Fueled by Zumba, giant fitness classes become the new big thing

If you sense something burning at the Franconia Fire Station, don’t worry — it’s just calories. Six days a week, Roberson Magalhaes and Leonardo Lins take over the station’s bingo hall, crank up the music and teach Zumba, a Latin dance-based form of fitness that’s celebrating its 10th year of getting participants to “Ditch the Workout, Join the Party.”

Maybe that slogan should really be “Ditch the Gym.” That’s because popular instructors are building such enormous followings that they can’t fit inside typical health club exercise studios, which are rarely designed to handle more than 50 students. So several have started businesses to cater exclusively to the hordes of Zumba zealots, and they’re finding that no matter where they set up shop, they often don’t have enough space to meet demand.