JUMP! JUMP! JUMP AROUND!

Spring-load your body with athleticism (and confidence) by jumping on the trampoline trend.

- MICHAEL J. LEWIS

I CAN'T STOP watching my feet. I've spent the past 15 minutes jumping up and down on a mini-trampoline, and each time my body rises upward, my eyes gaze down. If I don't do this, I worry that my feet will land on the very edge of the tramp's surface, I'll lose my balance, and I'll tumble off.

It's a new and uncomfortable feeling, but so is just about everything about my Bounce Essentials class at the Ness, a New York City group-fitness studio that focuses on a unique implement, the minitrampoline, which is about 40 inches wide and a foot off the floor. For 50 minutes, Shaina McGregor, the impossibly upbeat instructor for this madness, pushes me and the rest of the class through a series of ultra-intense trampoline drills, torching my glutes, calves, and abs.

For years, I've thought of trampolines as more of a diversion than a workout, the kind of thing that belongs at Chuck E. Cheese. A trampoline workout? That's a punchline, not a legitimate way to build muscle or blast fat. Studios like the Ness, though, are changing that perception and filling a major gap in the fitness industry, too. Trampoline jumping is even an Olympic sport now.

Trampoline workouts push you to find serious air time. This is different from simply jumping off the ground. When you leap off the ground, your body knows exactly what to expect, because you're controlling how high you'll go. When you jump on a tramp, the device actively propels you upward. This makes it easy to lose your balance, tipping backward or forward, so you need to use your arms and core muscles to find aerial equilibrium. This challenge is absent from gym workouts, which basically tether you to the floor to lift weights, and HIIT classes, which often trap you on cardio machines, with only occasional skater lunges and explosive squats.