PainSci summary of Simons 2002?This page is one of thousands in the PainScience.com 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 abstract†Abstracts 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.
- “Microscopic features and transient contraction of palpable bands in canine muscle,” an article in Am J Phys Med, 1976.
- “Accelerated muscle fatigability of latent myofascial trigger points in humans,” an article in Pain Med, 2012.
- “Two-dimensional ultrasound and ultrasound elastography imaging of trigger points in women with myofascial pain syndrome treated by acupuncture and electroacupuncture: a double-blinded randomized controlled pilot study,” an article in Ultrason Imaging, 2015.
- “Induction of muscle cramps by nociceptive stimulation of latent myofascial trigger points,” an article in Exp Brain Res, 2008.
- “Assessment of myofascial trigger points (MTrPs): a new application of ultrasound imaging and vibration sonoelastography,” an article in Conf Proc IEEE Eng Med Biol Soc, 2008.
- “Uncovering the biochemical milieu of myofascial trigger points using in vivo microdialysis: an application of muscle pain concepts to myofascial pain syndrome,” an article in Journal of Bodywork & Movement Therapies, 2008.
- “Ability of magnetic resonance elastography to assess taut bands,” an article in Clin Biomech (Bristol, Avon), 2008.
- “Spinal cord mechanism involving the remote effects of dry needling on the irritability of myofascial trigger spots in rabbit skeletal muscle,” an article in Archives of Physical Medicine & Rehabilitation, 2011.
- “Myofascial trigger points: spontaneous electrical activity and its consequences for pain induction and propagation,” an article in Chin Med, 2011.
- “The myofascial trigger point region: correlation between the degree of irritability and the prevalence of endplate noise,” an article in Am J Phys Med Rehabil, 2007.
These two articles on PainScience.com cite Simons 2002 as a source:
- PS Trigger Points & Myofascial Pain Syndrome — A guide to the unfinished science of muscle pain, with reviews of every theory and self-treatment and therapy option
- PS The Trigger Point Identity Crisis — The biological evidence that a trigger point is a lesion in muscle tissue
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:
- A Bayesian model-averaged meta-analysis of the power pose effect with informed and default priors: the case of felt power. Gronau 2017 Comprehensive Results in Social Psychology.
- The neck and headaches. Bogduk 2014 Neurol Clin.
- Agreement of self-reported items and clinically assessed nerve root involvement (or sciatica) in a primary care setting. Konstantinou 2012 Eur Spine J.
- Effect of NSAIDs on Recovery From Acute Skeletal Muscle Injury: A Systematic Review and Meta-analysis. Morelli 2017 Am J Sports Med.
- Association of Spinal Manipulative Therapy With Clinical Benefit and Harm for Acute Low Back Pain: Systematic Review and Meta-analysis. Paige 2017 JAMA.