CHAPTER 1
THE NATURE OF MUSCLES AND TRIGGER POINTS
Movement is a fundamental characteristic of life, and the musculature plays the major role in that activity. Motion, both gross and subtle, is an essential body function resulting from the contraction and relaxation of muscles. In humans the musculature constitutes 40 to 50 percent of total body weight. Considered as a single entity, the musculature can be regarded as the body’s largest internal organ.
There are three primary functions of the muscles. First, they contribute to the support of the body and containment of the internal organs. Second, they allow movement of the body as a whole, as well as movements of the organs and substructures. Many kinds of motion rely on the integrated functioning of bones, joints, tendons, ligaments, muscles, and fascia. Both the maintenance of our upright posture as well as all body movements—walking, sitting, writing, chewing, breathing, and so forth—take place as a result of appropriate muscular activity. Internal, organic movement that is the hallmark of life relies on appropriate muscular activity: the beating of the heart and the movement of blood throughout the arterial vessels; digestion, peristalsis, and elimination; the emptying of the bladder; the very ability to draw a breath. Finally, this movement produces heat and therefore contributes to the regulation of body temperature, the third primary function of the muscles.
The three types of muscle—skeletal muscle, visceral muscle, and cardiac muscle—provide these functions. Each of these tissues exhibits four principal characteristics:
The focus of this manual is the contractile, voluntary skeletal muscle tissue. There are two types of skeletal muscle: phasic muscles and postural, or tonic, muscles.
Phasic muscles produce a contraction known as a phasic contraction. A phasic contraction is sufficient for the muscle to produce movement of its attachments. Phasic muscles are mainly comprised of fast-twitch fibers, which tend to produce rapid contractions and therefore function to produce rapid movements. There is a generally low capillary supply to phasic muscles and, as a result, these muscles tend to fatigue quickly. Phasic muscles tend toward the rapid accumulation of lactic acid. When there is muscular dysfunction, phasic muscles tend toward weakening.
Those that are generally considered to be phasic muscles include the midthoracic portion of the erector spinae; the rhomboids; the lower and middle trapezius; the abdominal portion of pectoralis major; triceps brachii; vastus medialis and vastus lateralis; gluteus maximus, gluteus medius, and gluteus minimus; rectus abdominis; and the external and internal obliques.
Postural, or tonic, muscles produce a sustained partial contraction of the muscle known as a tonic contraction. With a tonic contraction a portion of the muscle cells in the muscle are contracted at any given time while others are relaxed. This causes some contraction of the muscle; however, because enough fibers are not contracted at the same moment in time, a tonic contraction does not produce movement of the skeletal attachments.
During a tonic contraction an individual motor unit does not function continuously; rather, individual motor units within the muscle fire asynchronously, thereby relieving one another in a smooth and continuous manner. The result is a muscle contraction that can be held for long periods of time. As the name implies, these postural, or tonic, muscles act in the maintenance of upright posture; they are considered to be “antigravity” muscles. Postural muscles tend to be comprised mainly of slow-twitch fibers. There is generally a high capillary supply to these muscles, and as a result they do not tend to fatigue rapidly. Lactic acid production is minimal. When there is muscular disturbance, postural muscles tend toward shortening.
Those that are generally considered to be postural muscles include the scalenes, sternocleidomastoid, levator scapulae, pectoralis major, biceps brachii, the cervical and lumbar portions of the erector spinae, quadratus lumborum, iliopsoas, the hamstring group (biceps femoris, semitendinosus, semimembranosus), rectus femoris, tensor fasciae latae, the adductor group (adductor magnus, longus, and brevis), pectineus, gracilis, piriformis, gastrocnemius, and soleus.
Skeletal muscles, both phasic and tonic, are extremely vulnerable to injury due to overuse and the wear and tear of daily life, yet this musculature is often overlooked as a major source of physical pain and dysfunction.
In order to clearly understand the nature of an injured muscle we must first understand the qualities of normal muscle. Normal, healthy muscle tissue feels supple and elastic. The underlying structures—bones, joints, and viscera—may be easily palpated through the skeletal muscle. There is uniform consistency and plasticity within a normal muscle, and it is not tender when palpated. A healthy muscle will contract in response to nervous impulse, returning to its normal shape after contraction. Individual bundles of muscle fibers (fascicles) cannot be differentiated while palpating normal muscle.
