q000175:diagnosis / Q000503:physiopathology / Q000534:rehabilitation*; D004856:Postural Balance / Q000502:physiology*; D011312:Pressure; D055815:Young Adult
keywords: Muscle fatigue; Neck pain; Standing balance