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Muscle Overuse Trigger Points

Issue: Summer 2009
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When any muscles in the body are exposed to abuse thru overuse, symptoms will inevitably occur. The intensity and duration will vary, but typically will increase as the duration of the problem persists.

For decades researchers have been classifying and redefining different types of muscular pain and dysfunction. Some areas of classification overlap, but some distinct characteristics remain. For example, fibrosis was first defined in 1904, then in 1990 officially redefined as fibromyalgia. Travell reports fibromyalgia as a “…central augmentation of nociception which causes generalized deep tissue tenderness that includes muscles.” Myofascial pain syndrome has both a general and specific meaning. Dentists and others have used the term to describe a regional muscle pain of any soft-tissue origin that is associated with muscle tenderness. The other more specific meaning is a myofascial pain syndrome caused by trigger points. A trigger point is defined as “a hyperirritable spot in the skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band. With compression the point is painful causing referred pain, referred tenderness, motor dysfunction/weakness, and autonomic phenomena.” Trigger points were described as early as 1843 by Froriep. In 1942, Travell first described trigger points and, in 1983, the Trigger Point Manual was first published; the second edition following in 1999. To more fully understand the relationship of trigger points/muscle dysfunction to dentistry, a little more detail is necessary.

Supporting the working position can alleviate the cumulative muscle stress that leads to back, neck, and shoulder pain.

Normal healthy tissue is not painful to palpation, and is not associated with parasthesias or weakness. The tenderness and other symptoms related to a trigger point develop when a muscle is overloaded with acute, sustained, or repetitive activities. In the case of a sustained muscle contraction, as in dentistry, the intramuscular pressure increases and stays increased, impeding blood flow. This decreased blood supply starves the tissue of oxygen and nutrients while causing an increase in the buildup of metabolic waste. According to Jennifer Lake, PT, “a static muscular effort can only be maintained for a short period of time before pain and tissue injury ensues.” This is because tissue requires a constant blood supply to be healthy. What does this have to do with dentistry? In dentistry, the forward lean position is the most practical and desirable position of treatment as it allows direct vision to the work area. This forward lean position is not a problem in itself as it is well within the normal physiological parameters of spine movement. The position is not the problem, but trying to sustain that position through muscular effort is a problem. The forward lean position, although minimal, requires ongoing/sustained muscle contraction resulting in a decrease in blood flow through the area. Maintaining even a “good” posture requires muscle effort and eventually will result in fatigue and symptoms.

According to Travell and Simons, pain as well as paresthesias (numbness and tingling), muscle dysfunction in the form of weakness, loss of coordination, decreased work tolerance, and autonomic dysfunction and sleep disturbances are all symptoms often seen in patients with trigger point problems.

 Functionally, the muscle with a trigger point develops a threefold problem. First, it is more sensitive to irritation; it reacts more quickly to overuse than a normal muscle. Second, the irritated muscle takes longer to relax once the effort is removed. Third, the muscle fatigues more quickly than healthy tissue. Combined, these factors increase workload and reduce work tolerance.

We see this scenario with many dental practitioners who have pain and related symptoms. It takes less time on Monday morning to begin to feel fatigue and pain, then, at the end of their workday/workweek, it takes longer for them to feel relief. Travell and Simons state that the motor effects (weakness, inhibition) may be the most important part of the problem as the motor dysfunction produced by trigger points may result in overload of other muscles, spreading the trigger point problem from muscle to muscle. We see this often in dentistry and other situations where the primary problem begins in one area of the low back and, over time, spreads out to include the other side of the low back, the upper back and neck, and possibly/likely the extremities as well. Often patients are misdiagnosed when trigger points are involved. Many muscles of the scapular and upper extremities frequently produce referred pain and referred dysthesias, including muscle weakness/dysfunction. For example, according to Travell and Simons; “…carpal tunnel syndrome is likely to be diagnosed when the patient has active trigger points in the pronator teres, flexor carpi radialis and/or brachialis muscles.” They go on to say, “…the referred pain from even more distant trigger points in the sternocleidomastoid, infraspinatus, and subscupularis muscles have tempted some to make the carpal tunnel diagnosis.” The above-mentioned two muscle groups are in the forearm and scapular areas, respectively, and frequently cause symptoms into the arm and hand. When these trigger points are effectively treated the result is an increase in blood flow that accompanies the relaxation of the tissue. This leads to improved tissue health and resolution of symptoms.

As muscle relaxation is key to tissue health, why not avoid overworking the muscles in the first place? This can be achieved with support of the trunk—the majority of the mass involved— from the front, allowing the back muscles to remain in a relaxed state during the procedure. It is the same as when we lean back in our recliner. Because our trunk is supported, our abdominal muscles remain relaxed. Try assuming the same position without support and see how long your abdominal muscles will last. The situation is the same in the inclined (forward-lean) position with the back muscles at work. Supported, the muscles can rest, avoiding fatigue and the inevitable pain and dysfunction. Unsupported, it’s only a matter of time before the cascade of events mentioned above begins.

Kurt Klemm is a practicing physical therapist with a specialty in spine rehab; and is certified in Mechanical Diagnosis & Therapy of the Spine. After years of treating dental practitioners who had back problems, he developed the AnterioRest; a device that attaches to the patient chair, providing a stable support for the preferred forward lean. See more about how and why the AnterioRest works at www.anteriorestdental.com. Kurt may be reached at 866-704-8455 or klemmcei@newnorth.net.