In the daily game of treadmill versus trying new things at the gym, treadmill always wins out. So despite the fact that I’ve been meaning to give an online elliptical workout a go for months, I kept putting it off. Finally, however, this weekend, I had a change of heart.

I walked into the gym with one mission: To revisit the old-school cardio machine and see what it could do for my fitness game. “Who are these elliptical devotees?” I wondered to myself as I stepped onto a machine in a very crowded row. After flipping on the TV to see The Devil Wears Prada playing (a pleasant surprise), I busted out my phone to stream the NEOU Fitness elliptical workout.

I’m greeted by Jane Do trainers Jacey, Dani, and Cristin, two of whom are on ellipticals to muscle through the sweat sesh with me. The workout itself is 20 minutes of “Taking it Back to the 80s,” so once the music’s cued up, I immediately start gliding with attitude. We start with a warmup, of course, which involves low intensity to get the legs and arms used to the flowing movement—and this requires lots of attention to form, helping to take the workout up a notch.

While your legs are moving back and forth, your arms are pushing and pulling the handlebars, and you’re keeping your core engaged, being sure not to let your quads do all of the work. It takes me a few minutes to get this down, but once I do I start to really feel my entire lower body fire up—not just my quads, which tend to do a lot when I run. “Don’t let the elliptical machine deceive you,” says Jacey Lambros, co-founder of Jane Do who’s instructing the class. “A total body workout, the elliptical targets your quads, hamstrings, glutes, core, and upper back, depending on the choreographic choices you make. The beauty of the elliptical is that you can dictate which muscles you want to focus on, and you can manipulate the resistance.”

She’s right—I start really sweating and getting out of breath as we slowly increase the resistance, and even start pedaling backwards for more of a butt-slash-hamstrings focus. At one point, we literally stop and squat (and pulse and hold it) on the machine, which is so hard and I feel like my butt is going to break. Then, we alternate between gliding with only one arm pushing and pulling at a time, which really challenges your balance skills. The peak is probably when we’re told to crank up the resistance to a 10 on our perceived difficulty scale, climbing an invisible hill via the elliptical, at which point my legs are on fire up until the cool down. The whole workout actually flashes by so quickly and there was way more variety to it than I pictured was even possible on an elliptical.

I stepped off the machine with wobbly legs, drenched in sweat, and panting. Who knew—the elliptical machine can truly kick your ass.

Before you see for yourself, here’s how to use an elliptical properly (and avoid the most common mistakes trainers see people make). And this is Jennifer Aniston’s 20-minute elliptical workout, because she’s in on it, too.