Put simply a myofascial trigger point is a small area of muscle where the chemistry has gone wrong. Effectively the normal biological mechanism for causing a muscle fibre to contract or shorten becomes interfered with.
A small portion of the muscle becomes permanently contacted or shortened and can’t let go, this leads to a reduction in blood supply (ischaemia) through that area. This decrease in blood supply leads to pain.
This is the classic knot in the muscle that is often very tender to touch and can reproduce your pain if you press on it.
Another interesting thing about a these points is its ability to refer pain away from the area of tissue that it is in. So, if you press on one, you may actually feel the pain somewhere else.
A good example of this is the piriformis muscle in the buttock that refers pain into the back of the thigh in piriformis syndrome.
In a similar way to acupressure, pressure is applied to the offending point. This pressure can be applied by hands or elbows, or by using a device such as the back knobber. There are all sorts of devices out there to help you get the pressure on the right spot. The pressure somehow encourages a more normal exchange in the muscle fibre and reduces its permanently contracted state.
Trigger point release was initially advocated by authors Travell and Simons who wrote two classic textbooks on them. I use these regularly in my own practice to help people I see with this problem. They are fully illustrated and unfortunately very expensive.
An interesting alternative is the *The Trigger Point Therapy Workbook: Your Self-Treatment Guide for Pain Relief, which has very good reviews and contains useful illustrations.
Yes, probably in a similar way to acupressure. However, there have been no good research trials comparing this type of treatment in low back pain sufferers with a more proven type of treatment such as exercise. So there is no clear evidence that is works. However, there is good evidence that applying pressure to a point reduces its soreness (1) and we can probably apply some of the acupressure evidence also (2).
1.Fernbndez, D., Alonso, B., Fernbndez, C., & Carlos, M. 2006, "The immediate effect of ischemic compression technique and transverse friction massage on tenderness of active and latent myofascial trigger points: A pilot study", Journal of Bodywork and Movement Therapies, vol. 10, no. 1, pp. 3-9.
2. Hsieh, L. L. C., Kuo, C. H., Lee, L. H., Yen, A. M. F., Chien, K. L., & Chen, T. H. H. 2006, "Treatment of low back pain by acupressure and physical therapy: Randomised controlled trial", British Medical Journal, vol. 332, no. 7543, pp. 696-698.