The Science of Breath

In his book Light on Pranayama, B. K. S. Iyengar writes: “Prana is the breath of life of all beings in the universe.” It’s no surprise, then, that pranayama, or the regulation of breath, is an essential part of yoga practice. In fact, it’s unusual to take a yoga class that doesn’t have at least some focus on breathing. As Kripalu Yoga teacher Richard Faulds (Shobhan) says, “Unless practiced with sensitivity to the breath, yoga postures fall far short of their potential to foster healing and growth.”

Historically, pranayama techniques were aimed to increase life-force energy and help people access more subtle experiences—nadis, marmas, increased sensitivity to the world. These outcomes are difficult to measure using our current scientific models and methods; there may be benefits that our current research cannot capture. (A great resource for exploring the classical understanding of the practice is Pranayama: A Path to Healing and Freedom, by Allison Gemmel Laframboise and Yoganand Michael Carroll.) However, scientists have begun to collect data on the more observable physical and mental benefits of various pranayama techniques. While the research is preliminary, their findings may encourage you to get on your mat and breathe!

Dirgha Pranayama

Dirgha pranayama, also called Three-Part Breath, is a practice of slowing and deepening the breath. Dirga is an essential yogic breathing technique that is taught in most yoga classes along with postures. To practice this technique, slow down the breath and focus on the exhale—especially effective for increasing the relaxation benefits of the practice.

There is a small amount of research suggesting that slow yogic breathing can have an important impact on vagal tone, a physiological marker of resilience and stress reduction. Two recent studies have looked at how this breathing technique might lower blood pressure and improve vagal tone in those with hypertension. In one study, 120 subjects with hypertension were randomized into either a slow, yogic breathing group or a non-active control group. While this study did not measure blood pressure specifically, it did evaluate vagal tone and baroflex sensitivity (both measures are related to blood pressure). Results showed a significant, positive change in both areas in the breathing group as compared to the control group. A second study found similar results: enhanced baroflex sensitivity and reduced blood pressure in people with hypertension. Both studies suggest that Dirgha can be a helpful tool for those with hypertension, and may also improve physiological markers of stress more generally.

Nadi Shodhana

Nadi Shodhana, or Alternate-Nostril breath (ANB), is touted for its ability to reduce stress and still the mind. This practice consists of sitting quietly and breathing into each nostril separately by plugging one nostril and breathing in the opposite nostril. The instruction is to practice going back and forth between each nostril slowly and rhythmically. The practitioner plugs the left nostril, breathes in through the right; plugs the right nostril, exhales through the left. Then he or she repeats this on the other side: Plug the right nostril, breathe in through the left, and onward. 

Current research is pointing to some promising outcomes, specifically that ANB may decrease blood pressure and increase feelings of calm. For example, a study conducted in 2008 showed that a 30-minute practice lowered blood pressure, compared to participants who only practiced breath awareness. In a randomized control trial with 90 patients all who were hypertensive, patients were randomized into three groups—ANB, breath awareness, and no intervention. After 10 minutes of ANB, patients showed a significant decrease in systolic and diastolic blood pressure. The breath awareness group saw a significant drop in systolic blood pressure but not diastolic—and the control group saw no change at all.

Interestingly, as many yogis have noticed in their own practice, breathing through one nostril compared to the other produces different effects on the body. For example, a study found that breathing exclusively in and out of the left nostril decreases blood pressure, whereas breathing exclusively through the right nostril increases blood pressure. This aligns with the yogic view that breathing into the left nostril activates the ida, the energy channel associated with rest and relaxation, and that breathing into the right nostril activates the pingala, the energy channel associated with activity and action. Bottom line? Nadi Shodhana helps balance the nervous system, evening out differences in sympathetic and parasympathetic tone (i.e., it evens out the fight-or-flight system with the rest-and-digest system) and it also reduces blood pressure, promoting a greater sense of calm and relaxation.

Kapalabhati/Bhastrika

The practice of Kapalabhati, or Skull-Polishing breath, consists of a forceful exhalation and a passive inhalation. In 2009 researchers Meesha Joshi and Shirley Telles published an article on Kapalabhati, in The Journal of Alternative and Complementary Medicine. They were curious to discover whether or not the practice of Kapalabhati, which can be quite invigorating, could improve performance on cognitively challenging tasks. To investigate this query, they ran a study in which they invited participants to practice Kapalabhati at the speed of two exhalations per second, for one minute. Participants were asked to complete a challenging mental task before and after they practiced Kapalabhati. A second group practiced breath awareness in comparison. Results showed that the Kapalabhati group had a significant decrease in the amount of time it took them to complete the task. This suggests that practicing Kapalabhati may improve mental performance. Equally interesting and beneficial, the breath-awareness group showed an increase in neural resources in order to complete the task. This suggests that simply being aware of the breath helps to focus one’s attention.

While researchers are still exploring what contributes to this shift in mental ability, these researchers hypothesize that Kapalabhati provides a gentle stimulation of sympathetic system response, which increases one’s cognitive functioning in such a way that it improves mental performance.

Kapalabhati can be practiced for varying lengths of time, for a short time—as demonstrated in this study—or for longer periods. A word of caution: Kapalabhati can be quite stimulating and is contraindicated for certain conditions. If you are new to this practice, it is best to start under the supervision of a trained yoga teacher, and to consult with your doctor first.

Bhastrika

The Bellows breath, or Bhastrika, somewhat similar to Kapalabhati, is also meant to increase energy flow. Bhastrika is practiced by breathing fully and forcefully in and out of the nose. Researchers from the Department of Physiology at Nepal College were curious to see how Bhastrika would impact the nervous system. To investigate this, they invited a group of participants into their lab to practice Bhastrika. The participants were instructed to practice a slow-paced bhastrika: inhaling to maximum for a count of four, then exhaling to maximum to a count of six. At this pace, participants were breathing at a rate of six breaths per minute and they were asked to continue with this practice for five minutes.

Researchers found that Bhastrika produced a significant decrease in blood pressure and a slight decrease in heart rate. The researchers concluded that “slow-pace bhastrika pranayama (respiratory rate 6/min) exercise shows a strong tendency of improving or balancing the autonomic nervous system through enhanced activation of the parasympathetic nervous system, and thus can be practiced for mental relaxation and reduction of stress in daily life.” Bhastrika can also increase energy, release tension in the abdomen, and helps loosen congestion and decongest the lymph.

A Pranayama a Day

While all these studies are preliminary, it’s encouraging to see such promising outcomes. This is a first step in placing solid scientific data quantifying the benefits of yogic breathing practices. With future studies such as these, the prescription for a “pranayama a day” might get just a little bit closer.

© Kripalu Center for Yoga & Health. All rights reserved. To request permission to reprint, please e-mail editor@kripalu.org.

Angela Wilson, LMHC, RYT 500, is a Kripalu faculty member who has conducted research and written about the intersection between yoga, Western psychology, and science.

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