What Are Trigger Points?
Muscle Anatomy and Physiology
Muscles consist of many muscle cells, or fibers, bundled together by connective tissue. Each fiber contains numerous myofibrils, and most skeletal muscles contain approximately one thousand to two thousand myofibrils. Each myofibril consists of a chain of sarcomeresconnected end to end — it is in the sarcomere that muscular contractions take place.
A muscle spindle is a sensory receptor found within the belly of a muscle. Muscle spindles are concentrated where a nerve enters a muscle and also around nerves inside the muscles. Each spindle contains three to twelve intrafusal muscle fibers, which detect changes in the length of a muscle. As the body’s position changes, information is conveyed to the central nervous system via sensory neurons and is processed in the brain. As needed, the motor end plate (a type of nerve ending) releases acetylcholine, a neurotransmitter that tells the sarcoplasmic reticulum (a part of each cell) to release ionized calcium. The extrafusal muscle fibers then contract. When contraction of the muscle fibers is no longer needed, the nerve ending stops releasing acetylcholine, and calcium is pumped back into the sarcoplasmic reticulum.
If you have trigger points, the muscle fibers contract and stay contracted, instead of relaxing (see Trigger Point Physiology below).
How Will You Know if You Have Trigger Points?
The two most important characteristics of trigger points that you will notice are tender “knots” or tight bands in the muscles, and referred pain. You may also notice weakness, lack of range of motion, or other symptoms you would not normally associate with muscular problems.
Tenderness, Knots, and Tight Bands in the Muscle
When pressed, trigger points are usually very tender. This is because the sustained contraction of the myofibril leads to the release of sensitizing neurotransmitters via a cascade effect: the sustained contraction elevates metabolites such as potassium ions and lactic acid, which leads to elevated levels of inflammatory agents such as bradykinin and histamine, which activates pain nerve fibers, which then leads to the excretion of pain transmitters, such as substance P.
Pain intensity levels can vary depending on the amount of stress placed on the muscles. The intensity of pain can also vary in response to flare-ups of any of the perpetuating factors, and in the presence of central nervous system sensitization (see below). The areas at the ends of the muscle fibers also become tender, either at the bone or where the muscle attaches to a tendon.
Healthy muscles usually don’t contain knots or tight bands and are not tender to applied pressure. When not in use, they feel soft and pliable to the touch, not like the hard and dense muscles found in people with chronic pain. People often tell me their muscles feel hard and dense because they work out and do strengthening exercises, but healthy muscles feel soft and pliable when not being used, even if you work out. Muscles with trigger points may also be relaxed, so don’t assume you don’t have trigger points just because the muscle is not hard and dense.
Referred Pain
Trigger points may refer pain both in the area in which the trigger point is located, and/or to other areas of the body. These are called referral patterns. About 74% of commonly found trigger points are not located within their area of referred pain. The most common referral patterns have been well documented and diagrammed, and drawings are provided in each muscle chapter.
Unless you know where to search for trigger points, and you only work on the areas where you feel pain, you probably won’t get relief. For example, trigger points in the iliopsoas muscle (deep in your abdomen) can cause pain in your lumbar area. If you don’t check the iliopsoas muscle for trigger points and only work on the quadratus lumborum muscle in the lumbar area, you will not get 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 a result of trigger points entrapping the nerve.
Weakness and Muscle Fatigue
Trigger points can cause weakness and loss of coordination, along with an inability to use the muscle. Many people take this as a sign that they need to strengthen the weak muscles, but you can’t condition (strengthen) a muscle that contains trigger points — these muscle fibers are not available for use because they are already contracted. If trigger points aren’t inactivated first, conditioning exercises will likely encourage the surrounding muscles to do the work instead of the muscle containing the trigger point, further weakening and deconditioning the muscle containing trigger points.
