Research shows that most people have those tender spots in tight muscles that masseurs love to find, and that they cause rapid fatigue and pain upon exertion. In spite of this they are too often overlooked as a cause of unexplained fatigue.
What are those tender spots
Those tender spots in muscles are known as trigger points. They develop as lumps that are only painful when pressed upon. Those who have had a professional massage would understand most people have many without realising it. However, if they worsen or are aggravated they can start producing pain without being pressed upon. They are a major cause of many pain syndromes such as back pain, neck pain and shoulder pain.
Why they cause fatigue
Trigger points are discusses more thoroughly in our trigger point guide, but basically they are part of the muscle that have gone into spasm and will not relax. This causes the whole muscle to become tight, plus blood flow is restricted causing a depletion of oxygen and a build up of waste products. Simply, when a muscle is constantly pulling tight with restricted blood flow it will already be "semi-fatigued" with restricted oxygen. Further exertion will cause fatigue and pain
What they did
The researchers had the subject hold their arm straight out horizontally to the side, and maintain upward pressure for an average of over 7 minutes. They put electrodes on several muscles to measure their activity, and had the subjects assess the level of pain on a 0-10 scale. The performance of shoulders with trigger points was compared with those without them.
What they found
- Those shoulders with trigger points quickly became painful.
- In the shoulders without trigger points the the electrodes showed that the main muscles maintained their effort with little assistance. In those with trigger points the nervous system had to quickly recruit other muscles to help.
The diagnosis (or lack of)
Given these research findings, and that nearly 90% of pain free adults have them in their shoulders alone, latent trigger points would be a major cause of rapid fatigue and muscle pains upon exertion. Unexplained fatigue can have serious causes so a health care professional should be consulted. However, however, they don’t show up in laboratory tests or an x/rays so they are too often overlooked. We do not recommend people with unexplained fatigue though self diagnose trigger points. Rather one should download a copy of the practitioner version of this article and discuss the possibility with his or her health care professional. If appropriate, a simple clinical trial could be performed, where trigger points are treated and results monitored. For more information on the treatment of trigger points please see our Trigger point guide.
Ge HY1, Arendt-Nielsen L, Madeleine P. Accelerated muscle fatigability of latent myofascial trigger points in humans. Pain Med. 2012 Jul;13(7):957-64