September 9, 2008

VIBRATION^©

Lyn Paul Taylor, A.A., B.A., M.A., R.P.T.

(Editing Assistant and Computer Consultant: Joanna Soon, B.S.)

Although mechanical vibration has long been considered one of the acceptable tools of treatment in physical medicine, it has not been widely considered of much practical value in the clinical setting, except as a way of enhancing the effects of postural drainage.  This may be because the greatest part of published research on the subject has focused on vibration's ability to evoke or facilitate mild muscular contraction.  This, of course, puts it in the category of being non-essential for the clinical practitioner who prefers any number of instruments that provoke much stronger involuntary muscular contractions and are more efficient to use.*

The earliest investigators of the effects of vibration on muscle tissue were able to demonstrate that vibration (repeated quick stretch) of a tendon or muscle could produce an involuntary contraction from the muscle (the response being greater from application to the tendon than to the muscle).  They showed that the provoked contraction emanated from within the muscle itself as a stretch reflex, and not as a higher center response to tactile sensory nerve stimulation.  They additionally demonstrated that the strength of contraction was directly proportional to the amplitude of the force of vibration.

Later investigators established that the muscle spindle was the organ within the muscle responsible for the involuntary contraction produced by vibration.  They showed that the slowly developed muscle contraction depended on the muscle spindle's afferent proprioceptive (sensory) influence over certain supraspinal centers.  Vibration initially caused the muscle spindle to respond with the phasic stretch reflex, which is immediately inhibited by the supraspinal centers (after the extrafusal muscle twitch occurs).  If stimulation continues, the supraspinal centers respond to the continuing proprioceptive input from the muscle spindle by provoking the muscle spindle's contractile elements to begin to slowly contract and, through the tonic stretch reflex, cause the extrafusal muscle to also begin contracting (increasing muscle tone).  This slow developing contraction is conventionally called the tonic vibratory response (TVR).  The TVR is present in skeletal muscles when the spinal cord is intact, though it is not found in the facial muscles or tongue.  Notably, it was found that vibration of a muscle's tendon at frequencies of from 50 to 100 cycles per second (Hz) gradually increased its activity (tone) and conversely decreased the neuromuscular tone of its antagonist.  They also found that the facilitatory effects of vibration on the muscle generally disappeared thirty seconds after cessation of vibration, and that the subject could stop the involuntary response (muscle contraction).

Later clinical electromyometric (EMM) studies and case study observations (performed by the author and associates) of the inhibitory effects of vibration on the antagonists of muscles vibrated (at the low frequencies of 30 and 60 Hz), showed that the inhibitory effects of vibration continued to develop for up to 14 minutes after cessation of vibration, and that the resultant resetting of the muscle spindles and their influence over the involved supraspinal centers often lasted considerably longer.  These findings would seem to imply that vibration is indeed a valuable treatment tool, not only as a muscle contraction facilitator, but also as a contraction inhibitor.

The most common vibrator available on the market is the rotary vibrator that oscillates back and forth to produce its vibration.  Because of the sliding motion that it imparts to the skin beneath the vibrator, the vibration is spread out and less exact than the practitioner might desire.

The vibrator most recommended here for clinical use is a linear vibrator that provides its vibratory action as a series of repetitive taps or up and down motions, much like a jackhammer.  Consequently, it may be applied with more exactitude than the rotary vibrator, since its vibratory action is concentrated solely under the head of the vibrator.

Application:

Neuromuscular Responses

• The subject should be placed in a position, which will be comfortable for the duration of the treatment session.

• If its construction allows it, the vibrator should be preset to deliver the required force at an appropriate frequency (usually 30 or 60 Hz).

• The vibrator should be turned on.

• The head of the vibrator should be placed over the treatment site and held there with the appropriate amount of steady hand pressure.  The vibrator should be held lightly for tactile sensory stimulation, but with more pressure to induce muscular contraction and reciprocal inhibition.

• To induce muscular contraction, the vibration should generally be applied over the target muscle's origin, insertion, or tendon.  Vibration of the treatment site should continue as long as required by the treatment technique (one minute over each treatment site for neuromuscular response, several minutes for spastic sphincter control or sensory effects).

• Following application, the vibrator should be lifted from the subject's skin before being turned off or applied to another treatment site.

• For neuromuscular responses, after vibration is over, the subject should remain relatively motionless for an appropriate period (at least six minutes) before leaving the treatment area.

Circulation Enhancement

Clinical experience has demonstrated that vibration may stimulate capillary bed activity (capillary circulation).

• If its construction allows it, the vibrator should be preset to deliver 0.5 pounds per square inch (psi) at a frequency of 60 Hz.  A towel should cover the treatment site or other protective cover to avoid shearing as the vibrator is moved over the skin's surface.

• The head of the vibrator should be placed over the treatment site and moved evenly over the area for two minutes or more.

• Ideally, treatment should be applied twice daily (ideally, by the subject in the home environment) until the soft tissue circulation has sufficiently improved.  It should not be applied just before bed because of the excitatory affect it has on the nervous system (i.e., it will keep the subject awake).

