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The "Why" Behind Nasal Breathing

Updated: May 12, 2020



I was first introduced to this topic when I was reading through Cal Dietz' work years ago. He frequently referenced conditioning methods involving taping his athlete's mouth shut. I could't help but think:

Couldn't this be dangerous?

How important might this be if he's taken the time to convince all these kids to tape their mouth shut?

I've got to learn more about this.

Luckily, Cal referenced a great resource to learn more about the topic, The Oxygen Advantage by Patrick McKeown. I immediately purchased it and read through it in a matter of days. It's truly a great read that requires no scientific background to grasp and understand. I would recommend it if any of the below details or future blog posts interest you.


The premise comes down to the way that we tolerate carbon dioxide (C02) in our system. As you may know, our body relies on our respiratory system to bring in oxygen and expel C02. What is lesser known is that C02 is the most relevant part of that equation when it comes to our breathing and our training.


Oxygen is extremely abundant in our blood with a normal blood oxygen saturation of 95-100%. Personally, mine has always measured at 97-99%. A lot of phones have a blood oxygen saturation measurement tool and you can test yourself. Try testing at rest then begin a high intensity workout. Are you able to drop the measurement 1-2%? You may be shocked at how much effort is required to make such a small change. Alternatively, you could try doing a series of breath holds to see what changes that makes. Again, you may be surprised how little it changes. (I cannot attest to the accuracy of the sensors built into phones but it is an easy way to experiment).


C02, on the other hand, is what your body is on high alert for. The mechanism in your brain that forces you to breath against your conscious will when holding your breath is also the mechanism that increases your breathing rate when you exercise. That mechanism is triggered by high C02, not low oxygen. Now, consider what the limiting factor to your endurance is. When you play your sport or go for a long distance run is it the muscles in your legs that get so sore you can't continue, or is it your breathing that gets so heavy you have to slow down? Chances are it's the later. Therefore, one of the best things we can do for our aerobic fitness and sport endurance is increase our tolerance to C02. In other words, delay the mechanisms in our body that freak out in response to elevated C02 levels.


This brings us to the root of the issue, our daily breathing habits. Mouth breathing during the day and mouth breathing while you sleep cause us to over breath. Most people do one or the other, if not both. Remember, C02 is the most relevant factor. When we breathe through our mouth we are breathing too much air at too fast a rate. This doesn't change our blood oxygen saturation because under normal conditions we are already maxed out (do you really need to get from 98% to 99%? You wouldn't notice this change anyway.) Instead, by over breathing you're emptying your blood of C02. When you do this day after day you naturally decrease your bodies tolerance to high C02 levels because there's never any exposure to significant C02 in the blood. Heavy breathing causes low C02 tolerance, which causes us to breathe heavier and the feedback loop continues.


Here lies another interesting issue; when C02 levels are low we actually limit the availability of oxygen in our cells. When oxygen travels through our bloodstream attached to red blood cells there is a positive correlation between C02 levels and the oxygen's ability to separate from our red blood cell and enter our tissues. In other words, as C02 levels rise oxygen is more readily available to the cells in our muscles, organs, and other vital tissue cells. As C02 levels decline, as with over breathing, oxygen clings to our red blood cells harder making it functionally useless. This leads to another counter-intuitive fact, breathing less causes more oxygen to enter our tissues where we need it most.


Let's move on the the practical side of things. What can you do today to begin increasing your C02 tolerance?


Disclaimer: The recommendations below are meant to be educational in nature only. It is up to you to consult a physician before attempting any of the exercises/techniques and consider any conditions you may have (ex: asthma) that may compromise your ability to safely participate. With that said, these techniques are widely considered beneficial for asthmatic symptoms (I may or may not have helped someone with severe asthma with some of these principles). Be smart, be safe, and seek proper supervision/guidance.


You can begin by testing your BOLT (Blood Oxygen Level Test) Score. Here's the protocol:

  1. Rest up to 10 minutes before testing to ensure an accurate resting measurement.

  2. Take a small/natural breath in followed by a small/natural breath out. Do not breathe in or out too deep here.

  3. After your small breath out pinch your nose and hold your breathe. Use a timer to track duration starting from the breathe hold.