This group saw an increase in parasympathetic activity during trigger point acupuncture. This is probably a nonspecific effect of needling, but of significance nonetheless!!
Spectral Analysis of Heart Rate Variability During Trigger-Point Acupuncture of Various Muscles
Objective: The aim of this research was to clarify changes in cardiovascular autonomic nervous system function due to trigger-point (TP) acupuncture; the current author evaluated differences in responses among acupuncture at TPs of various muscles using spectral analysis of heart rate variability.
Materials and Methods: Subjects were 48 healthy men. Before measurements began, subjects were assigned to a TP acupuncture or control group based on presence/absence of referred pain on applying pressure to a taut band within the right extensor digitorum muscle, tibialis anterior muscle, gluteus medius muscle, or masseter muscle. Measurements were conducted in a room with a temperature of 25°C, with subjects in a long sitting position after 10 minutes of rest. Acupuncture needles were retained for 10 minutes at 1 site on the right extensor digitorum muscle, tibialis anterior muscle, gluteus medius muscle, or masseter muscle. Electrocardiography was performed simultaneously with respiratory-cycle measurements. Based on the R–R interval on the electrocardiograms, frequency analysis was performed, low-frequency (LF) and high-frequency (HF) components were extracted, and the ratio of LF to HF components (LF/HF) was evaluated.
Results: All subjects in the TP acupuncture group showed a transient increase in the HF component, but no significant changes in heart rate (HR) or LF/HF. In the control group, no significant changes were observed in HR, HF component, or LF/HF.
Conclusions: These data suggest that acupuncture stimulation of TPs of the right extensor digitorum muscle, tibialis anterior muscle, gluteus medius muscle, and masseter muscle increases parasympathetic nerve activity transiently.