The link between Breath and Nervous System – Foundation of Pranayama
In this post, we will discuss the link between the breath and mind – which forms the foundation of Pranayama, the fourth limb of Ashtang Yoga (Ashtang means 8 limbs in Sanskrit) as formulated by the Lord Patanjali in his Yoga Sutra.
There are different schools of thought in defining the mind. According to Yogic texts, the mind is the awareness of consciousness. The consciousness is itself is an unexplored subject when it comes to neuroscience. Hence, for simplicity, we will consider the mind as manifestations of high-level functions – cognition, emotion, memory, that take place within the nervous system. These higher-level functions are largely influenced by the state of the autonomic nervous system.
Hatha Yoga Pradipika, a classic fifteenth-century text authored by Swami Svatmarama – considered to be the most influential text on Hatha Yoga, in verse 29 of chapter 4 defines the link between the body, mind and breath as:
“इन्द्रियाणां मनो नाथो मनोनाथस्तु मारुतः” (in Sanskrit)
The Mind (मन) is the master of Senses (इन्द्रि), and the Breath (मारुत) is the master of the Mind.
The modern science so far considered the mind to be outside any conscious control. It was believed that the autonomic nervous system lies outside of our awareness and runs entirely unconsciously and autonomously. It is only recently that neuroscience research is evidencing the aspect of consciously controlling the mind through breath – the foundation of Pranayama. So, let’s look at the link between the breathing and autonomic nervous system and how it is used in the practice of Yogasana and Pranayama to gain control over the state of mind.
The Basics of Nervous System
Readers not familiar with the nervous system can refer to our previous blog posts. Here is some background.
The nervous system is the most important function that allows us to experience the external world. It is divided into two components – both of them highly interconnected:
- Central nervous system – It includes the brain and spinal cord. They are protected by the skull and vertebrae respectively.
- Peripheral nervous system – It includes nerves outside the central nervous system. The peripheral nervous system is further divided into the autonomic nervous system and the somatic nervous system.
The autonomic nervous system has three branches – the sympathetic nervous system (stress response or flight-and-fight), parasympathetic nervous (relaxation response or rest-and-digest) and enteric nervous system (second brain – the link between the gut and the brain).
The autonomic nervous system normally works in an automatic and autonomous way – silently adjusting the balance between the sympathetic and parasympathetic nervous systems. The enteric nervous system, though quite independent, goes side-by-side with the parasympathetic nervous system. Various functions of the body – heart rate (circulatory system), breathing rate (respiratory system), peristalsis (digestive system), neurotransmitters (nervous system), hormone release (endocrine system), muscle tone (skeleton-muscular system) are manipulated so as to keep the operating parameters of the body within desired range.
The sympathetic nervous system is energizing. When stimulated, it increases the heart rate, blood pressure and breathing rate as the body needs more oxygen and other nutrients (glucose in particular) for emergency situation. The parasympathetic response is calming and restorative and hence reduces the level of these parameters – allowing you to rest and digest. The balance between the sympathetic and parasympathetic nervous systems is reciprocal and determines the overall state of the autonomic nervous system at any given moment. Both of them are perpetually ON to some extent. It is only the relative proportion of each that changes based on the current situation. The sympathetic nervous system dominates during the time of fear, stress and emergencies, while the parasympathetic nervous system dominates when there is no perceived threat. For more information, read the post titled “Understanding Autonomic Nervous System from Neuroscience Perspective”.
According to Yogic science, the sympathetic nervous system belongs to Pingala Nadi and the parasympathetic nervous system belongs to Ida Nadi.
How the Nervous System affects the Breath?
Breathing is unique as a physiological function. The rate, depth and duration of breathing is adjusted subconsciously by the medulla oblongata (part of the brainstem) based on the requirement of oxygen due to change in metabolism at any given time. The level of involvement of different respiratory muscle groups – diaphragm, intercoastal, clavicular, is changed accordingly. See the different types of breathing in a post titled “Understanding the basics of breathing from a Neuroscience perspective”.
