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“The Inhalation Is Heating And The Exhalation Cooling.” Is This Actually True?

in YD News, YogaDork Ed

YAM Group Work at Simply Yoga--2by Timothy McCall, MD

Years ago, a famous professor of medicine announced to his graduating class that half of what he had taught them was wrong, but that he didn’t know which half. Much of what we learn in yoga has been passed down from a line of teachers, and from ancient yoga texts. And as much credence as we tend to give them, it is the job of yoga practitioners and teachers to not simply take everything they’ve learned at face value. Instead, yoga teaches you to bring the ancient wisdom into your own practice to see what feels true for you. Direct experience, according to yogic thinking, is the highest form of knowing. It trumps the testimony of the masters and the ancient scriptures.

Like many of you, I was taught that the inhalation is heating and the exhalation is cooling. In a way, this makes sense because it has been demonstrated that the inhalation is tied to the activating sympathetic nervous system, aka the “fight or flight” system, and the exhalation to the relaxing parasympathetic nervous system. The deeper I got into my own practice of asana and pranayama, though, the more I found this piece of ancient yogic lore wasn’t true for me. So I decided to do an informal study of the mostly yoga teachers and health care professionals who take the Yoga As Medicine Seminars my wife Eliana and I teach.

Over the course of several workshops we asked attendees to sit in a relaxed upright position and initiate gentle Ujjayi (Victorious) breathing with inhalation and exhalation of equal length. After they’d settled into a comfortable rhythm, we asked them to tune into the sensations of warmth they felt in their bodies, particularly in the head area, first during the inhalation, then during the exhalation. Then we asked them to check a box on a questionnaire whether the inhalation or the exhalation felt more warming, or whether they felt more or less the same.

Results

Here are the results of the 144 completed questionnaires:

Inhalation Warmer……13
Exhalation Warmer…..95
The Same…………………36

So more than seven times as many people found the exhalation more heating than the inhalation. The last time I was in India, I asked Chandukkutty Vaidhyar, the Ayurvedic master I’ve been studying with for the last ten years, which he thought was more heating to the body. His answer: “The exhalation.”

My experience also suggested to me that the longer the exhalation relative to the inhalation, the more heating it was to the body. So we asked workshop attendees to return to the Ujjayi breath they’d just done with a 1:1 ratio, i.e. the inhalation equal in length to the exhalation. We asked them to again tune in a notice how heating this felt. Then we asked them to gently lengthen the exhalation, ideally coming to a 1:2 ratio, as long as they remained perfectly comfortable doing so, with no breath hunger or gasping. For example, if they’d been inhaling for 3 seconds, they would exhale for 6. Again we asked them to notice how heating it felt, and compare that to what they’d just experienced with the 1:1 breathing. We suggested, if they had any doubts, to go back and forth between 1:1 and 1:2 breathing a few times.

Here are the results:

1:1 Inhalation Warmer……34
1:2 Exhalation Warmer…..90
The Same………………………20

More than 2.6 times as many people found the longer exhalation more warming to the body.

inhalation-exhalation

image via http://blm1128.blogspot.co.uk

Discussion

The reason the exhalation appears to be more warming may be due to the contraction of the abdominal muscles on the exhalation that comes with yogic breathing. Both Ayurveda and Traditional Chinese medicine believe that the body’s heat comes primarily from the solar plexus area or “hara.” The compressive effects on this region during the exhalation may render it more heating, while the expansive effects of the inhalation make it more cooling, as both these ancient medical traditions suggest.

We cannot rule out the effects of climatic conditions on the results. These workshops were taught in indoor settings, usually within a narrow range of “comfortable” room temperatures. Perhaps in India on a broiling hot day, the inhalation would feel more heating to most people. Ujjayi is also an inherently heating practice, though we instructed participants to do it mildly. It is also possible that while the exhalation may feel more heating to many yoga practitioners that in the longer-term, stressing the exhalation is more cooling. N.B. This study did not examine the relative heating effects of breath retention (kumbhaka) or bandhas.

I don’t pretend this is a definitive study, yet the results suggests that we may need to revisit the notion that the inhalation is heating and the exhalation is cooling that so many of us have heard in yoga classes and teacher trainings. This could have an effect on what practices we recommend to yoga therapy clients with particular imbalances, e.g. pitta dosha increases could be exacerbated by heating practices, and which yoga practices we emphasize in different seasons.

From a broader perspective, the results might also be a cause for more humility and less certainty about the correctness of various dogma that get passed down from our teachers and the tradition in general. I, for one, for years taught precisely what I no longer believe. The biggest take home message I believe is that the deeper we go into this practice, the more we can trust our own direct experience — even when it doesn’t match the theory.

