Q: I am teaching a Pranayama workshop and linking it to Brain Physiology. I checked this article and I am confused. According to your article, inhalation stimulates the SNS (sympathetic nervous system) and exhalation triggers PNS (parasympathetic nervous system). Is this your personal experience or are you pretty sure about this correlation because I did not find this in any Yoga textbooks or articles.
Just think about Kapalabhati Pranayama: The inhalation is very passive and exhalation is very forceful. If your correlation is true, at the end of Kapalabhati pranayama, you need to feel more relaxed and calm (exhalation-PNS). But this is not what we typically experience. The nature of Kapalabhati pranayama is such that it makes an individual more active, there is more heat generated in mind and body and it awakens an individual from stupor. I guess this is due to activation of SNS. So this would be contradictory to what you mentioned. What is the correct explanation?
A: I love it when my readers take some aspect of the practice of yoga and begin to look a little deeper! I just reread my post How Your Breath Affects Your Nervous System on the effect of the length of the inhalation/exhalation (like a five-minute pranayama practice of one second inhalation and two second exhalation, for example) over time and the indirect influence it has on the brain and the “tone” of the autonomic nervous system (ANS). The length of your inhalation and/or exhalation influences your heart rate (cardiovascular system) by slowing or speeding it up, which then has a feedback effect on your brain’s perception of safety or danger, activity or rest, and may then shift the overall balance of your sympathetic/parasympathetic tone in one direction or the other. This assumes the person doing the pranayama does not have any other factors at play that might be more activating or quieting to their nervous system. For example, a new practitioner unfamiliar with breathing practices might be nervous and anxious about getting the practice right, and a breath ratio, such as 1:2, that might normally turn on the parasympathetic parts of the the ANS could be overridden by the background mindset of the person practicing it and actually stimulate the sympathetic nervous system instead.
In fact, the Autonomic Nervous System is by no way a simple system of the Fight or Flight response (sympathetic nervous system) being turned on and the Rest and Digest response (parasympathetic) being turned off, or vice versa. The ANS is much more subtle and nuanced than that. Why, just this past week, anatomy teacher and yogi Leslie Kaminoff’s colleague Amy Matthews wonderfully articulated this concept in this video clip.
As for the other kinds of breath practices our reader mentions, such as Kapalabhati pranayama, where the practitioner is quickly exhaling audibly, and quietly and more passively allowing the inhale to happen, and doing so at a pace that can be slower at first for newer practitioners or much faster in pace for more experienced practitioners, the typical effect is more stimulating for the ANS.
This would be true also for Bastrika pranayama, where both the inhalation and exhalation are quick and audible.
In all of this, keep in mind that it is not a simple formula of “this leads to that.” You will need to consider many factors when anticipating the effect that any particular breath practice might have, and, after practicing, also assess for yourself whether your predicted effect, either stimulating or quieting, really played out in the end!
—Baxter
by Baxter
When I read the posts of my fellow YFHA bloggers, I often learn new perspectives that might differ from my own as well as new information that I was previously unaware of. Reading the posts also highlights occasions where I could have been clearer or given better information on a particular topic. As an example, I have written about breath techniques and their effect on the autonomic nervous system, as did Timothy in his awesome follow-up post on the buzzing bee breath, Bhramari Pranayama with Mudras. And we often mention that extending or lengthening the exhalation triggers the parasympathetic nervous system, the Rest and Digest part of our nervous system’s balancing program. This made me realize that I could add a bit more detail to explain how that actually happens.
It turns out the Autonomic Nervous System (ANS) that connects brain to body is a two-way street. If I am anxious and nervous or stressed out by events in my life or simply the thoughts about those events, my brain, via the nerves of the ANS, will likely turn on the Sympathetic part of that system (the Fight or Flight response), which could result in faster heart and breathing rates, and increases in blood pressure, to mention just two of the most obvious physiological changes.
But the cool thing is that the lungs and heart can feed back to the brain and essentially convince the brain that things are calm and peaceful, even when there are still stressful circumstances. One neat way this happens involves the relationship of the heart and lungs and the nerves between them. In each round of breath, during your inhalation, your heart gets stimulated to beat a little faster. Then during the exhalation that follows, your heart gets told to slow down a tad. The overall effect is very little change in the heart rate from minute to minute. But when you make one part of the breath cycle, either the inhale or the exhale, longer than the other, and you do this for several minutes, the accumulated effect is that you will either slow the heart rate down or speed it up from where you started. When you make the inhales longer than the exhales, for example, by using a two-second inhale and a one-second exhale, and you keep this up for several minutes, the heart rate will go a bit faster. This will send a feedback message to the brain that things need to activate more in the brain and body for whatever work there is to be done, stimulating the Sympathetic portion of the ANS.
