Chapter 5 Mechanical, Physiological, Psychological, and Therapeutic Effects of Soft Tissue Manipulation

Soft tissue manipulation is an ancient art, practiced in many cultures and studied by both ancient and modern scholars. Despite its longevity and widespread use, however, comparatively few scientific studies were undertaken until the twentieth century. Before the early 1900s, the scientific literature on massage consisted largely of descriptive reports and observational records of the areas under study. The methods and standards used today did not exist 100 years ago. In fact, much of medical science was devoted to a description of anecdotal reports and deductive reasoning based on them. Also, the investigative methods available in the first half of the twentieth century were extremely crude by today’s standards. It is easy to forget that electricity was only available as a public utility shortly after 1900 and that the modern electronic age only began in the 1930s. Suffice it to say that the electronic devices (especially computers) that are considered to be indispensable and taken for granted today did not exist in the early decades of the twentieth century. Indeed, much of the modern understanding of human physiology only began to take shape in the late 1890s and early 1900s. This was the era of Sir Charles Sherrington, who is known as the father of modern physiology. With these thoughts in mind, this chapter reviews both the historical understanding of how massage has its effects and some of the modern literature that continues to shed light on this ancient treatment.

The primary effect of manipulating the soft tissues of the body is mechanical in nature. The pressing, pulling, lifting, stretching, rubbing, and squeezing obviously impart a mechanical deformation on the tissues, and this occurs before most, but not all, of the other effects. These mechanical effects result in a wide variety of physiological and psychological responses. All three types of effect give rise to the therapeutic uses. It is worth noting at this stage that the anticipation of receiving a massage treatment is usually a positive experience for the patient. Therefore, a psychological effect might be produced even before the treatment begins.

According to the great Arabic philosopher and scholar Avicenna (980–1037), “The object of massage is to disperse the effete matters [metabolites] formed in the muscles and not expelled by exercise. It causes the effete matter to disperse and so removes fatigue” (Gruner, 1930). This statement from Avicenna clearly shows that classical scholars were very interested in understanding the mechanisms by which manipulation of the soft tissues (including massage) might have beneficial effects; however, the majority of writings have concentrated more on describing the techniques and the observed effects of treatment rather than on investigating these effects scientifically. The general effects of massage have been described and classified in several ways. Mennell (1945) referred to mechanical (pressure and tension), chemical, reflex, and psychological effects, but other authors described only general and local effects. This edition of the text continues to use the simple classification of mechanical, physiological, and psychological effects developed from the fourth edition.

The primary effects (mechanical, physiological, and psychological) are considered separately here, although they are interdependent. Each area has been subdivided into several sections, together with the appropriate research. In this way, relevant research findings have been classified according to the specific effects of massage—for example, the effect of massage on pain. Numerous studies have reported on the general effects of massage compared with other treatment techniques (e.g., Taylor et al., 2003); however, this text concentrates on the specific effects of massage. The reader interested in the more general effects and comparisons of massage with other treatments is referred to computer databases such as the Centre for Reviews and Dissemination (2005). A meta-analysis of massage therapy research can be found in the Database of Abstracts of Reviews of Effectiveness (Issue 2, DARE-20043309). The specific effects, indications, therapeutic uses, and contraindications for each of the basic massage strokes were presented in Chapter 4.

MECHANICAL EFFECTS

The mechanical forces associated with squeezing, pulling, stretching, pressing, and rubbing strokes affect the tissues in a variety of ways. For example, the various techniques of kneading and wringing would be expected to have a considerable mobilizing effect (loosening or stretching) on the skin, subcutaneous tissue, and muscle tissue. In contrast, the gradually increasing pressure of effleurage would be expected to push the venous blood and lymph in the superficial vessels toward the heart, thus promoting good circulation and resolving chronic edema and hematoma. In a similar manner, the pressure and direction of stroking and effleurage techniques can promote movement of the intestinal contents.

The principal effects of each of the basic massage techniques were outlined in Chapter 4. Although the mechanical effects of massage are important to identify, it is the physiological effects that need to be considered in some detail, because these give rise to the therapeutic potential of soft tissue massage. The primary effect of massage, then, is to produce mechanical deformation of the tissues by means of rhythmically applied pressure and stretching. Applied mechanical pressure compresses and stretches the soft tissues and thereby distorts both the excitable and the nonexcitable tissues of the body. Excitable tissues are those structures that respond in some measurable and immediate way to an externally applied mechanical stimulus. Obvious examples are sensory nerves. The nonexcitable tissues are composed of structures such as bone, ligaments, and cartilage. Although these structures do not appear to respond immediately to the applied mechanical stimulus, they do in fact respond, but over a much longer period of time, sometimes taking several months. For example, a muscle that has undergone adaptive shortening (contracture) will obviously feel tight when stretched. If a mechanical stretch is applied to the muscle, especially on a continuous basis (serial casting), the body will re-engineer (lengthen) parallel and series elastic components, but this takes many weeks. Although the immediate effect of the stretching appears nonexistent, over time it becomes apparent. For example, Threlkeld (1992) investigated the mechanical effects of massage on connective tissues.

