Polyvagal Theory and the Breath

By Valerie Knopik for Yoga Digest.

I don’t know about you, but I’ve been hearing a lot about the vagus nerve of late. From its association to stress, mental health and wellness to heart rate variability and respiratory sinus arrhythmia (and a related term called vagal tone), this nerve certainly seems to play an important role in our lives. For those of you newer to the vagus nerve, here are some interesting facts – it is a cranial nerve (number 10 of 12 cranial nerves, in fact) that originates in the medulla, and the name ‘vagus’ can be translated as ‘wandering’. It is called the wandering nerve because it influences the function of multiple organs (heart, lungs, and digestive tract to name a few), and it is the longest nerve of the autonomic nervous system in the body. The vagus nerve is a primary component of the parasympathetic branch (“rest and digest”) of our autonomic nervous system, as opposed to the sympathetic branch (“fight or flight”). Specifically, research suggests that stimulating the vagus nerve activates the parasympathetic branch of the nervous system; a ‘vagal brake’ if you will.

Polyvagal theory (‘poly’ meaning many) is a term used to describe the multiple associations between the vagus nerve and things like emotion regulation, social connection and our fear  response (Porges, 1995). This theory proposes an evolutionary model of how the vagal pathways respond to stressful and novel external stimuli. Essentially, it is proposed that there are two vagal systems that can behave differently: (i) a more primitive path that is shared with reptiles and amphibia which leads to fainting, freezing, or ‘playing dead’ when threatened so as to conserve metabolic resources; and (ii) a more evolved branch unique to mammals that is involved in self-soothing and calming behaviors in stressful situations. Each of these adaptive behavioral strategies are inhibitory in nature and thus, in line, with parasympathetic activation. And, given the evolutionary nature of this theory, it is thought that when the more evolved branch fails, the primitive branch takes over.

By now, you might be saying to yourself, “Okay, cool. But what does this have to do with yoga and the breath?” Interestingly, the wandering vagus nerve runs behind the throat, suggesting that we can gently stimulate the vagus nerve when we do things like chanting, om-ing, and yes, breathing….particularly deep yogic breathing (Kromenacker et al., 2018). In fact, there is research to suggest that we can stimulate these inhibitory responses to our nervous through our breath (Senthilnathan et al., 2019). If you are anything like me, you might be wondering how to measure vagus nerve activation. Well, earlier in this piece, I mentioned the term ‘vagal tone,’ which is defined as vagus nerve activity. It has become quite popular as a novel way to measure stress vulnerability and can be measured in various ways. The most common non-invasive way is through heart rate and heart rate variability, or measuring the variability in the time interval between heartbeats. Increased vagal tone (and thus vagal action) is generally associated with a lower heart rate and increased heart rate variability. And guess what else  High heart rate variability is also associated with better emotion regulation, decision-making, and attention (Thayer & Lane, 2009). As with most scientific theories, there are some who strongly believe in polyvagal theory and others who question its validity; however, the role of the vagus nerve in calming the body through parasympathetic nervous system activation is clear. And while we
don’t have much control over most of our autonomic nervous system functions, the breath is one way to access the vagus nerve and thus our ‘rest and digest’ response as a means to find balance (or homeostasis) in our system.

Here is a simple technique to bring some awareness to your breath:

1. Lie on your back with knees bent and feet flat on the floor about hip-distance apart.
2. Place a palm on your abdomen and breathe comfortably for a few moments, noticing the quality of your breath. Does the breath feel tense? strained? uneven? shallow? Simply observe the breath without any judgment.
3. Gradually begin to make your breathing as relaxed and smooth as possible, introducing a slight pause after each inbreath and outbreath.
4. Once the breath feels relaxed and comfortable, notice the movement of the body. As you inhale, the abdomen naturally expands; as you exhale, feel the slight contraction of the abdomen. In a gentle way, try to actively expand the abdomen on the inhale and contract the abdomen on the exhale to support the natural movement of the diaphragm and experience the pleasure of giving yourself a full, relaxed breath.
5. Continue the practice for 6 to 12 breaths.
6. Take a few moments after the practice to observe and notice how you feel physically, mentally, and emotionally after spending a few moments focused on your breath.