When you are doing light exercise, the need for extra oxygen is satisfied by breathing more deeply without increasing the rate of breathing. But, when you exert further, just raising the depth alone does not help and you need to raise the respiration rate. Further, during excessive exertion, you can’t raise the rate of respiration when breathing diaphragmatically, as you can’t breathe faster that way – and hence thoracic breathing becomes prominent. In an extremely stressful situation, clavicular breathing may also additionally get activated. This is made possible by the medulla oblongata, which dynamically speeds up the activation of the intercostal muscles (and clavicular, if required) and slows down the diaphragmatic action. Hence, by changing the rhythm this way you can achieve as high as twenty times increase in the air intake.
This is the reason you see yourself breathing rapidly and through the chest when the sympathetic response is stimulated e.g. during physical exercise (running, aerobics, backbend Yogasana), emotional stress, anxiety. Once the stress response is alleviated and the relaxation response is activated, the diaphragmatic breathing dominates.
Subtler Aspects of the Breath
So far, we looked at the gross level of relation between the nervous system and breath. There are subtler aspects that are not known to many.
- Inhalation vs Exhalation – At a physiological level, when the lungs are being expanded during inhalation, they put pressure on the passage of venous blood coming from the heart to the lungs. This pressure reduces during exhalation – as a result the heart rate decreases, which effectively generates an effect similar to increase in parasympathetic tone, and is relaxing to the mind. This difference in heart rate during the inhalation and exhalation is called “Respiratory Sinus Arrhythmia (RSA)”. Higher RSA indicates a good health, whereas a low (or zero) RSA is indicator of some health problem. A high RSA is a positive indicator of health promoted by deep and slow breathing, where diaphragm is involved, as against the case when it is prominently thoracic. The increase in parasympathetic tone during exhalation is the reason why you are told to lengthen the exhalation in various Yogasana poses, Pranayama techniques like Viloma-II, and other relaxing techniques like 2:1 breathing.
- Left vs right nostril breathing – The breathing in humans alternate between the left and right nostrils. One nostril dominates anywhere from a few minutes to a few hours. The same continues even during sleep. The left nostril, according to Yogic science, is governed by Ida Nadi, which is associated with the parasympathetic tone. The right nostril is connected to Pingala Nadi, the sympathetic branch. The alternating effects of left and right-nostril breathing are correlated with parasympathetic and sympathetic dominance. There is a technique to shift the breathing voluntarily to a particular nostril by constricting the flow of blood through the other side armpit. For example, if you sleep on the right side or compress the armpit by Yoga-danda (a wooden staff used by Yogis), the left nostril becomes active. This way one can shift the balance between sympathetic (right nostril breathing) and parasympathetic (left nostril breathing) states. The Pranayama techniques of Chandra Bhedana, Surya Bhedana, and Nadi Shodhana are based on this principle of nasal laterality.
- Left vs right hemisphere – The dominance of the right hemisphere corresponds to parasympathetic relaxation stimulation, while that of the left hemisphere dominance corresponds to the sympathetic nervous system activation. From a neuroscience perspective, this is associated with increased alpha-wave activity in the EEG of the right cerebral hemisphere and increased beta wave activity of the left cerebral hemisphere respectively. The brain waves are covered in the post titled “Brain Waves – A Neuroscience measure of the state of mind“.
- Chest vs diaphragmatic breathing – As discussed above, there is a close connection between the breathing rhythm and sympathetic/parasympathetic dominance of the autonomic nervous system. When the demand for oxygen is high, you need to breathe rapidly, and hence by using the ribcage (chest) because breathing from diaphragm cannot be performed fast enough to meet that demand. Hence in the state of the dominance of the sympathetic nervous system, thoracic breathing (or chest breathing) is prominent. And, we breathe abdominally when the parasympathetic nervous system is in dominance.
How to consciously control the Autonomic Nervous System?
Breathing is the only physiological process that can be either voluntary or involuntary. We can breathe consciously as we wish, or just ignore it and the body simply breathes on its own. The body cannot operate without the breath, and hence if conscious control of the breath is abandoned, then the unconscious part of the mind (the medulla oblongata in the midbrain) reflexively takes over the control and breathing happens automatically. In this case of automatic breathing controlled by the medulla, the rhythm of the breath (automatically changes based on the condition of the autonomic nervous system. We will refer to the rate, depth, duration and pattern of breathing collectively as ‘rhythm’.
