The Science of Chiropractic Treatment
The rapid speed of the high velocity, low amplitude thrust of chiropractic treatment sets off a barrage of high-threshold mechanoreceptors. According to the gate theory of pain (whose owner received the Nobel Prize in physiology), the activation of high threshold mechanoreceptors is necessary for the inhibition of pain. Low speed mobilization does not activate these receptors. The cavitation created during an adjustment has been shown in numerous studies to stimulate these receptors.
Individuals with chronic pain undergo a process called synaptogenesis that results in long-term potentiation of spinal pain. Several studies have indicated that stimulation from chiropractic adjustments affect mechanoreceptive afferents, which proceed to the brain including the cerebellum, then the thalamus, the cortex, the hypothalamus, the peri-aqueductal grey, then the raphe magnus nucleus, where from serotonergic neurons project to the dorsal root ganglion. There, at the “gateway” of nociceptive pain input, serotonin actually has the ability to degenerate maladaptive synapses that perpetuate spinal pain. To my knowledge, chiropractic adjustments are the only treatment modality that produces this effect. For more information, see JMPT June 2004;27(5):314-26—the article title is “Central neuronal plasticity, low back pain and spinal manipulative therapy.”—authored by renowned neurophysiologist Richard Gillette.
The rapid speed associated with the chiropractic adjustment treatment also creates a reflex in the golgi tendon organ within muscle tissue resulting in reduction in spasm and increases in control and coordination (proprioception). A 2006 in the German medical journal Manual Therapy, found that a single chiropractic adjustment led to improved contractability of the transverses abdominis (a “core” muscle associated with spinal stability). This is especially significant since Vladimir Janda, MD, demonstrated that the transverses abdominis becomes inhibited in individuals with low back pain.
There are 3 phases to healing injured tissue. Inflammatory, regenerative, and remodeling. We know that the regenerative and remodeling phases are guided by joint motion. We know that immobilization during healing leads to contracted, disorganized scar tissue that is less elastic and more sensitive to pain. Ultimately, tissue cannot heal where motion is not complete.
There are 3 types of motion; active, passive, and motion into the paraphyisiologic space. If, by using your finger muscles alone, you attempt to extend your forefinger as far as possible, that is termed active range of motion If you use your other hand to push your finger back further, it will move a great deal more—this ispassive motion. Lastly, if a well-trained individual (chiropractor) applies a short thrust to the joint into extension, the finger will move even further. This motion is still within the anatomical limits of motion, and does not injure capsular ligaments when performed by a chiropractor (this is movement into the paraphysiologic space).
This adjustment is capable, however, of breaking down capsular adhesions and fibrosis to restore normal motion in an impaired joint. Therein lies the magic of chiropractic—no other healing system trains is practitioners to be so adept at palpating segmental joint movement, diagnosing joint dysfunction, and lastly restoring normal, full range of motion to a joint. Obviously restoring movement to a joint produces optimal healing. Less obviously, normal movement leads to normal afferent firing patterns and normal motor organization in the brain. With normal movement patients achieve both normal optimal biomechanics and proprioceptive activity–this optimizes healing and decreases chronic pain.