Table 5-1 lists various tissues as excitable or nonexcitable based on their ability to respond immediately to an external mechanical stimulus. Note that the stimulus does not necessarily have to produce its effect directly. The effect can be produced by the activation of an appropriate reflex. For example, during the percussion strokes, the high-speed mechanical tapping of the skin and muscles activates the Ia sensory endings in the muscle spindles of the muscle being percussed, thereby activating the stretch reflex and thus facilitating the muscle.

Table 5-1 Examples of Excitable and Nonexcitable Tissues

Excitable Tissues	Nerve cells of all types
	Nerve fibers of all types
	Voluntary motor fibers
	Autonomic muscle fibers
	Cardiac muscle fibers
	Abdominal organ cells
	Glands
Nonexcitable Tissues	Skin
	Bone
	Cartilage
	Collagen tissues
	Ligamentous tissue
	Tendon tissue
	Hair
	Teeth
	Nails

Tissues labeled as excitable are capable of an immediate response to an external mechanical stimulus. The response can be mediated via an appropriate reflex or be the result of direct activation. Those tissues classified as nonexcitable show no immediate response to an externally applied stimulus; however, over time, with repeated stimulation, structural changes may become apparent.

The externally applied mechanical pressure can also affect the flow of blood and lymph and can therefore stimulate the circulation. This is a particularly important mechanical effect because the net result is an increased flow of blood and lymph in the target area, and this facilitates healing. A similar direct mechanical effect can occur in the lung tissue, where the percussion and vibration strokes can help to loosen mucus and promote drainage of excess fluids from the lungs (see Chapter 10).

Box 5-1 summarizes the mechanical effects of soft tissue manipulation using two primary categories: the effect that produces movement and the effect that mobilizes the tissues. In the case of the movement effect, the emphasis is on the movement of fluids in the circulatory system (blood and lymph). In the case of the mobilizing effect, the emphasis is on loosening and promoting intertissue mobility. These concepts are discussed in detail in the next section dealing with the physiological effects of massage.

The two primary effects of soft tissue manipulations are the movement of fluids and the mobilization of tissues. These effects have important physiological consequences, which give rise to the therapeutic uses for the various techniques.

It is important to remember that tissues that have adaptively shortened (contractures) cannot be suddenly made longer. The process of lengthening is one in which the natural mechanisms (collagen turnover) are stimulated by the mechanical stresses placed on the tissues. In effect, the tissues undergo an adaptive lengthening. Serial casting, where needed, can greatly facilitate this process as this places a continuous mechanical stretch on the tissues. Of course, soft tissue massage techniques can be used to prevent contractures from developing in the first place.

PHYSIOLOGICAL EFFECTS

The mechanical stimulus given to the tissues during soft tissue massage causes the body to respond in different ways. It is appropriate to consider these responses as the physiological effects of massage, as they are the direct and indirect effects of the individual massage techniques (Goats, 1994a, 1994b). Some of the effects are immediate, whereas others are only apparent over time. This gives rise to the idea that massage can trigger a response in the tissues that begins a cascade of other effects, and some of these effects can be long lasting. This section considers the physiological effects under categories that relate to various tissues. The physiological effects of soft tissue manipulations are listed in Box 5-2 and discussed in the following sections.

Effects on Blood Flow

Because all massage techniques involve some degree of manipulation of the skin and underlying tissues, it is reasonable to expect that they would have a considerable effect on the flow of blood and lymph in these tissues. In addition, swelling that has accumulated in such tissues would be expected to be similarly affected. However, Mennell (1945) believed that it is impossible to affect arterial circulation directly via the mechanical effects of massage. He theorized that applying massage pressure in the direction of the venous flow is comparable to the effect of squeezing any soft tube to empty it of fluid. If the muscles are relaxed, they constitute a soft mass containing tubes filled with fluid. Any pressure applied to the mass should push the fluid in these tubes in the direction in which the pressure is applied; therefore if sufficient pressure is applied to the entire mass, the deeper veins will also be emptied. Such pressure might at the same time retard arterial blood flow if it is forceful enough to compress the arteries and the veins.

Theoretically, if massage can increase the amount of venous blood brought to the heart, the heart rate or the stroke volume might increase and a greater amount of arterial blood would thus be carried to the periphery. In fact, there is little evidence of such a simple mechanical reaction of the arterial and arteriolar system to massage. Wakim (1949, 1955) found that following deep stroking and kneading massage, the average increase in total blood flow in normal, rheumatoid, arthritic joints was inconsistent. Moderate, consistent, and definite increases in circulation were observed after such massage to flaccid, paralyzed extremities. Vigorous, stimulating massage resulted in consistent and significant increases in average blood flow of the massaged extremity but produced no change in blood flow in the contralateral unmassaged extremity.

According to Pemberton (1932, 1939, 1950) the nervous system, probably through the sympathetic division, contributes to a reflex influence on the blood vessels of the parts concerned. He believed that it is probable, therefore, that vessels in the muscles or elsewhere are emptied during massage, not only by virtue of being squeezed but also through a reflex action. Pemberton stated that microscopic observation thus reveals that massage may cause almost all the smaller vessels to become visible because it promotes blood flow through them. Although there is little information on the type of massage that was used, several convincing experiments have been performed that show that massage increases circulation of the blood.