Muscles containing trigger points are fatigued more easily and don’t return to a relaxed state as quickly when you stop using the muscle. Trigger points may cause other muscles to tighten up and become weak and fatigued in the areas where you experience the referred pain, and they also cause a generalized tightening of an area as a response to pain.
Other Symptoms
Trigger points can cause symptoms that most people would not normally associate with muscular problems. For example, trigger points in the abdominal muscles can cause urinary frequency and bladder spasms, bed-wetting, chronic diarrhea, frequent belching and gas, nausea, loss of appetite, heartburn, food intolerance, painful menses, projectile vomiting, testicular pain, and pain that feels like it is in an organ, in addition to causing referred pain in the abdominal, mid back, and lumbar areas.
Trigger points may also cause stiff joints, generalized weakness or fatigue, twitching, trembling, and areas of numbness or other odd sensations. It probably wouldn’t occur to you (or your health care provider) that these symptoms could be caused by a trigger point in a muscle.
Sensitization of the Opposite Side of the Body
For any long-term pain, it’s not unusual for it to affect both sides of the body eventually; for example, if the right lumbar area is painful, there may be tender points in the left lumbar area. Often the opposite side is actually more tender with pressure. This is because whatever is affecting one side is likely affecting the other: poor body mechanics, poor footwear, overuse injuries, chronic degenerative or inflammatory conditions, chronic disease, or central sensitization (see below). For this reason, I almost always treat both sides on patients, and I recommend that you do self-treatments on both sides. You may find that you have trigger points only on one side for any given muscle, but always check both sides before making that assumption.
Active Trigger Points vs. Latent Trigger Points
If a trigger point is active, it will refer pain or other sensations and limit range of motion. If a trigger point is latent, it may cause a decreased range of motion and weakness, but not pain. The more frequent and intense your pain, the greater the number of active trigger points you are likely to have.
Trigger points that start with some impact to the muscle, such as an injury, are usually active initially. Poor posture or poor body mechanics, repetitive use, a nerve root irritation, or any of the other perpetuating factors can also form active trigger points. Latent trigger points can develop gradually without being active first, and you don’t even know they are there. Most people have at least some latent trigger points, which can easily be converted to active trigger points.
What Causes and Perpetuates Trigger Points?
Trigger points may form after a sudden trauma or injury, or they may develop gradually. Common initiating and perpetuating factors are mechanical stresses, injuries, nutritional problems, emotional factors, sleep problems, acute or chronic infections, organ dysfunction and disease, and other medical conditions.
You will have more control over some perpetuating factors than others. Addressing any pertinent perpetuating factors is so important that you may obtain either substantial or complete relief from pain without any additional treatment. If you don’t eliminate perpetuating factors to the extent possible, you may not get more than temporary relief from self-help pressure techniques or practitioners’ treatments. Hopefully, you will learn enough about perpetuating factors that at least if you choose not to resolve them, you are making an informed choice about whether the relief of pain is more important to you than continuing to do things that make you feel worse.
You cannot realistically make all of the changes discussed in the perpetuating factors chapter at once, but make a list of the perpetuating factors that might apply to you. Prioritize and work on resolving those you think might be the most important.
Other Things to Consider . . .
When you apply pressure to the trigger point, you can often reproduce the referred pain or other symptoms; however, being unable to reproduce the referred pain or other symptoms by applying pressure does not rule out involvement of that specific trigger point. Try treating the trigger points that could be causing the problem anyway, and if you improve, even temporarily, assume that one of the trigger points you worked on is indeed at least part of the problem. For this reason, don’t work on all the possible trigger points in one session, since you won’t know which of the trigger points treated actually gave you relief.
It is important to note that a primary, or key, trigger point can cause a satellite, or secondary, trigger point to develop in a different muscle. The satellite trigger point may have formed for one of three reasons: it lies within the referral zone of the primary trigger point; or it is in a muscle that is either substituting for or countering tension for the muscle that contains the primary trigger point. When doing self-treatments, be aware that if some of your trigger points are satellite trigger points, you won’t get lasting relief until the primary trigger points have been treated. This is why it is important to work in the direction of referral (see General Guidelines chapter).
