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

by Scott Carney

Now, instead of taking in a deep breath and holding it, let most of the air out of your lungs like you would at the end of a normal breath (by which I mean, don’t force it) and hold your breath with mostly empty lungs. Your body will quickly deplete the oxygen stores available in the lungs and have to rely solely on what is available in the bloodstream. When you get close to needing to gasp, you can extend your limits in two ways. The first is the same as with basic breathing, slowly letting out what is left of the air in your lungs. The second method will become critical later for controlling vasoconstriction. It consists of a rolling set of muscle contractions that you start at your feet and sequentially tighten until you reach up to your