CHAPTER 6

Functional anatomy and physiology*

Fascia

The term fascia is described as the “soft tissue component of the connective tissue system that permeates the human body.” Fascia could also be described as fibrous collagenous tissues that are part of a body-wide tensional force transmission system. The complete fascial net then includes not only dense planar tissue sheets (like septa, muscle envelopes, joint capsules, organ capsules, and retinacula), which might also be called “proper fascia,” but it also encompasses local denser areas of this network in the form of ligaments and tendons. Additionally, it includes softer collagenous connective tissues like the superficial fascia or the innermost intramuscular layer of the endomysium. The skin, a derivative of the ectoderm, as well as cartilage and bones are not included as parts of the fascial tensional network. However, the term fascia does include the dura mater, periosteum, perineurium, the fibrous capsular layer of vertebral disks, and organ capsules as well as bronchial connective tissue and the mesentery of the abdomen.

Current understanding indicates that the effects of massage are derived through interrelationships of the peripheral and central nervous systems (and their reflex patterns and multiple pathways) and the autonomic nervous system, neuroendocrine control, and response of the fascial network to mechanical forces applied during massage.^†

This content supports reading comprehension. Do not attempt to memorize the information. Instead, read through it multiple times and look up words you do not understand using the glossary, dictionary, and internet.

Neuroendocrine structure and function

The nervous system is anatomically and functionally connected throughout the entire body, but it may be structurally divided into the central nervous system (CNS) and the peripheral nervous system (PNS), which, in turn, is functionally divided into the somatic or motor nervous system and the autonomic nervous system. Endocrine hormone functions are interrelated as well because they also help regulate homeostasis. Massage application is a demand for the body to respond, which generally affects every part of the nervous and endocrine systems, targets all aspects of these functions. Proper function of the nervous and endocrine systems is especially important for health care clients because most injury and disease processes involve these systems at some level.

Massage influences CNS processing of cognitive perception and the peripheral somatic and autonomic nervous system (ANS), including fluctuations in neurotransmitters and hormones that influence nervous system response.

Massage can affect the nervous system in several ways. Massage causes the body to respond to the sensory input, creating the necessity for homeostasis to be restored. It stimulates nerve receptors in the tissues. On a sensory level, the mechanoreceptors that respond to touch, pressure, warmth, and so on are stimulated. Generally, a reflex effect leads to relaxation of the tissues and a reduction in pain, although the opposite can also happen.

Central nervous system

The central nervous system (CNS) consists of the brain and the spinal cord. The brain is divided into three parts—the cerebrum, brainstem, and cerebellum. The cerebrum, which is the largest portion of the brain, is generally responsible for higher mental functions and personality. The frontal lobe area of the cerebrum also contains the motor cortex, which controls voluntary movement. The parietal lobe of the cerebrum contains the sensory cortex, which receives information about touch and proprioception. The brainstem is the center for the automatic control of respiration and heart rate. The cerebellum controls muscle coordination, motor tone, and posture.

The limbic system and the hypothalamus integrate emotional states, visceral responses, and the muscular system through endocrine and neurotransmitter chemicals. Emotions can alter muscle tension by increasing motor tone, primarily through increased sympathetic dominance in the autonomic nervous system (ANS). States of anxiety and depression commonly create sustained increased in muscle tension.

The typical neuron has a cell body, which contains the genetic material and much of the cell’s energy-producing machinery. Extending from the cell body are dendrites, branches that are the most important receptive surface of the cell for communication. The dendrites of neurons can assume a great many shapes and sizes, all relevant to the way in which incoming messages are processed. The output of neurons is carried along what is usually a single branch called the axon. It is in this part of the neuron that signals are transmitted out to the next neuron. At its end, the axon may branch into many terminals.

The workings of the brain depend on the ability of nerve cells to communicate with each other. Communication occurs at small, specialized gaps called synapses. The synapse typically has two parts. One is a specialized presynaptic structure on a terminal portion of the sending neuron that contains packets of signaling chemicals, or neurotransmitters. The second is a postsynaptic structure on the dendrites of the receiving neuron that has receptors for the neurotransmitter molecules.

The usual form of communication involves electrical signals that travel within neurons, giving rise to chemical signals that cross synapses, which, in turn, give rise to new electrical signals in the postsynaptic neuron. The complexity of the brain is such that a single neuron may be part of more than one circuit. The organization of circuits within the brain reveals that the brain is a massive information processor.

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Some places in the brain are specialized for particular functions. The cerebral cortex, the layer of neurons with its surface area increased by outpouchings, called gyri, and indentations, called sulci, can be functionally subdivided. The back portion of the cerebral cortex (i.e., the occipital lobe) is involved in the initial stages of visual processing. Just behind the central sulcus is that part of the cerebral cortex that is involved in the processing of tactile information (i.e., parietal lobe).

Just in front of the central sulcus is the part of the cerebral cortex that is involved in motor behavior (frontal lobe). In the front of the brain is a region called the prefrontal cortex, which is involved in some of the highest integrated functions of the human being, including the ability to plan and the ability to integrate cognitive and emotional streams of information.

Beneath the cortex are enormous numbers of axons sheathed in the insulating substance, myelin. This subcortical “white matter,” because of its appearance on freshly cut brain parts, surrounds groups of neurons, or “gray matter,” which, like the cortex, appear gray because of the presence of neuronal cell bodies.

The white matter can be thought of as the wiring that conveys information from one region to another. It is within this gray matter that the brain processes information. Gray matter regions include the basal ganglia, the part of the brain that is involved in the initiation of motion (affected in Parkinson’s disease), but that is also involved in the integration of motivational states and becomes dysfunctional with addictive disorders. Other important gray matter structures in the brain include the amygdala and the hippocampus. The amygdala appears to play a special role in aversive or negative emotions such as fear and is involved in determining the emotional meaning of events and objects. The hippocampus initially encodes and consolidates specific memories of persons, places, and things.

