Outlive: The Science and Art of Longevity: The Million-Copy Bestseller

by Peter Attia

Let’s say I’m just sitting on the couch, watching a movie. At rest, someone my size might require about 300 ml of oxygen per minute in order to generate enough ATP, the chemical “fuel” that powers our cells, to perform all the physiological functions necessary to stay alive and watch the movie. This is a pretty low level of energy demand, but if I go outside and jog around my neighborhood, the energy demands ramp up. My breathing quickens, and my heart rate accelerates to help me extract and utilize ever more oxygen from the air I breathe, in order to keep my muscles working. At this level of intensity, someone my size might require 2,500 to 3,000 ml of oxygen per minute, an eight-to tenfold increase from when I was sitting on the couch. Now, if I start running up a hill as fast as I can, my body’s oxygen demand will increase from there: 4,000 ml, 4,500 ml, even 5,000 ml or more depending on the pace and my fitness level. The fitter I am, the more oxygen I can consume to make ATP, and the faster I can run up that hill. Eventually, I will reach the point at which I just can’t produce any more energy via oxygen-dependent pathways, and I’ll be forced to switch over to less efficient, less sustainable ways of producing power, such as those used in sprinting. The amount of oxygen that I am using at this level of effort represents my VO2 max. (And not long after that, I will “fail,” meaning I am no longer able to continue running up the hill at that pace.)