You also need to be aware that central sensitization can cause the referral pattern to deviate from the most common pattern found in each muscle chapter. It may also cause trigger points in several muscles within a region to refer pain to the same area, making it more difficult to determine trigger point locations. This means you can’t absolutely rule out the role of a potential trigger point based only on consideration of common referral patterns, since other factors may cause you to have an uncommon referral pattern. The more intense the earlier pain, the more intense the emotions associated with it, and the longer pain has lasted, the more likely central sensitization will cause deviation from the most common referral patterns.
A small percentage of people will get worse before they get better, mostly in complex cases. Or the pain may move around, or you may have the perception that the pain moved around only because the most painful areas have improved and now you are noticing the next most painful area more. I’ve only had a few cases where I wasn’t able to help patients: they were so frustrated after receiving little or no help from one professional after another that they only allowed me to treat them a few times before giving up, even if they had improved. If you get a little worse before you get better, you may be inclined to give up in the initial stages of treatment. So with any therapy you try, I encourage you to go to at least five appointments before you decide it isn’t working, even if your condition initially gets worse. Just give your practitioner some time to learn your body and observe how you use it. However, if your practitioner doesn’t seem to care or have time for you, then by all means look for someone who does care about you getting better.
Trigger Point Physiology: Contractions and Inflammation
One of the current theories about the mechanism responsible for the formation of trigger points is the “Integrated Trigger Point Hypothesis.” If a trauma occurs, or there is a large increase in the motor end plate’s release of acetylcholine, an excessive amount of calcium can be released by the sarcoplasmic reticulum. This causes a maximal contracture of a segment of muscle, leading to a maximal demand for energy and impairment of local circulation. If circulation is impaired, the calcium pump doesn’t get the fuel and oxygen it needs to pump calcium back into the sarcoplasmic reticulum, so the muscle fiber stays contracted. Sensitizing substances are released, causing pain and stimulation of the autonomic nervous system, resulting in a positive feedback system with the motor nerve terminal releasing excessive acetylcholine . . . and so the sarcomere stays contracted.
Another current theory is the “Muscle Spindle” hypothesis, which proposes that the main cause of a trigger point is an inflamed muscle spindle (Partanen, Ojala, and Arokoski, 2010). Pain receptors activate skeletofusimotor units during sustained overload of muscles via a spinal reflex pathway, which connects to the muscle spindles. As pain continues, sustained contraction and fatigue drive the skeletofusimotor units to exhaustion, and cause rigor (silent spasm) of the extrafusal muscle fibers, forming the “taut band” we feel as trigger points. Because the muscle spindle itself has a poor blood supply, the inflammatory metabolites released will be concentrated inside the spindle and lead to sustained inflammation.
In a ground-breaking study, Shah et al. (2008) were able to measure eleven elevated biochemicals in and surrounding active trigger points, including inflammatory mediators, neuropeptides, catecholamines, and cytokines (primarily sensitizing substances and immune system biochemicals). In addition, the pH of the samples was strongly acidic compared to other areas of the body. In a study conducted by Issbener, Reeh, and Steen (1996), it was discovered that a localized acidic pH lowered the pain threshold sensitivity level of sensory receptors (part of the nervous system), even without acute damage to the muscle. This means that the more acidic your pH level in a given area, the more pain you will experience compared to someone else. Further investigation is needed to determine whether body-wide elevations in pH acidity and the substances mentioned above predispose people to the development of trigger points.
More studies, therefore, are needed to determine the exact mechanisms of trigger point formation and physiology.
Central Sensitization, Trigger Points, and Chronic Pain
The autonomic nervous system controls the release of acetylcholine, along with involuntary functions of blood vessels and glands. Anxiety and nervous tension increase autonomic nervous system activity, which commonly aggravates trigger points and their associated symptoms.
