Long before he emerged as one of the best men’s marathoners in the world, Cameron Levins was just trying to run faster than his friend next door.

Levins was an energetic second-grader in Black Creek, British Columbia, a small town on Vancouver Island, when he ran his first race, on a two-kilometer course near his school. He placed 11th, which was respectable. The problem, he said, was that his friend, Myles Delange, placed 10th.

“And for the next seven years or something, that’s how we placed in every single race, which was Myles finishing just ahead of me,” Levins recalled in a recent telephone interview.

There was something about the challenge of beating Delange that motivated Levins, now 34, and has perhaps stayed with him as a professional runner.

“I certainly wouldn’t have hated losing as much, if not for him,” Levins said.

On Sunday, Levins will tackle his first New York City Marathon as one of the favorites.

Last year, after coping with injuries, self-doubt and a poor performance at the 2020 Summer Olympics, he rebounded in a big way, placing fourth in the men’s marathon at the world championships in Eugene, Ore. And in March, he broke the North American record for the 26.2-mile distance when he finished fifth at the Tokyo Marathon in 2 hours 5 minutes 36 seconds.

“Running is something where you’re really rewarded based on the effort you put in,” he said.

Marathoners are known to be a masochistic breed. Even among them, Levins is an outlier. He often runs 170 to 180 miles a week, which, at the top end of that range, averages out to nearly 26 miles a day.

How does he do it? Three to four times a week, he runs three times a day — once in the morning, once in the afternoon and once at night, almost always on his own. He typically does his evening run at home in Portland, Ore., on a treadmill in an oxygen-deprivation tent. The idea is to simulate the aerobic effects of running at high altitude.

Jim Finlayson, his coach, said it took a “unique mind-set” to train that way.

“The fact that Cam can not only handle the mileage physically but handle it psychologically,” Finlayson said. “I mean, most people would never run the volume that he runs because of the boredom of it or the lack of desire to keep doing something that’s so monotonous. But for him, it’s probably on a meditative level.”

Levins first emerged as a star in college at Southern Utah University, where he captured the attention of the running community by backing up his enormous training load with huge results. As a senior, he doubled as the N.C.A.A. Division I champion in the 5,000 and 10,000 meter races. He placed 11th in the 10,000 and 14th in the 5,000 at the 2021 Olympics in London.

His career seemed to crater, though, after he sustained serious injuries that required surgery before the 2016 Olympics in Rio de Janeiro. He was sidelined for nearly a year and wondered whether he was finished as a professional runner.

“I think what really kept me going,” Levins said, “was that I didn’t want to go out like that. I wanted to go out on my own terms.”

Once he returned to running, Levins turned his full attention to the marathon, hiring Finlayson in 2019. Finlayson said he quickly realized that their relationship needed to be collaborative.

“He comes to the table with a lot of training history under various coaches, and he has connections to a lot of people at the elite level,” Finlayson said. “So he brings his own ideas, and I’m always happy to listen. He knows his body better than anyone.”

In 2018, Levins made a particularly strong marathon debut when he placed fourth at the Toronto Waterfront Marathon in 2:09:25, breaking a longstanding Canadian national record.

But marathoning is a hard business, and he faded badly in the brutal heat at the pandemic-era Tokyo Olympics, placing 71st among 75 finishers.

It was a confounding and heartbreaking result, and Levins again found himself mulling retirement. It was a disappointment for Finlayson, too. He told Levins he should do what he felt was best for his career, even if it meant finding another coach.

Levins, though, enjoyed working with Finlayson, and rather than overhaul their existing approach, Levins decided to augment it: What else could he do to improve?

That meant seeing a sports psychologist, Dr. Judy Goss, who helped him work through some of his unforgiving profession’s obstacles; adding speedier sessions to his weekly training; and lifting weights for the first time in his career as a marathoner, which Levins described as “possibly the most beneficial thing that I’ve done.”

It even meant studying how to grab his water bottles along the race route without getting jostled by a pack of aggressive runners.

“Because that’s where mayhem happens,” Levins said. “And I think that was an experience that I was very unprepared for in Tokyo.”

His subsequent performances at last year’s world championships and at the Tokyo Marathon, Finlayson said, “let us know that we were doing the right things.”

“It doesn’t stop there, of course.” he added. “We’ll keep looking for things to refine it a little bit more, to get more out of his body.”

Ideally, Levins said, New York’s undulating terrain would offer some preparation for the 2024 Summer Olympics in Paris, where a hilly course is expected to be demanding. The steepest climb in Paris is a 13.5 percent grade, which seems almost inhumane.

But Levins has never been afraid of doing the hard stuff, not since he was competing against his childhood friend next door.