The World’s Toughest Race

Hark! Fireworks demolish the silence of a January predawn in Koochiching County’s northern riviera—International Falls, Minnesota, the Icebox of the Nation (U.S. trademark number 3375139). Oh, to shiver in the boreal cold with the frozen sun shirking below the horizon. Arrowhead 135 racers hop for warmth, their bellies aflutter with excitement and fear because they will soon begin one of the most difficult races to grace the hide of this good earth.

“Release the hounds!” the starter yells.

It’s 7:30am, and the racers are off. They travel on foot, ski, fat bike, and kick sled. The fastest may finish in twelve hours. More than half will quit—heartbroken, exhausted, and relieved. Others will spend sixty hours crossing 135 miles of frozen woods to the finish line at Fortune Bay Casino in Tower. Tower lacks a patented slogan like International Falls, yet it’s statistically the coldest populated area in the lower 48 states, with a record low of 60 below. From the frying pan into the fire! Or whatever the opposite is.

Leah Gruhn has completed eleven Arrowhead 135s and will be going for a dozen in January 2026. The Duluth geologist made her first attempt on skis before switching to fat biking. The bike is “by far the fastest,” she said. The Arrowhead bike record is under twelve hours, while the fastest time on foot is more than double that, at twenty-eight hours. A new ski record of twenty-and-a-half hours was set in 2025.

Times and success rates are highly dependent on snow conditions and temperature. In an average year, less than half of racers finish, while the frigid winter of 2014 had a success rate of just 35 percent. Usually, though, cold and snow are an advantage, leaving a consistent snowpack to travel upon. Gruhn has started but not finished the race three times—including her first attempt on skis, another when a foot of snow fell during the race, and again during a recent warm year, when she rode through sun-softened snow and crashed hard on bare ground. “Typically, when you crash on a fat bike, it’s like falling into a pile of pillows,” Gruhn said. But she feared she’d break a bone when she wiped out in 2024.

Jeremy Kershaw was among the first to complete the Arrowhead a’Trois, meaning he finished the race by bike, foot, and ski. Kershaw, who has heavy cycling credentials, like founding the Heck of the North gravel race and, in 2017, biking 2,700 miles from Banff to Mexico in twenty-two days, prefers doing the Arrowhead on foot. He said, “There’s something about the simplicity of walking and running it that appeals to me.”

The Arrowhead 135 starts from a city park in International Falls, follows a spur snowmobile trail to the Arrowhead State Trail, then follows this snowmobile trail through Kabetogama State Forest. In its first year, 2005, ten people raced. The race quickly grew, attracting people from the Midwest and around the world (most years, the Arrowhead has racers from Brazil, home to the Brazil 135 Ultra Journey). For a time contestants were capped at 135. In 2025, 190 racers registered and 164 started—84 by bike, 74 on foot, six on ski, and two by kick sled.

In 2023, Minnesota filmmaker Marius Anderson released Forty Below: The Toughest Race in the World, a full-length film chronicling the 2019 Arrowhead, which unfolded in the grip of a polar vortex that pushed temperatures to forty below. Marius framed the film around Bill Bradley, a Californian who turned to extreme endurance events to escape depression stemming from losing his fortune, wife, and friends following the bankruptcy of his video rental business. “The race is very different from any sporting event in the world,” Marius said. “Even different from any ultra marathon in the world.” The filmmaker is a runner but doesn’t see himself attempting the Arrowhead, though his time documenting the race has had a lasting effect: “I don’t really like being completely alone for a long period of time. I admire what these athletes do. I want to run my first full marathon. That event and those racers are big motivators for me.”

Leah Gruhn embraces the social aspect of the race, while Jeremy Kershaw favors a solitary journey into what he calls his “lizard brain,” which involves, he said: “basic bodily functions—I gotta eat, I gotta pee. It’s moving and monitoring—how do I stay warm, eat, sleep, and do rudimentary chores. It’s not easy, but you’re not worried about your taxes or your kid in college.”