Wolfson (1931) studied the effect of deep kneading massage on venous blood flow in normal dog limbs and showed that massage greatly increased flow initially, followed by a fairly rapid decrease to a less than normal rate even before the end of stimulation. Immediately after cessation of the procedure, he noted that the flow rate slowly increased again to normal. He concluded that the actual volume of blood that passes through the limb during the period of stimulation and recovery is not greater than normal but that there is more complete emptying for a short time, so that a larger volume of fresh blood is brought to the part. He suggested that it would seem logical to use short but frequent massage treatments. Recently, Gregory and Mars (2005) have shown that massage (using controlled compressed air and an animal model) increases capillary dilation and therefore blood flow in skeletal muscle.

Carrier (1922) showed that light pressure produces almost instantaneous, though transient, dilatation of the capillary vessels, whereas heavier pressure may produce more enduring dilatation. Microscopic observation of fields in which only a few capillaries are open shows that pressure may cause nearly all the smaller vessels to become visible.

Pemberton (1945) described the work of Clark and Swanson, who made cinematographic studies of the capillary circulation in the ear of a rabbit utilizing a permanent window for observation. These studies demonstrated that following massage, more capillaries were opened and the rate of flow was faster. The sticking and emigration of leukocytes evidenced a change in the blood vessel wall. The increased blood flow as a result of massage was demonstrated as long ago as the mid-1890s (Brunton & Tunnicliffe, 1894–1895).

Many practitioners have claimed that the reflex effect of superficial stroking improves cutaneous circulation, especially blood flow in superficial veins and lymphatics; aids in the exchange of tissue fluids; increases tissue nutrition; and assists in the removal of the products of fatigue or inflammation. However, as long ago as 1939, Wright stated that such claims must be examined critically in the light of present-day knowledge of physiology. He maintained that it was difficult to make positive statements about reflex effects produced by massage. The situation today is in many ways similar.

Severini and Venerando (1967) reported that superficial massage produced no significant changes except in skin temperature. Deep massage did, however, increase blood flow and systolic stroke volume and decreased systolic and diastolic arterial pressure and pulse frequency. Interestingly, deep massage was also associated with increased blood flow in the untreated, contralateral limb. Bell (1964) demonstrated this effect using plethysmographic studies. He showed that blood volume—and thus the rate of blood flow—had doubled following deep stroking and kneading of the calf of one leg for 10 minutes. Moreover, Bell showed that the effect lasted 40 minutes, as compared with only 10 minutes following exercise. Bell recommended massage to treat edema of fractures because of its effects on venous and lymphatic flow.

Severini and Venerando (1967) also combined massage with a hyperemia-producing drug containing vanillyl and butoxyethyl nicotinate. The combined treatment led to a significant and prolonged rise in skin temperature. When the drug was used alone or with superficial massage, there was no change in circulation in muscles; but with deep massage, there was an appreciable and effective increase in blood flow in muscles. On a more central level, Barr and Taslitz (1970) showed that systolic and diastolic blood pressure tended to decrease after a 20-minute back massage. Delayed effects were an increase in systolic pressure and a small additional decrease in diastolic pressure. The heart rate increased. In addition, high blood pressure and associated symptoms were shown to reduce with massage therapy (Hernandez-Reif et al., 2000).

Massage has been studied for its effect on the circulation, as a means of preventing pressure sores (Dyson, 1978; Ek, Gustavsson, & Lewis, 1985; Olson, 1989). Massage for this purpose, however, does not follow traditional massage techniques. In most cases, it takes the form of a short period (30 to 60 seconds) of skin rubbing, the intention being to stimulate circulation to the areas of skin that are prone to develop pressure sores. Not surprisingly, the results of this kind of massage are difficult to interpret, let alone to use as a basis for making recommendations. In some studies, this type of massage seemed to increase local circulation; in others, it appeared to decrease it. It seems unlikely that a rapid skin friction massage would produce the kind of genuine increase in circulation that would prevent pressure sores. This is because this type of massage simply produces a small degree of mechanical friction on the skin surface. This would probably show up as a slight and short-lived change in surface temperature. On the other hand, a different kind of massage would be expected to produce a more profound effect on the circulation, especially if it involved deep kneading to muscles around the area, were that possible. A more efficient way of producing a rapid change in skin blood flow is massaging the area with an ice cube. In this case, it is the cold stimulus that produces profound vasodilation after the initial vasoconstriction (Michlovitz, 1996). Undoubtedly, a brief massage (1 to 3 minutes) with an ice cube is likely to be much more effective than a similar period of skin rubbing.

Effects on the Lymphatic System

In the lymphatic capillaries and plexuses of the skin and subcutaneous tissue, lymph can move in any direction. Its movement depends on forces outside the lymphatic system. Its course is determined by factors such as gravity, muscle contraction, passive movement, and massage. If obstruction of the deeper lymphatics occurs in a part, it is still possible to keep the superficial lymphatics open, and if the part is massaged or given opportunity to drain by gravity, lymph moves through these other channels in the direction of the external force. These issues are considered in detail in Chapter 12.