The central nervous system includes the brain and spinal cord, and its function is to integrate and coordinate all activities and responses of the body. The purpose of the acute stress responses of our bodies is to protect us by telling us to pull away from a hot stove burner, flee from a dangerous situation, or rest an injured body part due to pain. But when emotional or physical stress is prolonged, even just for a few days, there is a maladaptive response: damage to the central nervous system, particularly to the sympathetic nervous system and the hypothalamus-pituitary-adrenal (HPA) systems. This is called central nervous system sensitization.
Pain causes certain types of nerve receptors in muscles to relay information to neurons located within part of the gray matter of the spinal cord and the brain stem. Pain is amplified there and is then relayed to other muscles, thereby expanding the region of pain beyond the initially affected area. Persistent pain leads to long-term or possibly permanent changes in these neurons, which affect adjacent neurons through neurotransmitters.
Various substances are released: histamine (a compound that causes dilation and permeability of blood vessels), serotonin (a neurotransmitter that constricts blood vessels), bradykinin (a hormone that dilates peripheral blood vessels and increases small blood vessel permeability), and substance P (a compound involved in the regulation of the pain threshold). These substances stimulate the nervous system to release even more acetylcholine locally, adding to the perpetuation of trigger points.
Central sensitization may cause the part of the nervous system that would normally counteract pain to malfunction and fail to do its job. As a result, pain can be more easily triggered by lower levels of physical and emotional stressors, and also be more intense and last longer. Prolonged pain caused by central nervous system sensitization can lead to emotional and physical stress. Conversely, prolonged exposure to both emotional and physical stressors can lead to central nervous system sensitization and subsequently cause pain. Just the central nervous system maladaptive changes alone can be self-perpetuating and cause pain, even without the presence of either the original or any additional stressors, creating a vicious cycle of pain and trigger point formation.
Once the central nervous system is involved, because of central sensitization, even if the original perpetuating factor(s) causing trigger points are resolved, trigger points can continue to form and be reactivated. So the longer that pain goes untreated, the greater the number of neurons that get involved and the more muscles they affect, causing pain in new areas, in turn causing more neurons to get involved . . . and the bigger the problem becomes, leading to the likelihood that pain will become chronic. The problem gets more complex, more painful, more debilitating, more frustrating, and more time-consuming and expensive to treat. The longer you wait, the less likely you are to get complete relief, and the more likely it is that your trigger points will be reactivated chronically and periodically. The sooner pain is treated, including addressing the initiating stressors and perpetuating factors, the less likely it will become a permanent problem with widespread muscle involvement and central nervous system changes.
Other Trigger Point Information
- 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.1
- Women are more likely than men to develop trigger points.2 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.3
- People who exercise regularly are less likely to develop trigger points than those who exercise occasionally and overdo it.4
A Word About Fibromyalgia
Allopathic (Western) medicine defines fibromyalgia as a chronic disorder associated with widespread muscle and soft-tissue pain, tenderness and fatigue. Diagnosis is made by pressing 18 areas to check for tenderness, and if at least 11 of the points are tender and the pain has been present for at least three months, you are diagnosed positive for fibromyalgia. Usually you will be prescribed some kind of pain medication and counseling for chronic pain management.5
[NOTE: Unfortunately, this was never intended as a method for diagnosing Fibromyalgia; in a research study this was used as a criterion for admitting patients into the study, not to diagnose patients. Patients may have widespread tenderness and not have Fibromyalgia, and other patients may have Fibromyalgia and not have at least 11 of the 18 specific tender points.]
