In a recent study, heart rate was used to demonstrate increased parasympathetic nervous activity when trigger points in the leg muscles receive compression.

The study, “Compression on trigger points in the leg muscle increases parasympathetic nervous activity based on heart rate variability,” involved six healthy females with an average age of 21. Each woman’s daily work routine was carried out mostly in a standing position, from 8:30 a.m. to 4 p.m.

After a day’s work, subjects were asked to rest supine while baseline measurements were taken for 20 minutes. This occurred during the 20 minutes following the hands-on intervention as well. These outcome measures included electrocardiograms, instantaneous lung volume, systolic blood pressure and diastolic blood pressure.

A subjective fatigue scale also was filled out by participants before and after the trigger-point compression. The questionnaire asked subjects to evaluate their fatigue levels on a five-point scale ranging from “very fine” to “exhausted.”

Analysis of each subject’s heart-rate variability was used to assess parasympathetic nervous activity, and the transfer of instantaneous lung volume to heart rate also was evaluated.

Each massage session lasted 20 minutes and consisted of the manual application of pressure over trigger points in the lower-limb muscles where subjects reported fatigue and discomfort after

These sessions were performed by the same massage therapist, using a technique the study’s authors call “ischemic compression.” The intensity of pressure was controlled to a level each subject could describe as “comfortable pain.”

Results of the study showed trigger-point compression decreased heart rate, systolic blood pressure and diastolic blood pressure; increased parasympathetic activity; increased the gain from instantaneous lung volume to heart rate; and improved fatigue scores.
According to experts, the role of the parasympathetic nervous system may be described as “rest and digest,” as opposed to the “flight or fight” effects of the sympathetic nervous system.

“These findings suggest that [trigger-point] compression can elevate the activity of the parasympathetic nervous system,” state the study’s authors, “and provide some insight into the physiological mechanisms of pain relief induced by the pressure application over [trigger points].”

Authors: Kohichi Takamoto, Shigekazu Sakai, Etsuro Hori, Susumu Urakawa, Katsumi Umeno, Taketoshi Ono and Hisao Nishijo.

Sources: Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi Japan. Originally published in the Journal of Physiological Sciences (February 2009).

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