Animal experiments show that there is little lymph flow when a muscle is at rest. Von Mesengeil’s and Kellgren and Colombo’s studies on the effects of massage on lymph flow observed increased lymph flow when the muscles were massaged. Cuthbertson (1933) noted that Von Mesengeil

repeatedly injected China ink into corresponding articulations of rabbits. One joint was massaged and the corresponding one left as a control. In the legs without massage, the tendency of the colored material to pass toward the heart was very small, but in those legs subjected to massage, there was great absorption of the ink above the joint in the intermuscular connective tissues and in the lymphatic glands. The lymphatics passing up to the glands were deeply stained black.

Kellgren and Colombo found that

Massage always had a sure and effective influence in increasing the rapidity of the absorption of substances injected into animals in all the organs which can be subjected to manipulations— subcutaneous tissues, muscles, articulations, and serous cavities. The course which the injected substance followed during its absorption, was always that of the nearest lymphatic vessels and the glands into which they pass. Deep Effleurage was probably less effective than the squeezing and rolling of muscles and subcutaneous tissue.

McMaster (1937) also showed that massage increased lymph flow by experiments in which the limbs of normal healthy subjects were massaged after intradermal dye injections.

Drinker and Yoffey (1941) cannulated the cervical lymph trunks in an anesthetized dog and were able to sustain lymph flow all day long by massaging the head and neck above the cannulas. When the massage was stopped, lymph flow either ceased or was negligible. The investigators stated that, in treating chronic inflammatory conditions in which fibrosis is sure to advance if tissue fluid and lymph remain stagnant in the part, massage in the direction of lymph flow is the preeminent artificial measure for moving extravascular fluid into lymphatics and for moving lymph onward toward the bloodstream. Drinker and Yoffey also found that the effects of posture were obvious and that lymph flow from a dependent, quiescent part was practically negligible. Therefore, to influence the flow of lymph most efficiently in any area, it seemed logical that the part should be elevated during the application of massage. Elevation means placing the part higher than the heart. In addition, the pathway for the fluids should be as straight as possible.

Ladd et al. (1952) compared the effects of massage, passive motion, and electrical stimulation on the rate of lymph flow in the forelegs of 15 dogs and found that massage was “significantly more effective than either passive motion or electrical stimulation in this series of animals.” All three procedures were found to increase lymph flow much above that of the control period.

The idea of using mechanical forces to affect the circulation of blood and lymph is not limited to manual massage techniques. A variety of pneumatic devices have been developed that deliver a series of controlled (and often graduated) pressure changes along a limb surface. In effect, these devices perform a kind of mechanical massage. They have proved to be of considerable benefit in the treatment of many acute and chronic circulation disorders but especially in the treatment of lymphedema (Yamazaki et al., 1988). Of course, manual massage techniques also have an important role to play in the management of lymphedema (Andersen, 2000: Casley-Smith, 2000; Forchuk et al., 2004; Little & Porsche, 1998; Mason, 1993; Nickalls, 1996; Weinrich & Weinrich, 1990). See also Chapter 12 for an in-depth discussion on the concept of decongestive therapy for the management of lymphedema.

Effects on the Blood

In 1904, Mitchell stated that in both healthy and anemic persons, the red cell count increased after massage. In anemic subjects the increase is greatest 1 hour after treatment. Schneider and Havens (1915) also showed that abdominal massage increases the hemoglobin and red cell count in blood taken from the finger at ordinary barometric pressures. Pemberton (1950) stated that massage unquestionably increases the hemoglobin and red cell values in the circulating blood and that there is a limited but definite increase in the oxygen capacity of the blood after massage. Lucia and Rickard (1933) found that massage consisting of gentle but firm stroking of a rabbit’s ear at the rate of 25 strokes per minute for 5 minutes caused a local increase in the blood platelet count.

Bork, Karling, and Faust (1971), reporting the effects of whole-body massage on serum enzyme levels in normal persons, showed a significant rise in serum glutamic oxaloacetic transaminase, creatine phosphokinase, lactic dehydrogenase, and MK. These effects caused the authors to advocate that whole-body massage should be contraindicated for patients with dermatomyositis, especially serious cases.

Ernst et al. (1987) showed that a 20-minute whole-body muscle massage causes a dilution effect and changes blood fluidity. This effect was observed in both normal subjects and patients with ankylosing spondylitis. When these effects are coupled with the increased blood and lymph flow produced by massage, it is clear that this form of treatment has a significant role to play in maintaining and enhancing the overall nutrition of the tissues.

The changes described briefly here are not produced by a direct effect on the blood itself, but rather they reflect the overall effects of massage given to the person. Because the vascular system pervades every part of the anatomy, it is not surprising that the blood reflects the mechanical and physiological effects of massage. Increased or decreased levels of various substances carried in the blood are, in most cases, simply the result of the massage given to the soft tissues rather than a direct effect on the blood itself.

Effects on Metabolism and the Healing Process

Very little recent experimentation has been reported on the effects of massage on metabolism, although several studies were performed more than 50 years ago. Cuthbertson (1933) reviewed the existing literature on this subject and conducted several experiments of his own. He arrived at the following findings:

• Urine output increases, especially after abdominal massage.

• Excretion of acid is not altered, and there is no change in the acid-base equilibrium.

• Excretion rates for nitrogen, inorganic phosphorus, and sodium chloride increase.

• In normal persons, there is no immediate effect on the basal consumption of oxygen or on pulse rate or blood pressure.