With the very useful Bhramari breath Timothy expanded on Bhramari Breath with Mudras, we do the opposite. As we hum during the exhalation, the exhales get longer relative to the inhales, as when we do a 1:2 ratio breath practice without the humming. This new respiratory cycle begins to slow down the heart rate, sending a message to the brain that everything is more peaceful and calm than five minutes ago, allowing the brain to support this shift further by activating the Parasympathetic portion of the ANS (the Rest and Digest or Relaxation response) that goes back from brain to body.
Research has shown that the vagus nerve as well as certain chemical neurotransmitters account for these effects of breath patterns on heart rate and subsequently on shifting the balance between the Sympathetic and Parasympathetic parts of the ANS. Keep in mind that the ANS is trying to keep all background systems in balance and responding appropriately to ever-changing circumstances of our day.
I’m providing this information for those of you who want to go a bit deeper in your understanding of how breath patterns affect the nervous system balance and either excite the system or quiet it. Our conscious choice of breathing differently can shift us to a more desirable part of the ANS, either by stimulating the active Sympathetic branch or the quieting Parasympathetic branch. Most of us need more of the latter, but not always!
For a little more background on how the Respiratory system influences the Cardiac system, which in turn influences the Autonomic Nervous System, see The human respiratory gate as well as Effects of yoga on the autonomic nervous system, gamma-aminobutyric-acid, and allostasis in epilepsy, depression, and post-traumatic stress disorder. (The observation that treatment resistant cases of epilepsy and depression respond to vagal nerve stimulation corroborates the need to correct PNS underactivity as part of a successful treatment plan in some cases. According to the proposed theory, the decreased PNS and GABAergic activity that underlies stress-related disorders can be corrected by yoga practices resulting in amelioration of disease symptoms. This has far-reaching implications for the integration of yoga-based practices in the treatment of a broad array of disorders exacerbated by stress.
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When I read the posts of my fellow YFHA bloggers, I often learn new perspectives that might differ from my own as well as new information that I was previously unaware of. Reading the posts also highlights occasions where I could have been clearer or given better information on a particular topic. As an example, I have written about breath techniques and their effect on the autonomic nervous system, as did Timothy in his awesome follow-up post on the buzzing bee breath, Bhramari Pranayama with Mudras. And we often mention that extending or lengthening the exhalation triggers the parasympathetic nervous system, the Rest and Digest part of our nervous system’s balancing program. This made me realize that I could add a bit more detail to explain how that actually happens.
It turns out the Autonomic Nervous System (ANS) that connects brain to body is a two-way street. If I am anxious and nervous or stressed out by events in my life or simply the thoughts about those events, my brain, via the nerves of the ANS, will likely turn on the Sympathetic part of that system (the Fight or Flight response), which could result in faster heart and breathing rates, and increases in blood pressure, to mention just two of the most obvious physiological changes.
With the very useful Bhramari breath Timothy expanded on Bhramari Breath with Mudras, we do the opposite. As we hum during the exhalation, the exhales get longer relative to the inhales, as when we do a 1:2 ratio breath practice without the humming. This new respiratory cycle begins to slow down the heart rate, sending a message to the brain that everything is more peaceful and calm than five minutes ago, allowing the brain to support this shift further by activating the Parasympathetic portion of the ANS (the Rest and Digest or Relaxation response) that goes back from brain to body.
I’m providing this information for those of you who want to go a bit deeper in your understanding of how breath patterns affect the nervous system balance and either excite the system or quiet it. Our conscious choice of breathing differently can shift us to a more desirable part of the ANS, either by stimulating the active Sympathetic branch or the quieting Parasympathetic branch. Most of us need more of the latter, but not always!
For a little more background on how the Respiratory system influences the Cardiac system, which in turn influences the Autonomic Nervous System, see The human respiratory gate as well as Effects of yoga on the autonomic nervous system, gamma-aminobutyric-acid, and allostasis in epilepsy, depression, and post-traumatic stress disorder. (The observation that treatment resistant cases of epilepsy and depression respond to vagal nerve stimulation corroborates the need to correct PNS underactivity as part of a successful treatment plan in some cases. According to the proposed theory, the decreased PNS and GABAergic activity that underlies stress-related disorders can be corrected by yoga practices resulting in amelioration of disease symptoms. This has far-reaching implications for the integration of yoga-based practices in the treatment of a broad array of disorders exacerbated by stress.
Copyright © 2012 Elsevier Ltd. All rights reserved._)
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