Building tolerance to carbon dioxide

Building tolerance to carbon dioxide (CO2) is a simple and effective way to leverage the Bohr effect (see my last post), improve our well-being, and boost athletic performance. But what is CO2 tolerance?

We all know someone who gets short of breath quickly–perhaps climbing a couple of flights of stairs or even walking to the water cooler. Fitness and CO2 tolerance are related but separate–being out of breath doesn’t always mean that you are out of shape. Contrast this with freedivers who have high CO2 tolerance that supports long breath holds and relaxation.

When you hold your breath, the discomfort you feel comes from the chemoreceptors in the brainstem reacting to the buildup of CO2 in your blood, which lowers blood pH. Despite what many think, it’s not caused by your body craving oxygen. The desire to breathe is the brain signaling that it’s time to expel the excess CO2 and bring more oxygen into the system. In plain speak, the more CO2 you have in your system, the higher the compulsion to breathe. The higher your tolerance to CO2, the longer it takes for that compulsion to kick in. 

The good news is that you can increase your CO2 tolerance–unless you’re already an elite freediver, in which case, great work! Our base tolerance will dictate how we approach training. If the only exercise you have done in the last six months is walking to the washing line, your first run wouldn’t be a marathon. Likewise, if your CO2 tolerance is low, the exercises you start with will be short and low-stress. The latter point is important. Suffocation is a primal fear and breath-holding can cause anxiety attacks in some people. If you’re prone to anxiety or aren’t sure if you might be at risk, seek help from a breathing coach before you attempt any kind of breath holds. 

Improved CO2 tolerance also has the added benefit of reducing the load on your diaphragm. This is important because the diaphragm is a key stabilising muscle–forget the six-pack abs, work the diaphragm. It works with the pelvic floor, deep core muscles, and deep back muscles to create stability. However, when it tires it defaults to its primary role of breathing and we lose stability. If you’ve ever been running and felt like you were sinking, there’s a good chance your diaphragm stopped performing its role as a stabiliser.

For those wanting to improve their tolerance, breath holds of only a few seconds while seated might be your starting point. In contrast, a person with high CO2 tolerance might do breath holds during a HIIT workout. Ideally, do a breathing assessment with a coach before you start. Whoever you are, a good starting point is nasal breathing. From there, various breathing exercises can be added, and ultimately mixed with exercise.

As your CO2 tolerance increases, so will your efficient use of oxygen–remember the Bohr effect? Your endurance will improve, and as your desire to breathe is reduced, you will take fewer breaths. The result? You won’t feel as breathless and will be able to exercise for longer with better form. And for those who don’t want to run a marathon or go to the gym, the benefit might be as simple (and life-changing) as walking a flight of stairs without becoming short of breath.

In my next post, I’ll reveal other amazing benefits of CO2 training–yes, there’s more.

This blog is for informational purposes only. It is not medical advice. Always consult a healthcare professional for personalized guidance and treatment.