Pemberton (1939) believed, “In general the studies which have been made suggest broad and general influences may be exerted by massage and that it has no immediate or large effect on general metabolism per se.” He agreed with the view that its cumulative effect on various metabolic processes lies in its effects on the circulation of the parts concerned.

The resolution of acute trauma or of chronic inflammation (healing) consists of a cascade of interrelated changes in the affected tissues. These changes depend entirely on the efficiency of the local circulation to the part, as all of the materials needed to resolve the inflammatory process must arrive at the scene via the bloodstream. In addition, all of the waste products must be removed from the area via the blood and lymph channels (Evans, 1980). Because massage has such profound effects on the blood and lymph systems, it seems obvious that it has the potential to be useful in stimulating the healing process, especially in the subacute and chronic phases of recovery.

It is important to remember the crucial importance of the lymphatic system in removing plasma proteins and other large molecules once they have been deposited in the interstitial fluid. These molecules are too large to reenter the capillaries and can only be eliminated via the lymphatic system. Facilitation of healing is therefore the by-product of the other (more direct) effects (e.g., increased blood and lymph flow) on the tissues.

Effects on Muscle Tissue

More than 100 years ago, Maggiora (1891) described the physiological action of massage on muscle tissue. Many other writers have also described the effects of massage on muscle tissue. Much of the literature contains a relatively large number of positive statements and implications about the effects of massage on muscles, as compared with its effects on other systems and tissues of the body. Some of these statements cannot be substantiated by clinical observation or by scientific research. The present review considers separately the effects of massage on normal and abnormal muscle tissue.

Normal Muscles

Kellogg (1919) observed that “Massage produces an actual increase in the size of the muscle structures. The muscle is also found to become firmer and more elastic under its influence.” McMillan (1925) wrote, “The muscles are strengthened and made to grow by manipulation.” According to Despard (1932), “Massage improves the nutrition of the muscles and consequently promotes their development.” These observations are not supported by the contemporary literature, which generally agrees that massage alone does not increase muscle strength. Of course, if the massage is used as a method of preparing muscles for exercise (e.g., in sports massage, see Chapter 13), then strengthening would be expected to occur, providing a suitable regime of exercise was performed. Nonetheless, exercise, not the massage, is the reason why muscle strength would increase.

Mennell (1945) believed the theory that advocated kneading a muscle (working a muscle up) and thereby making it stronger was a complete delusion. He stated,

By one means alone can muscular strength be developed, and that is by muscular contraction, and no form of massage can do more than aid means indrectly.

and again,

To use massage aright we must consider it entirely as a means to an end, that end being restoration of fuction.

As a means to an end, massage may make it possible for a muscle to perform more exercise and thus develop its strength. This fact has been proven by experimental work done by Rosenthal, Mosso, and Maggiora (and by others cited in Cuthbertson [1933]), who have shown that a muscle fatigued by work or by electrical stimulation will be restored much more rapidly and thoroughly by massage than by rest alone of the same duration.

Nordschow and Bierman (1962) studied 25 normal, healthy, active subjects to determine whether massage manually applied could cause measurable muscle relaxation in normal human subjects, expressed as increased muscle length. A finger-to-floor test was used to measure tension in the posterior muscles of the back, thighs, and legs as each subject, standing with knees straight, bent forward and attempted to touch the floor with the fingertips. Following such an attempt, each subject then assumed a comfortable, well-supported prone position for 30 minutes of rest. The finger-to-floor test was then repeated. The subject then reassumed the prone position and was given 30 minutes of massage, 15 to the back and 15 to the posterior aspect of the lower extremity, allowing 7.5 minutes per limb. The authors concluded that manual massage causes relaxation, which is expressed as increased muscle length. Bell (1964) reported that muscle fatigue was relieved more quickly by massage and rest than by rest alone and suggested alternate bouts of exercise and massage in therapy (a method applied in some sports).

Smith and colleagues (1994) studied the effects of athletic massage on delayed-onset muscle soreness, creatine kinase, and neutrophil count. Their results indicate that massage reduces the negative effects of exercise on normal muscle. Presumably these effects are due to the increased circulation of blood and lymph, effectively washing out the metabolic by-products of exercise. The positive effects of massage on muscle recovery following intensive exercise are well known and have been studied in a variety of professional sports (Perkes et al., 2004; Robertson et al., 2004; Weerapong et al., 2005).

The term muscle tone is often used to describe the quality of a muscle that is firm and ready to contract; however, muscles at rest show no electromyographic activity (Goodgold & Erberstein, 1983). Therefore a muscle that exhibits tone cannot be at rest; it must be in a state of contraction. Although some statements in the literature imply that massage increases muscle tone, evidence to support this claim is inconclusive at best. Theoretically, however, several massage strokes would be expected to increase the fusimotor drive to a muscle. For example, any of the percussion (tapotement) strokes (hacking, clapping, beating, and pounding) would be expected to increase muscle spindle firing and, therefore, fusimotor output. Indeed, this is the mechanism by which massage strokes facilitate muscle contraction. It amounts to direct stimulation of stretch reflexes within the stimulated muscle.

