The first time Jarell Carter entered a Pilates studio, he was expecting an easy workout.

A fitness influencer and a former N.F.L. athlete, Mr. Carter is able to squat more than 500 pounds. He bench-presses more than 400. But less than 20 minutes into his first Pilates session, his “legs were shaking uncontrollably,” he said.

“I was struggling and sweating profusely,” he added. “Making noises that I just couldn’t control. I was just trying to hold it together.”

His first coherent thought? “Whoever created Pilates hates men.”

Around the country, men have burst into the Pilates studio. Tom Brady has done it. So have LeBron James and Cristiano Ronaldo. The fitness app ClassPass said the number of men taking classes has nearly tripled since 2023. At Equinox gyms, male participation is up over 50 percent in both group classes and private sessions in the last 18 months.

Nationally, 4.1 million men took Pilates last year, up from 2 million in 2021, said the Health and Fitness Association, a trade association. Overall this year, about one out of every three Pilates participants is a man, the organization added.

It’s a shake-up for the popular exercise method, which is closely associated with the “Pilates princess” aesthetic that has come to define the space — matching athleisure sets, slicked-back ponytails and post-class matcha lattes all but required.

“I thought it was just for women,” Mr. Carter, 31, said.

Now, some men are finding Pilates is making it easier to pick up their grandchildren and swing a golf club. They feel younger, more mobile and unashamed that Pilates is a reason why.

The shift is in line with the less gendered approach to exercise more broadly, said Greta Wagner, the president and chief executive of the Health and Fitness Association. “You see women in the weight room now and you see men in Pilates,” she added.

The low-impact, full-body workout emphasizes core strength, stability and slow, controlled movements — a far cry from the weight lifting “bro splits” of the gym. It comes in many forms, but the two best known are mat Pilates (which takes place on the floor) and reformer Pilates (taught on sliding-carriage machines called reformers, with spring-based resistance).

Some men are taking men-only, pop-up classes or joining men-only workshops. But mostly, they are showing up at coed classes. Mr. Carter’s first time in a group Pilates session, he felt at ease. “Everyone was smiling. Everyone was happy,” he said.

The insertion of masculine energy has left a few people in a huff. “They’re sweating all over everything and not wiping down their machines,” said Eve Tilley-Coulson, a lawyer in Los Angeles, who added with disdain that some even wear basketball shorts. “They’re incapable of even doing the move because they aren’t in the right clothing to be able to do it,” she said.

But many women are welcoming. Some are even leading the charge. Patricia Stevenson, the president of the Pilates Method Alliance and an instructor in Florida, said a number of her regular male students were originally dragged along by spouses or female friends. She estimates about half of her clientele is now male, up from less than one in 10 about 25 years ago.

Pilates was never meant to be a gendered workout. “The matching sets and the matcha all came later,” said Naimah Jackman, 34, a certified Pilates instructor in New York. Joseph Pilates developed what he called “Contrology” around World War I. A German circus performer and boxer, Mr. Pilates was interned in the United Kingdom during the war and began teaching his methods to his fellow inmates.

Soon enough, though, Mr. Pilates had moved to New York City, where dancers — many of them female — started booking sessions in his studio. From there, the number of female fans grew until Pilates became seen as a feminine workout.

“I made fun of guys that took Pilates,” said Gary Reisman, 63, who now attends classes regularly at KZ Pilates+ in New York. His first time trying it out, he booked a personal trainer, “so I didn’t have the issue of being embarrassed in a class full of women,” he said.

Hoping to make Pilates more welcoming to men, Ms. Jackman founded Men’s Pilates NYC, her monthly all-male Pilates club, in 2024. On an open-air rooftop in Times Square, she tries to mirror the energy of a gym, including by blasting trap music.

Krisi Frazee, the owner of Better Body in Virginia, designed her studio to be more gender-neutral. “Pilates can be intimidating for everyone, but especially for men,” Ms. Frazee said. Her goal is to make the class more welcoming to all. “We don’t have music. We don’t have microphones. It’s not pink and purple and beige. I just have equipment.”