The race began with 70 runners. By nightfall of the first day, the field had already started to thin. Kevin D. Liles

"You'll wonder how someone can inflict so much pain without a weapon," says the sixtysomething man who goes by Lazarus Lake. He is leaning against a metal barrier on his property in Bell Buckle, Tenn., wearing a red beanie embroidered with GEEZER. He has a bushy white beard, a pot belly and square-rimmed glasses. He looks like a lumberjack Santa.

It is 6:35 a.m. on an October Saturday. In a small clearing, just off an access road, Lake spray-paints a starting corral around a pack of six dozen men and women in tank tops and short shorts. We are just minutes from the start of the seventh running of Big Dog's Backyard Ultra, the multiday race that Lake thought of when he was a high schooler 50-odd years ago, thinking of ways to test the body's limits.

Ultrarunning—racing distances longer than a marathon—has grown rapidly in popularity over the last decade; there are now more than 150 100-mile races in North America, according to Ultrarunning Magazine. The sport inflicts a range of horrors on its athletes: gnarled toenails, battered joints, respiratory distress.

But the distinctive format of Big Dog's Backyard Ultra is especially diabolical. Runners must complete a 4.167-mile loop every hour. After finishing one hour's loop they can rest, eat and use the Port-a-Potties until the next hour's starts. Fail to complete a loop before time elapses, you're out. Complete one but fail to appear on time in the starting corral for the next one, you're out. During daylight hours the runners follow a leafy dirt trail in Lake's backyard. After dark the race moves to a road course, for safety's sake, then back to the backyard come morning. The race goes on—hour after hour, through daylight, darkness, sun and rain—for as long as there are still runners, plural, who can complete the loops. There is no finite distance to conquer. In other words: Run till you drop. The race has no finish line, is always tied, and is always sudden death. Of the 72 runners who have entered the event, only one will be credited with finishing. The rest, DNFs. The winner receives a small gold coin, inscribed I SURVIVED. Everyone else gets a silver one with I GAVE MY ALL IN BIG'S BACKYARD.

As the sky above Lake's backyard brightens with a late-autumn sunrise, he offers his final prerace announcement: "If you're not in it, you're not in it. Pretty simple concept, right? Don't poop in the woods. The dogs will roll in it and I will not be happy." For the runners waiting to start, this is the last peaceful moment they will have for days. Smiling, Lake raises a cowbell over his head and clangs it. The race is on.

Runners trace a road loop at daybreak. Kevin D. Liles

Lake says, "I'll show you the hardest part of the course: between the start line and the chairs." He points to rows of lawn chairs under a canopy near the starting corral. After each loop, runners use the chairs to plop down and prop up their feet—standing up and running again isn't always so appealing.

Between loops the rest area will swarm with runners and the 70-plus volunteers there to support them during the race. Many are ultrarunners who did not qualify for Big's; some are friends and family of participants. All 72 finish the first loop, casually stretch and refill their water bottles. Four-plus miles done, hundreds more to go.

Maggie Guterl, a 39-year-old who works in marketing for a performance beverage company in Durango, Colo., brought two friends to help her and two other runners during the race. Guterl finishes each of her first two loops with six minutes to spare. At 8:34 a.m., she's reclining on a lawn chair and snacking while her friends refill her drink bottles.

"It's kind of boring at the beginning," Guterl says. "You just kind of wait the day out, and don't get behind on calories."

Guterl entered her first Big Dog's Backyard Ultra last year. She ran 183 miles before a tight IT band knocked her out. Her goal for 2019 is to run more than 300 miles—the record at Big's is 283—and win the damn thing. She plans to maintain a steady pace, which will allow her, on average, five to seven minutes of rest between trail loops and 11 to 15 minutes' rest on the less demanding nighttime road loops.

Guterl is among the favorites, although a woman has never won. Shawn Bearden, a professor of exercise physiology at Idaho State, says that ultrarunning narrows the advantage men have in shorter races: "Very long distances require a runner to go much slower. And when anyone runs much slower, we're dealing with a different set of physiologic limitations than the ones we know predominantly benefit men in shorter races."

Which is to say that anyone can conquer Big Dog's Backyard Ultra. Or anyone capable of running 200-plus miles, anyway.

***

Lazarus Lake is not his real name. He's actually Gary Cantrell. Cantrell and his wife, Sandra, live in Bell Buckle (pop. 532), just miles from where they first met, in Murfreesboro, in an accounting class at Middle Tennessee State. Cantrell, a self-described hillbilly, will not give his age. "I am 43. I would have been older, but I have been held back a lot."