Deep massage to normal muscle tissue will obviously have a strong mechanical mobilizing effect on the physical structure of the tissue itself. The mechanical effects (stretching, twisting, pressing, etc.) are likely to trigger physiological changes, especially in the series and parallel elastic components, effectively making it possible for the muscle to lengthen over time. The effect of stretching on human muscles is a complex issue, but the biophysics have important implications for soft tissue massage techniques and the use of passive stretching movements (De Deyne, 2001; Magnusson, 1998), especially in the sports sciences (Hemmings et al., 2000).

Pathologic Conditions of Muscle

Fibrosis tends to occur in muscles that have been immobilized, injured, or lost their nerve supply. Significant shortening of the parallel and series elastic components (contracture) is often the end result. The muscle as a whole becomes shorter than its normal resting length, mainly because the fibrous tissue lacks elasticity and adhesions form between adjacent layers of connective tissue.

With the careful use of various massage techniques, it is possible to apply tension on this fibrous tissue, the objective being to prevent adhesions from forming and to break down small adhesions that have already formed. The techniques best suited to this purpose are various pressure manipulations (pétrissage) and the deep transverse friction technique (Iwatsuki et al., 2001). When supplemented by appropriate exercise and stretching regimens, massage techniques are an essential component in the restoration of muscle length and normal function.

A number of experimental studies have investigated the effects of massage on both injured and denervated muscle. These are considered separately here because the issues involved in each case differ significantly.

Injured Muscle

Lucas-Championnière (cited in Mennell [1945]) described some of the earliest experimental work in this area and summarized the results of Castex’s work on the effects of massage on injured muscles. Animal muscles were subjected to crushing injury; then massage was given to one group and another group was used as a control. The researcher later microscopically examined the muscle tissue of both groups. The untreated parts showed the following characteristics: (1) dissociation into fibrils of the muscle fibers, as shown by well-marked longitudinal striation; (2) hyperplasia (often simple thickening) of the connective tissue; (3) an increased number of nuclei in the connective tissue; (4) interstitial hemorrhages; (5) an enlargement of blood vessels, with hyperplasia of their adventitious coats; and (6) usually intact sarcolemma (but, in one section, multiplication of nuclei gave an appearance that somewhat resembled interstitial myositis). In contrast, the massaged limbs had the following features: (1) normal-looking muscle, (2) no secondary fibrous bands separating the muscle fibers, (3) no fibrous thickening around the vessels, (4) greater general muscle bulk, and (5) no signs of hemorrhage.

Denervated Muscle

Although massage has been used quite extensively for the treatment of a muscle that has lost its nerve supply (denervated muscle), there is little information in the literature on its effectiveness. Some studies have been performed, however, mainly in an effort to determine its effect on the histopathological changes in the muscle itself, on atrophy, and on the strength of the muscle. No firm conclusions can yet be drawn from these results.

Chor et al. (1939) conducted an experiment to study the effects of massage on atrophy and the histopathological changes that occur in denervated muscle in primates. Two groups of rhesus monkeys were subjected to unilateral section of the sciatic nerve; the researchers then immediately sutured the nerves and immobilized the extremity in a plaster cast. After 4 weeks, they applied massage (stroking and kneading) and passive motion daily for 7 minutes to one group while keeping the control group at complete rest. After intervals from 2 months for some animals to 6 months for others, the researchers examined the muscles microscopically to determine the histopathological changes. The muscles kept at rest were pale and surrounded by thickened septa of fibrous tissue with whitish and yellowish streaks throughout. Microscopically, this fibrosis was clearly demonstrable, both surrounding muscle fibers and replacing atrophic ones. The massaged muscles were supple and elastic and showed considerably less fibrosis and adhesions. The extent to which muscle function is restored after reinnervation is determined largely by the ratio of functioning muscle fibers to fibrous tissue that has replaced degenerated muscle fibers. To some extent, by preventing the formation of inelastic fibrous tissue and adhesions, massage helped maintain a favorable ratio for greater recovery of function. This would be particularly important in terms of the overall length of a muscle, because this is a key factor in preserving the normal range of motion at any joint associated with the muscle.

In an earlier study, Chor and Dolkart (1936) compared muscle atrophy resulting from either disuse or denervation. They observed that disuse atrophy in a skeletal muscle develops slowly and is associated with simple structural changes. The loss of muscle bulk was attributed to a diminished quantity of sarcoplasm in the individual muscle fibers, the atrophic muscle fibers being narrower and packed closer together. The characteristic cross-striations persist, with no actual degeneration of the muscle fibers. The intramuscular blood vessels remain unaltered.

The muscle atrophy that follows nerve section or lesions of the anterior horn cells (e.g., poliomyelitis) is more than wasting from disuse. Its course is rapid, and characteristic changes occur. In addition to the shrinkage of the muscle fibers, degeneration of these cells follows. The cross-striations disappear, and the muscle cells begin to break down. In later stages, the disintegrated muscle cells are replaced by fibrous tissue and fat. Changes also occur in the intramuscular blood vessels. The number of capillaries increases, and the small intramuscular blood vessels show hypertrophy of the endothelium and an increase in their fibrous structure. Chor and coworkers believed that atrophy and degeneration of denervated skeletal muscle are inevitable and then showed that massage did not prevent atrophy up to a period of 6 weeks, but because of its effect on the amount of fibrous tissue formed, it did enable the muscles to return to normal more rapidly upon reinnervation.