The brain is chemically and structurally complex. As previously described, electrical signals within neurons are converted at synapses into chemical signals, or neurotransmitters, which then create electrical signals on the other side of the synapse. Two major types of molecules serve the function of neurotransmitters: small molecules, some well known, with names such as dopamine, serotonin, and norepinephrine, and larger molecules, which are essentially protein chains, called peptides. These include the endogenous opiates, substance P, and corticotropin-releasing factor (CRF), among others. A neurotransmitter can cause a biologic effect in the postsynaptic neuron by binding to a protein called a neurotransmitter receptor. Its job is to pass the information contained in the neurotransmitter message from the synapse to the inside of the receiving cell.

It appears that almost every known neurotransmitter has multiple receptors that can stimulate different signals on the receiving neuron. By definition, therefore, receptors that admit positive charge are excitatory neurotransmitter receptors. The classic excitatory neurotransmitter receptors in the brain use the excitatory amino acids glutamate and, to a lesser degree, aspartate as neurotransmitters. Inhibitory neurotransmitters act by permitting negative charges into the cell, taking the cell farther away from firing. Classic inhibitory neurotransmitters in the brain include the amino acids gamma aminobutyric acid, or GABA, and, to a lesser degree, glycine.

Most of the neurotransmitters in the brain, such as dopamine, serotonin, and norepinephrine, are not only excitatory or inhibitory but produce complex biochemical changes in the receiving cell that alter the way in which receiving neurons can process signals from glutamate (excitatory) or GABA (inhibitory). These neurotransmitters are responsible for brain states such as degree of arousal, ability to pay attention, and identification of the emotional significance of cognitive information. The effects of neurotransmitters influenced during massage may explain and validate the use of sensory stimulation methods for treating clients with chronic pain, anxiety, and depression. Some of the main neuroendocrine chemicals that may be influenced by massage include the following:

• Dopamine

• Serotonin

• Epinephrine/adrenaline

• Norepinephrine/noradrenaline

• Enkephalins/endorphins/dynorphins

• Endocannabinoids

• Oxytocin

• Cortisol

• Growth hormone

It is unlikely that massage sensation processed through the neuroendocrine chemicals target a specific chemical. Instead a more general influence on neuroendocrine function is more logical.

Dopamine

Dopamine influences motor activity that involves movement (especially learned, fine movement such as handwriting), conscious selection (the ability to focus attention), and mood (in terms of inspiration, intuition, joy, and enthusiasm). Dopamine is involved in pleasure states, seeking behavior, and the internal record system. Low levels of dopamine produce the opposite effects, such as lack of motor control, clumsiness, inability to focus attention, and boredom. Massage seems to increase the availability of dopamine in the body, which can explain the pleasure and satisfaction experienced during and after massage.

Serotonin

Serotonin allows a person to maintain context-appropriate behavior—that is, to do the appropriate thing at the appropriate time. It regulates mood in terms of appropriate emotions, attention to thoughts, and calming, quieting, comforting effects; it also subdues irritability and regulates drive states so that we can suppress the urge to talk, touch, and be involved in power struggles. Serotonin is also involved in satiety; adequate levels reduce the sense of hunger and craving, such as for food or sex. It also modulates the sleep/wake cycle. A low serotonin level has been implicated in depression, eating disorders, pain disorders, and obsessive-compulsive disorders. A balancing effect has been noted between dopamine and serotonin, much like those seen in agonist and antagonist muscles. Aggressive and impulsive behavior of individuals can be connected to imbalances in this area. Massage seems to increase the available level of serotonin. Massage may support the optimal ratio of these chemicals.

Epinephrine/adrenaline and norepinephrine/noradrenaline

The terms epinephrine/adrenaline and norepinephrine/noradrenaline are used interchangeably in scientific texts. Epinephrine activates arousal mechanisms in the body, whereas norepinephrine functions more in the brain. These are the activation, arousal, alertness, and alarm chemicals of the fight-or-flight response and of all sympathetic arousal functions and behaviors. If the levels of these chemicals are too high, or if they are released at an inappropriate time, a person feels as though something very important is demanding his or her attention and reacts with the basic survival drive of fight or flight (hypervigilance and hyperactivity). The person might have a disturbed sleep pattern, particularly a lack of rapid eye movement (REM) sleep, which is restorative sleep. With low levels of epinephrine and norepinephrine, the individual is sluggish, drowsy, fatigued, and underaroused.

Massage seems to have a regulating effect on epinephrine and norepinephrine through stimulation or inhibition of the sympathetic and parasympathetic nervous system. This generalized balancing function of massage seems to recalibrate the appropriate adrenaline and noradrenaline levels. Depending on the response of the ANS, then, massage can just as easily wake a person up and relieve fatigue as it can calm down a person who is anxious and pacing the floor.

It should be noted that initially, touch stimulates the sympathetic nervous system, whereas it seems to take 15 minutes or so of sustained stimulation for the parasympathetic functions to be engaged. Therefore, it makes sense that a 15-minute chair massage tends to increase production of epinephrine and norepinephrine, which can help people become more attentive, whereas a 1-hour slow, rhythmic massage engages the parasympathetic functions, reducing epinephrine and norepinephrine levels and encouraging a good night’s sleep, which is necessary for recovery and healing.

Enkephalins/endorphins/dynorphins

Enkephalins/endorphins/dynorphins are mood lifters that support satiety and modulate pain. Massage seems to increase the available levels of enkephalins and endorphins. The massage effect appears to be delayed until the enkephalin level rises, which usually takes about 15 minutes. Appropriate availability of these pain-modulating chemicals is essential for individuals who deal with pain.

Endocannabinoids

Endocannabinoids are a group of neuromodulatory chemicals involved in a variety of physiologic processes, including appetite, pain sensation, mood, memory, motor coordination, blood pressure regulation, and combating cancer. Endocannabinoids, which are endogenous, stimulate the same receptors as cannabis. Endocannabinoids are synthesized on demand, but the question is, what triggers the process? This question must be answered before theories about how massage would interact with these chemicals are formed.

