27 April 2026 · Dr. Lara Pajk · 8 min read · science
CO₂ Tolerance: The Overlooked Fitness Marker
Most people think breathing is about taking in more oxygen. The deeper truth is the opposite: it's about tolerating more carbon dioxide.
Here is a counterintuitive truth that quietly transforms how athletes train and how anxious people heal: the urge to breathe is not driven by lack of oxygen. It is driven by the build-up of carbon dioxide. The fitter your nervous system, the more CO₂ you can comfortably tolerate. The Bohr effect CO₂ is not waste gas. It is the molecule that tells your red blood cells to release their oxygen into…
Tags: CO2, oxygen, performance