Psychophysiology of slow breathing exercises using heart rate variability measurements for stress reduction

Slow breathing exercises, associated with meditation and other eastern style modalities like tai chi and hatha yoga, are now increasingly employed in mainstream medicine to reduce stress, attenuate moderate hypertension, and alleviate symptoms of lifestyle-related illnesses. The clinical literature on slow breathing exercises includes studies employing various physiological measurements, including heart rate variability (HRV), galvanic skin response, and changes in skin temperature. HRV has been increasingly used to measure the activity of the autonomic nervous system in various human studies employing healthy and chronically ill subjects. 1. Objective: To understand the effects of slow breathing exercises on heart rate variability as a complementary intervention for stress reduction. 2. Method: Four subjects, through repetitive trials, were instructed to slow down their breathing following a metronome at 10 breaths per minute or 6 breaths per minute or spontaneously relax to slow down their respiratory rate. The ECG, heart rate, and respiratory rate were recorded using a Powerlab set-up (ADI). 3. Key Results:  Results showed an increase in amplitude of heart rate variability during these slow breathing exercises, either through the metronome-guided or spontaneous slow-breathing exercises, especially around a breathing frequency of 6 breaths per minute. The increased amplitude of heart rate variability can be seen as a positive sign, a marker for sympathovagal balance. 4. Conclusion: HRV measurements have shown that slow breathing exercises can increase heart rate variability.  Future protocols for clinical trials are being projected using the HRV technique and other physiological measurements for studying effects of yoga-based complementary interventions for stress reduction