Orange Theory Fitness uses real time heart rate data to give members what it calls the “best one hour workout in the country.”

Ten minutes before the 3:30 p.m. class is set to start, the lobby at Orange Theory Fitness is already full. Between stuffing their things into a locker and taking a few final sips of water, each member stops by the front desk and picks up a sleek black pod, which they cinch around their chests.

These black pods are heart rate monitors, and they’re connected to a computer system that tracks each member. Big screens in the gym show everyone’s heart rate data in real time—so if you’re not working hard enough, everyone knows it.

“Our goal is to get you to be at 84 percent of your max heart rate for 20-26 minutes,” explains Corey Rubenstein, general manager of the Fort Myers Orange Theory Fitness. “We use a basic equation using age and gender to determine your max heart rate,” he adds.

The theory behind Orange Theory is to get members working hard enough to create excess post-exercise oxygen consumption, or EPOC. Research has shown that when you exercise at a higher intensity, your body consumes more oxygen—thus burning more calories—in the hours following your workout than it would during a longer, slower workout. Orange Theory Fitness says that its 20-ish minute cardio session plus its 20ish minute high-heart-rate strength training will give you the maximum post-workout bang for your 60 minute investment. And, because everyone works at their own heart rate level, 20-year-old college athletes can work out next to their 50-something parents.

“We get these macho guys in here that just die,” says Rubenstein, “because it’s really about keeping that heart rate up, even during the weight training.”

The gym is set up with a dozen treadmills, a dozen rowing machines, plus a weight room with TRX Suspension Training ropes and BOSU Balance Boards. Half the class—Orange Theory can accommodate 24 at a time—starts on the treadmills while half heads to the rowing machines and weights. The teacher pumps up the music and gets everyone warmed up. And when he says “crank it up to your orange zone,” he means it. Those slacking get called out.

“I really, really like it,” says Kathy Kartoska of Cape Coral. “I come four times a week and I drive half an hour to get here.” Kartoska says that she loves that the workout is totally structured, that there’s always someone telling you exactly what to do. “I like the metrics too, it really gives me something to work towards. And there’s a real encouragement in the group—but it’s not a competition—it’s camaraderie.”

Forget orange being the new black, in Fort Myers, orange is the new fit.