A dysfunctional muscle will contract, but it will not return to its normal shape following contraction. It will instead remain fixed in a shortened position, one that often results in local reduction of blood flow, lymph drainage, and range of motion. Over time a chronically contracted muscle can undergo changes in the tissue, either throughout the functional unit or within individual bands. These changes are often characterized by an increase in muscle tone, greater resistance to palpation, and decreased suppleness. Contracted musculature is no longer able to perform its activities optimally. Being shortened, it cannot perform its full range of contraction and release. Its range of motion is impaired, resulting in weakened functioning.
Taut bands, individualized bundles of muscle fiber, may be differentiated during palpation of a contracted muscle. The muscle may harbor ropelike areas, cordlike bands that can vary in thickness from thin strings to cables as much as a few centimeters thick. (Generally, bands formed in small muscles feel stringy while bands formed in larger, thicker muscles feel “ropy,” or like cables.) Contracted muscle is generally reported to feel tender when mild pressure is applied. Underlying structures may be more difficult to palpate clearly, and in cases of very strong contraction, underlying structures may be completely obscured to palpation.
All of us harbor areas of constricted muscle, contracted in varying degrees, that maintain holding patterns in tight, chronically utilized muscles. These patterns can be seen in such common postural habits as holding the shoulders elevated, the chest constricted and dropped, the upper back rounded, or the lower back strongly arched. Whether due to emotional or physical patterns of overuse, our posture, our ability to move, and our ability to operate in a physiologically optimal manner are all affected by holding patterns of muscular constriction. When the constriction is chronic, other aspects of our physiology, such as blood flow, lymphatic drainage, and nervous innervation, are eventually affected as well. Our overall health is therefore intimately related to our muscular health.
One of the many factors that may contribute to the pain and dysfunction of a muscle is the development of trigger points within it. In her encyclopedic work on trigger point therapy, Dr. Janet Travell defines a trigger point as “a hyperirritable locus within a taut band of skeletal muscle, located in the muscular tissue and/or its associated fascia.”1 Myofascial trigger points—that is, those that are located in muscle (generally, skeletal muscle) or muscle fascia—are most prevalent and symptomatic; however, trigger points can also be present in cutaneous, ligamentous, periosteal, and nonmuscular fascial tissues as well. A myofascial trigger point is that area, that point, along a taut muscular band in which the tenderness reaches its maximum. The patient will feel the greatest degree of sensitivity at the trigger point; the practitioner will feel that area to have the greatest resistance to palpation (that is, it will feel like the hardest area on the taut band). A trigger point is painful upon compression. It can give rise to referred pain, tenderness, and autonomic phenomena such as visual disturbances, redness and tearing of the eyes, vestibular disturbances, space-perception disturbances, coryza (mucous membrane inflammation), reduction in local vascular activity, and skin temperature changes. The implications of such extensive effects are important in regard to the examination and treatment of many disorders that are generally not considered to be related to muscular problems.
The size of the muscle is not the characteristic that defines the degree, severity, and extent of pain caused by a trigger point within that muscle. Rather, it is the degree of hyperirritability of the trigger point that defines the degree of pain. The more hyperirritable the trigger point, the greater the degree of pain throughout the course of the referred pain pattern.
A trigger point may begin with muscular strain or overuse that becomes the site of sensitized nerves, increased cellular metabolism, and decreased circulation. From an anatomic perspective, areas that tend to develop trigger points are generally areas in which increased mechanical strain or impaired circulation are likely to develop due to physical activities or postural stresses. Trigger points most frequently develop in the sternocleidomastoid, upper trapezius, levator scapulae, infraspinatus, thoracolumbar paraspinals, quadratus lumborum, gluteus medius, and gluteus minimus; however, trigger points can develop within any fascicle in any muscle of the body.
Trigger points can be latent or active. Both will cause stiffness and weakness of the affected muscle and restrict the muscle’s full range of movement. (Stiffness is most notable after periods of inactivity, while weakness tends to be more variable.) Both active and latent trigger points are tender to palpation.
Active trigger points are differentiated from latent trigger points in that they produce pain. Therefore, active trigger points are generally considered to be of greater clinical significance. This pain tends to be referred away from the affected muscle in a characteristic pain pattern; the relationship between an active trigger point and its characteristic pain pattern has been extensively researched by Travell and Simons. There may be an abrupt onset of pain or dysfunction, whereby a specific incident is noted to be the cause of the myofascial difficulty, or the onset may be gradual, the muscle having been overloaded for some period of time. Myofascial pain may be characterized as steady, deep, dull, and aching; it is rarely described by the patient as burning, throbbing, tingly, or numb. Pain varies in intensity from low-grade to quite severe, and it may occur at rest or in motion.