The endocannabinoid system modulates anxiety-like behaviors and stress adaptation. Most research studies suggest that acute stress triggers the release of the endocannabinoid chemicals, which then bind to cells’ receptors. This causes changes in cell function, which causes changes in emotional behavior, reversing the stress response. The endocannabinoid system functions as a neuromodulator of the CNS.

Oxytocin

Oxytocin is a hormone that has been implicated in pair or couple bonding, parental bonding, feelings of attachment, and care taking, along with its more clinical functions during pregnancy, delivery, and lactation. Massage tends to increase the available level of oxytocin, which could explain the connected and intimate feeling of massage.

Cortisol

Cortisol and other glucocorticoids are stress hormones produced by the adrenal glands during prolonged stress. Elevated levels of these hormones indicate increased sympathetic arousal. Cortisol and other glucocorticoids have been implicated in many stress-related symptoms and diseases, including suppressed immunity states, sleep disturbances, and increases in the level of substance P. Individuals with medical concerns are particularly susceptible to increased and sustained cortisol levels. Massage may affect levels of cortisol and substance P secondary to reduction of sympathetic autonomic dominance by supporting relaxation.

Growth hormone

Growth hormone promotes cell division and in adults has been implicated in the functions of tissue repair and regeneration. This hormone is necessary for healing and is most active during sleep. Massage indirectly increases the availability of growth hormone through increased vagal stimulation, predisposing to parasympathetic dominance, encouraging sleep, and reducing the level of cortisol.

Spinal cord

The spinal cord, which is a continuation of the medulla oblongata of the brain, travels through the vertebral canal from the foramen magnum to the lumbar spine. It relays sensory impulses from the periphery up to the brain, and motor impulses from the brain out to the periphery.

Information from all four classes of sensory receptors—the mechanoreceptors, proprioceptors, chemoreceptors, and nociceptors—send information to the spinal cord, which stimulates countless reflexive adjustments in the body to maintain homeostasis, without any active thought from the person.

The spinal cord becomes individual spinal nerves as they exit the vertebral column through openings between the sides of the vertebra called the intervertebral foramina. Anatomically, this is where the peripheral nervous system begins.

Peripheral nervous system

The PNS (peripheral nervous system) consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. These nerves carry sensory impulses from the periphery into the brain and spinal cord, and motor impulses from the brain and spinal cord out to the periphery. The peripheral nerves are vulnerable to compression and irritation at the nerve roots in the area of the intervertebral foramen, as well as entrapment, irritation, or compression in the extremities. They can become restricted or entrapped by adhesions in the connective tissue spaces or hypertonic muscles though which they travel. Nerve pain tends to radiate and follow traceable pathways in the body.

The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

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Somatic nervous system

The somatic sensory nerves relay information to the CNS regarding pain, temperature, touch, and pressure from the skin. These nerves also convey pain signals, proprioceptive information about movement, and position and mechanoreceptor information from the muscles, tendons, ligaments, joint capsules, and periosteum.

Epithelial tissue

The epithelium and the nervous system are derived from the same embryologic tissue, the ectoderm. Therefore, our skin is an extension of the nervous system. The skin is the body’s largest organ and contains blood vessels, glands, muscles, connective tissue, and nerve endings.

The skin contains sensory nerve receptors called mechanoreceptors, which communicate with every other part of the body. The mechanoreceptors are sensitive to touch, pressure, movement, superficial proprioception, pain, and temperature. Skin provides sensation, information, and protection, assists with water balance, and regulates temperature.

Sensory information from the skin communicates with the spinal cord, where reflex connections are made to muscles, internal organs, and blood vessels. Skin pain can cause a contraction in the skeletal muscle or internal organ symptoms, and vice versa, with skeletal muscle and internal organs referring pain to the skin. Massage accesses the body through the skin and sends signals of pressure, movement, stimulation, and so forth, for the body to process.

Somatic sensory nerves

The somatic motor nerves relay information from the brain, through the spinal cord, and then to the skeletal muscles. The somatic sensory nerves are the principal means by which the massage therapist communicates with the body. Each touch and movement sends a message to the CNS (spinal cord and brain), which, in turn, communicates with every other part of the body. Soft tissue consists of four basic categories of sensory nerves, including the following:

• Mechanoreceptors, which respond to touch, pressure, and movement

• Proprioceptors, which respond to changes in position and movement

• Chemoreceptors, which are sensitive to acid-base balance, oxygen, and so forth

• Nociceptors, which detect irritation or pain

The main proprioceptors influenced by massage are the muscle spindle and the Golgi tendon organ. Also influenced are the mechanoreceptors of the skin and connective tissue because of stretching, compression, rubbing, and vibration. Stimulation of joint mechanoreceptors affects adjacent muscles, and stimulation of the skin overlying muscle and joint structures has beneficial effects caused by shared innervations.

Somatic sensory nerves are specialized receptors that relay information to the CNS about four types of sensation: touch, pressure, position, and movement. Touch and pressure originate from the skin sensory nerve endings located in the superficial and deep layers of the skin, which communicate light touch, deep pressure, temperature, and pain. These nerve endings respond to external information from the environment. Massage stimulation of the skin and superficial fascia provides effective communication with these sensors.

Proprioceptors and mechanoreceptors are located in fascia, muscles, tendons, and joints and communicate information about body position and movement. Massage interacts with these receptors through active and passive movement, and the various mechanical forces of bend, shear, torsion, tension, and compression. Compression, irritation, or illness and injury can cause dysfunction in these sensory nerves.

