In Part 1, we discussed why the nose is so important in breathing and what the health benefits are to nasal breathing.
Today, we will look at the relationship between oxygen and carbon dioxide when it comes to efficient oxygen uptake and how a low tolerance to Carbon Dioxide will impede athletic performance.
First, we need to understand a process called the Bohr Effect which describes how the pH of the blood impacts the affinity of oxygen to hemoglobin. When the pH of the blood drops, it becomes more acidic and oxygen is more readily released by hemoglobin so our cells can use it. Conversely, as the pH rises and becomes more alkaline, hemoglobin will hold onto oxygen so our cells cannot use it.
Carbon dioxide is one such gas that makes the blood more acidic. Therefore the more carbon dioxide there is in the blood, the more readily oxygen is released from hemoglobin for our cells to use.
The rate and volume of breathing are determined by receptors in the brain that are sensitive to levels of carbon dioxide, oxygen, and blood pH level. When carbon dioxide rises and blood pH falls, we are stimulated to increase our rate of respiration to expel the carbon dioxide. Crucially, some carbon dioxide is retained in the body and correct breathing patterns rely on this.
Those who over-breathe (habitual mouth breathers) have a habit of breathing more air than is required and too much carbon dioxide is expelled. When this habit lasts for weeks, months, or years, it results in the body having chronically lowered levels of carbon dioxide which causes our brains to develop an increased sensitivity to lower levels of carbon dioxide.
Carbon dioxide is a by-product of metabolism; as our activity levels increase, so does the production of carbon dioxide. If we have a lower sensitivity to carbon dioxide then lower levels of intensity will cause us to breathe more heavily, pant, struggle to breathe, and ultimately "gas out" much earlier than we should.
You may be thinking that breathing more heavily gets us more oxygen, but this is not quite the case. Blood oxygen saturation is the percentage of oxygen-saturated hemoglobin relative to total hemoglobin in the blood. In normal folks, it sits between 95-99% regardless of whether we are at rest or undergoing intense exercise - it is very carefully regulated. What this means is that even under increasing levels of intensity our blood does not carry more oxygen.
To truly develop our aerobic system’s efficiency, we need to increase our tolerance to carbon dioxide and use breathing mechanics appropriate for the level of intensity.
Whilst we will discuss breathing mechanics during exercise more in our next blog post, it is worth noting that breathing through the mouth is appropriate at certain times, but to be able to control our use of our energy systems, we need to learn to control our breathing.
So, how can you tell if you have a problem with carbon dioxide tolerance? You can perform the following test below, all you need is yourself and a stopwatch…
Find a comfortable sitting or lying position
Breath in and out through the nose for 1-2 minutes
When you are ready, perform a full exhale, hold your breath and start the timer.
When you feel the need to breathe in, stop the timer.
If your timed exhale breath-hold is less than 20 seconds you have a very low tolerance to carbon dioxide which will be having an adverse impact on your general health and your performance in the gym.
Stay tuned for the next blog in the series to learn how we can begin to address this!