The Vagus Nerve & Yoga

Updated: Feb 4, 2019



Why do I feel so good after a yoga class? How does yoga help me relax? I know how I feel but what is happening in my body?


We all know that yoga can reduce stress levels, improve sleep, digestion, fertility and overall wellbeing. But why is this?


It is widely acknowledged that a regular yoga practice helps to activate the parasympathetic nervous system, the part of our autonomic nervous system responsible for our “rest & digest” & “feed & breed” responses.


Recent research suggests that the main reason for this is due to something called vagal tone or the level of reactivity & response in our vagal nerves. Today we are going to explore what this means. Bear with me, here comes the science bit...


What is the vagus nerve?


The Vagus Nerve is the 10th cranial nerve. A cranial nerve is a nerve that emerges directly from the brain as opposed to spinal nerves that emerge from segments of the spinal cord. The vagus nerve stimulates & gives feedback to our brain about our heart rate, major blood vessels, lungs, oesophagus, stomach & intestines. It keeps our heart rate steady (or not), controls sweating, blood pressure & controls peristalsis (contraction) of the gastrointestinal tract.


It is the main nerve associated with our Parasympathetic Nervous System. Our what?!! Read on...


Our Nervous System


Our autonomic nervous system (ANS) is responsible for managing our organ function. It is our unconscious body management circuitry providing communication & feedback between our brain & organs.


Within the ANS we have two branches; the sympathetic nervous system (SNS) which is responsible for our survival and our parasympathetic nervous system (PNS) which is responsible for our daily function, relaxation & sleep.


The sympathetic nervous system creates in our body our “fight or flight” response; to prepare our bodies to run or fight for our lives.


When we experience stress or fear our brain reacts releasing epinephrine, opinepherine & other hormones including cortisol & adrenalin resulting in


  • Increased heart rate and blood pressure

  • Dilation of pupils to take in as much light as possible so we can see where we are going as we run for it or punch someone

  • Constriction of the veins in the skin to send more blood to major muscle groups; hence why we feel cold or get goose bumps when we are scared

  • Increased blood-glucose level to fuel rapid movement

  • Tensed skeletal muscles, energized by adrenaline and glucose, ready to fight or run

  • Relaxation of the smooth muscle to allow more oxygen into the lungs (but also in the walls of the bladder resulting in you peeing your pants in fear)

  • Shut down of nonessential systems (like digestion and immune system) to allow more energy for running or fighting

  • A brain focused only on the big picture in order to determine where threat is coming from (& associated loss of focus on small details)


In a modern lifestyle where we experience high levels of stress, you can see why we have increased aggression/road rage, poor health & digestive issues, difficulty concentrating on small tasks & increased levels of type 2 diabetes. Our lifestyles are literally making us ill as we are push our bodies deeper & deeper in to a stress response on a daily basis. The SNS is great if you are living in the savannah being stalked by a lion or going in to battle but not so great in the queue at the traffic lights or in a meeting with your boss!


But what about the second branch of the ANS? The parasympathetic nervous system (PNS), is associated with our rest & digest functions and our feed & breed functions. This part of our nervous system is active when we are resting, sleeping & relaxing. The hormones associated with the parasympathetic nervous system are prolactin (key in breastfeeding & regulating dopamine levels), oxytocin (the hormone of connection/bonding & love released when we touch & hug someone or make love), vasopressin (controls blood volume, water levels & our circadian rhythms), and the neurotransmitter acetylcholine (manages control of muscles & regulates brain areas responsible for learning, memory, attention & arousal).


The hippocampus and prefrontal cortex of the brain control & help to balance the sympathetic and parasympathetic nervous systems. They feed back to one another depending on the perceived level of safety in our external environment to either prepare us for fighting or flight or to stop & rest.


Our hippocampus, the area of the brain that is used for spatial learning and memory, tries to turn off our fight or flight mode but needs our prefrontal cortex to be listening to turn off this response. It does so by activating the parasympathetic nervous system (via the vagal nerves) in order to balance out the physiologic stress response, which comes from the sympathetic nervous system.


When the parasympathetic nervous system is activated, our brain & body experience short-term and long-term benefits.


In the short terms we experience a release of prolactin, oxytocin, vasopressin, and acetylcholine. Our brain & body relaxes and is more receptive, we feel more at peace, we sleep better. Our digestion works better because increased blood flows to our intestines & stomach meaning we are better nourished. Our heart rate decreases & blood pressure drops. We feel more connected to people around us, more loving & calm, The long term benefits result in better ability to deal with stress, better digestion & sleep & improved memory function.