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Muscle and motor tone

Muscle tone is a mixture of fluid pressure and tension and density in the connective tissue elements of the myofascial structure of muscle. The fluid aspect of muscle tone includes interstitial fluid around the cells, the fluid aspect of connective tissue ground substance, and fluid in the various lymph vessels, capillaries, veins, and arteries. Muscle tone is influenced more by mechanical massage applications that target the water and ground substance components of tissue. Motor tone is a low level of continuous contraction of a muscle. It is produced by motor neuron excitability and is influenced by reflexive massage application that inhibits or stimulates motor neuron activity. The most common reason for increased motor tone is the increase in sympathetic arousal and sustained sympathetic dominance. Another cause is proactive muscle guarding/splinting after injury and nervous system damage.

The basic premises of therapeutic massage applied to address muscle and motor tone include the following:

• Substitute a different neurologic signal stimulation to support a normal muscle resting length

• Influence muscle and motor tone by lengthening and stretching muscles and connective tissue

• Normalize fluid dynamics

• Reeducate the muscles involved by encouraging normal movement

• Stimulate neurochemical balance

• Support homeostasis

In general terms, total sensory input to the central nervous system affects overall motor tone throughout the body. This is why nonphysical emotional and mental stress can lead to physical symptoms, such as headache, digestive problems, and muscular discomfort. Massage works on many levels to reduce the symptoms that cause negative sensory input and to increase positive/pleasurable sensory input. This accounts for the general well-being that people usually feel after receiving massage.

Sensory nerve receptors of muscle

Five types of sensory nerve receptors supply each muscle. These sensory nerves respond to pain, chemical stimuli, temperature, deep pressure, muscle length, the rate of muscle length changes, muscle tension, and the rate of change in tension.

• Type 1a is a primary muscle spindle.

• Type 1b is a Golgi tendon organ (GTO).

• Type 2, a secondary muscle spindle, includes paciniform and pacinian corpuscles, which are sensitive to deep pressure.

• Type 3 consists of free nerve endings that are sensitive to pain, chemicals, and temperature.

• Type 4 is made up of nociceptors.

The two classes of sensory receptors that have particular significance for the massage therapist are the muscle spindles and the Golgi tendon organs. They detect length and tension in the muscle and tendon, set the resting motor tone of the muscle, adjust the motor tone in a muscle for coordination and fine muscular control, and protect the muscles and joints through reflexes that contract or inhibit the muscle automatically.

Muscle spindles are specialized muscle fibers called intrafusal fibers, which are located in a fluid-filled capsule embedded within the muscle belly. These muscle spindles respond to slow and rapid changes in muscle length; the secondary endings respond to slow changes in muscle length and are sensitive to deep pressure. The spindles also play a role in joint position, muscle coordination, muscular control, and tone of a muscle. Because muscle spindles detect changes in muscle length, stretching a muscle will increase its rate of signal discharge.

The more refined the muscle’s function, the greater is the concentration of spindles. The greatest concentration of spindles is found in the lumbrical muscles of the hand, the suboccipital muscles, and the muscles that move the eyes.

States of anxiety or emotional or psychological tension can cause an increase in the firing rate of muscle spindles. This increase causes the muscle tone to be “set” to high, creating hypertonicity and stiffness. If the muscle spindles are set too high, the firing rate can be decreased in three ways, causing the muscle to relax (decrease in motor tone):

• Decrease muscle length by bringing the proximal and distal attachments toward each other.

• Contract a muscle isometrically, as is done for contract and relax methods. This method causes the spindle activity to stop temporarily, allowing the muscle to be set to a new, more relaxed length.

• Use inhibiting compression in the belly of the muscle to decrease firing.

Golgi tendon organs are sensory receptors that take the form of a slender capsule located along the muscle fiber at the musculotendinous junction. They sense changes in muscle tension and fire during minute changes in muscle tension. They perform the protective function of preventing damage to a muscle that is being contracted forcefully. Discharge of the Golgi tendon organ stimulates nerves at the spinal cord, called inhibitory interneurons, causing the muscle to relax. Abnormal firing of the Golgi tendon organ can set the resting tone of the muscle too high, creating hypertonicity.

The Golgi tendon organs can be influenced in three ways:

• Muscle energy methods can reset the muscle to its resting length and tone, but the exact mechanism is not fully understood.

• When a muscle voluntarily contracts isometrically, the Golgi tendon organ increases its discharges, which has an inhibiting effect on the muscle, causing it to relax.

• Inhibiting compression at the tendons can also decrease Golgi tendon organ activity.

When these methods are used in combination with stretching, the tissue seems to be more able to tolerate the stretching process.

Massage application

Dysfunction of soft tissue (muscle and connective tissue) without proprioceptive hyperactivity or hypoactivity is uncommon. It is believed that proprioceptive hyperactivity causes tense or spastic muscles and hypoactivity of opposing muscle groups.

Deep, non-painful broad-based massage has a minimal and short-term inhibitory effect on the motor tone of muscle as the result of motor neuron activity. It is used primarily to support a muscle reeducation process such as therapeutic exercise or to temporarily reduce motor tone so that muscle firing patterns can be reset or more mechanical methods can address tissue shortening without causing muscle spasm. Active movements of the body, including techniques such as active-assisted joint movement or the application of active muscle contraction and release used during muscle energy methods of tense and relax and combined methods and contract/relax/antagonist/contract positional release do seem to improve motor function by interacting with proprioceptive function.

Chemoreceptors

As mentioned previously, chemoreceptors are sensory receptors that respond to changes in acid-base balance, oxygen, and so forth. Chemoreceptors may be irritated, for example, when the body is inflamed or when a muscle is in a sustained contraction, thus decreasing the amount of oxygen in the tissue. These chemicals interact with fibroblasts, mast cells, and other cells to create a neurogenic inflammatory response, called neurogenic pain.

Massage may purposefully use controlled focused pain, such as pressure on accupuncture points to release pain-inhibiting chemicals. Tension in the soft tissues or the stress response can cause overactivity in the sympathetic nervous system. By reducing soft tissue tension, massage can help to restore balance and can stimulate the parasympathetic system, resulting in a positive effect on minor and sometimes major medical conditions, such as high blood pressure, migraine, insomnia, and digestive disorders.

