Elevate Interval Fitness’ David Magida, left, keeps clients on track during workouts by letting them check their heart rates, shown on TV screens around the gym. (Teddy Wolff/For Express)

Gasping for air, the students at Elevate Interval Fitness slowed their treadmills down from a sprint to a recovery walk.

“Everybody made it to red,” cheered David Magida, founder of the new 14th Street boutique. He wasn’t referring to their faces — although some had turned quite rosy. He meant their individual, color-coded heart rate zones. Elevate students strap monitors to their chests, so their beats per minute and level of effort can be displayed continuously on TV screens around the studio.

For interval training, it’s helpful to visualize how adjusting the intensity of a routine translates into “peaks and valleys,” Magida explains. The nifty bit of tech is also a way to appeal to exercisers who demand more from a gym: “You don’t just want to assume you’re getting a good workout.”

Access to the numbers — during class and in an email sent right after — turned Dupont Circle resident Kevin Burr, 45, into a repeat customer. “I’m a little competitive,” admits Burr, who’s hoping his stats improve.

Heart rate tracking, meanwhile, is getting a lot more competitive, with a growing number of gyms offering it. Orangetheory, a national chain that takes a heart rate-focused approach to workouts, has opened three D.C.-area clubs over the past year (in Fairfax, Arlington and Gaithersburg, Md.), and a fourth (in Ashburn, Va.) debuts later this month.

XSport Fitness has rolled out a similar program (called X-IT) at several of its clubs, including the one in Woodbridge, Va. Fitness manager Rob Matthews says the extra cost is worth it for members, who know they can’t cheat.

No place takes this technology as seriously, however, as Life Time Fitness. The chain suggests in-depth metabolic assessments to calculate heart rate zones (rather than relying on the standard age-based formula). And it insists on screenings for anyone in T.E.A.M. Weight Loss, so coaches can customize workouts.

“I learned that I was working hard, but not hard enough,” says Susannah Palik, 44, who’s lost 17 pounds through the program at the Reston, Va., club and is eager for her next assessment — heart rates shift as folks shape up.

Heart rates are integral to several other Life Time offerings, including its new Performance Plus Cycle classes. Reston’s metabolic specialist, Brian Crow, can use the data he gathers to dictate both diet and exercise plans. Listening to your heart, he says, can lead to real results.

Life Time Fitness recently released its LT Connect app to encourage heart rate-based workouts.

Learn it by heart
Life Time Fitness just released LT Connect, a free smartphone app that encourages members to train using heart rate data both in and out of the club. It comes preloaded with workout plans designed to leverage heart rate zones and maximize fat burn. Members working with a trainer also gain access to customized routines.

You might also like:

Fuse Ladder introduces students to a new Pilates apparatus and forgotten muscles

Three ways to improve your next race time — without running

For a better run, tread(mill) carefully