Myoelectrical Activity and Muscle Morphology in a Rat Model of Myofascial Trigger Points Induced by Blunt Trauma to the Vastus Medialis

Acupunct Med. 2013 Mar;31(1):65-73. doi: 10.1136/acupmed-2012-010129. Epub 2013 Jan 17.

Abstract

Objectives: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Disease Models, Animal
  • Electricity
  • Male
  • Muscle Contraction / physiology
  • Myofascial Pain Syndromes / etiology
  • Myofascial Pain Syndromes / pathology*
  • Myofascial Pain Syndromes / physiopathology*
  • Myofibrils* / pathology
  • Myofibrils* / physiology
  • Pain Threshold
  • Physical Conditioning, Animal / physiology*
  • Physical Stimulation
  • Quadriceps Muscle / injuries*
  • Quadriceps Muscle / pathology
  • Quadriceps Muscle / physiopathology
  • Random Allocation
  • Rats
  • Rats, Sprague-Dawley
  • Reflex
  • Trigger Points / pathology*
  • Trigger Points / physiopathology*