So what is Vagal Tone?


Vagal Tone represents the balance between the 2 parts of the autonomic nervous system which controls our organs & function being the parasympathetic & sympathetic nervous systems. Poor vagal tone has been linked to depression, anxiety & chronic illness, in particular those which involve chronic inflammation in the body such as heart disease or stroke, and some autoimmune disorders, such as rheumatoid arthritis and lupus.


A good vagal tone on the other hand means that your body can switch between activity & relaxation, stresses & calm effectively and this enables you to respond to the ups & downs of life in a more balanced way.


Vagal tone is measured in the changes in heart rate that occur with the breath. This is referred to as Heart Rate Variability or HRV. Healthy vagal tone involves a slight increase in heart rate on the inhalation and a decrease of heart rate when you exhale.


Certain yoga practices have been shown to improve heart rate variability & therefore vagal tone. So what are they?


Yoga Techniques for Improving Vagal Tone


Pranayamas

Breath holding pranayama - anuloma viloma khumbaka alternate nostril breath with breath holding.


Singing & Humming (Brahmari pranayama buzzy bee breath)


Deep breathing with the diaphragm - ujjayi pranayama


Asana


Using gentle restorative poses to allow the heart rate to slow & the breath to be easy focusing on

  • Heart opening poses to stretch the front of the body & activate the vagus nerves,

  • Tummy stretching poses - cat/cow, puppy pose.

  • Restorative restful backbends - supta baddha konasana

Please see this Tummee Sequence for a lovely & gentle restorative practice to help improve vagal tone.


Dhyana & Dharana /Meditation


Yoga Nidra. Ancient meditation technique which works to put you in a deeply restful state between wakefulness & sleep, allowing your body to take deep rest and perfect for activitate the PNS


There are free practices here


Metta or “Loving Kindess” Meditation.


Just as an active PNS promotes feelings of love/connectedness & calm, by using practices that actively help you reconnect with a feeling of calmness & love towards others you can activate the PNS & strengthen vagal responsiveness. There is growing evidence to suggest that our continued sense of love & connection can help us to feel both improvements in our physical & mental health.


A Mettā Meditation or Loving Kindness Meditation is an ancient practice in the Tibetan Buddhist tradition with roots also found in ancient and medieval texts of Hinduism and Jainism.


How to Practice:


Sitting or laying in a comfortable position, establish an easy & comfortable breathing rhythm. You can then begin to repeat the following phrases, cultivating a sense of love & tenderness towards yourself. Repeat these phrases (or a variation that resonates & works for you) for 5-10 minutes until you feel a sense of love permeating your whole body.


May I be filled with loving kindness.

May I be safe from all danger.

May I be well in mind & body.

May I be happy & at ease.


We then shift our awareness to someone close to us, who has had a big influence in our lives or means a lot to us & repeat the phrases, directing our loving kindness towards them.


We then direct our awareness to a larger group of friends & family and then to our community and then to all beings. We can even put someone in there who we are struggling to be connected with, someone we don’t like or who is challenging us. In this moment this enables us to experience the feeling that even when we are struggling with someone we can still be compassionate & loving towards them.


Moving our awareness from ourselves, to those close to us, to those further away, to strangers & ultimately to all beings helps us create a sense of connectedness with those around us; it works to strengthen our relationships with those close to us, within our community & increases our sense of compassion to those we do not know, understand or like.


All of these practices help to activate your PNS and stimulate the vagus nerve which ultimate results in that feeling of well-being & peace at the end of a class.


For a gentle yoga class to help improve your vagal tone you can join me on Tuesday mornings in Les Allues at 10:30am-12. Please contact me to book your place.


Sources:


Yoga & Heart Rate Variability source article

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4959333/


Neurobiological Changes Show How Mindfulness Meditation Improves Health

https://www.ncbi.nlm.nih.gov/pubmed/27021514


How Positive Emotions Build Physical Health: Perceived Positive Social Connections Account for the Upward Spiral Between Positive Emotions and Vagal Tone

https://journals.sagepub.com/doi/abs/10.1177/0956797612470827


Effects of Yoga on the Autonomic Nervous System, gamma-aminobutyric-acid, and allostasis in epilepsy, depression, and post-traumatic stress disorder

https://www.sciencedirect.com/science/article/pii/S0306987712000321


Yoga Improves Executive Function by attenuating Stress Levels

https://www.sciencedirect.com/science/article/pii/S030105111630312X


#vagaltone #yoga #yoganidra #meditation #dhyana #dhranana #asana #nervoussystem #yogapractice #yogaeffects #metta #pranayamas


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