The Body's "Global Response" to the Adjustment

For decades, many in the medical establishment have debunked the basis of chiropractic, the adjustment. When confronted to "prove" that spinal manipulation works, the chiropractic profession has responded with a myriad of anecdotal clinical results and a number of studies touting the effectiveness of the adjustment.

Now a study published in the January 15, 1999 issue of Spine¹ provides direct evidence of the beneficial effects of the adjustment. The study, co-authored by Walter Herzog,PhD, David Scheele, BSc, and Philip Conway,DC, documents the "electomyographic responses of back and limb muscles associated with spinal manipulative therapy."

Study Methods

Ten male asymptomatic subjects received a series of 11 "spinal manipulative treatments" (SMT, high-speed, low-amplitude) in the following order:

(The first seven treatments were administered with subjects in the prone position):

• Treatments 1-2: prone cervical SMT, applied to the lateral aspects of C2-C3;


• Treatments 3-4: applied to the upper thoracic spine (over the left/right transverse processes of T2-T3);


• Treatments 5-6: same as 3-4, except applied at the midthoracic region (T5-T7);


• Treatment 7: applied to the transitional thoracic vertebrae (T11-T12).

(The last four manipulations were administered with the subjects in the side-lying position):

• Treatment 8: spinous push at L2-L4, subjects left side up;


• Treatment 9: anterior inferior sacrum thrust, subjects left side up;


• Treatments 10-11: same as 8-9 except subjects lay right side up.

Prior to the adjustments, the subjects were fitted with 16 pairs of electromyographic electrodes to record responses. An electromyographic response was "said to occur if the signal increased at least three times baseline value within 500 msec of the onset of the treatment thrust."

Results of the Study

Each of the 11 treatments produced consistent reflex responses in a target-specific area. These responses occurred 50-200 msec after the onset of treatment and lasted for between 100-400 msec.

Responses in the Cervical Spine

"SMTs [to the cervical spine] resulted in electromyographic activity in most muscles of the neck and back."

Responses in the High and Midthoracic Spine

"SMTs in the high and midsections of the thoracic spine elicited a strong electromyographic response across all back muscles."

Responses in the Low Thoracic Spine

"SMTs applied to the low thoracic spine (bilateral treatment) elicited a consistently strong, symmetric and repeatable electromyographic response in the neck and back muscles located close to the spinal column."

Responses in the Lumbar Spine

"SMTs elicited a consistent electromyographic response in all muscles of the back and both gluteal muscles."

Responses in the Sacroiliac Joint

"SMTs elicited a strong electromyographic response in most of the muscles on the treatment side of the back and in those muscles located close to the spine on the nontreatment side."

So what's this all mean? Walter Herzog,PhD, told DC:

"The exciting thing to me was that during these treatments, we found a ... very global response to treatment. The second thing we are excited about is that some of these responses were in the linked muscles. To me that would suggest that the treatment could easily have effects on the muscles and joints that are remote to the treatment. By comparison, the reflex responses for the Activator-type treatment were very local and seemed to be a single receptor response, whereas in the spinal manipulative treatments, the response seemed to have a global effect on the body."

Dr. Herzog hopes to continue this work and have additional information to report in the next year or two. He is particularly interested in where the reflex responses derive.

For more information or to request a reprint of this study, contact:

Walter Herzog,PhD
Human Performance Laboratory
Faculty of Kinesiology
University of Calgary
2500 University Drive NW
Calgary, AB T2N 1N4 Canada
walter@kin.ucalgary.ca

Reference
1. Herzog W, Scheele D, Conway PJ. Electromyographic responses of back and limb muscles associated with spinal manipulative therapy. Spine, Jan. 15, 1999;24(2):146-153.