In an early study, Langley and Hashimoto (1918) considered the effects of massage in denervated muscles from a single rabbit. Firm massage was begun on the third postoperative day. Treatment was discontinued on the seventh day because open lesions developed on the limb. Treatment was started again on the eleventh day with “gentler” massage, which was continued until 23 days after denervation. The researchers concluded that the effect of the treatment on atrophy was slight at best and that an increase in the growth of connective tissue is a possible result of massaging denervated muscle. Although interesting in itself, this study offers limited possible conclusions.

Hartman and colleagues (1919) tested both weight and work capacity of denervated muscles in 37 rabbits. One leg of the animals was given kneading and stroking massage. Both legs were given passive exercise. Treatment continued for periods of 7 to 190 days. The investigators noted no significant differences. They suggested that the weight of the muscle did not necessarily indicate the amount of contractile tissue present, because structural mass and function of the muscles differed considerably in 17 of the muscles tested.

Hartman and Blatz (1920) later tested the power of denervated gastrocnemius muscles of 60 rabbits. The muscles on one side were massaged for periods of 2 to 20 minutes daily, and both legs were given daily passive movement. The investigators tested the muscles at intervals of 10 to 14 days. They concluded (1) that “the treated limb on the whole did not appear to be any better off than the control”; (2) that massage was of no value; and (3) that there was invariably a decrease in power and no significant difference between treated muscles and controls.

Wright (1939) stated that more rigorous proof was required for the claims that muscle wasting can be prevented or muscle nutrition improved by providing massage but not movement. He believed that some local effects are undoubtedly produced in the muscle and that they may be due to chemical agents liberated into the blood to produce local or general effects. He also believed that massage might release some of the metabolites of muscle activity. He questioned whether direct mechanical stimulation could produce a direct muscle response in denervated muscle as reflex reactions are obviously excluded.

Suskind and colleagues (1946) studied the denervated gastrocnemius muscles of cats. Two 5-minute periods of effleurage and kneading were given daily to one limb; the other limb served as the control. The investigators measured the strength and weight of the muscles 28 days after sectioning. Results showed that the denervated muscles treated with massage were heavier and stronger than their untreated contralateral controls. The effect on muscle weight was slight but statistically significant. It seemed that massage had slowed down the gradual loss of contractile strength observed in skeletal muscle after denervation.

Wood and associates (1948) reported the effects of massage on weights and tensions of the anterior tibial muscles of 14 dogs. Bilateral section of sciatic nerves was performed, and one leg was given a daily period of massage (stroking and kneading) lasting for 10 minutes. The other leg was used as the control. The researchers tested the muscles at intervals from 13½ to 36 weeks following denervation. Results showed that all anterior tibial muscles in the treated animals appeared pale and small in size, compared with normal anterior tibial muscles. There was also a greater proportion of tendon to total bulk than in normal muscles, as well as a greater proportion of fatty tissue. It was impossible to distinguish treated tissue from untreated muscle on gross examination. Histological sections from anterior tibial muscles of treated animals (treated and untreated muscles) showed no significant histological differences. Wood concluded, “Massage was not effective in delaying denervation atrophy, as indicated by losses in strength and weight and by examination of histological sections in experimentally denervated anterior tibial muscles of the dog.”

The primary effects of massage on muscle tissue can be summarized as follows:

• Massage does not directly increase the strength of normal muscle; however, as a means to an end it is more effective than rest in promoting recovery from fatigue produced by excessive exercise. Theoretically, then, massage makes it possible to do more exercise, which, in turn, increases muscular strength and endurance. This is an important factor in treatment. It would seem logical that massage should be given between periods of exercise when exercise is used to develop muscle strength and endurance. This is particularly relevant for sports medicine.

• Generally speaking, massage does not increase muscle tone, but certain strokes can be used to facilitate muscle activity (especially percussion techniques; see Chapter 9) that inevitably develops in immobilized, injured, or denervated muscle.

• Massage may reduce the amount of fibrosis.

• Massage does not prevent atrophy in denervated muscle. Even though a muscle may undergo considerable wasting, if fibrosis is minimal and circulation and nutrition are good, a small muscle may have greater power than a muscle with larger mass if the mass is the result of overgrowth of fibrous tissue that interferes with the function and recovery of the remaining innervated muscle fibers.

• The aims of massage in the treatment of denervated muscle should be to maintain the muscles in the best possible state of nutrition, flexibility, and vitality, so that after recovery (if this is possible) from trauma or disease, the muscle can function at its maximal potential.

Effects on Bones and Joints

Key and colleagues (1934a, 1934b) conducted an experiment to determine the effects of heat, massage, or active exercise on local atrophy of the bone caused by immobilization of the part. Ten patients with normal lower extremities were used. Both extremities were placed in casts, which were bivalved and removed during treatment. One extremity was used as a control; the other was treated. The massage was given for 10 minutes, twice daily for 6 weeks. Roentgenograms were made before and at the end of the experiment. The investigators observed no significant differences between the treated and control limbs. They concluded that short periods of heat (five patients), massage (two patients), or active exercise (three patients) had little, if any, effect on local atrophy of bone secondary to immobilization in a plaster of Paris cast. These results are interesting; however, the experiment was performed on very small numbers of subjects and the results are certainly inconclusive.

