The fuse in the heat chamber tripped at 135 degrees, just as the experiment ended at the University of Montana.
It was just as well: One of the world’s most dominant ultrarunners had met his match, his core temperature rising to dangerous levels, his heart racing and his pace slowing.
But did the test prove Scott Jurek to be superhuman?
The Weather Channel and its series, “Freaks of Nature,” will reveal the answer Sunday when it airs the episode featuring Jurek, one of the world’s top runners who is known for his ability to excel in extreme heat.
To test Jurek’s unusual skills, the show’s producers enlisted the help of Brent Ruby, director of the Montana Center for Work Physiology and Exercise Metabolism at UM.
Ruby took his classic Airstream trailer and crew to Death Valley in May to film the episode. He hasn’t seen the results, but he’s guessing the edited version of the show will present some freakish conclusions regarding Jurek and the tests.
“We went down there with the idea of doing some basic evaluations on the host of the show and placing him alongside one of the best ultramarathoners in the world,” Ruby said. “They wanted to showcase Jurek, given his success running in Death Valley.”
Located in southeastern California within the confines of the Mojave Desert, the valley holds the highest reliably recorded temperature on Earth – 134 degrees. In May, as the film crew rolled onto the scene, temperatures were already pushing the mid-90s.
Ruby’s crew outfitted Jurek with monitoring equipment to track his heat stress in real-time data. With the film crew in pursuit, the runner was put to the test, as was the host of the show. Jurek performed well – the host didn’t. Ruby said the results were expected.
“We monitored (Jurek’s) metrics to heat stress so we could tell the producers he was unusual,” Ruby said. “He’s just very well acclimatized to those settings. They made it seem as if it was crazy hot. It was in the mid- to upper 90s.”
While 90-degree temperatures are hot indeed, they weren’t warm enough for the producers to declare Jurek a freak of nature. For that, the crew would follow Ruby and company back to UM and the center’s regulated heat chamber.
In the chamber, Jurek began running in temperatures starting in the mid-90s, similar to those in Death Valley. The mercury climbed over the next 60 minutes as Ruby monitored the athlete’s physiological response to the increasing heat.
In the end, Ruby said, the runner cracked as temperatures reached 135 degrees. The lab shut the experiment down for safety reasons, just before the fuse tripped. The equipment wasn’t rated to go that high, Ruby said, and neither was Jurek.
“He had to lower his pace and yet his heart rate kept driving up,” Ruby said, adding that Jurek’s core temperature had climbed to 104 degrees. “That’s about the limit we allow people to get in our chamber.”
While Jurek is acclimated to perform well in the heat, Ruby said the ultrarunner cannot avoid the effects of external temperatures and the slow toll they take on the human body.
“When it gets that hot outside, he’s not unloading heat, but rather, he’s collecting heat from the environment, plus the heat he’s producing,” Ruby said. “The body is always producing heat as a function of normal metabolism, and you have to offload that heat.”
The only way to expel that building heat, Ruby said, is to seek shade or slow down. Sweating, he laughed, is a gift to the human species.
“Humans are the best around at thermal regulation,” Ruby said. “Jurek is so smart because he has been there hundreds of times. He knows how it feels and what to do when it gets that hot.”
Ruby won’t go so far as to call Jurek’s ability superhuman. Yet he admits the ultrarunner possesses unique abilities — something Jurek has proven while competing in temperatures most would consider unbearably hot.
Jurek is among the most dominant long-distance runners in the world. He has won the sport’s most prestigious races multiple times, including the Badwater Ultramarathon – a 135-mile dash through Death Valley.
“He definitely is very well acclimatized to that setting because he has put in the time training in it,” said Ruby. “He brings to the table just a very well-tuned aerobic system. If you’re an aerobic animal, you have a protective capacity to endure the heat.”
The "Freaks of Nature" episode featuring Jurek and Ruby is set to premier on The Weather Channel on Sunday at 8 p.m. Mountain Time.