[Here is an excerpt from my working draft of the forthcoming Better Breathing In Freestyle book. It’s going to be loaded with useful stuff you don’t commonly find in swimming books!]
There are two main gases that your exercising body needs to deal with. It needs to take in oxygen from the air and deliver it to your cells. And it needs to take carbon dioxide away from the cells and expel some of it from the body. But it is not that simple. The brain is carefully tracking the levels of these two gases in the blood and a certain balance is required between them to trigger the proper responses in the body. The two gases work together in a feedback system inside the body in a process known as the Bohr Effect.
When most people think of breathing distress, they may assume it is a result of insufficient oxygen – hypoxia – like what many high altitude mountain climbers experience when working long hours in thin air. And, it may also be commonly understood that the body needs to get rid of a build up of carbon dioxide or the muscles will start to feel sluggish and slow down. However, just as exercise distress can be triggered by too little oxygen or too much carbon dioxide, it can also be triggered by too little carbon dioxide in the system. That deficiency can be caused by breathing too frequently and too shallow – what is more commonly known as hyperventilation. In this mode of breathing you are you are giving off too much carbon dioxide too quickly (Fried, 1999, p. 26).
When athletic exertion starts, oxygen levels in the blood stream decrease and carbon dioxide levels increase and this triggers heavier breathing seconds later. Oxygen levels go down, but just by a small % – there is actually a great surplus still available in the blood that keeps you going even if you held breath for a while (this is one reason why a person doesn’t die immediately if their breathing stops). Some level of carbon dioxide is actually necessary in the blood, even at rest, and more is necessary during exertion. The first urges you feel for heavier breathing is the prompt to dispose of the excess amount of carbon dioxide, that which is above and beyond the necessary amount.
To keep relatively comfortable in athletic exertion, the body needs to keep the oxygen-carbon dioxide ratio in a certain range – not too much and not too little – and it does this best by using the proper breathing mode for that activity. Keeping that ratio within proper range at every effort level is not just a matter of breathing at the right frequency (how many times you take a breath per minute), but also by what kind and how much air is exchanged on each breath during those breaths – we might call this the ‘quality of the breath’. That quality is greatly affected by where the breath comes from – from thoracic breathing or from diaphragmatic breathing.
In his book The Oxygen Advantage, Patrick McKeown writes, “CO2 is the doorway that let’s oxygen reach our muscles.” (McKeown, 2015, p.23) A certain critical amount of carbon dioxide must remain in the blood to trigger a more abundant release of oxygen to the cells because “…hemoglobin releases oxygen when in the presence of carbon dioxide.”
In Breathe Well, Be Well, Robert Fried PhD writes, “In hyperventilation, so much carbon dioxide may be lost that blood becomes more alkaline (base) than it should be, and the magnetism of the hemoglobin molecules increases so that it may give up less oxygen to the tissues as it makes the rounds.” Furthermore, “…chest [thoracic] breathers must breathe more rapidly in order to maintain an adequate minute-volume rate. With their increased respiration rate, chest breathers are likely candidates for hyperventilation because they will expel more than the normal amount of carbon dioxide from their body.”
If you are one who feels like you are out of breath so easily and needs to take a breath every second stroke, even at your slower speeds, it is not certain, but it is possible that you are hyperventilating. The body is screaming for oxygen but not because there is too little available in the blood, but because the abundantly available oxygen is bound up in the hemoglobin and not being released due to such low carbon dioxide levels. Your breaths are frequent but unknowingly they are also quite shallow, thus giving off too much carbon dioxide, too quickly. It is not more breathing that will bring relief, but a different mode and quality of breathing. Deeper breaths, particularly from diaphragmatic breathing, could bring relief and allow even less frequent breaths.
Fried, R. (1999) Breathe Well, Be Well. New York, NY: John Wiley & Sons, Inc.
McKeown, P. (2015) The Oxygen Advantage. New York, NY: Harper Collins.
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