This Race Tests the Limits of Human Endurance

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The forbidding Montane Yukon Arctic Ultra race provides more than just an athletic challenge. Here’s what scientists are learning from the event.

When you race 430 miles across the Yukon, you learn a thing or two about yourself. In taking part in the Montane Yukon Arctic Ultra (MYAU) on four different occasions, 33-year-old Jessie Gladish has learned that she enjoys the challenge of making her way across the frozen terrain. She’s also learned that it allows her a sense of freedom she can’t find anywhere else. Scientists recognize this, too, and for the past four years, have studied the athletes who take on this beast of a race, and the impact its conditions and demands place on their bodies.

“I like the feeling of pushing past discomfort, reasonable pain, mental suffering, and physical suffering,” Gladish said. “I feel stronger and more confident. I like being alone and dependent on myself; I do my best work when I don't have distractions or external pressures/ideas/thoughts.”

February marked the 16th year of the MYAU, which bills itself as the world’s coldest and toughest ultra. It follows the Yukon Quest Trail, one of the world’s most difficult sled dog races and offers distances including a marathon, 100 miles, 300 miles, and every other year, the 430-mile option.Athletes cover the distance by fat-tire mountain bike, cross-country ski or by foot, with the help of snowshoes.

This year, a total of 76 athletes participated in the events, 60 of them men and 16 women, representing 20 different countries. Gladish was one of 40 competing in the longest distance and one of 12 who finished.

Grueling race conditions make the MYAU a prime environment for discovering what humans are physically capable of. For the fourth consecutive year, researchers studied participants throughout the race, monitoring their energy expenditure, body composition, sleep and heart-rate variability. The study was originally launched by Mathias Steinach of the Center for Space Medicine and Extreme Environments Berlin, but for the third year in a row, Robert Coker with the Institute of Arctic Biology at the University of Alaska assisted.

Coker is interested in learning how the human body can operate efficiently under such difficult conditions; he hopes the results may be applied to other harsh environments, as in space or military missions.

“Initially, I was interested to see whether lean tissue mass would be preserved under these challenging conditions,” he said. Coker’s early results suggest that human bodies can adapt rather quickly to manage extreme conditions. In 2017, for instance, he found that in spite of running at a 2,000 calorie per day deficit (they burned approximately 6,000 calories per day and ate only 4,000), the athletes were able to maintain their muscle mass.

Made for research

In this latest study, Coker was focused on drilling down on how much food the athletes would need to consume during the race to perform at a high level in challenging environments.

The cold and stress of the race through the Yukon has implications for astronauts in space, where food is readily available, but the conditions are taxing. “We are working to expand the bandwidth of astronaut capacity in space. How far we can go and how much we can do in space will be directly proportional to our ability to sustain our metabolic requirements,” Coker said.

This year marked Gladish’s first year trying the race on cross-country skis; her previous three races were on foot (she completed the 430-mile distance twice and the 300-mile distance once). She finished out in twelve-and-a-half days, the only cross-country skier to reach the finish line.

Also competing in the 430-mile event this year was 33-year-old Gillian Smith, a critical-care flight nurse who, like Gladish, lives in the Yukon. It was her second attempt at the full distance, having not finished last year due to health issues. She completed the 100-miler in 2016. “I feel like I have an advantage because I live and train here,” she said. “I have a lot of experience with the weather and can practice layering my clothes and understand what freezes and what doesn’t.”

Most competitors pull sleds weighing up to about 75 pounds in order to carry all their gear and be self-sufficient in any situation. There are checkpoints about every 50 kilometers along the route, and Smith said that amounts to encountering about one a day.

“I bivouacked by the lake one night and when I got up, there were fresh wolf tracks all around my camp ... I just kept going and tried not to think about it.”

While there are numerous challenges for each athlete, Smith said it’s the isolation that gets to her most. “You’re out there by yourself and face a lot of stressful moments,” she said. “You have to manage your fear.”

Even the most adept and confident, like Smith, have their moments. “I bivouacked by the lake one night and when I got up, there were fresh wolf tracks all around my camp,” she said. “I just kept going and tried not to think about it.”

Athletes make their way through the brutal conditions of the Montane Yukon Arctic Ultra.

Athletes make their way through the brutal conditions of the Montane Yukon Arctic Ultra. (Photo Credit: Mark Kelly and MYAU)

After the race, athletes receive the results of their own personal blood draws, which researchers take four times along the way. Both Gladish and Smith were among the 20 participants in the research this year, plus six individuals—aid-station volunteers—who served as sedentary controls, receiving testing at the same intervals as the athletes.

Coker is unsure how the two groups will compare. Gladish wants to learn what she’s doing to and for her body in these events. “Am I pushing it too much?” she wondered. “Does it make me healthier to do long distance racing, or not?”

While the 2019 research results aren’t in yet, Coker said that both researchers and athletes can take away these key points from past results:

  •     The athletes are able to maintain their lean muscle mass throughout the event, something the researchers didn’t expect. The study revealed that, on average, the race athletes consumed about 4 kilocalories or 4,000 calories per day, according to Coker. After researchers comb through the data, they hope to have further details on what macronutrients those calories were comprised of.
  •     Those with low body-mass indexes (a measure of body fat based on body weight relative to height) of 18 and below didn’t fare as well as those in the 23 to 24 range, which suggests higher fat composition is a bonus here.
  •     At earlier checkpoints, athletes showed an elevated rate of fat metabolism, which settles back down the longer they are out there, suggesting the body is efficient at using the nutrients that are available.

Over the history of the race, fewer than 50 percent of MYAU athletes usually finish out their events, despite excellent preparation. “We’ve learned that humans can endure a tremendous amount of physical and environmental stress,” said Coker.

Due to the fewer number of female athletes, Coker said, there’s work to be done to determine if there are significant differences between how women and men perform under the taxing race conditions.

But when the final 430-mile results were tallied, only women finished.

For her part, Gladish hopes to return to the 430-mile distance at least once more, this time in the only mode she has yet to try: a bike. “Distance racing, I’ve discovered, is never enough,” she said. “I always want to go further and do another.”

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