We discussed above how the state of the mind – and hence the state of the autonomic nervous system changes the rhythm of breathing. It is not just a one-way stream. The reverse is also true – the change in the breath changes the state of mind and nervous system dominance. You can experience this by chronically chest breathing. You will be able to perpetuate or cause a state of sympathetic nervous system arousal. Similarly, when you are feeling anxious or stressed, just doing diaphragmatic breathing will induce relaxation. Hence, the autonomic functioning of the nervous system that otherwise happens subconsciously, can be brought under conscious control by the changes in breathing through the practice of Yogasana and Pranayama. The science of Yoga is intimately connected with the autonomic nervous system and brings its functions under conscious control through modulation of the rhythm of breathing.
The body, breath and mind are inseparably interlinked. And hence it will be too narrow a thought process to define Pranayama as purely working on the breath and Yogasana as solely focused on the physical body. Pranayama defines the techniques through conscious modulation of rate, depth, duration and rhythm of breathing. Yogasana doesn’t define such techniques explicitly. But, in Yogasana, the movement of the body to attain a pose and staying that pose cannot be achieved without (unconsciously) modulating the parameters of breathing to achieve those poses. Hence the breath, though seem to be playing a supporting role, has a profound impact on the state of the mind through modulation of the autonomic nervous system.
As a matter of fact, many styles of Yoga (specifically Iyengar Yoga) prohibit the Yogasana practitioners, particularly beginners, from focusing on the breath. The primary reason for such prohibition is to avoid them from fiddling with the breath which may become problematic, if not done properly. But, the focus on alignment and positioning is so detailed that the effect of the breath over the nervous system is achieved as a positive side effect – without consciously controlling the breath. If practiced correctly, it is not only Pranayama but also Yogasana, that work at the physiological and psychological level – giving you control over the mind. Hence breathing plays a primary role in Pranayama with the body in a supporting role. While in Yogasana the body plays the primary role with the breath in a secondary role. Both of them modulate the state of the mind – and hence provide significant therapeutic value in neurological, psychological, emotional, psychosomatic disorders.
Here are some examples through which the autonomic nervous system is shifted towards sympathetic tone energizing the body and alerting the mind:
- Thoracic breathing triggers a sympathetic response. In an extreme physical exertion that is highly sympathetic in nature, the clavicular breathing is activated along with thoracic breathing.
- energizing Yogasana like backbends.
- stimulating Pranayama like Brastika and Kapalbhati. They should only be practiced under expert guidance and that too in moderation. We will cover in a future post, how excessive Pranayama can make you hyperventilate and result in various disorders.
- a short kumbhaka (retention) following inhalation. Please note that kumbhaka is highly stimulating and should only be practiced under the supervision of experienced teachers.
- constricting the flow of air through left nostrils so that right gets activated.
- constricting the flow of blood through left armpits. This will shift the breath to the right nostril which is stimulating to the sympathetic nervous system.
Some examples of shifting towards parasympathetic tone giving relaxation to the body and calmness to the mind:
- Adbomino-diaphragmatic breathing is highly parasympathetic in nature and hence recommended to alleviate excessive stress.
- restorative reclining poses like Supta Baddha Konasana.
- relaxing Yogasana like forward bends.
- inversion Yogasana (where Baroreceptors are stimulated).
- Ujjayi and Viloma II Pranayama.
- loud chanting of OM (A-U-M) – typically performed at the beginning of a session is highly parasympathetic in nature.
- a long kumbhaka after exhalation.
- constricting the flow of air through right nostrils so that left gets activated.
- constricting the flow of blood through the right armpit. This will shift the breath to the left nostril which is stimulating to the parasympathetic nervous system.
We will cover these points in depth in our future posts.
The information contained in YogChikitsa blog posts is for educational and informational purposes only. It is not intended as health or medical advice. Always consult a qualified medical professional or qualified health provider regarding any questions you may have about a medical condition or health objectives. Also, Yoga should be practiced under the guidance of an experienced teacher.