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
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