What is the chemistry of a muscle knot? Specifically, what’s the condition of the tissue fluids in and around them?
The science of myofascial trigger points has been dominated for years by the theory of a poisonous feedback loop, a vicious cycle. The idea is that knots generate a lot of tissue fluid pollution, waste products of muscle cells that are metabolically “revving” with intense contraction … and those “exhaust” molecules then accumulate, mostly causing pain, which irritates the trigger point even more.1
This is called a metabolic energy crisis. I call it “sick muscle” syndrome. This picture has always been just an educated scientific guess. “The feedback loop suggested in this hypothesis has a few weak links,” wrote Dr. David Simons, a trigger point researcher.2 And some skeptics have been a lot more critical than that.3 However, some 2008 research helped to firm up the theory.
Starting with a simpler study in 2005,4 and then a more thorough one early this year,5 a group of scientists using “an unprecedented, most ingenious, and technically demanding technique” have reported that there really are irritating metabolic wastes floating around the neighbourhood of trigger points: “… not just 1 noxious stimulant but 11 of them,” Dr. Simons explains. “Instead of just a few noxious chemicals that stimulate nociceptors [nerves endings that detect tissue damage]6, nearly everything that has that effect was present in abundance.”
The researchers analyzed tissue samples from in and around trigger points and compared it with samples from healthy muscle tissue. The differences were significant.
If they are right, the muscle tissue at the location of trigger points appears to be just rotten with irritating molecules: molecules associated with inflammation, with pain, and with immune function.
Personally, I was pleased to see evidence that trigger points are also strongly acidic. I guessed that this might be the case in about 2002. (The pioneer of trigger point research, Dr. Janet Travell, had already suggested the same thing, but I didn’t know it then.) I often told my patients that trigger points were “acidic,” because it seemed likely to be true and because … well, it just sounded good, I guess.7 Lucky for me, this new research now gives some strong support to that old opinion. It doesn’t prove it, but it’s certainly noteworthy.
Trigger points really are strongly acidic which means that, for instance, it is actually plausible that deep breathing — which lowers blood acidity slightly — might be relevant to treatment.8 One of the possible goals of massaging trigger points is to “flush” trigger points by physically pushing stagnant tissue fluids out of the area of a trigger point, sometimes called “blanching.” Perhaps if fresh, less acidic blood re-perfuses the area, the trigger point will recover more easily? It’s a reasonable guess.
We shouldn’t accept the results of this experiment at face value simply because it seems to confirm an idea much beloved by massage therapists. Rubbing trigger points is probably not “detoxifying” — that’s not what this research suggests, even if it’s correct.9 Which it isn’t necessarily.
In a complicated and very technical experiment, it is all too easy for researchers to find the result that they want to find. Rubbing trigger points is probably not “detoxifying” — that’s not what this research means, even if it’s correct. I think that’s exactly what happened in a popular study supposedly showing that massage reduces inflammation, a related idea.10 This is why independent confirmation from other experiments is always essential. As of fall 2016, this research has still not been replicated as far as I know. And it has been criticized and dismissed by some.11 So take it all with a grain of salt for now.
Professionals are strongly encouraged to read David Simons’ analysis of both the new evidence about the chemistry of energy crisis in trigger points, as well as another new scientific article on the use of magnetic resonance elastography (MRE) imaging — a promising new way of taking pictures of muscle knots.
Simons writes that this technology “may open a whole new chapter in the centuries-old search for a convincing demonstration of the cause of trigger point symptoms.”
Unfortunately, most casual readers will be stumped by Simons’ thick scientific jargon. For much more readable analysis information about muscle knots, see my tutorial for patients and professionals (very detailed), or one of the more:
Some other free reading about trigger points:
I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.
— Major update. Extensive editing. Added a few key citations. Upgraded the article to use footnotes instead of inline citations. Added some related reading recommendations. Added some substantive commentary on a criticism of Shah et al, and on the subject of de-toxification.
— Minor edit — Just enough miscellaneous improvements to justify logging an update. :-) Made notes for more revision coming soon.
— Added acknowlegement of scientific controversies and uncertainties during a period of very high traffic to the article.
The most well-known explanation for the trigger point phenomenon is the “expanded integrated hypothesis,” which was first presented in this 2004 paper. It’s harrowingly detailed and technical, and mostly just filled in some details missing from the original integrated hypothesis (“a possible explanation”), which was put forward by Travell and Simons in 1999, which was in turn an elaboration on the energy crisis hypothesis that debuted in the first edition of their famous red textbooks in 1981. This has been a work-in-progress for quite a while. Here’s a simplified translation of the expanded integrated hypothesis:
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Under some circumstances, muscular stresses can cause patches of poor circulation, which results in the pooling of noxious metabolic wastes and high acidity in small areas of the muscle. This is both directly uncomfortable, but also causes a section of the muscle to tighten up and perpetuate a vicious cycle. This predicament is often called an “energy crisis.” It constitutes a subtle lesion. TrPs research has largely been concerned with looking for evidence of a lesion like this.
“These reported alterations in biochemical milieu are consistent with inflammation due either to tissue damage or to altered peripheral nerve function, in contrast to pathology necessarily being in the tissue sampled.” Interestingly, they do not dispute that Shaw et al. actually found altered tissue chemistry — they just dispute the interpretation, asserting that it could be due to some other cause. They suggest “tissue damage,” but what damage, other than the putative trigger point? This is apparently healthy tissue, other than a sore spot with the clinical features of trigger point. And they suggest “altered peripheral nerve function,” which just shifts the question of causality a little to the left: if misbehaving nerves can do this to tissue, isn’t that an equally interesting potential explanation for “trigger points”? And why are these nerves misbehaving anyway? Either way, there’s still a problem that needs splainin’! (In defense of this, they cite a paper about how peripheral nerves can play a “significant role in immune dysfunction in autoimmune and allergic diseases,” and that does not seem relevant to the clinical question here.)
Quintner, Bove, and Cohen take an extremely uncompromising position on this subject, and I doubt they would ever be willing to admit that any trigger point research is valid even if it actually was. But I have done my due diligence and explained who disagrees and why.BACK TO TEXT