Chiropractic: The Science of the Snap, Crackle and Pop
We enjoy answering questions about complementary and alternative health care. In our office we focus on chiropractic, quantum neurology rehabilitation, clinical nutrition, functional endocrinology, acupuncture and detoxification programs with our patients. We answer a lot of questions with individual patients, but also try to answer many questions through our blog posts that individuals might have. This morning, I heard the following question from the other side of the office, and I thought it would make a good post for those of you that may have wondered why chiropractors do what they do, and what the body actually does when it receives a chiropractic adjustment (manipulation).
Question: “What is the point of ‘cracking’ his joints when you treat him?” – Asked by a spouse of a chiropractic patient seeing Dr. Reece Hayden
Answer (Short): Chiropractic adjustments do not have to “crack” or “pop” to be effective. Chiropractic manipulations affect a variety of nerves in the body, helping them to work more efficiently. This is why patients with pain, sports injuries, loss of motion, dizziness/vertigo, movement disorders, headaches, colic, digestive problems, neuropathy, lactation problems, ear aches, and a wide variety of other symptoms report improvements with chiropractic care. As a general rule, unless it is a medical emergency, you should probably have a chiropractor check it out to see what he can do to help.
Answer (Long): The chiropractic adjustment stimulates a complex set of events in the body. The most scientific explanation for what chiropractic procedures do in the body may come from a review article in The Spine Journal, written by Joel G. Pickar, DC, PhD, of the Palmer Center for Chiropractic Research. His article, “Neurophysiological effects of spinal manipulation,” addresses many questions that doctors, researchers, and patients have had for years regarding the biological mechanism for why chiropractic care is so effective for a wide variety of physiological imbalances.
Prefacing the Dr. Pickar’s research, he states in the introduction, “Despite the clinical evidence for the benefits of and the apparent wide usage of spinal manipulation (chiropractic and/or osteopathic adjustments), the biological mechanisms underlying the effects of spinal manipulation are not know. Although this does not negate the clinical effects of spinal manipulation, it hinders acceptance by the wider scientific and heal-care communities and hinders rational strategies for improving the delivery of spinal manipulation. The purpose of this review article is to examine the neurophysiological basis for and the neurophysiological effects of spinal manipulation.” Dr. Pickar then proceeds to deliver 12 pages of research discussing what chiropractic adjustments are actually doing to the body.
The most widely accepted theory as to how chiropractic works is the relationship between changes in the normal anatomical, physiological or biomechanical dynamics of the vertebrae can affect function in the nervous system. Chiropractic adjustments, or spinal manipulation, are believed to correct these altered neurological functions. Dr. Pickar provides the following figure in his article in order to explain the relationship between chiropractic care, segmental biomechanics, the nervous system, and physiology.
When a doctor of chiropractic performs a specific chiropractic adjustment, it stimulates a variety of nerves that regulate sensory input (proprioceptive afferents) which have the ability to calm down the overactive nerves that are creating the spasm, pain, and tension (gamma-motoneurons). Illustrating this neurological concept, Dr. Pickar describes the neurological communication pathways of the chiropractic adjustment, and it’s subsequent effects with the following figure:
The group I and II afferents (nerves that handle proprioception) that are stimulated through chiropractic adjustments mostly appear to affect muscle spindle cell and golgi tendon organs. These two fibers within the muscle play a roll in regulating muscle length, spasm, tenderness, and range of motion. Dr. Pickar continues by citing other research that indicates that group III and group IV afferents, which are associated with other connective tissues in the body, including the joints, skin, ligaments, and muscles are also affected by the chiropractic adjustment. “Thus, all classifications of sensory neurons… could be affected, theoretically, by spinal manipulation.”
In addition to stimulating sensory nerves in the body, another affect of chiropractic manipulation comes from reducing the pressure that a spinal disc herniation imparts on a dorsal root, or dorsal root ganglion. An often quoted statistic in chiropractic circles is, “applying as little as 10 mm Hg pressure to the dorsal roots reduces by 20% to 30% nutritional transport” to the peripheral nerve. In other words, minimal pressure to the nerves once they leave the spinal cord, and go between the spinal vertebrae could potentially affect neurological problems further down the pathway. Herniated discs in one study averaged 53 mm Hg, over five times the pressure needed to decrease nerve health. In that same study, some herniated discs produced as much as 256 mm Hg on the nerve! Although studies are lacking in the realm of chiropractic manipulation’s effect of changing the measurable pressure on the dorsal root, or dorsal root ganglian, clinical observation is abundant with improved outcomes from the symptomatic patient.
The third area that Dr. Pickar discusses in relationship to the chiropractic adjustment is related to spinal manipulations effect on central facilitation. “Numerous studies suggest that spinal manipulation alters central processing of innocuous, mechanical stimuli, because pain tolerance or threshold levels increase.” Basically, chiropractic adjustments are great pain blockers in the body. Skin sensitivity, muscle tenderness, and generalized pain frequently improve after chiropractic manipulations. In one study, chiropractic “manipulation significantly increased (1.5 fold) pain tolerance levels within 30 seconds. Over the next 9.5 minutes tolerance levels progressively increased (up to 2.4 fold).”
The fourth and fifth areas of research address the somatosomato and somatovisceral reflexes that are affected through chiropractic adjustments. Somatosomato reflexes are the reflexes that most non-medical patients are aware of. When the doctor taps the reflex hammer on the patient’s knee, and they kick their leg out as a result, that is a type of somatosomato reflex. Other examples can include the flexor-withdrawl reflex (touch something hot, and you immediately pull away), and the righting reflexes (when you trip and fall and you spin while falling to try and protect yourself with your arms so that you do not hit your face on the ground). Somatovisceral reflexes allow for chiropractic adjustments to alter visceral (organ and glands) function. “Sensory input from paraspinal tissues can evoke visceral reflexes affecting the sympathetic nervous system and may alter end-organ function.” Somatovisceral reflexes have been “demonstrated in such sites as the gastrointestinal tract, urinary bladder, adrenal medulla, lymphatic tissues, heart and vessels of the brain and peripheral nerves.” It is due to the somatosomato reflexes, and the somatovisceral reflexes that chiropractic doctors and patients talk about taking chiropractic care beyond back pain relief.
Dr. Pickar concludes his review of his research on what the chiropractic adjustment does, by stating that a “theoretical framework has been presented for understanding the neurophysiological effects of spinal manipulation[chiropractic care].” It is this framework that illustrates that through the chiropractic adjustment, the body experiences:
