Tissue Movement

As the hands move along the superficial tissues, pressure to the tissues increases, and layers of tissue are moved. A light glide causes movement of the epidermis. If friction is maintained between the therapist’s hand and the patient’s skin, the epidermis moves with the hand and is gently stretched. There will also be some movement of the dermis because of the traction between the two layers. More pressure with friction, although still very light, results in traction between the dermis and the subcutaneous tissues. The end-feel of the stroke is when this traction reaches its limit and all layers are stretched.

Massage involves the interaction of energy between the person applying the massage and the dog, and the effects of touch to induce relaxation, communication, and a sense of general well-being. It may also produce movement of the tissues in subsequent layers as a result of traction of the tissue interfaces. Sensory and autonomic nerves may be stimulated, inducing changes in the nervous and circulatory systems, and movement may be affected in abnormal tissue, such as scar tissue or layers of adherent tissues. Reed and Held⁷ found no consistent systemic effect on autonomic nervous system parameters either acutely or cumulatively when comparing connective tissue massage and a placebo treatment (sham ultrasound) in healthy middle-aged and geriatric humans.

Therapeutic Effects

Massage is generally enjoyed by small animal patients and helps to relieve distress, anxiety, and discomfort. There are many postulated effects of massage reported in the literature. Unfortunately, many of these have not been substantiated by systematic scientific investigations.

Stroking young animals results in a reduction in the animal’s physiologic response to stress, demonstrated by a decreased output of adrenocorticotropic hormone.⁸ Young animals that are handled also show greater development of the cortex and the subcortex of the brain. They learn faster and have a more advanced stage of neural development than nonhandled animals.⁹ Resistance to infection later in life may also be beneficially influenced by cutaneous stimulation experienced by the infant animal.¹⁰

If a hand is placed over the surface of a dog’s skin, heat is felt between the two surfaces. If the hand is placed on the skin and held still, this heat increases. Rubbing over the surface of the skin causes friction, and this results in an even greater increase in heat. Heat is a form of energy, and some schools of massage, particularly those grounded in Eastern practices, use the energy field that exists around the body. This is sometimes referred to as an electromagnetic radiation around the entire body. It is felt as heat and can be felt a small distance from the body. Some also believe that other forms of energy fields run through the body, along specific pathways known as meridians. These are used in acupuncture and reflex therapy treatments.

Most of the research on the effects of massage has been done in humans. Most studies have evaluated healthy individuals, which may be misleading because physiologic compensatory mechanisms are extremely efficient in healthy tissues and any alterations in local blood flow may be compensated for by autoregulatory processes. Most of the research studies have also been performed on small groups and often without control groups. One study by Hansen and Kirstensen¹¹ gave little detail concerning the massage itself, such as the amount of pressure applied. Although the research supported the concept that massage increases blood flow in muscles, the lack of information regarding the type of massage and length of treatment make interpretation of the results difficult.

Changes in blood constituents following massage have provided information regarding the mechanism of action of massage.¹² Ernst¹³ found that a standard 20-minute massage treatment reduced the hematocrit and blood and plasma viscosity. It is believed that the fluid immediately surrounding poorly perfused vessels has low viscosity because of decreased cellularity and that the vasodilatation caused by massage aids in the recruitment of dormant vessels. It is desirable to increase local circulation to promote healing. The mechanical effect of the massage helps to remove low-viscosity tissue fluid into the circulation. The changes in blood detected within the vessels in this study support the belief that massage produces a flushing and mechanical effect on the circulation. In a more recent study, Hinds and colleagues⁶ showed no difference in femoral arterial blood flow, quadriceps muscle temperature, blood lactate levels, heart rate, or blood pressure when comparing post quadriceps exercise and massage to exercise and rest. They did show that skin blood flow and skin temperature were both significantly elevated in the massage group. They hypothesized that this potential diversion of blood flow away from the muscle could have a deleterious effect to recovering muscle tissue. They did not demonstrate a decrease in muscle blood flow, however, so this hypothesis is not supported by their work.

In a Cochrane database review, Furlan and colleagues¹⁴ critiqued 13 randomized trials and concluded that massage might be beneficial in the treatment of low back pain in acute and chronic cases, especially when combined with exercise and education.

Effects on Muscle

Massage may also affect skeletal muscles. Muscles have a natural resting tone that may be increased in postural muscles by external influences, such as cold or stress. This occurs because of the interaction of the muscle spindle and the central nervous system. Stretching a muscle may stimulate the muscle spindle and cause a reflex muscle contraction while reflex inhibition of the antagonist occurs. Massage may add an external stimulus to sensory organs and either increases muscle tone by stimulation or reduces it, probably by facilitating an accommodation of the spindle, causing it to reset at a lower threshold of excitability.

It is believed that the circulatory effect of massage may reduce muscle soreness and therefore aid clinical signs associated with muscle injury or postexercise recovery. Danneskiold-Samsoe and colleagues¹⁵ studied the effects of massage for shoulder and back pain in humans. Blood samples were evaluated for myoglobin concentrations. There was a statistically significant effect, with peak myoglobin concentrations occurring within 3 hours of the massage. Myoglobin concentrations gradually decreased; after seven treatments, there was no difference. In a systematic review of the literature published in 1998, Ernst¹⁶ concluded that most studies evaluating the effect of massage on delayed-onset muscle soreness were methodologically flawed, findings were inconsistent between studies, and, although there appeared to be some potential for a positive effect, the evidence was not convincing and warranted further controlled investigation.

