Neuromuscular Reflex Responses to Chiropractic Adjustments

Christopher J. Colloca, D.C.

"The fact that a reflex arc from mechanoreceptors in the spinal ligaments, disc, and joint capsule exists is an emerging concept. It is conceivable, therefore, that such reflex muscular activation bears a major responsibility for maintaining ongoing spine stability."

- Solomonow et al. 1999 Volvo Award Winner in Biomechanical Studies - Biomechanics of Increased Exposure to Lumbar Injury Caused by Cyclic Loading: Part 1. Loss of Reflexive Muscular Stabilitzation. Spine 1999; 24(23):24-26.

Spinal Stability & Vertebral Subluxation

Traditional concepts of spine stability have placed great emphasis of the role of the discoligamentous integrity in maintaining spine stability.

However, the passive discs and ligaments of the spine have more recently been found to represent a secondary stabilizing system, as the spinal musculature has come to the forefront as the primary structure associated with spinal stability (Gardner-Morse and Stokes, 1998;Gardner-Morse et al., 1995;Granata and Marras, 1995;Panjabi, 1992;McGill and Norman, 1986).

The musculature and the viscoelastic tissues of the spine, however, function synergistically, so that the desired movement is accomplished while the stability of the spine is preserved (Panjabi, 1992).

Recent evidence has demonstrated reflexogenic mechanisms from mechanosensitive afferents located in the spinal ligaments, discs, and facet capsules acting in concert with the lumbar multifidus and longissimus muscles in humans(Colloca et al., 2000;Solomonow et al., 1998) and in feline (Pickar and McLain, 1995;Stubbs et al., 1998;Solomonow et al., 1998), and porcine (Indahl et al., 1997;Indahl et al., 1995) models.

In these studies, strain of the lumbar viscoelastic structures was shown to excite the respective mechanoreceptive afferents and reflexively contract the multifidus muscles of the distracted functional spinal unit (FSU).

Activation to a lesser extent of the multifidus muscles of two to three levels above and below the tested FSU were subsequently also observed.

Such muscular forces provide sufficient stiffness to prevent excessive displacement of several vertebrae relative to each other and the consequent possible injury (Solomonow et al., 1998;Williams et al., 2000).

Of the many definitions that exist, excessive displacement or abnormal stress or strain resulting in dysfunction of an FSU is known as vertebral subluxation within the chiropractic profession.

Chiropratic Adjustment & Neuromuscular Reflexes: Origninal Research

Beneficial effects of chiropractic adjustments are thought to arise from a variety of mechanical and physiological mechanisms.

Of the many theories set forth to explain such mechanisms of spinal manipulation, stimulating or "resetting" of the somatosensory system and presynaptic inhibition of nociception are popular explanations today.

Our group and others have begun research investigating spinal neuromuscular reflex responses associated with chiropractic adjustments.

Typical electrode placement for lumbar spine sEMG assessments.
By placing surface electrodes on the skin overlying the erector spinae muscle group, we can record electromyographic (sEMG) signals in response to chiropractic adjustments.

We begin by recording baseline measurements from the prone laying patient by having them extend their trunk and shoulders off of the table and holding an isometric trunk extension effort for 3 seconds.

Once the appropriate gain settings are adjusted, we then begin a protocol consisting of three repeated isometric trunk extensions with 5 seconds rest between efforts.

We later average this data to determine each individual subjects muscular output to compare the subsequent reflex responses.

Segmental contact point to the L4 spinous process as sEMG recordings are made at the erector spinae at the L2 & L5 functional spinal units.
Using a modified spinal adjusting instrument equipped with an impedance head (Keller et al., 1999) we are then able to deliver chiropractic adjustments to the spine and measure the precise force-time relationship to the resultant neuromuscular reflex response.

In this manner neuromuscular reflex responses can be evaluated in comparison to baseline recordings or as a function of their percentage of trunk extension effort.

Load and acceleration profiles of the thrust and associated neuromuscular reflex responses observed at the L3 and L5 leads compared to baseline.

Force profile of the spinal adjustment as compared to the associated neuromuscular reflex responses derived as a function of the patients average percentage maximum trunk extension effort.

To date, we have recorded neuromuscular reflex responses to over 2,000 chiropractic adjustments in clinically relevant patients in my office.

Our work has corroborated the findings of others in asymptomatic subjects (Herzog et al., 1999;Symons et al., 2000) in actual patients that consistent neuromuscular reflex responses occur in response to chiropractic adjustments.

While the majority of our work has taken place in the lumbar spine, we have also begun to investigate neuromuscular reflex responses the thoracic and cervical spine.

Dr. Keller and I have categorized the reflex responses and begun to compare them to contact point, and patient's pain, disability and functional status.

More recently, we have measured neuromuscular reflexes using needle probe electromyography.

Although not conclusive at this point, we have observed numerous trends of clinical importance including an increased magnitude of the reflex response in patients with more frequent-constant low back symptoms.

We have reported this work at international scientific spine conferences and have noticed great interest in this field.

Not only will this research path assist to explain how chiropractic adjustments impact the neuromuscular system (nervous system), but we also believe that further research may lead to the use of neuromuscular reflex responses as a valuable objective analysis of spinal function in the near future.


