Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance

by Alex Hutchinson

In a wide variety of human activity, achievement is not possible without discomfort.

The limits of endurance running, according to physiologists, could be quantified with three parameters: aerobic capacity, also known as VO2max, which is analogous to the size of a car’s engine; running economy, which is an efficiency measure like gas mileage; and lactate threshold, which dictates how much of your engine’s power you can sustain for long periods of time.

endurance is “the struggle to continue against a mounting desire to stop.”

What’s crucial is the need to override what your instincts are telling you to do (slow down, back off, give up), and the sense of elapsed time. Taking a punch without flinching requires self-control, but endurance implies something more sustained: holding your finger in the flame long enough to feel the heat; filling the unforgiving minute with sixty seconds’ worth of distance run.

This is why the psychology and physiology of endurance are inextricably linked: any task lasting longer than a dozen or so seconds requires decisions, whether conscious or unconscious, on how hard to push and when.

“The machinery of the body is all of a chemical or physical kind. It will all be expressed some day in physical and chemical terms,” Hill had predicted in 1927. And every machine, no matter how great, has a maximum capacity. Worsley, in trying to cross Antarctica on his own, had embarked on a mission that exceeded his body’s capacity, and no amount of mental strength and tenacity could change that calculation.

“He’s a very strong personality, and he gets these really neat, innovative ideas, but instead of saying, ‘Wow, I’ve found a better way to explain this,’ he says, ‘Everybody else is wrong.’”

“Do you notice he’s not dead?” he’d say, pointing at Lee. “What does that tell you? It means he could have run faster.”

First, the limits we encounter during exercise aren’t a consequence of failing muscles; they’re imposed in advance by the brain to ensure that we never reach true failure. And second, the brain imposes these limits by controlling how much muscle is recruited at a given effort level

Just like a smile or frown, the words in your head have the power to influence the very feelings they’re supposed to reflect.

This shows that simply getting fitter doesn’t magically increase your pain tolerance. How you get fit matters: you have to suffer.

If you want running at 5:00-mile pace to feel easier, you should head out the door and run at 5:00-mile pace—a lot. Over time, your heart will get stronger, your muscles will grow more energy-producing mitochondria, and you’ll sprout new capillaries to distribute oxygen-rich blood. These changes will allow you to sustain 5:00 pace with less physiological strain, and they’ll also attenuate the distress signals that your muscles and heart send back to the brain. The pace will feel easier, so you’ll be able to sustain it for longer.

anything that moves the “effort dial” in your head up or down will affect your endurance, even if it has no effect on your muscles or heart or VO2max.

“If you’re being chased by a lion, or a car falls on a baby, you find something extra,” she said. “I think we’re just touching the iceberg of ‘How do we train that?’”