Getty Images / JEFF PACHOUD / Contributor

A marathon isn't enough anymore. Around one million people took part in the 42.1 kilometre distance in 2018 but ultramarathons are of running’s fastest growing fashions: participation is up more than 1,000 per cent over the last two decades. The business of ultramarathons is booming.

They can range from 50km races to hundreds of kilometres lasting over multiple days. Some of the most taxing races last for times – how far can you run in 24-hours – than set distances. To win: run further, or for longer than anyone else.


At the sport’s highest level is a new breed of professional, full-time runners who specialise in running super long distances. They run for hours at speeds many recreational runners can only sustain for five or ten kilometres and in the process push their bodies, and minds, to previously unreached levels. The men’s 160km (100 mile) world record has an average pace per kilometre of four minutes and 14 seconds. In comparison, the average UK 5km pace for men is a sluggish 5:50 per kilometre.

“Every single world record I have set hasn’t been a perfect race,” says US runner Camille Herron, who holds records over 80km (50 miles), 160km (100 miles), 12 hours and 24 hours. In the last of these, set at the end of 2019, she ran 270.116km at a pace of 5:20 per km. In preparation for these long distance races, athletes often don’t practice running anywhere near the time or for the distance that they will need to do on the race day.

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But elite runners training for ultramarathons do run a lot. Ahead of Herron’s 24-hour world record, she ran around 1,000 miles in two months of training. To build up for the race she spent 15 weeks preparing – the first month of this was spent regaining fitness after a period of rest. Herron says the longest runs she will do as part of her training reach around 32-35km, as she doesn’t get much benefit from running longer. Overall, she runs around 160km to 190km per week.

Herron puts her success down to repeated speed workouts, which are scattered between runs that help build up overall mileage. To build strength she will practice running for short intervals such as 90 seconds at a very fast pace, followed by a short rest. This process can be repeated up to 16 times in one workout. Other sessions include longer intervals – running one to three miles at speeds that would be closer to Herron’s 5km, or faster, average pace. There are also segments of her runs where she hits 80 to 90 per cent of her maximum heart rate.


So what’s the point of running so fast when during the gruelling demands of an ultramarathon, runners will be travelling at much slower average paces? Research has found that the fastest runners over shorter distances will have a greater chance of winning ultramarathons. Two studies have suggested that there’s a strong association between fast marathon speeds and the ability to sustain performance over much longer distances. (Other factors also make a difference, such as the number of miles run and physiological characteristics). “It helps to raise my ceiling on my upper-end leg speed,” Herron says.

There’s another big reason why ultrarunners don’t do huge training runs: the impact it has on their bodies. A literature review of ultramarathon research, which looked at 700 previous studies, highlighted some damning potential physical issues. These include potential problems with skeletal muscles, the heart, liver, kidney, plus immune and respiratory issues. “Undoubtedly, the completion of an ultra-marathon has no immediate health benefits,” it says. The physiological benefits of running long distances diminish after around 48km.

How ultrarunners are pushing the human body beyond all limits Long Reads How ultrarunners are pushing the human body beyond all limits

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American ultramarathoner Jim Walmsley perhaps logs more miles than any other runner. Since the end of November, the fewest kilometres he has ran per week is 136. However, most weeks are in the mid-190s with two weeks peaking at 280km each. “I do mostly volume based training,” Walmsley says, preferring longer runs over shorter intense workouts. This involves multiple runs per week that are around the full marathon distances (42km). “You have to sharpen up before the race,” he says. “I’ll do one to two proper workouts [per week].


If runners do include ultra-long runs as part of their training, they’re often designed to help practice the type of food that they will be eating, running while carrying extra clothing in a pack, and spending elongated periods of time on their feet. “In general top pros are getting much better at periodising their training,” Walmsley adds. “You’re doing specific blocks for a specific big race.” In reality this means that elite runners are planning out their training into blocks. They’ll have two to three target races per year and tailor their training to that. This weekend, Walmsley run in the US Olympic marathon trails and says this feeds into his other big goal for this summer of running the Comrades ultramarathon. It’s the biggest ultra in the world – with around 25,000 participants – and unlike a lot extreme races is run on the roads for all of its 90km length. “The types of races I like to choose are generally going to build off of each other,” he explains.

All the athletes spoken to for this article also pay attention in their training to the course that they’re going to be running on. Unlike traditional marathons, which are mostly ran on asphalt roads that are as flat as possible, ultramarathon courses can be hugely varied. They can be muddy, involve running through sand, and sometimes energy sapping river crossings. If an athlete is preparing for a mountain race, they’ll add plenty of hill sessions to their training regime to build strength. They want to simulate the course they’ll be racing on as accurately as possible. Ahead of his first 161km race, top British ultrarunner Tom Evans calculated the length and gradient of the courses’ three major uphill climbs and the pace he would need to hit to match the then-course record.

He wrote the details – for instance: one kilometre at a nine per cent incline at a speed of 12 kilometres an hour – down on laminated paper and placed it on a treadmill during a training camp in Ethiopia. “You’re not seeing things,” Evans says. “But you are giving your body a little bit of a run through of what to expect from the start.”

But ultramarathons aren’t just about the physical exertion. To travel 100 miles by foot or run around a track for a continuous 24-hours, there needs to be huge mental resilience. These sort of races are repetitive, involve hundreds of thousands of steps being taken, and are as much of a test of a person’s ability to push through monotony as they are a test of physical strength.

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During Herron’s first 12-hour race, she did not know what to expect mentally. As a result she says she had to learn to “mentally break up the race” and come up with a coping strategy to do so. What she settled on was focussing on the running watch she was wearing: it was set to beep every 30 minutes and acted as a reminder for her to take on nutrition. The distraction helped to pass the time.

Courtney Dauwalter, who has won races that are up to 240 miles long, says races that repeat the same loop hundreds of times can be some of the most mentally taxing. “You’re trying to utilise every minute that you can to keep moving forward,” Dauwalter says. “But it’s totally a head game of staying in it, because there are no beautiful views to distract you.”

There are times when sleep deprivation will take over completely. In one race 265km in, Dauwalter started hallucinating. She’s said she saw live puppets playing on a swing, next to the trail that she was running on. The objects around her, mostly trees and rocks, started to generate faces.

There are very few ways to deal with sleep deprivation, although Dauwalter says she is experimenting with taking short naps for some of the races she is planning to run. But ultimately, runners training and racing in ultramarathons will spend a lot of time on their own.

“There are so many hours of thinking,” she says. “Sometimes it’s nothing at all, sometimes rehashing memories or working through some problems that I’m dealing with or sometimes just brainstorming what sort of food I want to eat on the run is over. But I also just really love the silence and sometimes I just let that silence be the only thing in my head.”

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Matt Burgess is WIRED's deputy digital editor. He tweets from @mattburgess1

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