Colloca,C.J., Keller,T.S., Gunzburg,R., Van de Putte,K., Fuhr,A.W., 2000. Neurophysiological response to intraoperative lumbosacral spinal manipulation. J Manipulative Physiol Ther, 23(7), 447-457.

Gardner-Morse,M., Stokes,I.A., Laible,J.P., 1995. Role of muscles in lumbar spine stability in maximum extension efforts. J Orthop Res, 13(5), 802-808.

Gardner-Morse,M.G. & Stokes,I.A., 1998. The effects of abdominal muscle coactivation on lumbar spine stability. Spine, 23(1), 86-91.

Granata,K.P. & Marras,W.S., 1995. The influence of trunk muscle coactivity on dynamic spinal loads. Spine, 20(8), 913-919.

Herzog,W., Scheele,D., Conway,P.J., 1999. Electromyographic responses of back and limb muscles associated with spinal manipulative therapy. Spine, 24(2), 146-152.

Indahl,A., Kaigle,A., Reikeras,O., Holm,S., 1995. Electromyographic response of the porcine multifidus musculature after nerve stimulation. Spine, 20(24), 2652-2658.

Indahl,A., Kaigle,A.M., Reikeras,O., Holm,S.H., 1997. Interaction between the porcine lumbar intervertebral disc, zygapophysial joints, and paraspinal muscles. Spine, 22(24), 2834-2840.

Keller,T.S., Colloca,C.J., Fuhr,A.W., 1999. Validation of the force and frequency characteristics of the activator adjusting instrument: effectiveness as a mechanical impedance measurement tool. J Manipulative Physiol Ther, 22(2), 75-86.

McGill,S.M. & Norman,R.W., 1986. Partitioning of the L4-L5 dynamic moment into disc, ligamentous, and muscular components during lifting. Spine, 11(7), 666-678.

Panjabi,M.M., 1992. The stabilizing system of the spine. Part I. Function, dysfunction, adaptation, and enhancement. J Spinal Disord, 5(4), 383-389.

Pickar,J.G. & McLain,R.F., 1995. Responses of mechanosensitive afferents to manipulation of the lumbar facet in the cat. Spine, 20(22), 2379-2385.

Solomonow,M., Zhou,B.H., Harris,M., Lu,Y., Baratta,R.V., 1998. The ligamento-muscular stabilizing system of the spine. Spine, 23(23), 2552-2562.

Stubbs,M., Harris,M., Solomonow,M., Zhou,B., Lu,Y., Baratta,R.V., 1998. Ligamento-muscular protective reflex in the lumbar spine of the feline. J Electromyogr Kinesiol, 8(4), 197-204.

Symons,B.P., Herzog,W., Leonard,T., Nguyen,H., 2000. Reflex responses associated with activator treatment. J Manipulative Physiol Ther, 23(3), 155-159.

Williams,M., Solomonow,M., Zhou,B.H., Baratta,R.V., Harris,M., 2000. Multifidus Spasms Elicited by Prolonged Lumbar Flexion. Spine, 25(22), 2916-2924.

Related Research on Reflex Responses of Spinal Manipulation

Dishman,J.D. & Bulbulian,R., 2000. Spinal Reflex Attenuation Associated With Spinal Manipulation. Spine, 25(19), 2519-2525.

Herzog,W., 1996. Mechanical, Physiologic, and Neuromuscular Considerations of Chiropractic Treatments. In: Lawrence,D.J., Cassidy,J.D., McGregor,M., Meeker,W.C., Vernon,H.T. (Eds.), Advances in Chiropractic, pp. 269-285. Mosby-Year Book, Inc., St. Louis.

Herzog,W., 1996. On sounds and reflexes. J Manipulative Physiol Ther, 19(3), 216-218.

Herzog,W., 2000. The Mechanical, Neuromuscular, and Physiologic Effects Produced by Spinal Manipulation. In: Herzog,W. (Ed.), Clinical Biomechanics of Spinal Manipulation, pp. 191-207. Churchill Livingstone, Philadelphia.

Herzog,W., Conway,P.J., Zhang,Y.T., Gal,J., Guimaraes,A.C., 1995. Reflex responses associated with manipulative treatments on the thoracic spine: a pilot study. J Manipulative Physiol Ther, 18(4), 233-236.

Herzog,W., Scheele,D., Conway,P.J., 1999. Electromyographic responses of back and limb muscles associated with spinal manipulative therapy. Spine, 24(2), 146-152.

Murphy,B.A., Dawson,N.J., Slack,J.R., 1995. Sacroiliac joint manipulation decreases the H-reflex. Electromyogr Clin Neurophysiol , 35(2), 87-94.

Pickar,J.G. & McLain,R.F., 1995. Responses of mechanosensitive afferents to manipulation of the lumbar facet in the cat. Spine, 20(22), 2379-2385.

Suter,E., Herzog,W., Conway,P.J., Zhang,Y.T., 1994. Reflex response associated with manipulative treatment of the thoracic spine. J Neuromusculoskeletal Syst, 2, 124-130.

Symons,B.P., Herzog,W., Leonard,T., Nguyen,H., 2000. Reflex responses associated with activator treatment. J Manipulative Physiol Ther, 23(3), 155-159

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