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bibliography * The PainScience Bibliography contains plain language summaries of thousands of scientific papers and others sources, like a specialized blog. This page is about a single scientific paper in the bibliography, Simons 2002.

Endplate potentials are common to midfiber myofacial trigger points


Tags: muscle pain, trigger points doubts, diagnosis, etiology, muscle, pain problems, pro

PainSci summary of Simons 2002?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided at the bottom of the page, as often as possible. ★★★★☆?4-star ratings are for bigger/better studies and reviews published in more prestigious journals, with only quibbles. Ratings are a highly subjective opinion, and subject to revision at any time. If you think this paper has been incorrectly rated, please let me know.

This study is one of only two direct, simple investigations of the electrical characteristics of trigger points, usually referred to as endplate noise or spontaneous electrical activity (SEA).

End plate potentials (EPPs) are the waves of electrical activity that spread out from the point where motor neurons attach to muscles (which have a distinctive saucer-like appearance). EPPs can be measured with electrodes on the skin, or a probe inserted into the muscles. This is electromyography (EMG).

Simons, Hong, and Simons looked for three kinds of EPPs at trigger points, in the taut bands of muscle found with them, and endplate zones (the neuromuscular junction). They examined one test site and two control sites in eleven muscles in ten subjects. They found endplate “noise” at all the trigger points, in four muscles at endplate zones away from TrPs, and nowhere else. The closer they were to a TrP, the more endplate noise they found. The concluded that “endplate noise seems to be characteristic of, but is not restricted to, the region of a myofascial trigger point.”

Note that electromyography can be tricky — here be dragons — and there is plenty of room for errors in technique and interpretation. It certainly needs independent replication. Nevertheless, this evidence is suggestive.

~ Paul Ingraham

original abstractAbstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

OBJECTIVES: To compare the prevalence of motor endplate potentials (noise and spikes) in active central myofascial trigger points, endplate zones, and taut bands of skeletal muscle to assess the specificity of endplate potentials to myofascial trigger points.

DESIGN: This nonrandomized, unblinded needle examination of myofascial trigger points compares the prevalence of three forms of endplate potentials at one test site and two control sites in 11 muscles of 10 subjects. The endplate zone was independently determined electrically. Active central myofascial trigger points were identified by spot tenderness in a palpable taut band of muscle, a local twitch response to snapping palpation, and the subject's recognition of pain elicited by pressure on the tender spot.

RESULTS: Endplate noise without spikes occurred in all 11 muscles at trigger-point sites, in four muscles at endplate zone sites outside of trigger points (P = 0.024), and did not occur in taut band sites outside of an endplate zone (P = 0.000034).

CONCLUSIONS: Endplate noise was significantly more prevalent in myofascial trigger points than in sites that were outside of a trigger point but still within the endplate zone. Endplate noise seems to be characteristic of, but is not restricted to, the region of a myofascial trigger point.

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These two articles on cite Simons 2002 as a source:

This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights: