DES MOINES — Justin Gatlin walked into a small room underneath the concrete bleachers at Drake Stadium showing no sign of his age, save for a splotch of gray hair just above the center of his forehead. As he faced a group of reporters, he was asked whether he wanted to move closer to a monitor showing another men’s 100-meter heat. He shook his head.

“My eyes aren’t that old yet,” Gatlin said, smiling.

Gatlin is 37, entering middle age in broader society, beyond ancient in the sport he still forces to confront his formidable and polarizing presence. He remains a force in the 100 meters, still ranked second in the world, still the reigning world champion. On Thursday at the USATF Outdoor Championships, he finished second in a qualifying heat with such ease he started a scripted celebration about 10 meters from the finish line.

One year out from the Tokyo Games, the nationals are hosting a new wave of American sprinters, led by Christian Coleman, Noah Lyles and Michael Norman, who respectively present the possibility of an American sweep of the 100, 200 and 400 at the world championships in September and next summer at the Olympics. But when they get into the blocks in the 100 or 200, they may still have to compete with the man who won an Olympic gold medal in 2004, when they were starting elementary school.

The only man ranked ahead of Gatlin in the 100 ran two heats after him. Coleman, 23, breezed into Friday’s semifinals, in pursuit of his first outdoor national championship, which will be decided later in the night. At opposite ends of their careers, Gatlin and Coleman are America’s standard bearers in track’s marquee event.

“I always see different headlines with the passing of the torch, stuff like that,” Coleman said. “Obviously, he’s still in the mix. I try not to pay attention. I try to treat Gatlin just like any other competitor. He’s somebody I used to look up to. But when you step on the track, it’s no friends.”

Both acknowledged they are rivals. Last month at the Prefontaine Classic, Coleman ran 9.81 seconds to beat Gatlin. Off the track, where Coleman has butted heads with fellow American phenom Lyles, Coleman and Gatlin have bonded, using a method of communication Gatlin has had to adapt to.

“With these kids nowadays, we don’t even communicate through text message, regular phone,” Gatlin said. “We communicate through Instagram. We’re always DMing each other.”

Coleman has befriended a sprinter he grew up watching. His first recollection of track and field is the 2004 Olympics, when he was 8. The gold medalist in the 100 was Gatlin.

“I was not even thinking that one day I could be at that level,” Coleman said. “That’s pretty crazy.”

Coleman has yet to compete in his first Olympics, and he might be the favorite in Tokyo next summer. His motivations are obvious. Gatlin’s are less clear. He keeps going despite a career that has seen him reach the top of the world, be cast out of the sport and then come back to reach the top again.

Before Coleman reached high school, Gatlin had served a four-year doping ban, a suspension that lasted from 2006 to 2010 and hounds him to this day. Despite his longevity and accolades, Gatlin remains a villain, especially on the international stage. He upset Usain Bolt at the 2017 worlds, in Bolt’s last major championship race. The crowd booed him on the medal stand. As he won the 100 silver medal at the 2016 Games in Rio de Janeiro, the crowd jeered him.

Having won a gold medal, captured a world championship and stunned the fastest man ever, Gatlin has little more to achieve. On Thursday evening, when the public address announcer listed his accomplishments, he included Gatlin’s Drake Stadium record. Gatlin didn’t even know he held it.

And still, he competes despite the ire of so many fans across the globe. It raises an obvious question: What keeps him going?

“He likes winning,” suggested Isiah Young, who won Gatlin’s heat. “That keeps anybody going.”

Gatlin agreed, but the real reason is something more profound, the pursuit of something that might be impossible.

“You get to a point where you start chasing unicorns, man,” Gatlin said. “You want to put together the perfect race. You want to put together the perfect start. You’re chasing that thing that’s going to solidify your career. It’s like a runner’s high for sprinters.

“For us, it’s about that adrenaline rush, getting the middle of the race, everything in your sight is just a blur. That’s what it feels [like] to run fast: Everything around you is a blur, but you’re so dialed in and so focused, everything is slowing down. You want to feel that every time. When you come across the line, you want to excite yourself, like: ‘Man, look at that time I just ran. That’s crazy.’ I’m always chasing that. That unicorn, man.”

As the reigning world champion from 2017, Gatlin had guaranteed his spot at the world championships before he arrived here, and he will compete in Qatar regardless of his finish. In the moments after he finished, he was still deciding whether he would compete in Friday’s semifinals and finals.

“I’ll be back tomorrow,” Gatlin said, starting to break into laughter, “in some capacity.”

Even at his age, he was fast enough to treat a race against the fastest men in America as a glorified practice session. When he reached about 80 meters, Gatlin pointed at Young, his friend and training partner. As they crossed the line first and second, Young pointed back.

“It was kind of scripted,” Gatlin said.

Nearing the first post-Bolt Olympics, Gatlin described the state of the American 100 meters as “exactly where I want it to be.” Michael Rodgers, a 34-year-old who qualified for the semifinals and ranks third in the country, called the U.S. team “loaded.”

“Just being the best in the world,” Gatlin said. “The USA always has the depth when it comes to talent. I think in the last couple years, they gained the confidence back.”

Lyles, the fourth-fastest man ever in the 200, is sitting out the 100 at nationals, but he beat Coleman in a 100 early this season, which he declared afterward as the start of “my legacy” as a 100 and 200 sprinter. He has said he plans to run the 100 in Tokyo, part of his plan to win three gold medals at his first Olympics.

A trio of Coleman, Gatlin and Lyles in Tokyo would provide three distinct characters for American fans to choose from: a taciturn favorite, the ­been-there-forever veteran and an unabashed showman.

“I look at that 100: It’s like a boy band,” NBC analyst Ato Boldon said. “You look, and there’s going to be one guy in there your personality sort of meshes with, and that’s who you’re going to back. That’s what makes for a healthy sport. That’s the attraction of that 100.”

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