Although we might think that to do physical exercise it is better to breathe through the mouth, if we expel the air through that route we run the risk of losing too much carbon dioxide and running out of breath
When we go for a run or we lift weights in the gym, we often worry about what clothes and shoes to wear, how to warm up the muscles or even how many heartbeats to achieve for the training to be effective. However, we tend to ignore the effect of breathing on physical performance.Science has a lot to say about how to get more out of our gym hours by paying attention to how we breathe.
Oxygenation mechanism during physical exercise
We are all aware that the mission of the respiratory system is gas exchange. That is, it is responsible for both obtaining oxygen (O₂) from the outside to produce energy and eliminating the waste product, carbon dioxide (CO₂). Therefore, it allows us to live.
But let’s break down the process more technically. Air enters through the nose, circulating through the airways to the pulmonary alveoli, where gas exchange takes place. From there, oxygen passes into the blood to be transported to all cells. At the same time, the CO₂ they produce is transported to the lungs for elimination.
This is how it works under normal conditions, but what about when we exercise? Well, the muscles work much more intensely, consuming more oxygen and producing more CO₂. The frequency goes from 15 breaths per minute at rest to 40-60 per minute in full activity. As a consequence, the amount of air that enters increases, which goes from 12 to 100 liters.
During this extra exchange of gases, our respiratory system is responsible for keeping the acidity of the blood constant, which is measured by pH, by expelling CO₂.
Another detail to take into account is that oxygen reaches the muscles through the blood thanks to the red blood cells (the “carriers” that transport it from the lungs), specifically through a macromolecule called hemoglobin. Well then, for an oxygen molecule to be captured by the hemoglobin in the red blood cells that pass through the lung, another CO₂ molecule is needed that allows the hemoglobin to release oxygen at the destination. Ultimately, it is the amount of CO₂ in the body that determines the correct supply of O₂ to the muscles.
If we breathe through our mouth we run out of breath
Now that we know about hemoglobin, we cannot forget about a key property: the Bohr effect. It refers to the fact that when we activate our body, there is an increase in CO₂ and, therefore, in hydrogen ions, causing the pH to become acidic. This makes hemoglobin capture oxygen with greater affinity, achieving a greater contribution of O₂ in those areas of our body where more CO₂ is released.
Therefore, by exercising, our body generates more CO₂, and the Bohr effect kicks in. In short, the Bohr effect allows our friend hemoglobin to release more oxygen the higher our activity.
For this reason, when it comes to breathing, we should not only be guided by intuition. Although one might think that for physical exercise it is better to breathe through the mouth, if we expel the air through the mouth we risk losing too much CO₂. In fact, when we get out of breath while exercising, it is not because our muscles get tired, but because they are not receiving oxygen well because they do not have enough CO₂ to exchange.
After reviewing the scientific works of recent years, a recent publication concluded that it is not so clear that it is good to use the mouth to breathe during sport. Furthermore, the evidence suggests that exclusively nasal breathing is feasible for most people at moderate levels of aerobic exercise without specific adaptation, and that this approach to breathing can also be achieved during intense levels of aerobic exercise.
Airways open more
Another reason to breathe through the nose is nitric oxide (NO), a vasodilator that is produced in the epithelial cells of the nasal cavity as air passes through. It is known that nitric oxide, among other functions, participates in chronic inflammation processes and in the modulation of lung function. And it is also a powerful vasodilator that diffuses very quickly, achieving a greater opening of the respiratory tract.
This is very important for people who suffer from exercise-induced asthma. In fact, it has been shown that this pathology is greatly improved by breathing through the nose.
With maximum effort, the mouth opens
We have explained that nasal breathing helps athletes to obtain better performance, especially when the effort is sustained and moderate. Although breathing through the nose takes less air into the lungs, the air supply is sufficient to maintain activity and does not seem to cause problems.
However, things change when more demanding conditions are reached. With maximum effort, athletes automatically switch their breath to the mouth. Interestingly, scientists have shown that this change occurs earlier in women than in men when the intensity of the exercise increases, and they explain it because women tend to have smaller noses.
In the most demanding and fastest race, the 100-meter dash, athletes breathe through their nose and mouth simultaneously. Of course, in just 10 seconds. It is enough to observe Carl Lewis or Usain Bolt in the Olympic finals to verify it.
The exception of yoga and pilates
There are two exceptions to the cases we have previously considered: yoga and Pilates. In these two modalities of physical exercise, breathing is a very important part, and its technique is the first thing that is learned. This is always of the nose-mouth type (that is, it is inhaled through the nose and exhaled through the mouth). This is especially important in the case of Pilates, with a very determined execution that involves (and shapes) the muscles that surround the rib cage, exercising them both when breathing in and out.
Using a technique called EMG or “electromyography” to measure muscle activation in real time, the beneficial effects of pilates breathing have been shown. Specifically, in elderly people there are studies that show the great benefit of Pilates breathing to encourage muscle activation when exercising. And the benefits go further: spinal alignment is also improved and loss of balance is avoided.
There is, therefore, no single answer to the question of how we should breathe during physical exercise: it depends on the type of activity. What we are convinced of is that the next time you listen to the explanations of your instructor or coach on how to breathe, you will not think: “what a heaviness” or “what else does it matter”. Because a good breathing routine will influence your performance.