Muscle Spasm Etiology

This article is the second in a series about the role of trigger points in pain and spasticity conditions.

Muscular injury can occur when soft tissues are exposed to single or recurrent episodes of biomechanical overloading.

Muscular pain is often attributed to a myofascial pain disorder, a condition originally described by Dr. Janet Travell, Dr. David Simons & Dr. Lois Simons ((1999). Myofascial Pain and Dysfunction: The Trigger Point Manual (2 vol. set, 2nd Ed.). USA: Lippincott Williams & Williams). Muscles with activity or injury-related pain are usually abnormally shortened with increased tone and tension. This has also been supported by Chan Gunn’s work, which suggests the histologic structure of the shortened muscles with palpable sensitive or painful bands, or points. The presence of tender, and firm nodules are called trigger points.

Travell’s etiological definition of a myofascial trigger point is a cluster of electrically active loci, each of which is associated with a contraction knot and a dysfunctional motor endplate in skeletal muscle.

The classic clinical definition describes a hyperirritable spot in skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band. The spot is painful on compression and gives rise to characteristic referred pain, referred tenderness, motor dysfunction and autonomic phenomena. Palpation of this spot within the trigger point provokes radiating, aching-type pain into localized reference zones.

The evidence supports the notion of when a muscle fiber is damaged; the sarcoplasmic reticulum may be unable to take back the cytoplasmic calcium into storage. The contractile protein molecules cannot decouple because the high concentration cytoplasmic calcium. This results in persistent contraction for the muscle fiber, even without any further impulse from the motor nerve. If this energy consuming process continues, sensitive muscle bands are formed.

Early work on tenderness and motor points described the beginning of an important “new” medical subject, “neuropathic pain”. Electromyographic (EMG) evidence of neuropathy in the nerves, tender muscles, increased insertion activity, polyphasic action potentials, prolonged motor action potentials, etc., demonstrated this. Pain can be of muscular origin as well. This can be due to damaged muscle fibers leading to spasm. ( Dr. Chan Gunn: “Tenderness and Motor Points” (Journal of Bones and Joint Surgery,Vol. 58A, No.6 Sept. 1976)).

Mechanical, thermal and chemical treatments, which neurophysiologically, or physically denervate the neural loop of the trigger point, can result in reduced pain and temporary resolution of muscular over contraction.

Most experts believe that appropriate treatment should be directed at the trigger point to restore normal muscle length and proper biomechanical orientation of myofascial elements, followed by treatment that includes strengthening and stretching of the affected muscle.

Please watch  for the next article in this series….

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