Tenderness in response to palpation can occur within the pain pattern of a trigger point even if pain is not experienced in the point’s referral zone. This tenderness will dissipate after the trigger point is reduced. Pain or tenderness will generally increase with use of the muscle, stretching of the muscle, direct pressure to the trigger point, shortening of the muscle for an extended period of time, sustained repetitive contraction of the muscle, cold or damp weather, viral infections, and stress. Symptoms will decrease after short periods of light activity followed by rest, and slow, steady, passive stretching of the muscle, especially with the application of moist heat to the muscle.
Latent trigger points are far more frequent than active trigger points and are commonly found in patterns of muscular constriction that frequently define a person’s “normal” posture. Latent trigger points can become active through a number of circumstances. Activation of a trigger point can occur directly through acute overload of a particular muscle, chronic overload or overwork fatigue caused by excessive or repetitive actions or sustained contraction of the muscle, trauma to the muscle, or compression or chilling of the muscle. Indirect activation can occur as a result of leaving a muscle in a shortened position for extended periods of time, as in sleeping or sitting for extended periods or holding a phone between the ear and the shoulder. Indirect activation can also result from visceral disease, viral disease, emotional stresses, or the chronic muscular strain of trying to stabilize arthritic joints, or if the latent trigger points lie within the pain pattern produced by other, active trigger points. Generally the degree of conditioning of the muscle is the factor that most defines whether a latent trigger point will become active. The greater the degree of muscle conditioning, the lower the susceptibility to trigger point activation. However, while an active trigger point will frequently revert to latency with sufficient rest, trigger points will not be fully reduced without clinical intervention.
Only adequate, focused, specific palpation techniques allow the practitioner to identify trigger points within a muscle. Through palpation we identify generalized tightness of the musculature within the vicinity of the suspected trigger point. As we palpate we locate the specific muscle that is shortened and then locate the specific band within the muscle that is taut. Continued focused palpation will reveal an area along the band that is particularly tight and then a point within the area that is exquisitely tender. Here we have located the trigger point. Direct manual pressure to that trigger point elicits what Travell called a local twitch response—that is, a literal twitch of the muscle that is sometimes visible (depending on the placement of the muscle) and is often experienced by the patient.2 In addition, there may be a “patient jump sign”—that is, the patient jumps or cries out in pain.3 The pain that the patient expresses is often greater than the practitioner may expect given the degree of pressure applied. With extended pressure to the trigger point, the referred pain pattern may be felt in its entirety by the patient.
Once located, the trigger point must be reduced. This is accomplished primarily through needling or through ischemic compression. Depending on the specialty of the practitioner, needling may include acupuncture needling or dry needling, or trigger point reduction techniques developed within the medical community with the use of analgesic or anesthetic injection, or the injection of saline. Ischemic compression requires compressing the trigger point for 15 to 20 seconds, followed by manipulation of the surrounding bands of muscle tissue to reduce local constrictions and taut muscular bands. Spray-and-stretch techniques, that is, the application of cold while stretching the muscle, is often helpful as follow-up to needling or ischemic compression. Treatment is completed through the application of moist heat to increase circulation to the affected muscle.
Once there is sufficient reduction of the trigger points and associated constrictions, the patient is instructed in stretching techniques specific to the involved muscles. The stretches are aimed at keeping the muscle from returning to the shortened state. Repeated stretching throughout the day is unquestionably one of the most important aspects of treatment. Finally, depending upon the degree of weakness of the muscle, after it is clear that the muscle is not readily returning to a contracted state the patient is instructed on specific strengthening exercises to help him return to optimal activity levels and to prevent the muscle from tending to return to a state of disability.
It is important to note that the conditioning of a muscle is ultimately dependent upon the conditioning of the whole body. It is vitally important to help each patient attain an optimum level of health with a program that includes exercises that will generally strengthen both the musculature and the cardiovascular system. Every part is only as viable as the whole. To view and treat a single muscle or muscle group without consideration of the whole is insufficient treatment. An expansive view of the whole body must be integrated into the care of each patient.