The usual outcome of reflexive massage targeting neural chemical mechanisms is inhibitory and anti-arousal. Anti-arousal massage (relaxation massage) may influence motor tone activity in the same way that pharmaceutical muscle relaxers do, because the main reason for motor tone difficulties is sympathetic arousal.

Vestibular apparatus and cerebellum

The vestibular apparatus is a complex system composed of sensors in the inner ear (vestibular labyrinth), upper neck (cervical proprioception), eyes (visual motion and three-dimensional orientation), and body (somatic proprioception) that are processed in several areas of the brain (brainstem, cerebellum, parietal and temporal cortex). These reflexes affect the eyes (vestibulo-ocular reflexes), the neck (vestibulocolic reflexes), and balance (vestibulospinal reflexes) by sending and receiving information all at the same time about orientation to the surrounding environment. Many amusement park rides create disorienting sensations that contribute to the effects of the ride.

The vestibular apparatus and the cerebellum are interrelated. Output from the cerebellum goes to the motor cortex and brainstem. Stimulating the cerebellum by altering motor tone, position, and vestibular balance stimulates the hypothalamus to adjust functions to restore homeostasis. This is the point of complex processing of sensory information; there is overlap between mechanical and reflexive massage methods that are effective, so it is difficult to determine the mode of effect.

Massage application

The techniques that most strongly affect the vestibular apparatus and therefore the cerebellum are those that produce rhythmic oscillation, including rocking during the application of massage. Rocking produces movement at the neck and head that influences the sense of equilibrium. Rocking stimulates inner ear balance mechanisms, including the vestibular nuclear complex and the labyrinthine righting reflexes, to keep the head level. Stimulation of these reflexes produces a body-wide effect involving muscle contraction patterns throughout the body.

Massage can alter body positional sense and the position of the eyes in response to postural change. It can initiate a specific movement pattern that changes sensory input from muscles, tendons, joints, and the skin and stimulates various vestibular reflexes. This feedback information, which adjusts and coordinates movement, is relayed directly to the motor cortex and the cerebellum, allowing the body to integrate the sensory data and adjust to a more efficient postural balance and optimal movement strategies.

If massage application involves vestibular influences, short-term nausea and dizziness can occur while the mechanisms rebalance. Using massage to restore appropriate muscle activation pattern sequences and gait reflexes is valuable. Influencing the balance of massage can shift the relationship of the eyes, neck, hips, and so forth, and may affect positional balance, mobility, and agility.

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Nerve impingement/compression/entrapment

Soft tissue often impinges nerves. Tissues that can bind include skin, fascia, muscles, ligaments, joint structures, and bones. An increase in fluid in a particular area can impinge nerves. Shortened muscles and connective tissue (fascia) often impinge on major and minor nerves, causing discomfort. Tissues that are long and taut can also impinge. The specific nerve root, trunk, or division affected determines the condition, such as thoracic outlet syndrome, sciatica, or carpal tunnel syndrome.

Cervical plexus

The cervical plexus is formed by the ventral rami of the upper four cervical nerves. The phrenic nerve is part of this plexus. It innervates the diaphragm, and any disruption to this nerve affects breathing. Many cutaneous (skin) branches of the cervical plexus transmit sensory impulses from the skin of the neck, ear, and shoulder. The motor branches innervate muscles of the anterior neck.

Symptoms of cervical plexus impingement include headache, neck pain, and breathing difficulties. The muscles most responsible for pressure on the cervical plexus are the suboccipital and sternocleidomastoid muscles. Shortened connective tissues at the cranial base also press on these nerves.

Brachial plexus

The brachial plexus, situated partly in the neck and partly in the axilla, provides virtually all the nerves that innervate the upper extremity. Any imbalance that brings pressure on this complex of nerves results in shoulder pain, chest pain, arm pain, wrist pain, and hand pain. A person may also experience numbness or tingling in the upper extremity as well

The muscles most often responsible for impingement of the brachial plexus are the scalenes, pectoralis minor, and subclavius. Muscles of the arm occasionally impinge branches of the brachial plexus. Brachial plexus impingement is responsible for thoracic outlet symptoms, which often are misdiagnosed as carpal tunnel syndrome. Whiplash injury involves the brachial plexus.

Lumbar plexus

Lumbar plexus nerve impingement may cause low back discomfort with a belt distribution of pain, as well as pain in the lower abdomen, genitals, thigh, and medial lower leg. The main muscles that impinge the lumbar plexus are the quadratus lumborum and the psoas. Shortening of the lumbar dorsal fascia exaggerates a lordosis and causes vertebral impingement of the lumbar plexus.

Sacral plexus

The sacral plexus has approximately a dozen named branches. Almost half of these serve the buttock and lower limb; the others innervate pelvic structures. The main branch is the sciatic nerve. Impingement of this nerve by the piriformis muscle can cause sciatica. Ligaments that stabilize the sacroiliac joint can affect the sacral plexus. Pressure on the sacral plexus can cause gluteal pain, leg pain, genital pain, and foot pain.

Therapeutic massage techniques work in many ways to reduce pressure on nerves. These techniques can be used to do the following:

• Reflexively change the tension pattern and lengthen the short muscles

• Mechanically stretch and soften connective tissue

• Reduce localized edema

• Interrupt the pain-spasm-pain cycle caused by protective muscle spasm that occurs in response to pain

• Support the effectiveness of therapeutic exercise to shift posture and function

• Support the use of medications such as antispasmodics, analgesics, antiinflammatories, and circulation enhancers such as vasodilators.

