We have all probably experienced what is commonly called a muscle knot. Of course, a muscle cannot tie itself into a knot, so what can explain this sensation? We often seek massage for these knots, and applying pressure on them seems to provide relief.
A muscle knot is sometimes called a "trigger point." In Myofascial Pain and Dysfunction: The Trigger Point Manual (1983), Janet Travell and David Simons define a trigger point as an irritable nodule, often palpable, in the taut bands of fascia surrounding skeletal muscles. They note that direct compression and muscular contraction on the point can incite a startled response (jump sign), local tenderness, local twitch response, and referred pain somewhere distant to the trigger point. As the title of their book suggests, they attribute these trigger points to microcramps in the muscle and issues with the fascia, at least in part.
Despite the lack of scientific basis behind it, the myofascial pain theory still dominates, even among professional circles, as an explanation of muscle knots.
The book achieved great commercial success, but it relied on many assertions and beliefs that were derived without testing or without adequate scientific basis. In 1992, Dr. Fred Wolfe and colleagues performed a study on trigger points. They recruited a group of four myofascial pain experts, selected by Simons himself and including Simons, who examined four patients with myofascial pain. The examiners could take as much time as they needed to examine but were not allowed to interview the patients. The four patients were controlled against healthy subjects as well as subjects diagnosed with fibromyalgia without the examiners knowing who was who.
Even though these trigger point experts were the best—Simons cowrote the book on it—they could not find or agree on the trigger points. The lead author of the study, Wolfe, later revealed in a blog post:
It was a disaster. The examiners [the myofascial pain experts] were distraught. After the results were in, they protested and wanted to change the protocol and purposes of the study (post hoc). It wasn’t fair, they said . . . If we believed in trigger points and The Trigger Point Manual before, we were a lot less secure in our beliefs now. (Wolfe 2013)
Other scientists have tried to explain the phenomenon of muscle knots. Quintner and Cohen (1994) suggested that irritated or injured peripheral nerve trunks, rather than microdamage in muscle tissue, may be the cause of pain. Like the idea it is intended to replace, this hypothesis has advantages and problems; the main problem is that there is no obvious plausible mechanism for pervasive nerve irritation.
The reality is, to this day, we cannot clearly explain what a muscle knot is or the mechanism behind it. Yet few would argue the existence of muscle knots because we have probably all had one at some point. Whatever the mechanism behind these pesky irritants, here are a few methods worth trying for relief from them:
Resting
Stretching
Exercising
Hot and cold therapy
Self-massage or massage therapy
Physical therapy, particularly if the problem lingers, creates discomfort, and does not respond to treatments at home
Conclusion
Stiffness and tightness are vague terms that mean different things to different people. Many assumptions have been made about stiffness, and many products have been sold with a promise of relieving stiffness, though most are not founded in good science. Stiffness might be associated with reduced extensibility of a muscle and connective tissue, but it could also be associated with a dull ache in the region, muscle knots, or any other sort of mild pain. The potential causes of stiffness are many, and some of the time (maybe much of the time), the exact cause cannot be named.
We should also remember that the human body is a tensile structure, held together and able to move well because of a balance of tension and compression in a concept known as tensegrity. Tension helps us resist gravity and move in the many ways we do. While the words tension and tightness usually carry a negative meaning, they play an important role in making this body of ours functional.
[This article is an excerpt from my book The Physiology of Yoga.]
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