Breath is so powerful, yet so often taken for granted and forgotten. Taking a breath is the first thing we do after we are born, and the last thing that's done before dying. It is essential to our existence, so we probably should be more aware of its mechanisms. Breathing gives us energy – thanks to the transport of oxygen to the cells of our body. We need to nourish our cells with oxygen and get rid of waste products, like CO2. Breathing is key to neurological processing. Putting it short- we can't live without our breath or how we breathe is how we live.
Seeing this process physiologically, we can talk about respiration- the exchange of gas in our bodies, minute ventilation- the volume of air breathed into the lungs in a given minute, respiration rate – the number of breaths per minute or tidal volume – the amount of air displaced during inhalation. But how exactly the inspiration happens? The brain stem initiates the inhalation. Via the phrenic nerve, the diaphragm muscle contracts downwards. This changes the pressure in the lungs and pulls the air into the lungs. When the lungs are full, afferent baroreceptors feed the brain stem causing inhibition of inhalation. The exhalation is passive. Of course, this is very simplified, as there are more muscles used in breathing (intercostals, abdominals, or accessory muscles).

Breathing could be modified voluntarily, and the observation of the way someone breaths can tell us a lot about this person's state (relevant in grief, depression, anxiety). In yoga therapy, we use breathing assessment as a critical element of diagnosis, looking at the location, rate, intensity, and inhale/exhale ratio. The most optimal breathing is the diaphragmatic (belly) breathing, however some people present reverse breathing and, on some occasions, accessory (chest) breathing, like when we exercise.
Forced way of breathing may manifest in muscle tension, especially around the scapula, upper arm, and chest. Too much of the accessory breath may be the result of bad habits, respiratory disease, or stress. As a result, our accessory muscles get tight, diaphragm weakens, we get headaches, and we have reduced uptake of oxygen and feel stressed, as we are in a sympathetic arousal state.
There are many ways to adapt the breathing patterns to what can be potentially more beneficial for us, only by modifying the way we breathe. Prolonging the exhale is a simple adaptation skill to use in response to stress. When we want to signal our mind that we are relaxed- we should breathe into our lower lungs. It is because our lower lungs are richer with alveoli (end of the bronchioles), where the air exchange occurs. Their total surface is of 50-100sqm in a healthy person. Hemoglobin from the red blood cells will pick up oxygen and has more space to expand- its compliance is more significant in the lower part of the lungs, so it permits greater gaseous exchange. For our optimal health, we need 95-100% oxygen saturation- the amount of available hemoglobin that bounds to oxygen. It is problematic for people with anemia.

Yoga therapy offers useful tools to respond to the individual needs to adjust the breath location, rate, and intensity as well as ratio. The most relaxing breathing rate is 5-6 breaths per minute. During this slow breathing, we keep CO2 at an optimal level, so that the blood doesn't become too acidic. Once we speed up the respiration, there's more CO2 in the blood, making it more acidic. That's why we expel more CO2 during exercise. It's a by-product of glucose use that we need to get rid of. It can become a vicious cycle for people with anxiety. People engaged in relaxation consume less oxygen, as they are in a parasympathetic state. The longer exhalation sends signals from the nucleus via the vagus nerve to drop the heart rate.
A yogic perspective on energy, breath, and alignment
Yogic philosophy's view on breath starts with the concept of energy. According to yogic texts, prana is omnipresent universal energy. On a macro level, this manifests in electricity, magnetism, and heat. In the human body, this refers to the subtle body, connecting to the networks of channels, resulting in the physical and mental processes influenced by the level of the flow of this energy. The quality of prana can differ and is prone to change. We can work with prana by breathing practices but also regarding its quality in the environment that surrounds us as well as food that we consume.
Other misalignments may lead to various disbalances and diseases, depending on location in the body. Prana is subdivided into five vauys (bodily winds): prana, apana, samana, udana, and vyana. Prana vayus, located between diaphragm and base of the neck, controls all the other in an upward motion and is responsible for respiration, heart, and lungs functioning, as well as circulation. Apana, located in the pelvic region, is responsible for elimination and excretion (functions of kidneys, bowel, and bladder). Samana, located between navel and diaphragm, has a balancing role between apana and prana as well as controls the digestive system and our metabolism. Udana is located in extremities (arms, legs, neck, and head) and controls our senses, movements, and speech. It's a link between the heart and brain. Vyana is pervading the whole body and provides us a "second wind".
The alignment of the energy in our bodies, according to the yogic model, is represented in various koshas (our sheaths of functioning). In manomaya kosha, it results in clarity of mind, in vijnanamaya kosha- in a clear insight and anandamaya kosha in a pure experience of bliss.
Our way of influencing the energy in various koshas and prana centers is through breath control- pranayama. It literally means the extension of the vital force through deliberate control of respiration. Its purpose is to purify the energy and liberate us so that it leads to the power of the mind (steady breath=steady mind). Pranayama has been treated as a preparation for meditation and has a broad spectrum of techniques (ujjayi, sitkari, sitali, bhastrika, bhramari, murcha, plavini).
The aim of purification through the breath is connected with another conceptual model of nadis. Nadis are portrayed as energetic channels in subtle bodies through which prana flows. It is a universal concept for yogic and Chinese medicine (meridians). According to this theory, there is a central channel- Shushumna nadi, as well as left (ida) and right (pingala) nadis. They all originate from the base of the spine (root chakra- muladhara). Shushumna flows directly upward and ida and pingala coil around the central spinal column in alternate directions, crossing at various chakras. Yogi's aim is to balance the flow of prana between ida and pingala so that they are unified in shushumna. Then one can achieve a state of inner peace, and kundalini can rise till crown chakra, resulting in a samadhi state.

Ida and pingala are opposing forces. Ida governs the left side of the body, is related to the lunar energy, and represents introversion, relaxation, cooling qualities. Pingala rules the right side of the body, is related to solar energy, adding more dynamism, heat and is energizing. Shushumna is active only when both sides are in balance – achieving physical and mental neutrality. Reaching the point of balance is possible via alternate nostril breathing or respecting the nasal cycle and adapting our activities accordingly to the dominant nostril (Swara yoga).
Yogic work with energy is then through various activities: dietary regulation, asana practice (physical blocks of energy), satkarmas, pratyahara, breath practices(pranayama) as well as visualizations, meditation, and concentration practices. Our overarching aim is to achieve balance in prana as a vitalizing force to achieve mental, physical, and emotional clarity.