title: Myoelectrical activity and muscle morphology in a rat model of myofascial trigger points induced by blunt trauma to the vastus medialis.
abstract: OBJECTIVE
  To explore myoelectrical activity and muscle morphology of myofascial trigger points (MTrPs) in an injury model of rats.
  
  
  METHODS
  A total of 24 male SD rats were randomly divided into a control group (group A) and model group (group B). A blunt striking injury and eccentric exercise were applied to the vastus medialis (VM) of rats in group B for 8 weeks. Later, the palpable taut band (TB), local twitch response, myoelectrical activities and morphology in the two groups were examined.
  
  
  RESULTS
  An average of 2.5 (30/12) palpable TBs were detected in the VM in group B compared with none in group A. The MTrPs had two types of abnormal potential. Their amplitudes were significantly higher than those in the control group (p<0.01) but their durations showed no significant differences. A series of reflex contractions appeared in groups A and B in response to external stimulation to the ear. Their amplitude and duration in group B were significantly lower than those in group A. A series of lower fibrillation potentials repeatedly occurred in model MTrPs in group B. The morphology of MTrPs showed abnormal muscle fibres with large round or ellipse shapes in cross-section and enlarged tapering shapes in longitudinal section.
  
  
  CONCLUSIONS
  Active MTrPs can be provoked by repeated blunt injury. Active MTrPs are a group of muscle fibres with abnormal shapes and abnormal myoelectrical potentials. External stimulation provokes low-voltage responses in MTrPs, which is different from the response of normal muscle fibres.
authors: Department of Sports Medicine, Shanghai University of Sports, Shanghai 200438, China. huaqia404@yahoo.com.cn
authors: Qiang-Min
authors: QM
authors: Huang
authors: Gang
authors: G
authors: Ye
authors: Zhen-Yan
authors: ZY
authors: Zhao
authors: Jiao-Jiao
authors: JJ
authors: Lv
authors: Li
authors: L
authors: Tang
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004560:Electricity; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009209:Myofascial Pain Syndromes / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology*; D009210:Myofibrils / Q000473:pathology / Q000502:physiology; D017288:Pain Threshold; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010812:Physical Stimulation; D052097:Quadriceps Muscle / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex; D061028:Trigger Points / Q000473:pathology* / Q000503:physiopathology*