This technique is best used in combination with other circulation enhancing modalities including brushing, electrical stimulation, positive pressure, or ultrahigh frequency sound.

Precautions:

Except when applied for sensory effects, vibration should not be applied over a muscle belly.  It is not only less efficient than application to the muscle's origin, insertion, or tendon, but may also activate an indwelling trigger point formation (intrafusal muscle spasm) and its resultant referred pain pattern.

Vibration should not be applied over contused (bruised) soft tissue, thrombus (blood clot), or the site of phlebitis or varicose vein, because of the danger of additional thrombus development or the precipitation of an embolus.

Vibration should not be applied around the lips of children, even for desensitization of the lips.  Likewise, vibration should not be lightly applied to the S2, S3, or S4 sensory dermatomes of infants or children with immature gastrointestinal systems.

The vibration of phalangeal (finger) joints will almost certainly cause them to spontaneously swell (become edematous), sometimes to a gross extreme.  Edema may become so extreme that pitting edema may become evident in both the phalanges and in the metacarpal portions of the hand.

If vibration is used in combination with electrical stimulation for the treatment of extrafusal muscle spasm, trigger point formation referred pain, or to facilitate the lengthening of a muscle, it should be applied following the electrical stimulation.

*In her lectures at the University of Southern California, Margaret Rood expounded on the use of vibration to affect muscle tone in atrophied or underdeveloped muscle.  She reported that when used in conjunction with attempted voluntary contraction of the vibrated muscle (applied over the muscle belly), vibration could be used to increase the bulk of musculature that had never fully developed as a result of cerebral palsy paralysis (in the preadolescent subject).

References:

S.A. Ageranioti,, K.C. Hayes, "Effects of Vibration on Hypertonia and Hyperreflexia in the Wrist Joint of Subjects with Spastic Hemiparesis," Physiotherapy Canada, vol. 42, 1990. Pp. 24-33

R. Bianconi and J.P. Van der Meulen, "The Response to Vibration of the End Organs of Mammalian Muscle Spindles," Journal of Neurophysiology, vol. 26, 1963. Pp. 177-190

A. Brodal, Neurological Anatomy, Oxford University Press, Inc., New York, N.Y., 1981.

F. Echlin and A. Fessard, "Synchronized Impulse Discharges from Receptors in the Deep Tissues in Response to a Vibrating Stimulus," Journal of Physiology, vol. 93, 1938. Pp. 312-334

G. Eklund and K.E. Hagbarth, "Motor Effects of Vibratory Muscle Stimuli in Man," Electroencephalography and Clinical Neurophysiology, vol. 19, 1965. Pp. 613-620

An Exploratory and Analytical Survey of Therapeutic Exercise, American Journal of Physical Medicine, Williams & Wilkins Co., 46:1, February, 1967. Pp. 650-651, 1094

P. de Gail, J.W. Lance and P.D. Neilson, "Differential Effects on Tonic and Phasic Reflex Mechanisms Produced by Vibration of Muscles in Man," Journal of Neurology, Neurosurgery and Psychiatry, vol. 29, 1966.

K.E. Hagbarth and G. Eklund, "Motor Effects on Vibratory Muscle Stimuli in Man",  Muscular Afferents and Motor Control, Nobel Symposium I. John Wiley and Sons, 1966. Pp. 177-186

S.A. Hall, Inhibition of Muscle Spasticity by Localized Mechanical Vibration (Master's Thesis), University of Southern California, Los Angeles, Ca., August 1970.

E. Henneman and C.B. Camille, "Relation Between Structure and Function in the Design of Skeletal Muscles," Journal of Neurophysiology, vol. 28, Pp. 581-598

N.W. Hochreiter, M.J. Jewell, L. Barber and P. Browne, "Effect of Vibration on Tactile Sensitivity," Physical Therapy, 63:6, June 1983.   Pp. 934-937

S.W. Kuffler, C.C. Hunt and J.P. Quilliam, "Function of Medullated Small-Nerve Fibers in Mammalian Ventral Roots: Efferent Muscle Spindle Innervation," Journal of Neurophysiology, vol. 14, 1951. Pp. 29-54

W.K. Livingston, Pain Mechanism, The MacMillan Co., New York, N.Y., 1942.

G. Rushworth and R.R. Young, "The Effect of Vibration on Tonic and Phasic Reflexes in Man," Journal of Physiology, vol. 185, 1966. Pp. 63-64

R.S. Smith, "Properties of Intrafusal Muscle Fibers," Muscular Afferents and Motor Control, Nobel Symposium I, R. Granit (ed.), John Wiley and Sons, New York, NY, 1966.

S.A. Stockmeyer, "An Interpretation of the Approach of Rood to the Treatment of Neuromuscular Dysfunction,"  American Journal of Physical Medicine, vol. 46, 1967. Pp. 900-956

L.P. Taylor, The Effect of Vibration on an Isometric Contraction (Master's Thesis), University of Southern California, Los Angeles, Ca., 1973.

L.P. Taylor, T. Hui, The Taylor Technique of Soft Tissue Management, Inflammation: Evaluation & Treatment, 2002.  Pp. 94-100

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