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Relaxation, Yogic Breathing and The Vagus Nerve: It's All About the Exhalation
What is the number one thing anyone is told to do in moments of high intensity or stress? Breathe, of course. But do you know why?
It’s not a secret that your breath is the most accessible and powerful tool to help you stay calm, ward off anxiety, and combat the ill effects of stress. What, perhaps, is not as widely known is the role the vagus nerve plays in interrupting stress signals and facilitating relaxation in the body.
Here’s a clue: it has a lot to do with the way you’re breathing and the messages received by the brain.
Yoga Anatomy: Vagus Nerve 101
The vagus nerve is the longest cranial nerve, traveling from the brain stem to parts of the colon. It wanders through (or innervates) almost every major organ, including the heart, lungs, liver, spleen, stomach, kidneys, and intestines. Aptly named, the word “vagus” means “wandering” in Latin.
Its main function is to power up the parasympathetic nervous system (PNS), responsible for the body’s involuntary physiological relaxation response, also known as the “rest-and-digest” half of the autonomic nervous system (ANS). The other half is the “fight-or-flight” or sympathetic nervous system (SNS), responsible for the body’s stress response.
The autonomic nervous system is just that, automatic. It involuntarily, or unconsciously, regulates vital bodily functions, such as respiration, heart rate, blood pressure, pupil dilation, body temperature, sweating, and digestion.
Often described as the accelerator, the sympathetic nervous system rapidly speeds things up, increasing alertness, along with heart rate (pumping more blood to the muscles), in preparation for fight-or-flight in response to a perceived threat. Meanwhile, the parasympathetic nervous system works to calm everything down, bringing the body back into a state of equilibrium, or homeostasis, in preparation for rest and digestion during periods of safety.
The vagus nerve—commander of the parasympathetic nervous system—plays a vital role in putting the brakes on the body’s involuntary stress response, regulating everything from blood pressure and heart rate to digestion and sexual arousal.
Yoga and the Mind-Body Connection: A Two-Way Information Highway
Some cranial nerves have sensory functions, sending sensory information—including sights, sounds, smells, and tastes—to the brain. Others have motor functions—controlling the movement of the muscles and function of certain glands. The vagus nerve has both.
The long, wandering nerve senses your internal environment (via its sensory neurons) and sends information about the state of the viscera up to the brain. In return, the brain sends messages back down to your organs through the vagus nerve (via its motor neurons) to respond accordingly. Depending on the internal sensory information it receives, the brain will send signals back down to the body to either relax, rest and digest, or get ready to fight or run.
In other words, the information your brain receives about the state of your organs, through the vagus nerve, directly affects your internal environment, also through the vagus nerve. This creates the ultimate mind-body feedback loop.
Deep Yogic Breathing Triggers the Body’s Relaxation Response
With that in mind, let’s take a closer look at what happens when you deepen your breath.
The vagus nerve is essentially listening to the way we breathe through sensory nodes in the lungs known as stretch receptors, relaying the information up to the brain. Rapid, shallow breaths signal a threat to our brains, triggering sympathetic (fight-or-flight) activation. Deeper, fuller breaths indicate a level of safety, triggering parasympathetic (rest-and-digest) activity, which is carried back down to the associated organs through the vagus nerve’s motor neurons.
Heart rate and blood pressure lower, gastrointestinal and digestive activities increase, salivation and urination are once again promoted, among other involuntary parasympathetic nervous system functions. This induces an inner calm and peaceful state, all thanks to the vagus nerve.
It’s All About the Exhalation, Baby
However, the main reason you feel more relaxed after taking a few deep breaths is due to the vagus nerve’s powerful effect on slowing your heart rate. When stimulated, the vagus nerve releases a neurotransmitter called acetylcholine, which causes a reduction in heart rate. Deep, or abdominal, breathing activates the vagus nerve thus effectively lowering your heart rate.
But, it’s all about the exhalation.
Breaking down the mind-body feedback loop, when you breathe in, the vagus nerve sends sensory information up to the brain. And when you breathe out, the brain sends messages back down through the vagus nerve, telling the heart to slow down. It’s the exhalation when vagal activity is highest and heart rate lowest, that triggers the relaxation response.
Try it. Take one or two deep, full breaths, focusing on the exhalation. Notice the relaxation that occurs as you breathe out and if there’s a greater sense of release on the exhalation versus the inhalation.
And remember to take a few deeper breaths with long, slow exhalations, calling on the power of your vagus nerve to slow your heart rate and pump the brakes on the body’s stress response.
Also, read this article from Meagan McCrary - Yoga Anatomy: Tone Your Vagus Nerve to Combat Inflammation.
Meagan McCrary is an experienced yoga teacher and writer with a passion for helping people find more comfort, clarity, compassion, and joy on the mat and in their lives. She is the author of Pick Your Yoga Practice: Exploring and Understanding Different Styles of Yoga a comprehensive encyclopedia of prominent yoga styles, including each system’s teaching methodology, elements of practice, philosophical and spiritual underpinnings, class structure, physical exertion, and personal attention. Currently living in Los Angeles, Meagan teaches at the various Equinox Sports Clubs, works privately with clients, and leads retreats internationally. You can find her blog, teaching schedule, and latest offerings at www.MeaganMcCrary.com.