His interest in endurance dates to his days as a runner at Tullahoma High. "I was always at the end of practice running intervals," he says. "I was the strongest guy left." Cantrell, who has worked as an accountant, a city treasurer and a stone mason, put on his first ultramarathon in 1979. He is known not just for Big Dog's but for the grueling Barkley Marathons in Frozen Head State Park. That race, in which runners must finish a 100-mile course in 60 hours, has been successfully completed only 18 times in its 34-year history.

When it came time in 2012 to launch Big Dog's, he couldn't think of a better location than his own backyard, nor a better honoree for the race's name than his own big pit bull called, naturally, Big. (Big attends the race every year, where he sleeps under the scorer's table.) The backyard-ultra format has since caught on: In '19 there were over 30 backyard races in Sweden alone, not to mention qualifying events in Hong Kong, New Zealand and Brazil. To make the field for Big's, a runner must win one of the designated qualifiers or be hand-selected by Cantrell. This year's crop comes from more than 20 countries.

"Getting this place out in the woods was the realization of a lifelong dream," Cantrell says. He started work on the backyard trail even before he moved in. "I wanted to share [it] with my running friends."

***

"Too fast!" Cantrell shouts at a runner who has just completed a loop with more than 20 minutes to spare. Pacing is key to any race. But at Big's, it's especially significant. Run too slow, and you won't have time to perform maintenance between loops, but run too fast and you'll deplete your energy reserves. Cantrell likes to point out that in the history of Big's, no person who has finished in first place during any of the first 16 laps has ever won.

Eight hours into Day 1, 69 runners remain. Maggie Guterl is finishing her loops with just enough time to eat the slimy pierogi her friends have cooked on their camp stove. (At this stage, it's more important to have foods that are filling than healthy.) Guterl and the remaining runners begin the ninth loop, and Cantrell brings out a white flag that Sandra made overnight. The flag reads, in black marker, THERE IS NO. He tapes it onto the black, inflatable archway in front of the word, finish.

Gary Cantrell, aka Lazarus Lake, who created and oversees the event, is about the only smiling figure at Big Dog's. The runners suffer. Kevin D. Liles

Cantrell relishes the pain that the runners endure. When one drops out early, he says, "I regret that you couldn't have suffered longer. There's still a couple of days to go!"

Watching the race pass by from camp is a largely monotonous experience. Every 50 minutes or so racers return to their tents, and their crews go to work on them. As night falls Guterl's friends bustle around camp, heating cups of instant mashed potatoes, grits and pizza for her to eat between loops. Her tentmate John Sharp drinks a beer. (Carbs are carbs.) Her headlamp bobs into focus as she finishes a 46-minute loop in the pitch black.

The race begins in earnest, Cantrell says, once runners have reached the 100-mile mark and survived a night without sleep. And at dawn on Day 2, just over half of the runners remain, and five don't look like they'll make it another loop. Rain has made the trail slippery and more dangerous overnight. As the sky lightens, a foggy mist obscures the sun.

Overnight Cantrell rang his cowbell every hour. "I stay up all night," he says. "It's the least I can do." Around 6 a.m. he finally drifted off to sleep . . . for all of 10 minutes: "I set my alarm for 10 minutes and boom. I feel so refreshed. It won't last forever. But for at least a little while."

Like the rest of the field, Guterl has been running for 24 hours. She is struggling to focus her vision. "On the road you can kind of shuffle along and trust your feet, but on the trail there are so many rocks and leaves," she says later. The return to the trail after the road loops adds another layer of difficulty on the second morning.

After Loop 27, Amelia Boone, a 36-year-old lawyer for Apple, has run more than 112 miles. Her feet are a raw, mangled mess. She has been battling stomach problems for a day and has had only minutes of sleep. She knows that if she starts another loop, she will not complete it in time. Boone doesn't know how she wants to end her race. Give up at the starting line? Or start to run and time out? She chooses the latter and begins her final loop. As runners begin to pass her, she hugs and high-fives them. Her race is over.

What often fells runners is the so-called death spiral—a runner has a bad loop and their recovery times get shorter, causing them to have another bad loop, and an even shorter recovery, until they can no longer finish a loop in 60 minutes. "You don't have time to have a bad loop," Guterl says after the race. "If your nutrition falls behind, it's really hard."