Most fibromyalgia patients also have at least some trigger points, but there are also distinct differences. Trigger points restrict range-of-motion, while hyper-mobility is common with fibromyalgia. With trigger points, usually only the trigger point itself is tender, whereas fibromyalgia patients experience tenderness pretty much everywhere to some degree.6 Seventy-five percent of fibromyalgia patients also feel fatigued, don’t feel rested upon waking, and are stiff in the morning.7
Recent Western research has leaned toward a body-wide metabolic and neurochemical cause, including deficiency of the neurotransmitter serotonin8, which causes increased pain sensitivity.9 Although allopathic medicine has not found a definitive cause for fibromyalgia, in terms of Chinese medical diagnosis, there is always a component of dampness, and the tissues will feel somewhat “spongy” to the touch. Dampness easily combines with heat or cold, and typically the condition will be aggravated by either hot or cold weather, or the application of heat or cold. A damp-producing diet (see the section on Diet in perpetuating factors) will cause and keep fibromyalgia going, and needs to be changed. Living in a damp climate will aggravate fibromyalgia, and typically patients will feel better in a dryer climate. The digestive system is responsible for transforming fluids, and if it is not working well, you will tend to accumulate dampness in various body parts, and for some people that is in the surface layers of the body (see the section on Nutritional Problems in perpetuating factors). Acupuncture and damp-draining herbs and foods are very successful with treating fibromyalgia, as long as the practitioner is careful not to over-treat the patient. Massage will help with the acute part of the pain, but will not treat the underlying conditions causing fibromyalgia.10
If you have fibromyalgia, Fibromyalgia & Chronic Myofascial Pain: A Survival Manual, by Devin Starlanyl and Mary Ellen Copeland, is an excellent resource and it gives an in-depth look at the physiology of the condition. This Western resource discusses the concept of “interstitial edema,” which I believe correlates to the Oriental concept of “Damp-heat or Damp-cold in the Muscles.” Interstitial edema is where “interstitial fluid” is found in the “interstitial space,” or “Third Space.” It’s neither inside the cells nor outside the cells, so the structure of the interstitial space is hard to visualize, but there is a transfer of informational and other substances between blood and lymph through the interstitial space. Lymph fluid is composed of interstitial fluid, and it brings to cells substances that they need, and carries away excess liquid and metabolic waste. If something interferes with the flow of lymph, such as lack of exercise, improper breathing, constipation, or muscle tightness and restricted range-of-motion, all the excess liquid and metabolic waste can become trapped in the sluggish lymph, leading to swelling of the tissues.11
Treatment of trigger points with professional help and the self-help techniques on this CD ROM will help manage the pain associated with fibromyalgia, but you will also need to address the underlying causes and perpetuating factors in some manner in order to obtain lasting relief.
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Many of the Common Symptoms, Causes of Trigger Points, Helpful Hints, Stretches, and Exercises are drawn from Travell and Simons Myofascial Pain and Dysfunction: The Trigger Point Manual. Please assume that any text prior to a footnote is attributed to the source noted in the footnote.
1. http://osuergo.eng.ohio-state.edu/Institute/David G. Simons, MD.pdf (David G. Simons, M.D., speaker, STAR Symposium, Columbus, May 22, 2003)
2. Travell & Simons, M.D.s, Vol. I, pp. 12-14.
3. Author’s experience or education
4. Travell & Simons, M.D.s, Vol. I, pp. 2-14.
5. http:/my.webmd.com, search on Fibromyalgia, 12/03/03.
6. Travell & Simons, M.D.s, Simons, P.T., Vol. I, 2nd ed., pp. 39-40.
7. Travell & Simons, M.D.s, Simons, P.T., Vol. I, 2nd ed., pg. 38.
8. Travell & Simons, M.D.s, Simons, P.T., Vol. I, 2nd ed., pg. 38.
9. Travell & Simons, M.D.s, Simons, P.T., Vol. I, 2nd ed., pg.17.
10. Author’s experience or education
11. Devin Starlanyl and Mary Ellen Copeland, Fibromyalgia & Chronic Myofascial Pain: A Survival Manual, 2nd ed. (Oakland: New Harbinger Publications, Inc., 2001),