The Science of Breathing

Breathing, called ventilation in western medical science, has two phases: inspiration and expiration. During inspiration, the diaphragm and the muscles between the ribs, specifically the external intercostals, contract. The diaphragm moves downward and the external intercostals pull the ribs up and out, thereby increasing the volume of the chest cavity. This increase in volume lowers the air pressure in the lungs relative to the air outside the body. Air flows from regions of high pressure to regions of low pressure, so air is drawn into the lungs via the nose or mouth. With expiration, the diaphragm and external intercostals relax, thereby decreasing the volume of and increasing the pressure within the chest cavity. Air is pushed from the lungs to restore the pressure equilibrium until it all starts again with the next inhalation.

With each breath, respiration occurs. Respiration is the exchange of gases between the lungs and blood. The lungs are full of tiny capillaries containing blood from the pulmonary arteries. Oxygen from the air is loaded onto red blood cells and carbon dioxide is unloaded to be exhaled out of the body. This oxygenated blood flows back to the heart via pulmonary veins, which then pumps it out to the body. Oxygen is crucial for proper metabolism on a cellular level, while carbon dioxide is critical for achieving adequate pH levels in the body. In response to a change in blood gases, the pulmonary system adjusts breathing patterns to maintain a strict balance. Exercise, for example, raises carbon dioxide production and increases oxygen consumption. Should the available oxygen fail to meet the demand, energy production declines. Likewise, if carbon dioxide accumulates within the body without proper disposal, the blood becomes acidic and cellular damage occurs, leading to organ failure.

So how do our bodies control breathing? Our brainstems have a respiratory center, which is involuntary, automatic, and continuous. The regulation system between oxygen, carbon dioxide, and blood pH described above is called the metabolic control of breathing. However, breathing can also be voluntarily controlled. This behavioral control center of breathing is located in the cortex of the brain. Speaking, singing, and playing an instrument (like clarinet for instance) are good examples of behavior controlled breathing. In yoga, pranayama is a popular form of behavior controlled breathing. Pranayama is the practice of voluntary inhalation, retention, and exhalation that can be performed at certain paces. The word ‘prana’ refers to the life force or energy and ‘yama’ refers to control or practice. There is a direct connection between the energy of breathing (prana) and its effects on energy in the body. While the purpose of pranayama is not to override the body’s autonomic systems, there is evidence that pranayama breathing techniques can affect oxygen consumption and metabolism. It appears to shift the autonomic nervous system away from its sympathetic (fight or flight) dominance. Pranayama breathing has been shown to positively affect immune function, hypertension, asthma, and stress-related disorders. It should be noted that some of the pranayama breathing techniques can be quite complex to learn and often require practice outside of yoga. In fact, some studies have shown that fast breathing pranayama can cause hyperventilation, activating the sympathetic nervous system, and stressing the body more.

The bottom line with breathing is that we have to be able to expand the chest cavity, no matter whether the breath is controlled or involuntary. The ability to expand the lungs 360° often boils down to posture. Inviting breath through good posture is a great place to start! So, join me on the mat and just breathe. :)