PHILADELPHIA - The hard-muscled men of Haverford College's lacrosse team were primed for a fierce, preseason workout.

So they did a Happy Baby, lying on their backs, grabbing the soles of their feet, and rocking back and forth with glee.

For an hour, the 30 players stretched into Downward Facing Dog, Tree, Frog, and a dozen other yoga positions. Not exactly push-ups or wind sprints.

"It's a little shot at the masculinity," joked Joel Censer, 22, a defenseman with tight hamstrings who struggled with a contortion or two. "But, nah, it's great."

Long a fixture in spas and health clubs, yoga is winning over campus jocks. A growing number of college teams have rolled out the yoga mats to augment training regimens and improve flexibility, strength and mental grit, coaches and instructors say.

Haverford took up the ancient Eastern discipline in 2006, and other teams that have adopted it include football at Villanova and Princeton, women's soccer at Penn, women's crew at St. Joe's, and, since the fall, men's soccer at Swarthmore.

Training with yoga appears to have little downside other than, perhaps, the time it can take away from traditional workouts. Researchers also point out that the most-touted benefit - better performance - has not undergone rigorous scientific study.

That hasn't slowed the flow of followers. While no one tracks the number of college teams that supplement training with stretches, deep breaths and meditation, a new Yoga Journal survey indicates nearly 16 million Americans pursue the discipline - 8 percent of them in the prime college age range of 18 to 24.

Yoga has had U.S. adherents since 1893 when Swami Vivekananda introduced in Chicago the hatha form, which stresses physical aspects. Some pro teams, including the Eagles, have used the poses in workouts. Kareem Abdul-Jabbar has been a fan since the `70s. Shaquille O'Neal, Kyle Korver, the Williams sisters and other sports stars also train with yoga.

College and high school teams have adopted the exercises more recently.

"That influence trickles down," said Yoga Journal senior editor Diane Anderson said.

In many cases, the activity is stripped of its traditional Hindu flavor. Some instructors avoid Sanskrit names for poses in favor of English or no names at all, and add movements from other exercise forms.

"If I started to use yoga-speak, they'd shut me out," said Cara Bradley, owner of Verge Power Yoga in Wayne, who began training the women's soccer team at the University of Pennsylvania last month. "We don't `om', or anything." She even gave the class a more sports-appealing name: Balanced Athlete.

At Haverford, instructor Claire Brandon, 22, who is majoring in art history and Romance languages at Bryn Mawr College, interjects the occasional chaturanga (a push-up). But instead of the typical New Age music, she uses rock and reggae. The yoga appeals to enough players - who organize the weekly sessions themselves - that they come on Sunday (the only day off from practice) and pay the cost out of pocket.

"It makes us a little more in tune with our bodies," said attackman Mike Distler, 21. "It definitely stretches us out more than we ever would during the week."

On this day, the men squatted (Frog) and then moved to the aptly named Happy Baby before finally meditating for a spell.

"I'm all yogified," goalie Jake Mendlinger, 22, said with a grin as he grabbed his stick. "I'm ready to play."

Whatever the style, the goals are similar: Improved flexibility. Better concentration. Fewer injuries.

"We bring stability to the entire body," said Adam Marcus, cofounder of Enso Studio in Media. "It's not just about having strong quadriceps."

Over eight sessions at a cost of $1,600, Marcus trained the Swarthmore College men's soccer team in Budokon, a new form that fuses yoga, martial arts and Zen meditation. "You get that full-body training," Marcus said.

A favorite was the Komodo Dragon, for which players assumed a push-up stance and moved opposite legs and arms across the field-house floor to build strength and agility.

"It's a push-up unlike any you've seen or done," head coach Eric Wagner said.

By season's end, his men had captured an Eastern Collegiate Athletic Conference championship, a feat Wagner attributed in part to the mental focus those Budokon lessons built.

Experiences like that boost yoga's appeal. But, said Ralph La Forge, a physiologist at Duke University who specializes in mind-body exercises, "no trials have shown improved athletic performance."

Hatha yoga does help flexibility, he said. "Hypothetically, it should improve performance," La Forge said, "but I can only say hypothetically."

At Penn, Darren Ambrose, head coach of women's soccer, was betting off-season training with yoga would pay off on the field.

"As a coach, I want to give my kids every competitive advantage I can," he said while the team bent and twisted under Bradley's guidance. Soccer is "absolutely about mind, balance and agility."

Elite athletes marvel at the challenge. Some of the women began shaking as they tried to hold positions. "It humbles them from the first pose," Bradley said. "I rock their world a little bit."

Junior Debbie Bateman was skeptical, she said, when she encountered yoga training three years ago as a varsity rower for St. Joseph's University, where instructor Ed Harrold from Lewes, Del., shares his Flexibility for Athletes program.

Then the nostril breathing (in one side, out the other) and belly pumping (quick, short breaths) helped her push past pain and stay competitive while various poses strengthened core and lower-back muscles.

"I started to shed some of the doubt," she said.

Added Harrold: "There really isn't any separation between the ancient yogic warrior and the warrior you see on the athletic field."