Effect of instrumental chiropractic on heart rate variability in patients with musculoskeletal pain

Abstract

Introduction: Pain of musculoskeletal origin may be associated with disorders in the Autonomic Nervous System (ANS) and such changes may influence the perpetuation and intensity of symptoms. Chiropractic is a therapeutic approach that aims, among other aspects, to reestablish the correct modulation of pain inhibitory pathways and also the functioning of the ANS. Although these techniques are already widely disseminated in the literature and used in clinical practice, there is a gap regarding the real impact of instrumental chiropractic on the ANS. In recent years, the measurement of Heart Rate Variability (HRV) has been gaining ground and being used as a tool for evaluating the modulation of the Autonomic Nervous System (ANS). Objective: To compare the HRV pattern pre and post manipulative stimulus with instrumental chiropractic in patients with acute or chronic pain. Methods: This is an experimental study pre and post intervention with the application of manipulation using an instrumental chiropractic technique. Participants were electronically randomized into two groups: intervention group (IG) with instrumental chiropractic versus placebo group (CG). For both groups, 64 individuals with musculoskeletal pain were recruited, of both sexes, between 18 and 60 years old. The following were excluded: individuals with a history of neoplasia in the last year or undergoing treatment for cancer, with any neurological pathology, rheumatic conditions and pregnant women. All participants had heart rate variability (HRV) measured before and immediately after performing the techniques. The assessment was carried out using a Polar® heart rate monitor, model H10, Elite HRV application, and the data was exported to analyze in KubiusStandart software version 3.5.0. The intervention consisted of a single stimulus to the right and another to the left at the level of the transverse process of C1 (atlas), through Chiropractic Instrumental Therapy (TIQ) in the intervention group. The stimulus was carried out by using a device made in Brazil by the Livta Institute. In the placebo group, the device was positioned in the same location as the intervention group, but only an audible stimulus was performed and not the mechanical stimulus at the location. The HRV parameters analyzed were: SDNN (Standard deviation of all normal RR recorded in a time interval (ms) that is influenced by Sympathetic and Parasympathetic); LF/HF Ratio (Ratio of low and high frequency that represents the sympatho-vagal balance); Parameter NN50 that refers to the number of differences between the RR intervals (heartbeat intervals) that exceed 50 milliseconds; Parameter SD1 which refers to the dispersion of high frequency oscillations around the midline (which represents the cardiac parasympathetic influence); Parameter SD2, which refers to the dispersion of low frequency oscillations around the midline (cardiac sympathetic influence); SD1/SD2 ratio that represents the balance between the sympathetic/parasympathetic activities of the ANS. Data were analyzed using JASP V. 0.16.2 (2022) software. The results were presented using means and standard deviations. To compare the means within and between groups, repeated measures analysis of variance (Anova) was performed. Results: The average age of the population was 32 years (SD). 32 participants were included in each group. When comparing the means of the variables to characterize the sample (age, BMI, pain intensity and level of physical activity) it was identified that the groups were homogeneous, as there was no statistically significant difference (p> 0.05). It was found that (GI) showed a significant difference in HRV when comparing the means before and after intervention for the LF/HF Ratio variable (P = 0.013). The CG also showed significant differences when comparing the means before and after the placebo stimulus for the SD1/SD2 Ratio variable (P =0.02). However, no significant difference was identified in the comparison between groups for any of the HRV variables measured: SDNN (P = 0.948), NN50 (P = 0.625), PNN50% (P = 0.684), SD1 (P = 0.890), SD2 (P = 0.979), LF/HF (P= 0.688) and SD1/SD2 (P = 0.875). Conclusion: In young adult patients with musculoskeletal pain, chiropractic instrumental therapy at the level of the transverse process of C1 bilaterally does not demonstrate a difference in cardiac vagal modulation compared to a placebo stimulus. In this sense, it is concluded that the proposed intervention was not effective in interfering with the variables measured in the autonomic nervous system of the participants included in the study.