Next, we embark on our second 20-minute aerobic set, which includes John Travolta disco moves, Pete Townshend air guitar, rocking out side-to-side arm-pump hops, and Greased Lightning horizontal arm sweeps. By the end, we’re all dripping with sweat.

Then it’s time for the mat portion of class. " This works your olfactory senses, " Jasper jokes as we get closer to the floor of the Middle East than we’d normally ever want to be. " Yeah, get close with the beer and puke, " jeers Mancini. We stack two mats — makeshift, jaggedly cut foam strips — on top of each other and do sets of sit-ups and crunches. After pelvic-lifting exercises dubbed " slut butt, " and some light stretching, we’re done.

The casual, cool class is like none I’ve taken before. It’s both inclusive and irreverent, playful and professional. These girls are serious about just wanting to have fun. Mancini and Jasper seem post-ironic in their appreciation of punk; they’ve been there, done that, and now they’re back for more. Is punk in? Is punk out? Whatever. For them, punk’s alive and kicking. " It’s fucking for real, " says Mancini, when asked if there’s any element of joke to the class. " How do you think Iggy Pop got those abs? "

STILL, FOR some punk scholars (yes, they do exist) the idea of a punk-rock aerobics class sounds like an oxymoron at best, and an offensive appropriation of the genre at worst. " Wait, " says a laughing Lauraine LeBlanc, author of Pretty in Punk (Rutgers University Press, 1999), a study of women and girls in punk subculture, on the phone from Montreal. " You said punk-rock aerobics, right? "

Marc Beyer, who taught a class at Tufts University in 1998 on punk’s cultural, political, and historical impact worldwide, isn’t laughing. " Aerobics, well, that is the stuff of Olivia Newton John or Cher, not punks, " he quips. To him, the idea sounds " pretty damn dumb. " But Craig O’Hara, author of The Philosophy of Punk: More than Noise! (AK Press, 1999), understands the appeal. " When I worked a couple of years in a weight room in the basement of a building on Commonwealth Ave (Myles Standish Hall), we’d pump iron for hours a day listening to punk and always figured it superior dance music to that Olivia Newton John–type crap, " he scrawls in a note accompanying a copy of the slim book, for which Beyer wrote the introduction.

LeBlanc finds a more academic explanation. " It’s not entirely inconceivable, " she says. " You can ‘punk rock’ anything.... My finding in the book is how punk girls use the punk subculture to counter adolescent forms of femininity. Punk girls don’t do away with feminine things, but rather take them and turn them into a punk thing. "

Sure enough, Jasper and Mancini are so punk that they’re down with aerobics. They live the punk-girl contradictions that LeBlanc describes — part sweet, part nasty; part enthusiastic, part chill. One minute Mancini’s gleefully sharing an anecdote about being able to pick up her own amp after shows, thanks to her new, beefed-up muscles, and the next she and Jasper are trying to figure out how many drinks today’s earnings will buy. " You know we’re gonna go out drinking now, " she says with a devilish grin.

Jasper and Mancini are stripping aerobics of its attitude and creating a musical backdrop that makes people want to move uninhibitedly — with exercise almost as an accidental byproduct. In effect, they’re creating a script for a punk-rock Behind the Music that doesn’t need a downward spiral into sickness and addiction. " I want people to come to class and be like, ‘I totally fit in here. I can let my freak flag fly and not worry about it and actually get some exercise,’ " Mancini explains.

And that is precisely what happens for Elena Cotto, 23, when she comes to Spontaneous Celebrations for the second class of the day. " I’m a big Fuzzy fan, " says the small young woman, who sports spiky maroon hair, an eyebrow ring, and a pierced tongue. " When I saw Hilken’s name on it, I sort of freaked out. "

Before class, Cotto changes from a tight, black-and-white-streaked tank dress with bra straps into her workout ensemble: a white Nike sports bra and blue hospital scrubs. " I wonder if anyone’s going to say anything about these, " she says, looking down at her outfit. Back at her regular gym, Fitcorp in Brookline, " there are hard-core gym bunnies and everyone looks just like everyone else, " she sneers. The other day, when she put on her scrubs for a traditional aerobics class, people gave her the disdainful once-over with raised eyebrow. " They were like — " Cotto looks me up and down with an acid eye and a curled upper lip.

At Punk Rock Aerobics, no one even looks twice.