Effectiveness of Chiropractic Adjustment on Autonomic Nervous System

Effectiveness of Chiropractic Adjustment on Autonomic Nervous System

Reviewed By: Ahmad Reza Jenabi, D.C., C.C.C.N.


The aim of this study was to investigate the effectiveness of cervical and thoracic adjustment on Blood Pressure. In addition, to determine if a cervical adjustment elicits a parasympathetic response and if thoracic adjustment elicits a sympathetic response.


The parasympathetic nervous system (PNS) arises from the cell bodies of the motor nuclei of cranial nerves III, VII, IX, X, XI in the brainstem and from second, third, and forth sacral segments of the spinal cord. The PNS system is known as the craniosacral flow. The cell bodies of the sympathetic fibers are in the lateral horn of spinal segments T1 through L2, the so-called thoracolumbar outflow. Because of the proximity of the upper cervical vertebrae to the brainstem, parasympathetic influences dominate these segmental levels; and therefore, a cervical adjustments could likely result in a parasympathetic response (slowing down of heart beat, lowering of BP, constriction of pupils). In those spinal regions where sympathetic innervations is substantial (upper thoracic and upper lumbar), a chiropractic adjustment could elicit a sympathetic response (stimulation of heart beat, raising of BP, dilation of pupils).


The objective of this study was to investigate responses, pre- and post-cervical and thoracic chiropractic adjustments, in relation to the classic thoracolumbar- sympathetic and cervical-parasympathetic pathways.


The first 40 volunteers meeting the inclusion criteria of being between the ages of 21 and 55 years, non hypertensive, and with no history of heart disease were entered as participants in the study. Each of the 40 participants were evaluated

over visits spanning 2 weeks per subjects between July 2005 and May 2007. Chiropractic assessments included motion and static palpation, leg length symmetry measurements, and thermography. When assessment indicated the need for an adjustment, the force was administrated according to the diversified technique methodology. Systolic and diastolic BP and pulse rate were measured using a digital BP device. Blood pressure was taken on the left arm of the participant, measured one time pre-adjustment and one time post-adjustment. Heart rate variability (HRV) refers to the beat-to-beat variation in the heart rate. Five-minute recording yielding power spectral analysis of HRV was obtained using the Active ECG instrument from BioCom Technologies. On the day that an adjustment was scheduled to be administrated, the participant, after having his or her BP measured and while still in the seated position, had a self-adhesive electrode attached by taping it to the left wrist, over the radial and ulnar arteries. Participants were assessed approximately the same time of day, each recording within 15 minutes. A recording time of 5 minutes was followed throughout the study. Each participant was assigned a specific time to be adjusted to maintain constancy in regards to the known diurnal effect that has been associated with HRV. After the adjustment, within a 10-minutes time frame, the same protocol as described above was repeated; and data were recorded as post-adjustment.


It was hypothesized that, if thoracic segment was adjusted, a sympathetic response would be elicited because the sympathetic fibers go through L2-L3 interspace and because the upper thoracic , especially the C7-T1 junctions, involve the stellate ganglion that stimulates the sympathetic chain ganglion. As well, because of the relationship of the C1 and C2 vertebrae to the parasympathetic nerve fibers associated with the brainstem, it was hypothesized that, if an upper cervical segment was adjusted, a parasympathetic response would be elicited.


Somatovisceral reflexes are evoked following a spinal adjustment, causing a reduction in BP after an upper cervical adjustment. Neurophysiological effects

occurring as a result of spinal adjustment may inhibit or excite somatosomatic reflexes, which changes HR and BP.

In summary, it was found that diastolic pressure dropped significantly post- adjustment among those receiving cervical adjustments. The decrease in pulse pressure for those receiving thoracic adjustments was not statistically significant. This study could have the benefit of leading to a better understanding of the effects of chiropractic adjustments and autonomic responses regarding organ dysfunction in general.


1. Journal of Chiropractic Medicine, Oct.2008, 7(3): 86-93 Authors: Arlene Welch, Ralph Boone

2. DurbanUniversityofTechnology,2009 Authors: Pastellides, Angela Niky

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