Heart Rate Variability Modulation Following a Manipulation in Pain Free Patients Versus Patients in Pain

Background The chiropractic profession has in the past utilized research results from other fields of and extrapolated them into their science and clinical interpretation 1-4. More recently, chiropractic researchers looked into autonomic nervous system (ANS) adaptations in an animal model following a mechanical stress to the spinal column 5, a noxious mechanical stimulation 6 or a spinal manipulation 7.

In the human model, several investigations have been done to measure modifications of the heart rate variability (HRV) following cervical 8 and thoracic manipulations 9 or in a multisite clinical study 10 where details of the manipulation site were not provided. The site of interest for the chiropractic intervention was defined at the level of the lumbar spine, left and right L-5. This site was selected because most studies 8-10 measuring HRV have used the cervical or thoracic component of the spine. The effect of the lumbar parasympathetic nervous system has not been evaluated. In these studies 8-10, changes were observed in various HRV variables, while in two of those studies 8, 9, where sham groups were included, the sham conditions did not demonstrate any changes in the reported HRV parameters. There are strong indications that HRV is a good marker of ANS activity 19-24. Thus, in the three above mentioned studies, it appears that chiropractic interventions have an effect on the ANS.

At present, however, no studies to evaluate whether a lumbar spinal manipulation would produce a change in the HRV have been reported. Thus, the present study seeks to measure the effect of a lumbar adjustment, with a manually assisted mechanical force, producing a chiropractic adjustment, in participants without lumbar pain and a traditional adjustment in participants with lumbar pain on HRV. The hypothesis being that a lumbar intervention would have an acute effect on the ANS as demonstrated by the modulation of HRV variables.