In 2009, a study led by Richard A Roy and colleagues, the effects of chiropractic treatments on heart rate variability (HRV) were investigated in patients with and without lower back pain. The study aimed to compare HRV modulation following manual assisted mechanical force (Activator) or traditional diversified technique spinal manipulation.

The research involved 51 participants who were randomly assigned to control, treatment, or sham groups. HRV data were recorded using Suunto watches during an 8-minute acclimatization period and analyzed using Kubios software.

Results revealed interesting trends in HRV parameters. Across all groups, there was a general decrease in the high-frequency component except for the control group, which exhibited an opposite reaction. The very low frequency increased in all groups except the control group, while the low frequency decreased in all groups except the sham pain-free group. The low frequency-high frequency ratio decreased in the treatment pain group and the sham pain-free group, but increased in the sham pain group, control group, and treatment pain-free group.

Furthermore, the mean RR interval, reflecting the average time between heartbeats, increased in the sham pain-free group, treatment pain group, and control group, while it decreased in the treatment pain-free group and sham pain group.

The findings suggest that adjusting the lumbar vertebrae influenced the parasympathetic nervous system output, regardless of the type of adjustment. The observed differences in HRV modulation appear to be associated with the presence or absence of pain, indicating that the autonomic nervous system response may be specific and sensitive to the status of the effector organs.

This study contributes to our understanding of the physiological effects of chiropractic treatments on HRV, highlighting the importance of considering pain status in assessing autonomic nervous system responses. Further research in this area may provide valuable insights into optimizing chiropractic interventions for various clinical conditions.

Reference: Roy, R. A., Boucher, J. P., & Comtois, A. S. (2009). Heart rate variability modulation after manipulation in pain-free patients vs patients in pain. Journal of manipulative and physiological therapeutics, 32(4), 277-286.