Yoga Serge Braconi

Stretch Body and Mind©

How breathing affects the autonomic nervous system
Excerpt from "Anatomy of Hatha Yoga" by Dr. David Coulter

"... All of our concerns so far have been with how the nervous system influences breathing. These are all widely recognised. What is not as well known is that different methods of breathing can affect the autonomic nervous system and have an impact on the functions we ordinarily consider to be under unconscious control.
Abnormal breathing patterns can stimulate autonomic reactions associated with panic attacks, and poor breathing habits in emphysema patients produce anxiety and chronic over stimulation of the sympathetic nervous system.
By contrast, quiet breathing influences the autonomic circuits that slow the heartbeat and reduce blood pressure, producing calm and a sense of stability. Our ability to control respiration consciously gives us access to autonomic function that no other system of the body can boast.

One breathing technique that can produce a beneficent effect on the autonomic nervous system is 2:1 breathing - taking twice as long to exhale as to inhale. For those who are in good condition, 6-second exhalations and 3-second inhalations are about right, and if you can regulate this without stress, the practice will slow your heart down and you will have a subjective experience of relaxation.

As with almost all breathing exercises in yoga, both inhalation and exhalation should be through the nose. This connection between heart rate and breathing, known as respiratory sinus arrhythmia, involves reflex activity from the circulatory system to the brain stem that causes the heart to beat more slowly during exhalation than it does in inhalation. It is a natural arrhythmia, called "respiratory" because it is induced by respiration, and called "sinus" because the receptors that stimulate the shifts in heart rate are located in the aortic and carotid sinuses, which are bulbous enlargements in those great vessels.
If you take longer to exhale than to inhale, especially when you are relaxing, the slowing-down effect of exhalation will predominate. This is an excellent example of how we can wilfully intervene to produce effects that are usually regulated by the autonomic nervous system.

There are limits on both ends to the effects of 2:1 breathing. If you are walking briskly, exhaling for two seconds and inhaling one second, you will not get this reaction, and if you take it too far in the other direction, which for most people means trying to breathe fewer than five breaths per minute 8-second exhalations and 4-second inhalations), the exercise may become stressful and cause the heart rate to increase rather than slow down. The golden mean - that which is entirely comfortable - is best.

There is one well-known practical consequence of respiratory sinus arrhythmia. For decades doctors have known empirically that pursed-lip breathing against moderate resistance is helpful for those with obstructive lung disease. What is not generally realized is that the practice is helpful mainly because it lengthens exhalations, slows the heart rate, decreases the amount of air remaining in the lungs after exhalation, and reduces fear and anxiety. Knowledgeable yoga teachers realize that the same end can be accomplished through a different approach, lengthening exhalations by pressing in gently with the abdominal muscles while at the same time breathing through the nose."

David Coulter received a Ph. D. in anatomy from the University of Tennessee Center for the Health Sciences in 1968. From 1968 to 1986 he taught various microscopic, neuroscience, and elementary gross anatomy courses in the Department of Anatomy of the University of Minnesota (Medical School) in Minneapolis, MN. During that period he also served as a principal investigator for neuroscience research funded by the National Institutes of Health and the National Science Foundation. He next taught in the Department of Anatomy and Cell Biology at Columbia University College of Physicians & Surgeons (1986 to 1988), and since then has practiced and taught a style of bodywork called Ohashiatsu® in New York City and elsewhere. Dr. Coulter has been practicing yoga since 1974. He was initiated by Swami Veda (formerly Dr. Usharbudh Arya of Minneapolis, MN), trained under Swami Rama from 1975 to 1996, and studied under Pandit Rajmani Tigunait at the Himalayan Institute since 1988. From the inception of his interest in yoga, Dr. Coulter has been committed to correlating his understanding of the practices of that discipline with accepted principles of biomedical science
©Serge Braconi 2013