Chiropractic Adjustments Increase Maximal Bite Forces Through Effecting Cortical Changes
FEATURE
Mark Studin
DC, FASBE(C), DAAPM, DAAMLP and
William J. Owens
DC,
DAAMLP
Chiropractic has been shown in the literature to affect neural plastic changes. According to Wikipedia, “Neuroplasticity, also known as brain plasticity and neural plasticity, is the ability of the brain to change throughout an individual’s life, e.g., brain activity associated with a given function can be transferred to a different location, the proportion of grey matter can change, and synapses may strengthen or weaken over time. Research in the latter half of the twentieth century showed that many aspects of the brain can be altered (or are ‘plastic’) even through adulthood. However, the developing brain exhibits a higher degree of plasticity than the adult brain. Neuroplasticity can be observed at multiple scales, from microscopic changes in individual neurons to larger-scale changes such as cortical remapping in response to injury.” (https://en.wikipedia.org/wiki/ Neuroplasticitv) This article focuses on a specific piece of evidence to demonstrably verify the effects of those neuroplastic changes as sequela to a chiropractic highvelocity, low-amplitude spinal adjustment.
Haavik, Ozyurt, Naizi, Holt, Nefergaard, Yilmaz, and Tinker (2018) reported, “It has previously been proposed in the literature that chiropractic spinal manipulation has a central neural effect. This is because multiple studies have shown that spinal manipulation of dysfunctional spinal segments can impact somatosensory processing, sensorimotor integration, and motor control” (pg. 6). Haavik, Naizi, Jochumsen, Sherwin, Flavel, and Tinker (2017) supported the previous finding by reporting, “The results presented are consistent with previous findings that have suggested increases in strength following spinal manipulation were due to descending cortical drive and could not be explained by changes at the level of the spinal cord. Spinal manipulation may therefore be indicated for the patients who have lost tonus of their muscle and/or are recovering from muscle degrading dysfunctions such as stroke or orthopedic operations and/or may also be of interest to sports performers” (pg. 12).
Lelic, Niazi, Jochumsen, Dremstrup, Velder, Murphy, Drewes, and Haavik (2016) also supported the neural plastic changes of a chiropractic spinal adjustment by reporting their “study resulted in two major findings. Firstly, the study reproduced previous findings of somatosensory evoked potential (SEPs) studies that have shown that chiropractic spinal adjusting of dysfunctional spinal segments alters early sensorimotor integration (SMI) of input from the upper limb. The second major finding of this study was that we were able to show, using dipole source localization, that this change in SMI that occurs after spinal manipulation predominantly happens in the prefrontal cortex. The SEP peak showed multiple neural generators including primary sensory cortex, basal ganglia, thalamus, premotor areas, and primary motor cortex. The frontal N30 peak is therefore thought to reflect early SMI.”
Haavik, Ozyurt, Naizi, Holt, Nefergaard, Yilmaz, and Turker (2018) also found:
The major finding of this study was that chiropractic spinal manipulation (adjustment) increased maximum bite force immediately after the intervention and the increase in bite force remained at one-week follow-up. This is the first study to show that a single session of chiropractic spinal manipulation can increase jaw bite strength compared to a sham intervention.
This immediate increase in jaw bite force of 11% post spinal manipulation was unlikely to be due to the placebo effect, as all subjects were naive to chiropractic, and most of the subjects did not know which intervention was real upon questioning after both interventions. The 2.3% decrease in maximum bite force after the sham intervention may have been due to fatigue from maximum biting on the mold, or simply due to random variations in maximum efforts.
The current study now also suggests that cervical spine function can influence maximal bite force. The effort with which the subject’s bite would also influence maximum bite force, and for this reason the study was conducted in Turkey, where chiropractic is relatively unknown, to enable a more effective sham intervention. As no increase in strength occurred following the sham intervention, the effort is unlikely to have been the reason the subjects’ bite force increased after the spinal manipulation.
Increases in lower limb muscle strength in subjects with subclinical pain following chiropractic spinal manipulation has been reported. An increase in lower limb strength in elite athletes that lasted 30 minutes post spinal manipulation was shown. Chilibeck et al. reported that in subjects with imbalances in lower limb muscle strength, spinal manipulation resulted in increased muscle strength of hip abductors in their weak leg. Botelho and Andrade reported increases in grip strength in a group of nationallevel judo athletes following spinal manipulation.
Haavik et al. continued:
In two of these previous studies that showed lower limb muscle, maximum voluntary strength increases after chiropractic spinal manipulation H-reflex excitability and V-waves were also recorded. Both studies showed increases in maximum plantarflexion force and significant increases in the cortical drive to the plantar flexors (i.e., V-wave) following spinal manipulation, and that both these measures significantly decreased after the control intervention...The increase seen following the spinal manipulations was, therefore, most likely because of the increased cortical drive to the muscle.
