Mechanism of actionof high-velocity, low amplitudethrust technqiueby Julian Mesina, DVM, PhD, John Balmer, DO, Stephany Esper, DO, Erik Esper, DO, RobertEvans, DO, Donald Hampton, DO, Lake Erie College of Osteopathic Medicine, Lake Erie, PA

AbstractHVLA thrust techniques generate

a force sufficient to cause strongstretching of the restrictive musclewith subsequent generation of ad-equate tension to stimulate Golgi ten-don organs. Movement into the re-strictive barrier during HVLA thrusttechniques is made possible by therelaxation of the hypertonic muscleinitiated by the inverse stretch reflexmediated by the Golgi tendon organs.In addition, there is a concomitantcontraction of the antagonist musclevia excitatory connections of the lbfibers with motor neurons supplyingthe antagonist muscle.

High-velocity, low-amplitude(HVLA)) thrust technique involves –epositioning of the restricted joint to-ward the restrictive barrier and apply-ing a high-velocity, low-amplitudeforce on the joint into the barrier (inthe direction it will not move). HVLAis intended to benefit patients withjoint restriction by reducing pain.freeing motion, improving biome-chanical function, or reducingsomatovisceral reflex.' However, it isnot indicated for certain conditionssuch as traumatic contracture, ad-vanced degenerative joint disease, orankylosis. HVLA has several advan-tages over other osteopathic manipu-lative techniques which include: (1)immediate relief with decreased painand increased freedom of motion and,(2) efficient use of physician's time. 28/AA0 Journal

The precise mechanism of actionof HVLA thrust technique is notknown. One conjecture is that it in-volves the mechanoreceptors in thejoint capsule since a sudden stretchor change of position of the jointcauses a change in the afferent activ-ity of these mechanoreceptors, result-ing in release of muscle hypertonic-ity.' In this paper, we discuss physi-ological principles and cite laws ofphysics that would support the afore-mentioned conjecture and suggestthat the mechanoreceptor involved isthe Golgi tendon organ.

To a point, the more a skeletalmuscle is stretched, the stronger is itsreflex contraction. The mechanismfor this reflex contraction lies in themuscle spindle. The spindle is in-par-allel with the extrafusal fibers, sowhen the muscle is passivelystretched, the spindles are likewisestretched.' .'' When this occurs,muscle spindle discharge increasesand reflex shortening of the muscleresults. However, when the tensionproduced by stretching of the musclereaches a certain level, contractionsuddenly stops and the muscle re-laxes. This relaxation in response tostrong stretch is called the inversestretch reflex. The receptor mediat-ing the inverse stretch reflex is theGolgi tendon organs, which are ten-sion-sensitive mechanoreceptors, in-nervated by fast conducting Ib affer-ent fibers. When a muscle is passivelystretched, it develops by virtue of itselastic properties passive tension, by

analogy, active tension is used to des-ignate the force developed by musclecontraction.' Since the Golgi tendonorgans, unlike the spindles, are ar-ranged in series with the muscle fi-bers, they are stimulated by both pas-sive stretch and active contraction ofthe muscle." However, the levelofstimulation by passive stretch is notgreat because the more elastic musclefibers take up much of the stretch, andthis is the reason why it takes a strongstretch to produce relaxation.

HVLA thrust technique employsbasic laws of physics to generate theforce necessary to produce the strongstretch required to stimulate the Golgitendon organs of the restrictivemuscle. We will begin with the con-cept of velocity which is the first timederivative of the position vector. Theposition of an object can be specifiedby a single vector; namely, the dis-placement of the object relative to theorigin of the coordinate system.' Thisvector is called the position vector ofthe object. The components of theposition vector of a moving object arefunctions of the time. If the vector isthe position vector r of a moving ob-ject and the parameter is the time t;the derivative of r with respect to t iscalled the velocity, which is denoted v:

v = dr/dt (Equation 1)

Next, we need to apply Newton'sLaws of Motion to understand therelationship between velocity and thegeneration of force. The time rate of

Winter 1999

aAmerican Osteopathic

FOUNDATIONsupporting education_ research and the .fropothic profession

The American Academy ofOsteopathy encourages its mem-bers to support the AmericanOsteopathic Foundation. TheAOF generously contributes$25,000 each year to the AAO'sVisiting Clinician Program. Inaddition, the AOF provides loansand scholarships to osteopathicmedical students and adminis-ters research grant programs forscientific and clinical osteo-

pathic research.

