However, it's important to know that showing off your body means only what you are comfortable baring. In the four years that Costa has been teaching the class, not one person has ever gotten completely naked. He says that people are generally modest, preferring to take off only a hoodie or a T-shirt during class and saving the real risqué behavior for home ‑- be it in front of a spouse or a full-length mirror.

"There's no right or wrong here; it's all very interpretive. If your California Roll looks a little bit different than the person's next to you, great, because that's your body expressing what you're doing," Costa says. "That opened up Cardio Striptease to a bigger demographic ‑- older women, people who have never danced before, people who have spent their whole life on a treadmill. These women discover a part of themselves that they probably always knew was there but never got in touch with. When you see yourself out of the baggy gym clothes, you're going to present yourself in a very different way than if you were trudging down the street carrying groceries or carrying your kid. I've had so many makeovers with moms and wives and [women playing] every other role besides being a woman that they get into the class, and it's a rebirth for them."

The class is broken up into two parts. The first is learning and repetition of the steps ‑- that's what gets the heart rate up. The second is the performance, putting them all together, which gets other people's heart rates up. Costa gives unorthodox instructions like, "Pretend there's a crayon in your butt and draw a circle between your legs" to get you to loosen up and understand the steps he's teaching. Then, to spice things up, he adds props, like a chair or a light box that you spank to turn on and off.

"Anything to get people's minds off the fact that they're sweating, burning fat, burning calories. Anything to make the gym not be a grind anymore," says Costa, "and make it be a place to bump and grind."