Note : the following excerpt is a copy of chapter 16 of the book: Healing Through Touch, by John T. Cottingham, which is published by the Rolf Institute, 1995. It is reprinted on this website with permission of the author. For any further usage please contact the author for permission. You can order this book via the Rolf Institute website.

 

MUSCLE TONE, POSTURE, AND MOVEMENT

 

John T. Cottingham

 

... the motor act is the cradle of the mind.

- C.S. Sherrington

 

Overview

 

The skeletal or striated muscles, along with the connective‑tissue network, are responsible for posture, movement, and structural shape of the body. (See also Chapter 14.) The skeletal muscles are richly innervated by sensory and motor nerve fibers and therefore are regulated by the nervous system,, hence the name neuromuscular system.

The neuromuscular system has certain unique proper

ties that permit the carrying out of its functions (Chusid, 1976):

1. Contractility: the capacity to contract or shorten is found in all cells, but muscle tissue is specialized in this function.

2. Elasticity: depending on the pattern of nerve impulses, muscles will shorten or lengthen.

3. Extensibility: muscle has the ability to lengthen  when stretched.

4. Irritability: the capacity to respond to different forms of stimulation (e.g., touch, electrical, heat, etc.) by either contracting or lengthening.

Muscle tissue's property of irritability, to respond to

different forms of tactile stimulation, is the underlying basis for somato‑therapies' effects on muscle tone, posture, and voluntary movement.

 

 

 

Muscle Tone and Spinal Reflexes

 

Muscle tone refers to the constant state of contraction for a muscle in a given postural position (e.g., sitting, lying down, or standing). As shall be examined below, the amount of muscle tone in a given muscle is primarily dependent on the neural transmission from the spinal cord and brain.

It is known that sensory receptors or "sensors" within the myofascial tissues (i.e., muscle, fascia, ligaments, and tendons) react to mechanical stretching and shortening (Shepherd, 1983). There are two types of sensors involved: (1) the muscle spindles and (2) the Golgi tendon organs.

Muscle spindles are encapsulated structures located throughout the skeletal musculature. Because of their enclosed fusiform shape, they are referred to as intrafusal muscle fibers and are located within and parallel to the larger extrafusal muscle fibers that make up the contractile portion of the muscle. (See Figure 16.) (The muscle spindle's function in maintaining posture will be discussed in the next section.)

 

 

FIGURE 16 ‑ Gamma and alpha motor neuron systems. A gamma neuron is shown innervating a muscle spindle, while the alpha motor neuron innervates a larger, striated muscle. Note that the muscle spindle and striated muscle have a parallel alignment. A sensory fiber from the muscle spindle synapses in the spinal cord onto an alpha motor neuron. When the muscle spindle is "loaded" (stretched), this sensory fiber increases its firing rate, thereby increasing muscle tone; when the muscle spindle is "unloaded" (shortened), the muscle tone is decreased. Thus, the muscle spindle has been described as the "sensing element" of the neuromuscular system, keeping the larger skeletal muscles at a relatively constant length under different amounts of tension.

 

 

 

 

 

When the muscle is suddenly stretched, the encapsulated muscle spindles are also stretched. This stretching stimulates or "loads" the muscle spindle, which then sends nerve impulses to motor neurons (alpha) in the spinal cord, instructing the muscle to contract (i.e., increase its tone). (See Figure 16.) This contracting of a muscle, or group of muscles, that follows a quick stretching is called the stretch reflex. Note that the antagonistic muscles, having the opposite movement function, will lengthen.

If the muscle is mechanically shortened (e.g., tactile pressure to the belly of the muscle), the muscle spindle is shortened or "unloaded," decreasing its firing rate to motor neurons in the spinal cord. Thus the muscle is lengthened, and muscle tone is reduced. In this case the antagonistic muscles will be shortened. Such a procedure is frequently utilized in massage and soft‑tissue manipulation when a certain muscle is "hypertoned" and needs to be relaxed.

