Walk into most classes and if any men can be found, they are in the back corners, where they can fumble through poses without attracting much notice.
Anatomically, women are no better equipped than men to do yoga, said Larry H. Chou, a physiatrist at Premier Orthopaedic & Sports Medicine in Havertown.
"The resistance has been psychosocial. There was this perception that yoga was less manly," said Chou, who has consulted with professional sports teams and was a faculty member at the University of Pennsylvania's Sports Medicine Center.
Furthermore, because men in America tend not to stretch as much as women do, they are not as flexible, Chou said. "People like to do what they are good at," he said. "And they're not so fond of doing what they're not good at."
Though the gender imbalance in yoga classes has social advantages for some men after class, many find it demoralizing to be surrounded by women who, in general, can twist themselves into poses with much greater ease.
"It's a challenge," said Alain Benitez, who recalls his first yoga class as a humbling experience. "Out of a group of 30 or 40, I was the only man, except for the teacher's boyfriend. I learned a lot about how much ego we carry. It was kind of humbling."
In the five years since, Benitez has devoted himself to the practice. After studying with several teachers, Benitez began leading his own classes. Last year, he joined the small but growing number of yoga teachers offering classes geared exclusively to men.
"We have specific limitations," said Benitez, 32, whose day job is conducting allergy research at Children's Hospital of Philadelphia. "Our broader shoulders do not help with balance. Our minds race a little bit faster. We have a hard time getting into a meditative state."
In the safety of a yogic fraternity, Benitez said, his students feel more relaxed.
He helps them get there by speaking their language. When they lie prone for cobra pose, he tells them, "if anything needs adjusting, now is the time. We don't want pinching." And he notes there is something reassuring when more than half the men in the room cannot reach past their knees, let alone palm the ground.
"I see a lot of broken-down men, who are shrugged over and have no balance," said Robert Sidoti, 42, cofounder of Broga on Martha's Vineyard. Sidoti, an omni-athlete and former actor, started his male brand of yoga there with a friend in 2009.
The plan seems to be working. Broga now has licensed teachers across the country, with two dozen more in the works. A teacher-training is planned for January in Phoenixville.
The classes, he said, are minimalist: "Let's just focus on the breath and postures and get you through them in a healthy, safe way." Besides the basic poses, Sidoti said, he throws in some power moves. "Men can relate to a push-up, so for the guy who wants to get a little bit of a workout, we get the heart rate up."
For this, he said, Broga has been criticized by purists. "But the way yoga has been presented on the surface didn't speak to the buddies I was hanging out with," he said. The soft images on yoga websites, the lotus flowers and new-agey wording, put them off. "I wanted to repackage yoga," Sidoti said.
Jake Panasevich, who started teaching Yoga for Dudes in August at Maha Yoga Studio in Center City, has developed enough of a following that he plans a recurring series of workshops.
Panasevich, 28, a former college wrestler, was 5-foot-11 and weighed 225 pounds at his beefiest. "I was like a giant ball of muscle," he said.
A year after Panasevich graduated from the University of Pittsburgh and moved to Philadelphia, his girlfriend dragged him to a power yoga class.
Sweating profusely and struggling to get into the poses, he said, he was shocked by the intensity of the workout. "I tried to muscle my way through it. I couldn't touch my knees."
Five years later, he said, he is getting into poses his teachers told him he would probably never achieve.
"Oddly enough, I find yoga a lot like wrestling," he said. "If your mind is not in it, you're going to get hurt or lose . . . . There is something sweet about being focused in that way. It's very meditative and challenging," he said. "And it's not always bliss."
For muscular men trying yoga for the first time, patience is especially important, said Christopher C. Dodson, an orthopaedic surgeon at Rothman Institute and Thomas Jefferson University.
"Large muscle mass is great for many things, like moving couches and playing football. But with those larger muscles, you do lose flexibility," he said. "The way to prevent injury is to gradually build up. It's similar to if you've never run before, don't try to do a marathon."
Before starting his recent Saturday workshop at Anjali Power Yoga in Westmont, Benitez tried to put his students at ease. Built like a ballet dancer, his speech faintly spiced with a Cuban accent, he told them that when he started yoga, he was hopelessly inept.
"There is a difference between setting intentions versus expectations," he said. "If you set an intention to get into a pose, I want you to get there, but if you don't, so what?"
At the back of the room, David Share, 56, a nephrologist from Burlington County, hung on every word. Long and narrow with a slight stoop to his shoulders, Share had never taken a yoga class before. He had come, he said, at the urging of his wife, a "yoga addict" who had convinced him it would be good for him.
The more experienced Brad Oister, a 36-year-old flight attendant for American Airlines, had braved the front row. Wearing black Nike spandex shorts and a muscle T-shirt that exposed the bold black graphic tattoos sweeping across his formidable biceps, he settled on his mat with self-assurance.
"The hardest thing is to stop looking around at what everyone else is doing," Oister said earlier. In coed yoga classes, he found that his competitive instinct kicked in. "There's a tendency to push yourself in a bad way."
Other students included a hip, 23-year-old beer brewer, bearded and mustached, his head in a purple bandanna, and a snowy-headed 61-year-old commercial real estate broker.
"Do you think warriors go to war without weapons?" Benitez asked, picking up a strap and a yoga block. "These are your weapons."
He warned about the risk of muscling through, saying, "if you can't breathe, you've gone too far."
And finally, he said, listen to your body. If at any time you feel pain, "Drop the ego and step back," he said. "Trust me."