Unflappable and unstoppable in her neon green tank top, Lisa Duffy takes down all 20 Collingswood High School varsity wrestlers at once.
The amiably unruly crew of teenagers at Anjali Power Yoga in Westmont is suddenly at her command.
"Crank it up!" she says, or rather, shouts, striding through the sweaty rows of mats. "This is fun, right? We're here to sweat, right?"
During the team's one-hour weekly hot yoga session, the studio heats up to 93 degrees, the soundtrack thump-thump-thumps with party tunes, and shirtless, noisy boys try to bust on each other.
They'd love to bust on their instructor, too, but Duffy's having none of it; she's practiced yoga for seven years, and she wants to share its benefits with the boys.
"Extend your feet up into the sky. Press them into the sky," she says, continuously guiding, encouraging, narrating the flow - and noticing what her charges are up to at every moment.
Pity the poor fellow on the far side of the room who looks to be catching a bit of rest.
"This isn't break time," warns Duffy, a Haddon Heights mother of three. "No child's poses!"
She's also a marathon runner, a sport that appears to help the human body withstand hot yoga's extravagant temperature and humidity.
Duffy may never stop moving, but I'm exhausted after 10 minutes - and I'm sitting on the floor, in the corner, taking notes.
This must be what it's like to do journalism in a terrarium, or a sauna, I think, my glasses and smartphone fogging over yet again.
"Heat the room," Duffy is saying, as she prowls the rows with fellow instructor Corey Sumner. The two gently adjust the posture and positions of various wrestlers.
"Build a fire," Duffy adds.
"The room's already on fire," a wiseguy replies.
"Chaturanga!" shouts another, and then another; the boys seem to enjoy the sound of the Sanskrit word for a difficult pose resembling a stationary, low-slung push-up.
Panthers wrestling coach Dechlin Moody, who's on a mat near my corner, came up with the idea of supplementing the team's daily practice sessions with a different kind of workout.
"It was a gamble, because I didn't know how the kids would take it," Moody, who lives in Mount Ephraim, tells me later. "I said, 'Yoga is not a joke. Yoga is tough.' "
The nonstop stretching, twisting, posing, and balancing moves that make up this vinyasa flow class are "a good workout," says Colin Lex, 18, a junior. "It's more intense than I thought it would be."
"I was kind of shocked at first that we were going to a yoga class," junior Dan Habens, 17, says. "I didn't understand why we were doing it, but when I got in the room, I knew why."
"You use a lot of core strength," adds Micah Roth, 16, a junior.
"I'm down with anything that makes you more flexible," says James Thompson, 16, a sophomore.
By nature, their class is a bit looser than other yoga sessions, notes Sumner, 25, of Washington Township. "They're 20 teenage boys who aren't used to" the conventions - and the concentration - of a yoga practice, she says.
"These kids get so much stimulation, and it's good to unplug from all that," Duffy says. "It's important for them to have a grounding force, a centering."
Having practiced yoga for several years until sidelined by shoulder problems, I know it can foster mental, as well as physical, well being.
And even this most vigorous hot yoga session concludes with shavasana, the restful state that sounds far more appealing in Sanskrit than in English (it translates as "corpse pose").
Duffy dims the lights, and Anjali's misted-over windows along Haddon Avenue take on a soothing glow. Electronic dance music gives way to Coldplay; the bodies on the mats are motionless and at rest.
She calls them back to a seated position, and they all ohm three times, in unison. Before grabbing their gear and filing out the door into the bitter night, the boys applaud.
"Their energy is amazing," Duffy says. "It fuels my fire, too."