About Trigger Points
Muscle is the largest organ in the human body, and accounts for about 50% of its weight. There are approximately 400 muscles (there are individual variations), and any one of those can develop trigger points which can refer pain and cause dysfunction. Symptoms can range from intolerable agonizing pain caused by "active" trigger points, to painless restriction of movement and distortion of posture from "latent" trigger points.
The answer to "What Are Trigger Points?" is: research it still underway. But many characteristics have been observed for decades by researchers all over the world. With new testing methods and equipment, in the last ten years much has been learned about the physiology of trigger points. And even though not every mechanism is known, patients get better when their trigger points are treated!
More Trigger Point Information
- When pressed, trigger points feel like "knots" or tight bands in the muscle, and are usually very tender. Healthy muscles usually do not contain knots or tight bands, are not tender to pressure, and when relaxed, they feel soft and pliable to the touch, not hard and dense, even if you work-out. When trigger points are present, on the microscopic level, part of the muscle fiber is contracted into a small thickened area, and the rest of the fiber is stretched thin. Several of these muscle fiber contractures in the same area are probably what we feel as a "knot" in the muscle. These muscle fibers are not available for use because they are already contracted, which is why you cannot condition (strengthen) a muscle that contains trigger points. The sustained contraction probably leads to the release of sensitizing chemicals, producing the pain that is felt when the trigger point is pressed. Eventually some of the structural changes may be irreversible if trigger points are left untreated for long enough. The contractile portions of the fiber in the middle of the knot may separate and retract to each end, leaving an empty portion of the cell in the middle.
- Trigger points may refer pain both in the local area and/or to other areas of the body, and common patterns have been well-documented and diagramed. These are called "referral patterns." Approximately
74% of the time trigger points are not located where you feel symptoms, and working on the area you feel symptoms does not give you relief. These referral patterns do not necessarily follow nerve pathways. Pain levels can vary depending on the stress placed on the muscle and any of other the perpetuating factors that keep trigger points activated. Tingling, numbness, or burning sensations are more likely due to nerve entrapments, which may be a result of trigger points entrapping the nerve.
- If the trigger point is "active," it will refer pain or other sensations. If it is "latent," it may cause a decreased range-of-motion and weakness.8 Active trigger points often start with some impact to the muscle, such as an injury, poor posture or body mechanics, repetitive use, or a nerve root irritation. Any of the perpetuating factors can also indirectly activate trigger points and make you more prone to developing trigger points that are initiated by impacts to muscles. Active trigger points may at some point cease causing pain, and become latent. Latent trigger points can easily return to being active trigger points, often leading the patient to believe they are experiencing a new problem, when in fact it is an old problem being re-aggravated. Latent trigger points can be reactivated by overuse, over-stretching, chilling, or any other of the perpetuating factors. (The chapter on Perpetuating Factors can be found on the
Pain Relief with Trigger Point Self-Help CD ROM)
- In a study of thirteen healthy individuals with the same eight muscles being examined in each subject, two people had latent trigger points in seven of those muscles, two people had latent trigger points in six muscles, three had latent trigger points in five muscles, two had latent trigger points in three muscles, two had latent trigger points in two muscles, two had latent trigger points in one muscle, and only one person didn't have latent trigger points in any of the eight muscles! This means that most people have at least some latent trigger points, which could be easily converted to active trigger points. This also means that some people are more prone to develop problems with muscular pain than others.
- With pressure on the trigger point, you can often reproduce the symptoms, but being unable to reproduce the referred pain or other symptoms by applying pressure does not rule out specific trigger points. I still work on the trigger points that could be causing the problem, and if my patient improves, even temporarily, I assume that one of the trigger points I worked on is indeed the source of the problem. For this reason, I don't work on all the possible trigger points in one session, since I won't know which trigger point treated actually gave the patient relief.
- Trigger points can cause symptoms not normally associated with muscular symptoms, such as sweating, ringing in the ears, dizziness, urinary frequency, buckling knees, and tearing of the eyes.
- Trigger points may cause other muscles fibers to contract. They will also cause weakness and loss of coordination of the involved muscles and an inability of the muscles to tolerate use. Many people take this as a sign that they need to strengthen the weak muscles, but unless trigger points in the affected muscle are inactivated, strengthening (conditioning) exercises will likely encourage the substitution of other muscles, further weakening and de-conditioning the muscle with the trigger points.
- Trigger points limit range-of-motion due to pain. Some muscles are more likely to have a larger degree of restriction than others. Once trigger points are relieved, range-of-motion is restored.
- Muscles containing trigger points are fatigued more easily, and don't return to a relaxed state as quickly when use of the muscle ceases.
- Patients are often surprised that the same area on the opposite side is also tender, since that side isn't causing them pain. Over half the time, the opposite side is actually more tender with pressure. Unless it is a recent injury, usually both sides eventually get involved (i.e., if the right mid-back is painful, there are also tender points on the left mid-back). For that reason I almost always work on both sides and tell patients to do the self-help on both sides. One possible explanation is that after the initial increase in sensitivity with trigger point activation, and the problem becomes chronic, the body releases pain-masking chemicals and numbs the side of the original pain out somewhat (hypoesthia), and that has not yet happened on the opposite side.
- Women are more likely than men to develop trigger points. I have noticed this is particularly true in menopausal women. Some teenagers (of both sexes) going through puberty also seem to have a tendency to develop trigger points, leading me to believe there is a connection between hormonal changes and one potential cause of trigger points.
- People who exercise regularly are less likely to develop trigger points than those who exercise occasionally and overdo it.
- Part of the current hypothesis about the mechanism responsible for the formation of trigger points is the "energy crisis component." The sarcoplasmic reticulum is a part of the cell responsible for storing and releasing ionized calcium. The type of nerve ending that causes the muscle fiber to contract is called a "motor endplate." This nerve ending releases acetylcholine, which tells the sarcoplasmic reticulum to release calcium, and then the muscle fiber contracts. If it is operating normally, when contraction of the muscle fiber is no longer needed, the nerve ending stops releasing acetylcholine and the "calcium pump" in the sarcoplasmic reticulum returns calcium into the sarcoplasmic reticulum. If a trauma occurs or there is a marked increase in the nerve endplate release of acetylcholine, an excessive amount of calcium can be released by the sarcoplasmic reticulum causing a maximal contracture of a segment of muscle, leading to maximal energy demand and impairment of local circulation. If the circulation is impeded, the calcium pump doesn't get the needed fuel and oxygen to pump calcium back into the sarcoplasmic reticulum, and the muscle fiber continues to contract. This vicious cycle continues until there is outside intervention that stretches the contracted portion of the muscle fiber. The areas at the ends of the muscle fibers (either at the bone or where the muscle attaches to a tendon) also become tender as its attachments are stressed by the contraction in the center of the fiber.
- For a list of things that cause and keep trigger points going, see the section on perpetuating factors. (The chapter on Perpetuating Factors can be found on the
Pain Relief with Trigger Point Self-Help CD ROM)
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The Center for Acupuncture and Traditional Medicine