The Golgi tendon organs, like the muscle spindles, are encapsulated structures. But unlike the muscle spindles, they are located in the collagenous fibers of tendons, ligaments, and fascial sheaths‑usually near the bony insertions (Carpenter and Sutin, 1983). The Golgi tendon organs have sensory nerve endings that terminate within minute bundles of collagen fibers. Because they are in "series" with the tendon and fascial fibers, they primarily respond to tension.

When, for instance, the tendon is slowly and actively stretched (e.g., deep pressure), the Golgi tendon organs increase their firing rate. These impulses are sent to the spinal cord and inhibit alpha motor neurons and muscle tone. (See Figure 17.) At the same time, the tone of the antagonistic muscles is increased.

 

 

FIGURE 17‑ Golgi tendon organ. Slow and active stretching of a muscle tendon will increase the Golgi tendon organ's firing rate. These impulses are sent to the spinal cord, where they inhibit alpha motor neurons and relax muscle tone. Soft‑tissue manipulation and Hatha yoga both utilize the Golgi tendon reflex arc.

 

 

Soft‑tissue methods utilize the Golgi tendon organs and the associated spinal reflexes to lengthen muscles by actively stretching the fascial sheaths and applying deep pressure to tendon insertions, Similarly, the slow stretching produced by Hatha yoga postures also stimulates Golgi‑tendon reflex arcs. Note that a slow, steady rise in stretch force will relax the muscle tone, while a quick rise in stretch force will elicit a shortening of the muscle through the stretch reflex.

 

Posture

The effects of somato‑procedures appear to have more than just local consequences to the muscle under stimulation. Entire postural patterns of muscle tone have been reported to be altered by somato‑therapies. These clinical observations suggest that muscle tone and posture are not regulated solely by spinal reflexes.

In fact, it is known that higher brain centers are involved in the modulation of posture and associated muscle tone as well as movement. The brain regions include the brainstem, cerebellum, basal ganglia, thalamus, and cerebral cortex. (See Figure 18.)

 

FIGURE 18 - Higher neural center`s control of muscle tone, posture, and movement and the influences of tactile stimulation on this regulation.

 

While the alpha motor neurons control the contraction of the large extrafusal muscle fibers which produce active movement, it is the gamma motor neurons that innervate the muscle spindles (intrafusal fibers). (See Figure 16.)

The muscle spindles can be described as the "sensing element" of the neuromuscular system. That is, the muscle spindles register differences in length between themselves and the larger extrafusal muscle fibers that surround them. There are two types of muscle spindles: "dynamic" and "static." Dynamic muscle spindles respond to changes in muscle length produced by stretching or compression. Static muscle spindles respond to changes in the tensional force placed on the muscle (e.g., changes in the gravitational force as the body shifts).

Thus, the gamma motor neurons and muscle spindles function primarily at an unconscious level, regulating muscle tone, postures, and fine adjustments that form the "background" for active movement produced by the alpha motor neurons. Recent research indicates that the alpha and gamma systems are "co‑activated," the gamma system being activated only when there is some tension or "load" placed on the muscle.

Higher centers in the brain can influence the alpha and gamma motor neurons through descending nerve tracts that travel down the spinal cord. The higher centers may have either an excitatory (facilitatory) or an inhibitory effect on these two motor neuron systems. For example, any given excitatory input would have the end result of increasing muscle tone to certain muscle groups (e.g., flexors), while an inhibitory input would have the opposite result.

Experimental animal studies support the idea that different types of tactile stimulation will affect overall muscle tone and hence posture. The tactile sensory information is sent to the brain, where after "processing," output is sent to the alpha and gamma motor neurons, which in turn determine muscle tone and posture. The effects of various types of tactile procedures may be summarized as follows:

1.      Gentle stroking of the back reduced shivering in cats and was interpreted as an inhibition of the gamma motor neuron system (von Euler and Soderberg, 1958). Such light touch also produced autonomic changes, therefore indicating involvement of higher brain centers. (See Chapter 17.)

2.      Slow, deep pressure to the soft tissues of cats was associated with a reduction in electromylographic activity in muscles, indicating a relaxation of muscle tone (Johansson, 1962).

3.      Pinching, sudden deep tactile pressure, and other painful somato‑procedures are known to induce a general contraction of the musculature, particularly in muscles used in flexion (Eble, 1960; Jones, 1965).