Contact:

Leda Hanin, Executive Director

American Osteopathic Foundation

142 East Ontario

Chicago, IL 60611-2864

Phone: (312) 202-8234

OMM FELLOWSHIP/

RESIDENCY

Plus One OMM Fellowshipand OMM Residency (2-yearpost-internship program) posi-tions available July 1, 2000 atBotsford General Hospital inFarmington Hills, Michigan. Con-tact T. Reid Kavieff, DO,CSPOMM, at 248/926-1080 forfurther information or 248/471-8222 for an application.

OSTEOPATHIC PRACTICEOMM Practice for sale in the San

Francisco Bay area. Please only se-rious inquiries. For more informa-tion, send CV to the AmericanAcademy of Osteopathy, Box "11",3500 DePauw Blvd., Suite 1080,Indianapolis, IN 46268-1136.

change of the product of mass andvelocity is the 'change of motion' ofNewton's second law and, accordingto that law, is proportional to theforce.' In other words, the second lawcan be written as

F = d(mv)/dt (Equation 2)

where F is the force and a constantof proportionality taken as beingequal to 1.

The product of mass and velocityis called linear momentum and is de-noted by the symbol p. Thus,

p = my (Equation 3)

The mathematical statement ofNewton's second law may then bewritten as

F = dp/dt (Equation 4)

Simply stated, when the force ex-erted by the physician's hand acts onthe restrictive muscle, that force gen-erates a corresponding change in thelinear momentum of the muscle.

The application of high-velocitylow-amplitude thrust by the osteo-pathic physician on the joint in thedirection of the restrictive barrier pro-duces the strong stretch required togenerate sufficient tension on themuscle tendons to elicit the inversestretch reflex. Stimulation of theGolgi tendon organs produces relax-ation of the hypertonic muscle viainhibition of its motor neuron. Thisrelaxation allows joint movement intothe restrictive barrier. The movementof the joint is assisted by a concomi-tant contraction of the antagonistmuscle. The contraction is due to thefact that the stimulated lb fibers fromthe Golgi tendon organs, while caus-ing inhibition of the motor neuronsto the restrictive muscle, also makeexcitatory connections with motorneurons supplying the antagonistmuscle. 3 '4 When the osteopathic phy-

sician "locks out" the restricted joint,he/she is actually making the condi-tions optimal for the force of thethrust to be focused on the particularjoint. Moreover, this maneuver posi-tions the restricted bone(s) so it canmove in the direction of greatest ease.The net effect of HVLA thrust tech-nique is relaxation of the restrictivemuscle with concomitant contractionof the antagonist muscle and together'these two events allow movement ofthe previously restricted joint back toits normal resting position.

In conclusion, we wish to quoteI.M. Korr, PhD who wrote,' "To aphysiologist, it seems much more rea-sonable that the limitation and resis-tance to motion of a joint that char-acterize an osteopathic lesion do notordinarily arise within the joint, butare imposed by one or more of themuscles that traverse and move thejoint." It is our opinion that HVLAthrust technique does not directlymove the bones in a restricted jointbut rather, it exerts its effect on theGolgi tendon organs which allowmovement of the bones in the jointback to their normal resting positionvia relaxation of the restrictive muscleand a concomitant contraction of itsantagonist muscle.

ReferencesI. Kappler RE. Thrust Techniques. In: Ward

RC (ed) Foundation for Osteopathic Medi-cine Baltimore: Williams and Wilkins,1997. pp. 661-666.

2. Korr IM. Proprioceptors and somatic dys-function. JAOA 1975;74:638/123-650/135

3. Ganong WE. Review of Medical Physiol-ogy. Stamford, Connecticut: Appleton &Lange. 1997, pp. 119-127.

4. Berne RM, Levy MN. Physiology. St.Louis: Mosby, 1998. pp. 186-199.

5. lami L. Golgi tendon organs in mamma-lian skeletal muscle: functional propertiesand central actions. Physiol Rev 1992,72:623-666.

6. Fowles GR. Analytical Mechanics. Phila-delphia: Saunders College Publishing,1986; pp. 19-39.0

Winter 1999 AAO Journal/29