Most athletes would agree that lactic acid build-up in the muscles is the bane of all long-distance runners - but not American jogger Dean Karnazes.
The 53-year-old has a rare genetic condition that rapidly flushes lactic acid from his system, allowing him to run indefinitely without ever experiencing a cramp or a seized muscle. The extreme runner has completed a marathon to the South Pole at -25C, and completed 50 back to back marathons in 50 days. He's also jogged a whopping 350 miles in just 80 hours and 44 minutes, without any sleep!
When people exercise, glucose is converted into energy and a by-product of this reaction is lactic acid. As it builds up in the muscles, it causes cramps and fatigue, and signals the brain to stop. But in Dean's case, he never receives those signals because lactic acid never builds up in his muscles. So he's able to run for long distances over very long periods of time, giving him an edge in some of the toughest endurance competitions in the world.
"At a certain level of intensity, I do feel like I can go a long way without tiring," Dean said, speaking to The Guardian. "No matter how hard I push, my muscles never seize up. That's kind of a nice thing if I plan to run a long way. To be honest, what eventually happens is that I get sleepy. I've run through three nights without sleep and the third night of sleepless running was a bit psychotic. I actually experienced bouts of 'sleep running', where I was falling asleep while in motion, and I just willed myself to keep going."
Dean has been running since childhood, having discovered his extraordinary ability for endurance at a very early age. He ran a total of 105 laps around his high school's track at a fundraiser, while most of his classmates gave up after 15. But he did stop running after high school, returning to the activity only after his 30th birthday. Despite the gap in training, he was able to simply pick up where he left off, covering 30 miles in his very first run. Of course, he did suffer blisters, but his muscles showed no signs of tiring or slowing down. Since then, Dean has performed incredible feats such as completing the 200-mile 'Relay' from Calistoga to Santa Cruz all by himself. He did this no less than 11 times.
Amazed by his physical abilities, doctors have performed lactate tests on Dean to find out how long it takes for him to reach his threshold for lactic acid. The test usually ends in 15 minutes for most athletes, but in Dean's case, the doctors simply had to give up after an hour. Other runners do develop a better lactic acid threshold after years of practice, but in Dean's case, he appears to have been born with the ability to flush it out of his system.
"I was sent to a testing center in Colorado," Dean explained. "First, they performed an aerobic capacity test in which they found my results consistent with those of other highly trained athletes, but nothing extraordinary. Next, they performed a lactate threshold test. They said they would take it to 15 minutes, tops. Finally, after an hour, they stopped the test. They said they'd never seen anything like this before."
Dean, a father of two, believes other factors are at play here as well, like his low body fat percentage and his high alkaline, paleo-style diet. He almost always focuses on endurance and not speed. "I don't care how fast I go," he said. "I care about how far I go."