Jacobs¹⁷ advocated the use of massage for the relief of spasm of unknown cause but which resulted in a self-perpetuating muscle spasm cycle (Figure 27-2). Massage is also said to reduce tone in muscles that are tense or in spasm and to reduce the soreness and tenderness of exercised muscles. It is also used to prepare muscles for exercise. Hernandez-Reif and colleagues¹⁸ found that children with cerebral palsy who received 30 minutes of massage twice weekly for 12 weeks had decreased muscle spasticity of the arms, decreased arm muscle and overall tone, increased hip extension range of motion (ROM), and improved fine and gross motor function when compared with children with cerebral palsy who received 30 minutes of reading twice weekly.

Jones and Round¹⁹ discussed the process by which an analgesic substance, possibly potassium, is released when muscles maintain excessive tone or static contraction for prolonged periods. Eccentric exercise of muscles, which generates high forces in muscles, produces delayed-onset soreness and a feeling of stiffness. Jones and Round¹⁹ explained this by identifying swelling in muscles and inflammation of the connective tissue. Massage may help reduce or prevent the initial tenderness. It is also believed that massage may help to prevent subsequent postexercise pain. Regular massages may make the muscles softer and more pliable, and the stretching manipulations may increase extensibility and strength in the connective tissues.¹⁵ Willems and colleagues²⁰ demonstrated decreased muscle soreness in portions of the quadriceps muscle (vastus lateralis and rectus femoris), but not in the vastus medialis after massage following eccentric exercise–induced muscle soreness. They also demonstrated improved vertical jumping performance in the massaged leg 48 hours after massage when compared with the nonmassaged leg. Mancinelli and colleagues²¹ showed significant effects of massage versus control in vertical jump displacement, perceived muscle soreness, and algometer muscle pain readings, but not timed shuttle run in women collegiate athletes.

Pain experienced after exercising with the muscles in a lengthened position may also be due to inflammation of the connective tissue rather than muscle damage. Massage may assist by increasing pliability in the connective tissue around the muscle fasciculi. Massage assists mobility between the interfaces within the muscle and also stretches any fibrous adhesions or scarring in the tissue.

The effects of massage on the Hoffman (H) reflex, which indicates the excitability in α-motoneurons or anterior horn cells, has also generated interest. Goldberg and colleagues²² studied the effects of massage on healthy people and patients with spinal cord injuries. They applied one-handed petrissage to deep and superficial tissues. There was a 49% reduction in H reflex activity with deep massage, and a 39% reduction with light massage. From this study, it was concluded that stimulating cutaneous mechanoreceptors and pressure receptors reduces H reflex activity. Sullivan and colleagues²³ also demonstrated a reduction in α-motoneuron excitability of massaged muscles.

Effects on Pain and Sensation

The effects of massage on connective tissues, which helps to reduce muscle spasm and soft tissue discomfort, have already been discussed. However, Ueda and colleagues²⁴ demonstrated that postsurgical massage may facilitate the regression of sensory analgesia following an epidural block.

Carreck²⁵ evaluated the effect of massage on levels of pain perception in humans. She found that pain threshold was raised to significantly higher levels in the massage group and this work suggests that massage may be used to help manage pain and reduce treatment soreness.

Massage may cause traction at tissue interfaces. Horizontal plexi lie at interfaces in the tissues and gentle pulling on these vessels may stimulate the accompanying sympathetic nerves, which supply the mechanoreceptors. These receptors may be distorted by the massage, possibly lowering mechanoreceptor sensitivity and reducing pain and tenderness. If delayed-onset pain in the muscle is caused by connective tissue inflammation, the flushing effect in the surrounding fluids and removal of inflammatory mediators may increase the speed at which the inflammation resolves.

Effects of Massage on Connective Tissue

Following injury or disease, inflammation causes increased vascular permeability. The resulting edema contains fibrinogen, which may result in formation of fibrous tissue. Adhesions form within the tissues, binding tissue interfaces. These adhesions prevent normal sliding of tissues on each other and also reduce the ability of the fibers to spread apart. Massage is described as being able to stretch tissues that have become short, tight, or adhered. Petrissage massage stretches and pulls the tissues in various directions and mobilizes the adjacent connective tissue fibrils. The molecular cross-bridges between fibrils may be influenced and plastic changes may occur; their length may be maintained or increased because of elongation or creep. Mobility may also be increased at the fibrous cross-bridges between fibers and areas of adhesions by stretching connections between the fibers. This facilitates spreading and sliding at tissue interfaces, and longitudinal elongation helps to increase flexibility.

Following surgery, scars may form with adhesions of various tissue layers to the underlying tissues. Massage helps mobilize and soften adhesions by elongation, creep, and increased fluid exchange of tissues. Collagen fibers align themselves along lines of stress. Techniques that stretch the fibers and adhesions in different directions eventually restore their mobility, promoting remodeling along the lines of normal stresses.

Following injury, it is important to maintain local flexibility of the involved structures to assist overall suppleness and to reduce the possibility of reinjury resulting from decreased extensibility of normal and scar tissues. Massage should be used to promote the functional recovery of structures and prevent reinjury by maintaining mobility at the interfaces, both inside and outside the affected structures. Massage should be combined with controlled longitudinal stretching exercises.

One technique to mobilize scar tissue is deep-friction massage.²⁶ It is applied at 90 degrees to the fibers and delivers a stretch and separation between individual fibers. Deep friction is believed to create movement and induce reactive hyperemia,²⁷ stretch cross-bridges between fibers, and stretch adhesions within the structure. Fibrous scarring in tendons and their interfaces may become more pliable with massage. Although one researcher has suggested that deep friction application may result in some analgesia to the area,²⁸ there is little evidence to support this claim. Although many theoretical effects of massage have been put forth, there is little high-quality research evidence to support these claims. A Cochrane review evaluating the effect of deep transverse friction massage for treating tendinitis found no evidence of benefit with its use and concluded that there was the need for a high-quality randomized study using validated outcome measures to further evaluate its usefulness.²⁹