In the past, massage was used widely in the treatment of fractures, and it was considered beneficial for aiding repair of the associated soft tissue injuries. It has not been established, however, whether massage actually helps to heal bone. It was the opinion of the Fracture Committee of the American College of Surgeons that, in the process of normal bone repair after fracture, “The effectiveness and rapidity of growth of tissue are dependent upon efficient circulation in the parts.…Therefore every effort must be made from the beginning to help the efficiency of the circulation.”

Mock (1945) believed that because recent research had shown the tendency for callus to be formed along the lines of the new blood vessels formed at the site of fractures, any treatment that enhanced circulation in the area of the fracture without producing motion of the fragments should promote deposition of callus. Of course, this may be difficult with many of the deeper massage strokes, the objective of which is to deliberately squeeze and stretch the deeper muscle tissues. It is hard to see how these techniques can be given effectively without causing the bone fragments at a fracture site to move; however, if the fracture site is stable, massage techniques might be very useful.

Many of the structures that surround the various joints of the body, such as ligaments, bursas, capsules, and tendons, are often the site of chronic problems. In many instances of chronic dysfunction, the goal of treatment is to break down scar tissue in these structures and the adhesions between them. Traditionally, deep friction massage has been the technique of choice because its strong mechanical effect on scar tissue is useful in restoring a normal, painless range of motion to an affected joint (Cyriax, 1960, 1984; Hammer, 1993). (See also Chapter 9.)

Clearly, joints are designed to move under the influence of muscles and gravity, and there are many reasons why range of motion in a joint may be lost. Of course, continued loss of range in a joint contributes to chronic pain and adhesion, with the accompanying loss of function. Impaired range of motion can be restored to joints using a wide variety of treatments, including massage. This is particularly the case if the limited range is due to muscle spasm, pain, or contracture in the tissues surrounding the joint. Appropriate massage techniques can help to relieve pain and restore range of motion in these circumstances (Hernandez-Reif et al., 2001).

Effects on the Nervous System

Although the literature offers little direct information on the actual effects of massage on the function of the human nervous system, the mechanical effects of massage clearly give rise to a number of important physiological effects. Indeed, massage techniques specifically directed at peripheral nerves were in common use in the early decades of the twentieth century. In her book Massage and Medical Gymnastics, Lace (1946) described so-called nerve manipulations—such as nerve stroking, nerve pressure with vibration, nerve friction, and nerve stretching—as a significant category of strokes. These techniques, though rarely used today, are still being given for specific nerve problems (Jabre, 1994).

Despite a paucity of information, it is possible to describe some likely effects based on what is known of the neurobiology of the nervous system. For example, whenever the skin is touched or the underlying tissues are manipulated, sensory receptors in a variety of tissues are activated. Afferent signals pass into the spinal cord, form synapses with various spinal neurons, and eventually find their way to the sensory cortex and other brain centers. At a spinal level, several spinal reflexes could be triggered, depending on the type and depth of massage technique and the part of the body being massaged. Similar reflex activation is likely at a variety of autonomic centers and brain nuclei. Some of these concepts are discussed in the next section on the effects of massage on pain. Clearly, there are many potential pathways by which soft tissue massage might have direct and indirect effects on the nervous system.

A number of studies have shown that many direct effects are indeed possible. Clear evidence from several well-controlled studies shows that massage (kneading) performed directly on a muscle causes significant depression of the amplitude of the H-reflex (Hoffman reflex) response, but only during the period of massage (Morelli et al., 1991; Sullivan et al., 1991). This effect was also recorded in patients with spinal cord injury (Goldberg et al., 1994). In contrast, Dishman and Bulbulian (2001) compared the effect of spinal manipulation and massage on motoneuron excitability and reported that the effects were transient, but the effects on the tibial H-reflex produced by spinal manipulation lasted longer than those of massage.

Goldberg and colleagues (1992) studied the effect of two intensities of massage on H-reflex amplitude and showed that a deeper massage technique produced a more pronounced reduction in H-reflex amplitude than did superficial massage. In each of the studies cited here, the inhibitory effect of the massage on H-reflex amplitude effectively lasted only during the time when massage was applied. Some subjects (especially those with spinal cord injury) did show a tendency for the inhibitory effect to continue when the massage had ceased, but it did not last long enough to be useful therapeutically. These results are also important because they indicate that massage of muscle tissue and its related structures (e.g., skin, subcutaneous tissues) can change the level of excitability of the spinal motor neurons. The effect is reflex in nature and is likely to be associated with increased firing of the pressure-sensitive receptors in muscle, especially the Golgi tendon organs, which are known to inhibit their relevant alpha motor nerve cells.

Despite promising early experimental studies on reflex control of circulation and neuromuscular responses to massage (Cuthbertson, 1933; McMaster, 1937; Pemberton, 1945) and strong support for hypotheses that massage has definite reflex effects, such effects seem to be hypothesized for want of any other rational explanation. The specific reflex mechanism responsible has not been clearly identified, nor has how simple or complex the reflex action(s) may be. Much work still must be done to clarify and verify these concepts by controlled clinical and laboratory studies, correlated with current physiological and neurophysiological concepts.

The work of Barr and Norman (1970) and Barr and Taslitz (1970)

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