Major nerves and general intervention patterns be aware of include:

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• Musculocutaneous—muscles of the front of the arm

• Ulnar—forearm and hand

• Median—forearm

• Radial—forearm and hand

• Medial cutaneous—arm and forearm

• Sciatic – thigh and leg

• Femoral —thigh

• Obturator—adductors of the thigh

• Popliteal—leg and foot

• Fibular—leg and foot

Autonomic nervous system

The autonomic nervous system (ANS) is the part of the nervous system that innervates the heart, blood vessels, diaphragm, internal organs, and endocrine glands. It influences every other part of the body, including the muscular system, and has two main divisions: the sympathetic and the parasympathetic nervous systems.

Visceral sensation

Visceral sensory nerves are part of the autonomic nervous system and send pain and pressure information from the internal organs to the CNS. The visceral motor nerves transmit impulses from the ANS to the involuntary muscles, such as those found in internal organs, and glandular tissue.

Sympathetic nervous system

The sympathetic nervous system is responsible for the “fight-or-flight” response, excitement, anticipation, and performance, and it is active when a person is under stress. It releases adrenaline into the blood, causes constriction of the peripheral blood vessels, increases the heart rate, and inhibits normal movement of the intestines, so that blood is available to the skeletal muscles. When a person is under stress, motor tone of the muscles is increased because of the effects of the sympathetic nervous system. This process uses energy, and if the pattern is not reversed, fatigue can occur. Stress can lead to sympathetic dominance and a collection of problems such as breathing disorder, slowed healing, emotional agitation, digestive upset, sleep disturbance, and more.

Parasympathetic nervous system

The parasympathetic nervous system is responsible for energy building, food digestion, and assimilation. It restores homeostasis and is active when the body is at rest and recuperating. It causes a decrease in heart rate, stimulates the normal peristaltic smooth muscle movement of the intestines, and promotes the secretion of all digestive juices and tropic (tissue-building) hormones. A person can be in parasympathetic override (dominance), which contributes to lethargy, loss of normal motivation, and depression.

Many individuals have an underactive parasympathetic nervous system and an overactive sympathetic nervous system. One of the primary benefits of massage given in a relaxing manner is the stimulation of the parasympathetic nervous system. This induces a state of relaxation and promotes the healing and rejuvenation functions of the parasympathetic nervous system, which supports homeostasis.

Enteric nervous system

The enteric portion of the autonomic nervous system is a meshwork of nerve fibers that innervate the gastrointestinal tract, pancreas, and gallbladder. The ENS is sometimes called the “belly brain.”

Traumatic stress syndrome and state-dependent memory

Sensory input during massage may trigger a memory pattern of an emotionally charged event. Each memory—including all sensory information, nervous system functions, and endocrine functions in play at the time of the experience—is stored in a multidimensional way.

Compassion is required to support the client during these times. No verbal interaction is necessary. Referral to a psychiatrist or a psychologist may be necessary. The neurochemical aspect of the body-mind interaction is necessary for physical and emotional healing.

Stress response and effects of massage on the stress response

Excessive sympathetic output causes most stress-related diseases and dysfunction. Examples include headache, gastrointestinal difficulties, high blood pressure, anxiety, muscle tension and aches, and sexual dysfunction. Long-term stress (i.e., stress that cannot be resolved by fleeing or fighting) also may trigger the release of cortisol, a cortisone manufactured by the body. Long-term high blood levels of cortisol cause side effects similar to those of the drug cortisone, including fluid retention, hypertension, muscle weakness, osteoporosis, breakdown of connective tissue, peptic ulcer, impaired wound healing, vertigo, headache, reduced ability to deal with stress, hypersensitivity, weight gain, nausea, fatigue, and psychic disturbances.

Physical and tactile measures are effective for reducing arousal and promoting self-regulation and therefore result in the perception of comfort. Pleasure is an important experience in health and healing. Pain causes muscular contraction, withdrawal, abrupt movement, breath holding, increased heart rate, and increased generalized stress response. The perception of pain is heightened according to the psychological state, especially with anxiety or depression. Low self-esteem and apprehension reduce pain tolerance.

Pleasure can counteract the pain response. Massage provides a pleasurable sensation. Pleasurable pain often accompanies massage application. Pain sensation generated by manual techniques should result in pleasurable outcomes and should never be sharp, bruising, or tearing in nature.

Emotional states such as anticipation, anxiety, anger, depression, and tension usually result in an increased motor tone of muscles; relaxed states supported by pleasure sensation seem to reduce muscular motor tone. The limbic system modulates these responses. Applications of touch that are perceived as pleasurable are usually sedative and parasympathetic in nature. Initial adaptation to touch, as well as touch perceived as uncomfortable, aggressive, and nonproductive, increases sympathetic arousal. The importance of these pleasurable factors during massage is evident in supportive palliative care. Because of its generalized effect on the ANS and associated functions, massage can cause changes in mood and excitement levels and can induce the relaxation/restorative response. Massage seems to be a gentle modulator, producing feelings of general well-being and comfort. The pleasure aspect of massage supports these outcomes. The emotional arousal often seen in the health care environment also is favorably influenced.

Initially, massage stimulates sympathetic functions. The increase in autonomic, sympathetic arousal is followed by a decrease if the massage is slowed and sustained with sufficient pleasurable pressure and lasts about 45 to 50 minutes. Pressure levels must be relatively deep and broad based but not painful. Slow, moderate pressure, repetitive stroking, broad-based compression, rhythmic oscillation, and movement all seem to initiate relaxation responses. Superficial stroking stimulates the itch and tickle response, compression that is painful and a fast-paced massage style stimulate sympathetic responses and may lift depression temporarily.

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Environmental influences

The sympathetic autonomic nervous system supports the clients ability to monitor the environment for danger. Called vigilance this normal survival response can be overactive. The environment the massage is conducted in can affect the response to massage. If relaxation is the goal, then the environment needs to feel safe for the client. A quiet, pleasant atmosphere that is comfortable warm with soft lighting and pleasurable music will support relaxation.

Entrainment is the process of synchronization to rhythms The body entrains to external rhythms such as music in the environment. Any activity that uses a repetitive motion or sound, depending on its rhythmic speed or pace, quiets or excites the nervous system through entrainment and thereby alters the physiologic process of the body. Sometimes the body rhythms are disrupted. Multiple rhythms and noise out of sync in the same environment are disruptive.