Gruhn is less fond of her lizard brain and prefers to stay in a group when she can. She said: ‘There’s a biking phrase: ‘If you want to go fast, go alone; if you want to finish, go together.’ More people make better decisions than a single person. When I’m carrying on a conversation, I’m so much more stimulated and interested, and it’s easier to stay awake.”

Arrowhead racers are required to carry a -20-rated sleeping bag, a stove and fuel for melting drinking water, and 3,000 extra calories (to this end, Gruhn thickens her drinking water with maple syrup). Racers spread over the long course through remote country will be on their own for miles at a stretch. “At every organized marathon and Ironman,” Marius said, “you can have zero in the tank and collapse, and someone will pick you up and take care of you. In the Arrowhead, that’s not the case. There are only three checkpoints, and the third checkpoint is just a tent in the middle of the woods.”

For Kershaw, the first checkpoint, 25 miles in, is where fatigue hits hard. The checkpoint is at the Gateway General Store, located across Highway 53 from the Kabetogama Walleye—a giant fish sculpture topped with a saddle. Exhausted racers enter the convenience store, unroll their sleeping pads, and rest on the floor. Beyond the store lurks a long night of running alone through the dark. “I’m really tired, and I’m wet,” Kershaw recalled about reaching the store. “You still have over 100 miles to go. If you can get out of the spiderweb of that checkpoint, you’ll probably be ok. It’s a big jump to the next checkpoint—50 miles—through the middle of the night. Any time as a racer you get next to civilization, that’s where you gotta be really strong.”                                                        

Gruhn, traveling quicker by bike, finds the going gets hairy around the midpoint. “The trail gets really flat on an old railroad grade. When it’s hilly, it’s fun—pushing my bike up hills, going around curves. It gets to be a lot when the trail straightens and flattens in the middle of the night. You go over Wakemup Hill, the huge, last big hill. You drop down, and you’re in a swamp for twenty miles. You can see so far ahead. The monotony of those last twenty miles, you feel like you’re not getting anywhere.”

Everyone has a sleeping bag, but some racers don’t use them. Walkers and runners who take 48-60 hours to finish will camp two nights along the trail. Leah said, “It’s always my hope to just go through the night. It depends on how it goes and if I’m riding with someone or by myself. Sometimes I’m a little bored, maybe I’ll just lie down here. The people on foot are good at taking shiver bivy catnaps. A lot of people will nap for 15 minutes at a time.”

Physical exhaustion and sleep deprivation combine to create situations evocative of a hybrid between Hunter S. Thompson and the Coen brothers’ Fargo. Gruhn has hallucinated: “I’ll be walking along, and up there is a guy in a white t-shirt on a tractor plowing snow. I got up there—it was a tree stump with snow on it. Your mind is so bagged you’re kind of making stuff up to fill in the gaps.”

Kershaw has never slept much on the course: “You sit in a bag with your heart racing at about 120 beats per minute, shaking. But if you don’t take breaks, the sleep demons get you. I thought I was seeing the heads of babies and my high school friends in the trees—there was a ton of snow that year. I was like, ‘Don’t look off the trail.’ That year, I was following a pack of wolves with hand-sized prints, the biggest I’ve ever seen. I looked down, and I’m not afraid of wolves, but still. I started to fall asleep. It was like forty below. I started to jog. I started yelling out to the universe. I was literally yelling, ‘You’ve got to get moving! You’ve got to wake up!’ It was 3am, in the middle of a black spruce bog. If you lie down, you’re at a really big risk of cold injury. I was freaked out, yelling: ‘Go! Go! Go!’ I jogged seven miles to the finish. If you’d stopped, you would’ve frozen. How much pain can I stand? It’s kind of funny, but it’s kind of not. That element of danger is always a draw for certain people. There’s life on the trail, and there’s life at work. Life on the trail is all-encompassing.”

Marius Anderson’s Forty Below is streaming on Amazon Prime: http://www.bit.ly/amazon40below.