What Doesn't Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength

by Scott Carney

The urge to gasp for air is not directly linked to the amount of oxygen in the bloodstream. That’s because, for some reason that has been lost in the convoluted process of evolution, the body cannot sense oxygen, only its byproduct. Breathing is a two-part process—inhaling to bring oxygen to the lungs and exhaling to expel carbon dioxide (CO2). When the brain senses too much CO2 in the bloodstream, the chest tightens, vision blurs, and just about every muscle from the abdomen to the forehead clenches down hard. When we talk about this sensation we usually say that we need to take a breath. However, on a physiological level your body wants to expel CO2. It sounds counterintuitive but it’s easy enough to test. Take a deep breath in and hold it until you feel the urge to breathe. Then release a little bit of air. With less CO2 in your lungs you will feel like you can hold your breath a little bit longer. That’s because you’ve removed a potentially poisonous waste product from your body and your nervous system has turned off the alarm bells.