Myofascial trigger points show spontaneous needle EMG activity

Spine (Phila Pa 1976). 1993 Oct 1;18(13):1803-7. doi: 10.1097/00007632-199310000-00015.


Monopolar needle electromyogram (EMG) was recorded simultaneously from trapezius myofascial trigger points (TrPs) and adjacent nontender fibers (non-TrPs) of the same muscle in normal subjects and in two patient groups, tension headache and fibromyalgia. Sustained spontaneous EMG activity was found in the 1-2 mm nidus of all TrPs, and was absent in non-TrPs. Mean EMG amplitude in the patient groups was significantly greater than in normals. The authors hypothesize that TrPs are caused by sympathetically activated intrafusal contractions.

MeSH terms

  • Adult
  • Electromyography / methods
  • Female
  • Fibromyalgia / physiopathology*
  • Headache / physiopathology*
  • Humans
  • Male
  • Muscle Contraction / physiology*
  • Muscle Spindles / physiopathology
  • Muscles / innervation
  • Muscles / physiopathology*
  • Myofascial Pain Syndromes / physiopathology*
  • Sympathetic Nervous System / physiopathology