It has previously been proposed in the literature that chiropractic spinal manipulation has a central neural effect. This is because multiple studies have shown that spinal manipulation of dysfunctional spinal segments can impact somatosensory processing, sensorimotor integration, and motor control as mentioned in the introduction. This current study supports this notion, as spinal manipulation appears to alter maximum biting force in this group of subjects. This study, therefore, supports the growing body of research that suggests chiropractic spinal manipulation’s main effect is neuroplastic in nature that affects cortical excitability.
"It is possible that chiropractic spinal manipulation may influence the clinical outcomes for patients with TMJ disorders, as has been suggested by individual case studies."
Spinal dysfunction, even mild, recurrent spinal dysfunction, has been shown to be associated with maladaptive neural plastic changes, such as alterations in elbow joint position sense, mental rotation ability, and even multisensory integration, suggesting spinal dysfunction can alter the brain’s inner body schema and maps of the body and the world around us. This may be because spinal manipulation has been shown to change both cerebellumM1 processing as well as prefrontal cortex processing. In the current study, the subjects’ mild spinal dysfunction may have altered the somatosensory input from the neck to the brain centers involved in sensorimotor integration and motor control of the jaw, and that adjusting these dysfunctional segments therefore impacted on these same central regions altering the maximum bite force the subjects could perform.
Haavik et al. concluded, “Knowing that spinal function can have an impact on jaw function has functional implications for patient populations. It is possible that chiropractic spinal manipulation may influence the clinical outcomes for patients with TMJ disorders, as has been suggested by individual case studies.” A significant amount of other applications of maximal bite force in our population would also benefit from a chiropractic spinal adjustment when clinically indicated.
What’s not to be lost in this reporting of the literature, as mentioned previously, “multiple studies have shown that spinal manipulation of dysfunctional spinal segments can impact somatosensory processing, sensorimotor integration, and motor control.” There is a myriad of signs, symptoms, conditions, and disease processes that emanate from the malfunction of those centrally controlled functions in the human body. Although we have proven that a chiropractic spinal adjustment positively affects these functions, we are still at the forefront of fully understanding the full extent of how the adjustment influences a patient’s overall health, although these authors have seen evidence clinically for almost four decades, and chiropractors have been reporting the same since 1895.
Mark Studin, DC, FASBE(C), DAAPM, DAAMLP, is an adjunct associate professor of chiropractic at the University of Bridgeport College of Chiropractic: an adjunct professor at Cleveland University-Kansas City, College of Chiropractic: an adjunct professor of clinical sciences at Texas Chiropractic College: and a clinical presenter for the State of New York at Buffalo, School of Medicine and Biomedical Sciences for postdoctoral education. He teaches MRI spine interpretation, spinal biomechanical engineering, and triaging trauma cases. He is the president of the Academy of Chiropractic teaching doctors of chiropractic how to interface with the medical and legal communities (www.DoctorsPlProgram.com): teaches MRI interpretation and triaging trcmma cases to doctors of all disciplines nationally: and studies trends in health care on a national scale (www. TeachDoctors.com). He can be reached at DrMarkldAcademyofChiropractic.com or at 631-786-4253.
William J. Owens, DC, DAAMLP, is presently in private practice in Buffalo and Rochester, New York and generates the majority of his new-patient referrals directly from the primary care medical community. He is an associate adjunct professor at the State University of New York at Buffalo School of Medicine and Biomedical Sciences as well as the University of Bridgeport, College of Chiropractic, and an adjunct professor of clinical sciences at Texas Chiropractic College. He also works directly with doctors of chiropractic to help them build relationships with medical providers in their community.
He can be reached at dr.owens@academyofchiropractic, com, via www.mdreferralprogram.com, or at 716-228-3847.
References:
1. Neuroplasticity (2018) Retrieved from https://en.wikipedia.org/ wiki/Neuroplasticity
2. Haavik, H., Ozyurt, M. G., Niazi, I. K., Holt, K., Nedergaard, R. W., Yilmaz, G., & Tinker, K. S. (2018). Chiropractic Manipulation Increases Maximal Bite Force in Healthy Individuals. Brain Sciences, 8(5), 76.
3. Haavik, H, Niazi, I. K., Jochumsen, M., Sherwin, D., Flavel, S., & Tinker, K. S. (2016). Impact of spinal manipulation on the cortical drive to upper and lower limb muscles. Brain Sciences, 7(1), 2.
4. Lelic, D., Niazi, I. K., Holt, K., Jochumsen, M., Dremstrup, K., Yielder, P.,... & Haavik, H. (2016). Manipulation of dysfunctional spinal joints affects sensorimotor integration in the prefrontal cortex: A brain source localization study. Neural plasticity,2016
