I have a 45 minute commute every morning and evening, driving to Evolution from my home in Underhill, so I listen to a lot of podcasts. I recently listened to an interview with Dr. Stephen Porges, developer of polyvagal theory, which sparked my curiosity. Dr. Porges’s research deals with the autonomic nervous system, which has two branches- sympathetic and parasympathetic. You may have learned them as “fight or flight” (sympathetic) and “rest and digest” (parasympathetic) in high school health class like I did. It is these systems which regulate our heart rate, breathing, digestion, elimination, and sexual arousal. Specifically, he looks at how different aspects of the vagus nerve drive our autonomic response. According to Porges’s theory, the vagus nerve has evolved as the human brain has evolved. The newer part of the vagus nerve is termed the “myelinated vagus.” (myelin is the substance that lines the nerves and provides for improved conduction times when signals are being transmitted). This evolution was first part of our deep, primitive brain (called the brainstem) which provides us with the ability to both perceive and react to dangerous stimuli- the fight or flight part of our autonomic system. However, as we continued to evolve our higher brain centers, which allow for our ability to interact socially, the vagus nerve developed additional branches which lead to links between our behaviors and regulation of the autonomic nervous system. Specifically, as we utilize aspects of our facial and eye muscles, throat, inner ear, which often happens in response to another human being, there is a profound positive effect on our autonomic system through a reduction in heart rate, reduced arousal, and improved digestion.
How does this relate to some aspects of yoga? While it might appear that our autonomic nervous systems are not in our control, this research illustrates the science behind what we might feel are the effects of yoga. First, attending a yoga class likely activates our social engagement system as we interact with others in a profound and meaningful way. Second, practices that use sound such as chanting activate both the auditory and vocal aspects of the myelinated vagus, which, according to Porges, will help reduce the fight or flight response. The breathing practice Ujjayi breath, or victorious breath, may also stimulate the myelinated vagus through stimulation of the throat, production of sound, and regulation of the breath.
In order to practice Ujjayi breath, take a comfortable seat in a chair or on the floor. Take a moment to tune into the feeling of your legs and pelvis in your seat, as well as the rate and nature of your breath. Notice the inhale and the exhale. Allow your facial muscles to soften, and a slight smile come to your lips. Next, you will make the ujjayi sound, toning the throat and epiglottis like you are trying to fog a mirror with your throat. Allow this to be relaxed, which you can achieve by making the open sound of “Ahhh” in the back of the throat. This constriction of the throat muscles will continue on the inhale and the exhale, breathing evenly on inhale and exhale with a count of 5-10.
Reference: Porges, Stephen (2007). The polyvagal perspective. BioPsychol. Feb 74
(2) 116-143
Porges, Stephen and Tatta, Joe. (2018). Optimizing human experiences
through the polyvagal theory with Dr. Stephen Porges. The healing pain
podcast. Available at
– Michelle Downing DPT
For more about this and other breathing techniques, attend Michelle’s Anatomy of Breath workshop on Friday, November 9th.

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