Mind & Body

The Navy SEAL 40% Rule Can Help You Achieve Mental Toughness

If you've ever run a marathon, survived a natural disaster, or given birth, you know that your body is capable of much more than you think. One U.S. Navy SEAL has formalized this idea into something many call the 40 percent rule. That is, when your mind says you're done, you're only 40 percent done.

Mind Over Matter

This inspirational principle comes to us not directly from the Navy SEALs themselves, but from a California billionaire. Jesse Itzler, founder of Marquis Jet and husband to Sara Blakely, the founder of Spanx, was running a 100-mile relay in San Diego with six other people when he encountered a 200+ pound Navy SEAL running the entire race on his own. Itzler swears the man had broken all of the bones in his feet and given himself kidney damage, but finished the race anyway.

That SEAL is named David Goggins, and some call him the toughest man alive: he's an Ironman triathlete who finished fifth in the 135-mile Badwater Ultramarathon in Death Valley and once held the record for most pull-ups completed in 24 hours. Itzler did what any billionaire worth his salt would do: he paid Goggins to live with him for a month and teach him his ways.

Things got serious on the very first day Goggins came to live with Itzler. Itzler said that the first thing Goggins did was ask him how many pull-ups he could do. Itzler recounted, "I'm not great at pull-ups. I did about eight...He said, okay, take thirty seconds and do it again. So thirty seconds later I got up on the bar and I did six, struggling. He said, all right, one more time. We waited thirty seconds, and I barely got three or four, and I was done." But he wasn't done. Goggins told him they weren't leaving until he did 100.

Itzler thought it was impossible, but he kept trying, one at a timeā€”and eventually succeeded. "...He proved to me right there that there's so much more, we're all capable of so much more than we think we are." Thus, the 40 percent rule. "He would say that when your mind is telling you you're done, you're really only 40 percent done."

David Goggins runs 135 miles through Death Valley, California in the Kiehl's Badwater Ultra Marathon.

What The Science Says

Though the 40 percent rule is mostly backed by anecdote, there is some scientific research to support it. A number of studies have found that the placebo effect has a big impact on sports performance. That is, if you think something will improve your performance, it probably will. That suggests that a good portion of your strength and toughness is mental, not physical. For example, a 2008 study published in the European Journal of Neuroscience found that when you give people a sugar pill and tell them it's caffeine, then have them lift weights, they can work significantly harder.

So whether or not the 40 percent rule is truly scientifically accurate, you can consider it your sugar pill. The next time you think you can't do any more, remember that you probably can.

Want to supercharge your life with more lessons from the SEALs? Check out "Extreme Ownership: How U.S. Navy SEALs Lead and Win" by Jocko Willink and Leif Babin. The audiobook of the bestseller is free with a trial of Audible. When you use this affiliate link, any purchases help support Curiosity.

Watch And Learn: Our Favorite Videos About Mental Toughness

Navy SEALs Have a '40 Percent Rule' And It's the Key to Overcoming Mental Barriers

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Jesse Itzler and David Goggins

Hear an interview with the two men on CBS This Morning.

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Written By Ashley Hamer February 6, 2017