That somato‑intervention can evoke systemic changes in neuromuscular activity is given further support through numerous studies involving the use of photographs and radiographs. Investigators have demonstrated changes in posture and musculoskeletal alignment for several somato‑therapeutic techniques: Rolfing (Solit, 1962); Alexander technique (Jones, 1965); chiropractic spinal manipulation (Palmer, 1938); and osteopathic craniosacral therapy (Greenman, 1970).

 

Somato‑Techniques and Movement

Sherrington (1906) was the first to distinguish the differences between "active" voluntary movement and "passive" reflexive movement in terms of how they are regulated by the nervous system. Yet it is difficult to separate the "unconscious" movements involving postural adjustments from the larger, voluntary, "conscious" movements of walking, reaching, sitting down, and so forth.

In reality, voluntary movement is performed on a background of postural, spinal reflexes that keep the body in an upright and balanced relationship to the gravitational field (see preceding sections).

Complex movements appear to be based on rhythmic, sequential patterns of neuromuscular activity. Such "rhythm generators" have been found in the spines of dogs for walking and scratching (Evarts, 1979). The cerebral cortex and other higher centers can then modify the specifics of the movement pattern being generated.

The question that will be explored here is whether tactile intervention can affect complex movements by altering the pattern of neural outflow to the muscles.

In a study of human subjects involving multiple‑image photography, Jones (1965) reported that different basic movements can be modified by the application of gentle directional pressure to the body, by using the Alexander technique. (See Chapter 8.) The movements examined were: lying down to sitting up, sitting to standing, leaning forward to sitting erectly, and walking.

A subject's "habitual" movement patterns were first filmed as a pre‑test or control. This was then followed by the experimental or "guided" procedures by the experimenter and another post‑test filming.

The subjects filmed in the experimental condition showed the trajectory of the head to be higher and the arch of the movements to be smoother and more regular. The movement pattern was "characteristically" altered "when the relation of head and trunk" had been modified by the guided procedures. The most dramatic result obtained was in the sitting to standing movement, Jones interpreted the results as a facilitation of the "righting reflexes" of the head and neck that return the body to a normal upright posture in relation to gravity. Jones proposed that these postural, righting reflexes were normally masked by habitual, voluntary activity or "attitudinal reflexes"‑movement that is habitually used to obtain a special purpose (e.g., reaching for an object, lookup upward, etc.):

In the attitudinal reflexes, the head is drawn into a fixed position and tonus (tone) is redistributed in the trunk and limbs. In righting reflexes, again under the influence of the head, normal distribution of the tonus is restored.... The procedures employed in the experimental movements by releasing the head from its habitual attitude, facilitate the righting reflexes and bring the subject into a different orientation to the gravitational field. (Jones, 1965, p. 210)

Jones considered the attitudinal reflexes under the control of the cerebral cortex, while the antigravity righting reflexes were maintained at the subcortical and spinal levels (Jones, 1963, 1965).

Thus the smoother, efficient movements observed under the guided‑experimental condition are apparently due to an inhibition of higher conscious (cortical) centers of the brain. This inhibition in turn allows the spinal and subcortical postural reflexes and rhythmic movement patterns to function freely.

Hunt and Massey (1977) conducted an electromyographic (EMG) analysis concerning the effects of the Rolfing method on movement. (Electromyographic recordings measure the electrical activity in muscles.)

A control and an experimental group each containing 24 subjects all performed six activities: lying, throwing, lifting, jogging, stepping up onto a stool, and karate chop. The subjects were matched for age, birth defects, injuries, weight', and height. Telemetry electromyographic recordings were taken from 16 separate muscles as a pre‑test. The experimental group underwent ten sessions of the Rolfing method over a time of five weeks. Following the five‑week period, the experimental and control groups were again given a post‑test evaluation.

Hunt and Massey found that post‑tests for the experimental group showed a decrease in EMG activity in antagonist muscles. They interpreted this finding as representing more efficient movement patterns with less "joint excursion" and compression. The control's post‑tests; in contrast to the experimental group's, showed more electrical activity in both antagonistic and agonist muscles, suggesting that more energy was expended in carrying out the test movements.