Gate control theory

In 1965, Melzack and Wall proposed the gate control theory. Although some aspects of the original theory have been modified over the years, the basic premise remains viable. According to this theory, a gating mechanism functions at the level of the spinal cord. Pain impulses pass through a “gate” to reach the lateral spinothalamic system. Pain impulses are transmitted by large-diameter and small-diameter nerve fibers. Stimulation of large-diameter fibers prevents the small-diameter fibers from transmitting signals because they travel to the “gate of the spinal cord” first. Stimulation (e.g., rubbing, massage) of large-diameter fibers helps suppress the sensation of pain, especially sharp or visceral pain.

Hyperstimulation analgesia

Various massage methods, including pressure, positioning, and lengthening, provide this stimulation to the large-diameter nerve fibers at sufficient intensity to activate the gating mechanism and produce hyperstimulation analgesia.

Tactile stimulation produced by massage travels through the large-diameter fibers. These fibers also carry a faster signal. In essence, massage sensations win the race to the brain, and pain sensations are blocked because the gate is closed. Stimulating techniques, such as percussion or vibration of painful areas to activate “stimulation-produced analgesia,” and hyperstimulation analgesia also are effective. Pain management is a common massage outcome therefore, these methods are beneficial.

Pain sensation may be reduced by the application of manual techniques through the analgesia of the gating mechanism as well. The benefits of reflexology (foot massage) seem to be mediated by hyperstimulation analgesia.

Counterirritation

Counterirritation is a superficial irritation that relieves some irritation of deeper structures. Counterirritation may be explained by the gate control theory. Inhibition in central sensory pathways, produced by rubbing or oscillating (shaking) an area, may explain counterirritation. All methods of massage can be used to produce counterirritation. Any massage method that introduces a controlled sensory stimulation intense enough to be interpreted by the client as a “good pain” signal will work to create counterirritation.

Massage therapy in many forms stimulates the skin over an area of discomfort. Techniques that use friction to the skin and underlying tissue to cause reddening are effective. Many therapeutic ointments contain cooling and warming agents and mild caustic substances (capsicum), which are useful for muscle and joint pain. This is also a form of counterirritation.

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Fluid dynamics

The human body consists of approximately 70% water. Water is a constituent of all living things and often is referred to as the universal biologic solvent. The water content of body tissues varies. Adipose tissue (fat) has the lowest percentage of water; the skeleton has the second lowest water content. Skeletal muscle, skin, and the blood are among the tissues of the body that have the highest content of water.

The total water content of the body decreases most dramatically during the first 10 years and continues to decline through old age, at which time water content may account for only 45% of total body weight. Men tend to have higher percentages of water (about 65%) than women (about 55%), mainly because of their increased muscle mass and lower amount of subcutaneous fat.

Water is continuously lost from, and taken into, the body. In a normal healthy human, water input equals water output. Maintaining this equivalence is of prime importance in maintaining health. Approximately 90% of water intake occurs via the gastrointestinal tract (food and liquids). The remaining 10% is called metabolic water and is produced as the result of various chemical reactions in the cells of the tissues.

The amount of water lost via the kidneys is under hormonal control. The average amount of water lost and consumed per day is around 2.5 L (approximately 41/4 pints) in a healthy adult. Perspiration lost during exercise increases water loss and requires increased water consumption.

The body’s water, or fluid, is named for the tubes or compartments that contain it. Fluids include the blood in the vessels and heart, lymph in the lymph vessels, synovial fluid in the joint capsules and bursa sacs, cerebrospinal fluid in the nervous system, and interstitial fluid that surrounds all soft tissue cells. Water is found inside all cells (intracellular fluid). Water is bound by glycoproteins in connective tissue ground substance. The amount of water in connective tissue helps to determine its consistency and pliability.

The fluids in the body are moved in waves by pumps, which include the heart, the respiratory diaphragm, the smooth muscle of the vascular and lymph systems, and rhythmic movement of muscles and fascia. Fluid moves along paths of least resistance from high pressure to low pressure and flows downhill with gravity. Fluid also moves at differing speeds according to other variables present. Therefore, the properties of water must be considered when massage methods are applied. The goal of massage to influence fluid dynamics would attempt to mimic normal physiological function.

Water is in a constant state of motion inside the body, shifting between the two major fluid compartments, which are the lymphatic and circulatory systems. The walls of the blood vessels form a barrier to the free passage of fluid between interstitial areas and blood plasma. In the capillaries, these walls are only one cell thick. These capillary walls generally are permeable to water and small solutes but impermeable to large organic molecules such as proteins. Blood plasma tends to have a higher concentration of these molecules compared with interstitial fluid. Water from the blood moves through the capillary walls into spaces around the cells, thereby becoming interstitial fluid. Much of the interstitial fluid is taken up by the lymphatic system and eventually finds its way back into the bloodstream. Increased interstitial fluid is a common form of edema. Lymphatic drain massage methods support movement of interstitial fluid into the lymph capillaries.

Water and small solutes such as sodium, potassium, and calcium can be exchanged freely between the blood plasma and the interstitial fluid. The action of the kidneys on the blood regulates these electrolytes. This exchange depends mainly on the hydrostatic and osmotic forces of these fluid compartments.

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Force exerted by water, called hydrostatic pressure, is caused by the weight of water pushing against a surface, as in a dam in a river or the wall of a blood vessel. The pressure of blood in the capillaries serves as a major hydrostatic force in the human body. Capillary hydrostatic pressure is a filtration force that is caused when the pressure of the fluid is higher at the arterial end of the capillary than at the venous end. The pressure of the interstitial fluid is negative (−5 mm Hg) because the lymphatic system continuously takes up the excess fluid forced out of the capillaries.

