Two men were running side by side in Central Park on a recent morning when one of them bumped into a woman as they passed her. The woman was briefly furious, but her face softened once she saw the tether connecting the men by the waist.

Francesco Magisano, the man who had run into her, is blind, and his guide Nev Schulman nervously apologized for the accident. The men were running together for the first time in preparation for the New York City Marathon on Sunday.

Magisano, who was diagnosed with a rare eye cancer as a baby and lost his vision as a teenager, will be among more than 500 runners with disabilities and guides participating in this year’s race.

Marathons are physically and emotionally challenging, but the New York City Marathon has a unique set of difficulties for blind runners and their guides. The sheer number screaming spectators and runners — race officials are expecting approximately 50,000 finishers this year — make it difficult for guides to steer blind runners along the tightly packed 26.2-mile course.

So in Central Park, Magisano, 28, and Schulman, 39, were trying as best they could to prepare.

“Which side do you prefer?” Schulman asked Magisano before their run as they stood near the Central Park entrance at West 100th Street and Central Park West.

“I brush my teeth with my right hand, so I have my guides on my right side,” Magisano joked.

With the tether secured around their waists and Magisano’s right hand cupped on his guide’s left shoulder, the pair walked to the path.

“They’ve already started setting up for the finish line,” Schulman noted shortly after they began running. (The race, which goes through every borough in the city, begins in Staten Island and ends in Central Park in Manhattan.)

“So there are bleachers up already on the left,” Schulman added, giving Magisano a sense of the scene.

Magisano was diagnosed with retinoblastoma when he was 10 months old. He had always had low vision, but it was not until ninth grade that he lost his vision completely over a three-week period.

“I’d be walking home from school every day and see the lines on the street blur slightly more,” he said.

He didn’t pick up running until much later, in 2017, after an unexpected conversation in a grocery store on the Upper West Side of Manhattan. He had been standing with his cane in front of a stack of bell peppers, a useful food, he said, because it can be eaten uncooked. Then an older man tapped him on the shoulder.

“‘Do you run?’” Magisano recalled the man asking him. The man then told him about Achilles, a group of runners with disabilities who met twice a week for runs in Central Park.

“I’ve always been interested in trying new things — I’d never run before in my life,” Magisano said. That week he went on a run with the group. He signed up for his first marathon shortly afterward.

He now works as the director for the New York City Metro Region chapters of Achilles, and Sunday will mark his sixth time running the New York City Marathon. His goal is to run at a pace of 3 hours 30 minutes, which is approximately eight minutes per mile. Earlier this year, he completed a 321.6-mile triathlon — swimming, running and cycling — over three days in Florida.

Runners with vision impairments are allowed at most two guides in the New York City Marathon. Guides do not have to pay an entry fee, are not scored and do not receive an official finishing time. They must wear a guide bib and cannot push or pull the runner forward, according to guidelines from the New York Road Runners, which hosts the marathon.

Magisano will run with two guides. One will ensure that he is eating and drinking enough throughout the race. He likes to run with one new guide and one with whom he has run with before.

“That keeps it interesting,” Magisano said. He told Schulman, “You’re the newer one, which means you’re the fun one.”

Schulman is the producer and host of MTV’s “Catfish,” a reality show about whether people who meet online are actually who they say they are. He elected to be a guide this year because he wanted his seventh time running the New York City Marathon to be different. He recalled how his pace in his first marathon was slower than he had hoped, and how he got progressively slower as the race continued.

“I hear from behind: ‘Blind runner! Blind runner on your right!’ and two guides guiding what I guess was a 50-something-year-old woman and they just really flew past me,” Schulman said. It humbled him, and he knew that one day he would like to be a guide.

As Schulman recounted the story, a group of runners ahead of them — overhearing the phrase “blind runner” — parted to make way for him and Magisano, assuming that he was talking to them.

But one woman, seemingly mesmerized by how a stream of sunlight settled on a nearby tree, stopped in the middle of the path to take a photograph. Schulman gently grabbed Magisano’s elbow and shifted his own body rightward to guide him around her.

Guiding, Schulman said, would add a new level of fulfillment to the marathon. He said his goal was “simply to successfully navigate the course incident free, just get Francesco and myself to the finish line.”

The woman taking the photo wasn’t the only obstacle to clear. Schulman also made calculations about how to navigate around people they would soon overtake or ones who were moving toward them. He was alert for walkers and bikers who were trying to cross from one side of the path to the other. At one point, Schulman told Magisano to duck to avoid a low-hanging branch.

It was good practice.

“A lot of times, it’s hard to hear my guides, so there’ll be minutes where I can’t hear a word they’re saying so you have to go entirely by feel,” Magisano said of the New York City Marathon course. He said he focused on the feel of his guides’ elbows and knees.

“You can’t really see it, but our arm hairs are kind of like the ponytails in ‘Avatar,’ ” Schulman said. “They’re syncing just slightly enough that we can create, like, a bond.”

Magisano, who is quick to laugh, looks for an easiness in his guides, people with whom he can banter. He cherishes those guides who lead with confidence, are vocal and say what they are thinking.

And as much as the guides are helping Magisano, he’s also doing his fair share of guiding. He prefers not to run on the lines painted on the street, which can make the path uneven, so he reminds guides to move him off them. He asks them to tell him what pace they are running and how many miles they have completed. Above all, he’s looking out for their safety, too.

Magisano said it was common for guides to forget to eat and drink, which could be dangerous given the pace and distance they run during marathons.

“They’re just so focused on guiding that it’ll be like two hours and they haven’t eaten,” he said.

Magisano has trained hundreds of guides, and Achilles is always looking for more. He joked that before picking up running, his exercise was writing essays on the history of soccer. He now gets real physical exercise and has built a strong community of friends. And of course, there are life lessons to be drawn from marathon running.

“You got to struggle and feel pain,” Magisano said. “That kind of ties into disability where life is struggle, but you got to overcome it, otherwise you fail.”