» More: Instructors describe their indoor bicycle program and fitness benefit

Don’t let the lounge-style lighting fool you. Same goes for the popular live U2 track rumbling from the speakers.

Inside the mirrored room, the last one on the right off the YMCA indoor track, more than a dozen people are putting the work into work out.

This is a place where you push and push and push —even to have one of the floor fans kicked up a notch.

“I’m not putting it on high yet,” instructor Tatiana Kolovou tells her students during the warm-up. “You have to work for that.”

They do.

For 45 minutes, they ride on school bus-yellow bikes, adjusting gears, working with resistance and rising up out of the seat now and then—known as “out of the saddle.”

They pedal and they pant. They pant and they pedal.

And they leave afterward happy, smiling and sweating.

Linda Mongold, 54, calls the class very intense. A cyclist for 35 years, she’s been indoor biking for three years and credits it for helping keep her in shape.

Mongold and some of the others have been with Kolovou for a year. The bond is as apparent as the beads of sweat. There are five couples in the class.

“She’s an amazing coach, her lessons are so tight,” said Jim Morrison, after a recent Monday class. He admitted that he hadn’t wanted to come to class that night.

“If I stayed home, I’d still be tired and sluggy,” Morrison said. After 45 minutes on the bike, his condition had turned around—“500 percent better,” he said.

Enrolling in an indoor cycling class is just one way to heat up when it cools off. In fact, the popular program is year round at the YMCA.

Several of Kolovou’s students also ride outdoors, but there’s little to none of that during these shorter days and colder temperatures.

For some, the fitness struggle during fall and winter is not only moving the workout indoors but keeping it exciting despite being bound by four walls.

The key is finding an activity you like, whether it’s lifting weights, swimming, walking on the treadmill or taking a class.

In Kolovou’s class, which she splits with Mindy King, music and imagery help set the mood—and raise the heart rate. No cubicle vibe here. The ceiling fluorescent lights are off; the only light shines from a floor halogen lamp. The unusual lighting drew curious looks through the window from track walkers and a few racquetball players exiting the nearby court.

Kolovou coordinates each class perfectly. This particular one is divided into five six-minute sets that range in intensity and speed. The speed decreases from 100 revolutions per minute down to 60 with each set as the resistance increases to maintain intensity.

Kolovou, instructs, encourages, urges.

“If you don’t like the speed, it’s going to be over in one set,” Kolovou coaches, coaxing from her head-set mike. Then, she’s off her bike for “quality control,” checking on her students.

“There’s nothing like accountability with numbers,” she says of the requested rpm. “You’re hating me now, and that’s OK.”

Kolovou is in it with them; she calls them team. She knows their names. “How’s my Jim?” During the class cooldown, she inquires about a missing student.

Complementing her coaching is the music. Kolovou is a talented emcee, loaded with varying styles to help match the speed of each set.

Just as Larry Mullen Jr.’s drum beat picks up in U2’s “Where the Streets Have No Name” so does the pedal pace.

“Can you see yourself out on this road, out on this flat road?” Kolovou asks. “It’s your power that’s going to get you there. Let’s go team.”

The class winds up and then back down with The Police’s “Message in a Bottle.” Then it’s off the bikes to stretch.

Kolovou talks them through the cool-down. “Think about what’s for dinner,” she said. Something healthy is implied after all that work—though each will be back in the saddle in two days to do it all again.