Osmotic pressure is the attraction of water to large molecules such as proteins. Proteins are more abundant in the blood vessels than outside them, so the concentration of proteins in the blood tends to attract water from the interstitial space. Overall, near equilibrium exists between fluid forced out of the capillaries and fluid that is reabsorbed, because the lymphatic system collects the excess fluid forced out at the artery end and eventually drains it back into the veins at the base of the neck.

A similar situation exists between the interstitial fluid and the intracellular fluid, although ion pumps and carriers complicate the process. Generally, water movement is substantial in both directions, but ion movement is restricted and depends on active transport via pumps. Nutrients and oxygen, because they are dissolved in water, move passively into cells, whereas waste products and carbon dioxide move out.

Regulating fluid balance

The mechanisms for regulating body fluids are centered in the hypothalamus. The hypothalamus also receives input from the digestive tract that helps to control thirst. Antidiuretic hormone (ADH) regulates body fluid volume and extracellular osmosis. ADH influences the body in many ways. One of the major functions of ADH is to increase the permeability of the collecting tubules in the kidneys, which allows more water to be reabsorbed in the kidneys. If the body is lacking fluid intake, as during sleep or during heavy exercise, the result is a concentrated, darker-colored urine of reduced volume. Absence of ADH occurs when the individual is overhydrated. The urine is dilute, pale, or colorless and of high volume.

Primary factors involved in the triggering of ADH production include osmoreceptors and baroreceptors (pressure receptors). Secondary factors include stress, pain, hypoxia, and severe exercise.

Dehydration produced by water loss or lack of fluid intake or relative dehydration in which the body loses no overall water content but rather gains sodium ions stimulates osmoreceptors. The thirst response is connected to the osmoreceptors. How the response actually works is not yet completely understood. Moistening of the mucosal linings of the mouth and pharynx seems to initiate some sort of neurologic response, which sends a message to the thirst center of the hypothalamus. It is perhaps more important that stretch receptors in the gastrointestinal tract also appear to transmit nerve messages to the thirst center of the hypothalamus that inhibit the thirst response. Changes in the circulating volume of body fluid also stimulate ADH secretion that results in an increase or decrease in internal pressure monitored by baroreceptors.

A reduction of 8% to 10% from the normal body volume of water caused by hemorrhage or excess perspiration results in ADH secretion. Pressure receptors located in the atria of the heart and the pulmonary artery and vein relay their messages to the hypothalamus via the vagus nerve.

Electrolyte balance

An electrolyte is any chemical that dissociates into ions when dissolved in a solution. Ions can be positively charged (cations) or negatively charged (anions).

The major electrolytes and their charges found in the human body include the following:

• Sodium (Na⁺)

• Potassium (K⁺)

• Calcium (Ca²⁺)

• Magnesium (Mg²⁺)

• Chloride (Cl⁻)

• Phosphate (HPO₄²⁻)

• Sulfate (SO₄⁻)

• Bicarbonate (HCO₃⁻)

Interstitial fluid and blood plasma are similar in their electrolyte makeup, with sodium and chloride being the major electrolytes. In the intracellular fluid, potassium and phosphate are the major electrolytes. The following information describes the function of electrolytes.

Sodium balance

Sodium balance plays an important role in the excitability of muscles and neurons and is also crucially important in regulating fluid balance in the body. The kidneys closely regulate sodium levels.

Potassium balance

Potassium is the major electrolyte of intracellular fluid. Concentration within the cells is 28 times that in the extracellular fluids. As with sodium, potassium is important in the correct functioning of excitable cells such as muscles, neurons, and sensory receptors. Potassium also is involved in the regulation of fluid levels within the cell and in maintaining the correct pH balance within the body. The pH balance of the body also affects potassium levels. In acidosis, potassium excretion decreases, whereas the opposite occurs in alkalosis. Calcium (bicarbonate) increases in alkalosis.

Calcium and phosphorus balance

Calcium is found mainly in the extracellular fluids, whereas phosphorus is found mostly in the intracellular fluids. Both are important in the maintenance of healthy bones and teeth. Calcium is also important in the transmission of nerve impulses across synapses, the clotting of blood, and the contraction of muscles. If levels of calcium fall below the normal level, muscles and nerves become more excitable. Phosphorus is required for the synthesis of nucleic acids and high-energy compounds such as adenosine triphosphate. Phosphorus is also important in the maintenance of pH balance. Decreased levels of calcium in the body stimulate the parathyroid gland to secrete parathyroid hormone, causing an increase in the calcium and phosphate levels of the interstitial fluids by releasing them from the reservoirs of these minerals lodged in the bones and the teeth. Parathyroid hormone also decreases calcium excretion by the kidneys. If levels of calcium in the body become too high, the thyroid gland releases a hormone called calcitonin, which inhibits the release of calcium and potassium from the bones. Calcitonin also inhibits the absorption of calcium from the gastrointestinal tract and increases calcium excretion by the kidneys.

Magnesium balance

Most magnesium is found in the intracellular fluid and in bone. Within cells, magnesium functions in the sodium-potassium pump and as an aid to enzyme action. Magnesium plays a role in muscle contraction, action potential conduction, and bone and teeth production. Aldosterone controls magnesium concentrations in the extracellular fluid. Low magnesium levels result in increased aldosterone secretion, and aldosterone increases magnesium reabsorption by the kidneys.

Chloride balance

Chloride is the most plentiful extracellular electrolyte, with an extracellular concentration 26 times that of its intracellular concentration. Chloride ions are able to diffuse easily across plasma membranes, and their transport is linked closely to sodium movement, which also explains the indirect role of aldosterone in chloride regulation. When sodium is reabsorbed, chloride follows passively. Chloride helps to regulate osmotic pressure differences between fluid compartments and is essential in pH balance. The chloride shift within the blood helps to move bicarbonate ions out of the red blood cells and into the plasma for transport. In the gastrointestinal system, chlorine and hydrogen combine to form hydrochloric acid.

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