REPORT. UTMB: How ultra-trailers are advancing sleep research

Filling their flasks with water, eating, listening to the words of encouragement from their family... But also, testing their reflexes for three minutes. At the back of the vast white tent that serves as a refreshment base in Champex-Lac (Switzerland), at kilometer 128 of the Ultra-Trail du Mont-Blanc , Saturday, August 30, trail runners take turns in front of small computers to click as quickly as possible when a red circle appears on the screen. "Wow, that's bad," one of them whispers.

Of the 2,492 UTMB starters, 60 had their cognitive performance tested along the entire 175.3-kilometer route (with 9,985 meters of elevation gain) through France, Switzerland, and Italy. Three hours before the start, and then after 82, 128, 145, and 168 kilometers, they repeated the same exercise. They also wore a sleep tracker on their wrists.

All are part of the study conducted by the team of researcher Rémy Hurdiel, who specializes in sleep in the context of ultra-endurance (trail running, cycling, sailing, etc.), and his English counterpart Charlotte Edelsten. The title of the study: The effect of napping on the cognitive performance of ultra-trail runners of more than 160 kilometers.

Of the 60 volunteers, 23 received sleep training beforehand, while the others formed the "control group," like Cédric Caset. A physiotherapist by trade, he agreed to join the study, even if it meant giving up three minutes of his time five times: "If I can help... And I'm not in a hurry, so I have time to do the tests," smiled the trail runner on the eve of his first UTMB, completed in 40 hours and 15 minutes. With their students, mostly from the Université du Littoral Côte d'Opale, the scientific duo wants to "accumulate as much data as possible and model it" to then make predictions.

"We're trying to understand the limits of human beings. We want to know how to assess fatigue and find the points of no return."

Rémy Hurdiel, sleep researcher

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Rémy Hurdiel is convinced that these findings can be transposed to other situations of sleep deprivation, citing the cases of shift workers, healthcare workers, and firefighters. "We're going to ask ourselves when to rotate the shift so that the firefighter can rest, for example. We'd like to create an alert threshold using an algorithm," he explains.

Since 2007, the UTMB organizers have allowed scientists to conduct studies. In nearly twenty years, some fifty French and foreign research projects have been conducted in various fields (nutrition, cardiology, injuries, women's health, etc.). "We select studies that can provide a concrete answer to a real problem on the ground," says Laurence Poletti, coordinator of the UTMB medical team. " We want them to be useful to runners."

So, while the "dodo team" welcomed its volunteers on the mezzanine of the bib collection area in Chamonix on Thursday, August 28, another group received its own for a Franco-American study on the exposure of ultra-trailers to UV rays. Rémy Hurdiel has been studying the sleep of UTMB participants since 2013, testing various aspects—this year, for example, the notion of pleasure was added. Twelve years later, "they're still just as stoned when they arrive," he says angrily. " Everything has progressed: nutrition, training, poles, shoes, but there's still a lot of work to be done on sleep," summarizes Charlotte Edelsten.

The researcher assures that runners – and human beings in general – do not realize the impact of sleep deprivation "It affects decision-making: wondering if you're cold to cover yourself, drink, eat. They're too tired to think about it. It also affects their mood. They'll make the decision to give up much faster," she explains .

"It's normal to be tired, but not to have hallucinations. There's a big lack of information."

Charlotte Edelsten, researcher

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To overcome this frustration of not seeing participants adapt their sleep strategy, the duo added an educational component to their study this year, with the support of the UTMB: they gave a masterclass on the subject, during a weekend in May in Chamonix, to 23 ultra-trailers. Proof of the community's interest, hundreds of applications were received. "I've always done things empirically. I thought it was nice to be able to learn things," recalls Hervé Conesa, 53. "This training taught me that it was counterproductive to push fatigue too far and that naps shouldn't be minimized."

For 36-year-old Marthe Ducret, the worry was about being able to fall asleep... and get up afterward. During the training weekend, the trail runner from Lorraine discovered that lying down wouldn't "stop her from setting off again." "It helped me take the drama out of it. I saw that just lying down rested my brain and relieved my stress," she recalls. Over her 42-hour effort, she managed to sleep for five, then twenty minutes. A small victory for someone who had once considered completing the UTMB without sleep. At the finish line, British runner Anna Kirkman also praised the benefits of her naps: "At Champex-Lac, you saw me grumpy. I finally slept twice for twenty minutes out of four attempts on the course. And I did well, afterward I was like a battery."

Always ready to offer advice to exhausted runners, slumped over tables at the Champex-Lac and then Trient, Switzerland, base camps during the second night of the UTMB, Rémy Hurdiel and Charlotte Edelsten are keen to bring their knowledge outside of academic circles. "Our philosophy is that knowing how to fall asleep quickly for a few minutes can be learned," explains Rémy Hurdiel.

While the educational component of their study is not included, the two researchers will keep a close eye on the performance of their trained volunteers to measure the benefits of the training. "We're doing a pilot study. The goal would be to build a training project so that the data can benefit the trail runners." After being useful to science, the trail runners could then benefit from what they have helped to discover.