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Joe McConaughy has a serious case of cankles. His knees are puffy, swollen masses, walking is “a chore” and his appetite is unrelenting. Overall, he feels “pretty dead.”

It’s been five days since the 26-year-old Seattle native broke the Appalachian Trail (AT) thru-hike speed record, and the recovery is almost as brutal as journey itself.

“I’m definitely still out of it,” Boston-based McConaughy laughs, although his actions suggest otherwise. He’s already back at work (his employer, the travel and education company EF College Break, granted him a leave of absence to complete the hike) and thinking towards his next challenge. “Maybe Western States,” he says, referring to the 100-mile endurance race in California known for its beautiful but unrelenting landscape. The Long Trail in Vermont and the Wonderland Trail in Washington are also on the table.

This indefatigable drive for "more" explains how McConaughy, known on the trail as “Stringbean,” averaged 48 miles a day for six and a half weeks straight to finish the 2,189-mile AT in the fastest known time ever recorded: 45 days, 12 hours and 15 minutes. He tracked his effort via GPS, sharing regular updates on Instagram, and his time has been verified by the Fastest Known Time board member Peter Bakwin. (There is no official sanctioning body for AT records.)

What’s more, McConaughy completed the challenge self-supported, meaning he had no sponsors, crew or organized support and instead relied on hiker towns and road crossings to resupply food and water. Each day, he lugged a 25-pound backpack containing his clothes, sleeping bag, tent, medical supplies and a three-to-four day ration of food and water.

"I am in shock and pain, joyful and thankful, humbled and tired, in disbelief and exhilaration," McCougnahy wrote in an Instagram post announcing his finish. "I will be forever perplexed and appreciative of what the wilderness brings out in myself and others."

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McConaughy’s time smashed the previous self-supported record, set in 2015 by Heather Anderson, by nine days, and even eclipsed the supported record, set in 2016 by Karl "Speedgoat" Meltzer, by 10 hours. He finished on Thursday, August 31, summiting Maine’s Mount Katahdin at 6:38 p.m. after a sleepless 37-hour, 110.8-mile push, which is nearly double the furthest distance he’d ever run up until that point.

“Believe it or not, that [37-hour stretch] included some of the happiest times for me,” says McConaughy, who ran track and cross country at Boston College. “I did some of my best running then.”

He persevered through rain, hail, darkness and a throbbing ache in his left knee by keeping close tabs on his nutrition and hydration levels and hyping himself up as needed. “I’d tell myself, ‘This may suck now, but you gotta get through it and there’s always a light at the end of the tunnel.’”

That light came in the form of Katie Kiracofe, McConaughy’s girlfriend, and Josh Katzman, his friend, who hiked up 5,291-foot Katahdin to greet him at the summit. They welcomed an emotional, rain-soaked McConaughy with hugs, an emergency blanket and warm, dry clothes.

The trio hiked down the mountain and set up camp for the night, where McConaughy says he ate “like nine s’mores” for dinner. The next morning, they drove to Boston and McConaughy enjoyed his first “real meal” at The Deluxe Station Diner.

He ordered the “The Hungry Person” special, a greasy, colossal spread of pancakes, eggs, sausage, home fries and toast. He also ate half of Kiracofe’s breakfast.

McConaughy, who set the supported speed record for the 2,660-mile Pacific Crest Trail (PCT) in 2014, began seriously contemplating the AT self-supported challenge about ten months ago. “After doing the PCT, I thought 'What’s next?’” he says.”The AT seemed like a natural next step and it slowly grew as a seed in my mind.”

He trained for the task with several ultramarathons this spring, including the back-to-back Gorge Waterfalls 100K and the Lake Sonoma 50. (His friends made a documentary about the experiences and are now working on another film about his AT feat). He also spent a couple weeks in Canada’s Banff’s National Park, logging miles and miles on the mountainous terrain—although in retrospect, nothing could truly prepare him for the intensity of the AT, which traverses 14 states and includes more than 500,000 feet of elevation change. It’s a humid, buggy, rocky and densely wooded trek, and the Appalachian Trail Conservancy (the entity that maintains the trail) recommends hikers allot five to seven months to complete it end to end.

This article originally appeared on Runner's World.