~

Dr. Timothy McCall is an internist, yogi and meditator, author of Yoga as Medicine, long-time medical editor of Yoga Journal, and co-editor of forthcoming medical textbook of yoga therapy The Principles and Practice of Yoga in Health Care. Timothy and his wife Eliana Moreira McCall co-direct The Simply Yoga Institute in Summit, NJ, near Manhattan, where they teach Yoga as Medicine seminars and teacher trainings, as well as classes, workshops and yoga therapy privates.

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10 comments… add one

  • Dwayne

    Interesting article. I never had any teaching about whether inhale or exhale is cooling, and hadn’t devoted much thought to it. However, based on my experience with sitali [I'm too lazy to find the diacritic mark] pranayama, I always assumed that the inhalation is cooling!

  • Try the Sitali on exhalation and you’ll see how heating it is!

  • Dave

    What of the effects of evaporative cooling?
    http://www.ehow.com/about_6197274_evaporative-cooling-occur_.html
    http://96.8.85.123/outlook/weather-news/news/articles/evaporational-cooling-heat-exhaustion-stroke_2010-06-14
    When dogs pant they are passing air over their moist tongue. The moisture evaporates into the dry air and cools the tongue and blood inside the tongue.
    When a person breaths through their nose the incoming air is drier so there would be more cooling. The outgoing air is more moist so less cooling.
    Since the blood around our nose is so close to our brain the small effects may be much more noticeable than otherwise.

  • mmilver88

    as is with most things in yoga, my experience is “it depends” – particularily on the outside tempreature … don’t know where I learned this, but it was several years ago … using the ujjayi throat constrictions, you can make the inhalation and the exhalation warming or cooling, depending upon where you direct the flow of the breath from the nostrils into the lungs … on a warm day – less than 98.6 F – you can make the inhalation cooling by directing the outside air into the upper /top of your nostrils and over the roof of the mouth and down the back of the throat … this rush of air sends a cooling message to the brain and then out to the body … the exhale is then directed toward the front of the throat and through the lower / bottom of your nosrtils = keeping the warmer air – 98.6F – away from the temperature sensors at the back of the throat/top of the mouth … in winter, the process is reversed … inhale thru the bottom of the nostrils and into the front of the throat = keeping the cold air away from those temperature sensors at the top of the mouth and back of throat … and then exhale over the back of the throat and thru the top of the nostrils = sending a warming message to the brain and then out to the body … so you can actually “manage” your body’s reaction to outside tempreature changes with your breath … I’ve been doing this for so long, that it has become second nature and don’t even realize that I’ve shifted my breathing patterns as the seasons change – until that day when the light bulb goes off and I take notice that it has actually changed … of course, the closer the outside temperature gets to 98.6F, the less efficient this method becomes, then either breath thru the mouth or keep everything flowing across the front of the throat and out the bottom of the nostrils … this is a great discussion topic … I would be interested to find out if others have a similar experience … looking forward to more comments … mm

  • Great point, mmilver88. I completely agree you can modulate sensations of warming and cooling by consciously directing the breath as you suggest, yet I still find the exhalation is warmer than the inhalation is all combinations, at least is this 70 degree room I’m sitting in…

  • Chris

    When any gas (Air) is compressed it heats up. The lungs contract, to compress the air in the lungs, and increase its pressure (and temperature) above that of the ambient, thereby expelling the air in the lungs to the ambient.

  • Appreciating this article. Reminded once again how important our subjective experience is important. It’s so easy to listen to “research” or “the teachings” as “the truth” when what I really need is to fine tune my on internal listening and let that guide me.

  • Mihaiela

    Thank you for challenging dogma and encouraging independent thinking. Always good to take a cold shower on established beliefs.
    Nevertheless it is my understanding this study asked for predominantly local observations
    of I/E impact. The old thesis I-heating/E-cooling seems to refer to general, post effects of breathing. While exhalation feels warmer, the elimination of internal heat has a cooling post effect. Insisting on inhalation activates SNS with heating post-effects. So what kind of effects are we measuring?

  • Thanks for your comment. I absolutely can’t say there couldn’t be a longer-term heating effect of the inhalation. Yet my sense is that, as Ayurveda would suggest, the exhalation is more heating due to the compression near the core. I asked people to think about the effect in their head but also the general heating effect. When I only focus on the relative heating or cooling effects at my core, I still find the exhalation to be more heating. But your experience might be different! Which is I guess my major point…

  • PaulK

    At SVYASA (Vivekananda Yoga University, Bangalore, India), I was taught to notice the cool air while inhaling and warm air while exhaling by paying attention to the tip of my nose for Pranayama. My personal experience agrees with this.

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