They further reported that the post‑tests of the experimental group exhibited the most improvement in the action of deeper, intrinsic muscles located proximally (i.e., nearer) to the joints.

Similar to Jones' position and findings with the Alexander technique, Hunt and Massey concluded that the Rolfing treatments altered the neural control of movement in the direction of subcortical and spinal levels, away from the conscious cortical influence.

Both of the above‑cited research studies indicate that certain body procedures lead to the inhibition of "conscious" control over repetitive habitual movements, allowing the more "unconscious," spinal and subcortical levels of movement patterns to dominate.

 

Therapeutic Benefits

The neuromuscular system is affected by somatotherapies on three different levels: individual muscle tone, postural patterns, and voluntary movement.

1.      First level: Tactile stimulation through massage, pressure, and manipulation excites sensors within the individual muscles, fascial sheaths, and tendons, which induces spinal reflex arcs. These reflexes in turn increase or decrease the state of muscle contraction or tone in the stimulated muscle as well as in its antagonists. Such procedures are utilized extensively in the treatment of athletic injuries as well as for the management of muscular "tension" or "stress." For example, "muscle cramps" commonly experienced by athletes are reduced or eliminated by stretching the muscle to its full length and holding the stretch for approximately two minutes (deVries, 1966).

2.      Second level: Certain techniques of body therapy (e.g., Rolfing, Alexander technique, chiropractic, and osteopathy) have been shown to produce remarkable changes in individual postural patterns, indicating an overall integration of neuromuscular balance.

3.      Third level: Experimental, controlled studies have reported evidence that both the Alexander technique and the Rolfing method alter movement patterns towards more efficient use of muscular energy.

The last two levels suggest a particularly with the treatment of neuromuscular disorders: cerebral palsy, stroke, and nerve "compression syndromes." (See Chapters 14 and 15.) Athletic injuries as well as athletic performances are also areas that ‑have great potential.

wide range of benefits

A final potential of therapeutic use concerns prevention of neuromuscular injuries and dysfunctions. Though to date little research has been done, prevention may turn out to be the most significant benefit.

 

 

REFERENCES

-         Carpenter, M.B., and Sutin, J. Human Neuroanatomy. Baltimore/London: Williams and Wilkins, 1983.

-         Chusid, J.G. Correlative Neuroanatomy and Functional Neurology. Los Altos, CA: Lange Medical Publications, 1976.

-         deVries, H.A. Quantitative electromyographic investigation of the spasm theory of muscle pain. American Journal of Physical Medicine, 1966, 45, 119‑134.

-         Eble, J.N. Patterns of response of the paravertebral musculature to visceral stimuli. Americal Journal of Physiology, 1960, 198,429‑433.

-         Evarts, EX Brain mechanisms of movement. Scientific American, 1979, 241 (3), 164‑179.

-         Greenman, RE. Roentgen findings in the craniosacral mechanism. Journal of the American Osteopathic Association, 1970, 70, 24‑35.

-         Hunt, V.V., and Massey, W. A Study of Structural Integration from Neuromuscular, Energy Field, and Emotional Approaches. Boulder, Colorado: Rolf Institute, 1977.

-         Johansson, B. Circulatory response to stimulation of somatic afferents. Acta Physiologica Scandinavica, 1962, 62 (Supplementum 198), 1‑91,

-         Jones, F.P. The influence of postural set on pattern movement in man. International Journal of Neurology, 1963, 4, 60‑71.

-         Jones, ER Method for changing stereotyped response patterns by the inhibition of certain postural sets. Psychological Review, 1965, 72, 196‑214.

-         Palmer, B.J. Precise, Posture Constant Spinograph Comparative Graphs, Davenport, Iowa: Palmer School of Chiropractic, 1938.

-         Shepherd, G.M. Neurobiology. New York/Oxford: Oxford University Press, 1983

-         Sherrington, C.S. The Integrative Action of the Nervous System. New York: Charles Scribner’s Sons, 1906

-         Von Euler, C., and Soderberg, V. Co-ordinated changes in temperature thresholds for thermoregulatory reflexes. Acta Physiologica Scandinavica, 1958, 42, 112-129.

 

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