Between laps, runners eat, hydrate and stretch. Kevin D. Liles

Boone limps over to the tent she shares with Guterl. As she gingerly peels off her socks, it's obvious that the damage to her feet could linger for weeks. A blister on one big toe looks like a second big toe. She winces as a friend submerges her feet into a Ziploc bag filled with ice water. "It felt like running on razor blades," Boone says. She has run a personal best but has lost the race, as well as most of her toenails.

Her injuries are hardly the worst in the field. Andrés Villagran, a 35-year-old from Ecuador, has been running for hours with a right knee that is the color of a blueberry and the size of a grapefruit. Deep-red blood vessels are visible on the back of his leg. Crew members speculate about a hamstring pull. When Cantrell saw how bad the injury looked, he told Villagran's father, who was his crew, that his son should pull out, but the elder Villagran disagreed. Andrés ran on his busted leg for more than 158 miles in total before quitting.

As night falls on the second day, only 12 runners remain. Guterl's right knee is slightly swollen. (She had held off taking ibuprofen for as long as she could, but she relented late on Day 1.) Even so, as runners continue to drop out, she remains very consistent. She has her routine between loops down to a science: Stop, stretch, foam roll, eat, repeat.

Guterl puts on a headlamp and enters the starting corral, where she'll begin another set of 12 road loops. Race favorites Guillaume Calmettes, a Frenchman who won in 2017, and Joe Fejes, the first American to run 600 miles in a six-day race since 1900, have bowed out. It's anyone's race to win.

Overnight the field of 12 dwindles, and a strong camaraderie builds: The runners encourage one another to hang on. "This is the relationship the runners develop during the race," Cantrell says. "Shared suffering." There is also an unintended side effect to seeing a racer drop out. "It keeps someone else in for a little bit longer," Guterl says later.

Cantrell says, "It's part poker. You can't let your opponent know you're hurt, because that just feeds them. People don't quit when they can't go any further. They quit when they no longer believe they can win."

Guterl has been running for more than 48 hours. She staved off the urge to drink caffeine until just before sunrise on the third day. But with a few sips of a caffeinated sports drink and her knee soreness under control, she hits the 200-mile mark. By 7 a.m. on Day 3, there are only four runners left. Guterl wants to win, but she doesn't want the race to end. Two more hours pass; 208 miles; another runner drops out.

Will Hayward, a 51-year-old psychology professor at the University of Hong Kong, looks to be on the verge of a death spiral. He's dragging. Calmettes, who has stuck around like many other entrants, helps Hayward by shoving food into his mouth and pushing him back into the starting corral. After the race Guterl says, "The decision was not his own anymore. He was dragging his body to the finish. They were standing him back up, and he was going back out there over and over again." After another runner drops out, only Guterl and Hayward remain.

Hayward, on the verge of a death spiral. Kevin D. Liles

Says Cantrell, "The things that make it fun are of course seeing people really reaching inside themselves and finding something, and going beyond what they thought they could do."

***

As Hayward put it before the race, "There's no one here that's not a stubborn son of a bitch. That's why we got into this stupid sport."

A heavy rain rolls in as darkness envelops the course. Guterl and Hayward have been running head-to-head for seven hours, even though Hayward, soaked and haggard, now resembles a walking corpse. Many runners and crew members have stayed behind to watch the finish, canceling flights and work.

Loop 60 is the final trail run of Day 3. Guterl needs to finish it with enough time to shed her wet outer layer of clothes. She uses all of her energy to make it back to the finish line. The trail looks different now—new leaves fell during the day, hiding the jagged, slippery rocks underneath. Every time Guterl trips on one, she picks herself back up and keeps moving forward. She makes it to her tent, changes clothes, eats and lines up for Loop 61. With a minute to spare, Hayward is nowhere to be found. Cantrell counts down from 10. A crowd gathers at the starting line.

"Five . . . four . . ."

Guterl hears someone yell, "Make way for the runner!"

"Three . . . two . . ."

At "one," Guterl is alone at the starting line. Hayward, out of sight, could not finish the loop in time. After 60 loops and 250 miles, she has won the seventh Big Dog's Backyard Ultra.

Two-and-a-half days after the start, Guterl was the last of the 72 entrants racing and thus the first woman to win Big Dog's. Kevin D. Liles

"I find satisfaction in something where there is a little bit of suffering," Guterl says. It helps her "really enjoy the comforts of life, like going back to sleep in a nice warm bed."

Indeed, the collective agony experienced in Cantrell's races brings something out of the participants. Facing fear and desperation, sleeplessly and deliriously traversing a course when every last part of their bodies is telling them to quit, they keep going. They reach inward and push onward.

Cantrell focuses on simpler matters: "I love my backyard. I love for people to see my backyard."