Sweat’s dripping down my temples, my heart rate monitor looks like it — or maybe my heart itself — might burst, and I’m flopping around, off-rhythm, attempting jumping jacks with a massive medicine ball. I have Britney Spears to thank for all of this. Well, her and Flip Or Flop‘s Christina El Moussa.

Britney introduced me to OrangeTheory, with a promo for the group fitness classes blasting not-so-subtly in the background of her “Make Me Move” music video. That was my introduction, underscoring that product placement does work — sadly, even the most overt, eyeroll-inducing kind. Still, it wasn’t enough to get me to consider joining. The final push, actually, was all El Moussa’s doing.

She wasn’t trying to convert me, but after spending the day with her in Orange County for a story, learning about her diet and exercise routine, I was sold. The interior designer and HGTV star is fit. Insanely fit. While she credits that to eating healthy, a regular yoga practice and 3-mile runs, another fitness obsession stood out: OrangeTheory. Her nutritionist wasn’t crazy about the heart rate monitors they use, but they both admitted it’s an intense, full-body workout that gets results.

After finding myself in a workout rut, I decided to give it a try. Here’s what to expect.

What it is:

It’s an hourlong group fitness class led by a trainer, where you spend roughly half your time on a treadmill, doing cardio, and half doing strength-training and rowing exercises. You wear a heart rate monitor (sold separately, though in your first class it’s free to borrow) that shows how hard you’re working, projecting it on a screen with everyone else’s results.

Why they recommend the heart rate monitor:

Real talk: I’ve chosen not to shell out $120 for a heart rate monitor wristband to wear to class. Many people just use a Fitbit or smartwatch, if they want to take advantage of that aspect of the workout. OrangeTheory calls for one because its workouts are designed to let your heart rate set your pace.

The gym’s created five heart rate zones, showing how hard your body’s working. During the workout, instructors suggest you stay within zones 3-5 to burn fat, with the goal of spending 12 minutes or more in zones 4 and 5 while you’re on the treadmill portion of the workout.

The vibe:

SoulCycle-ish exercise club. The lights are low, the music’s pulsing (though what type depends on your instructor, or if it’s a themed class, like ’80s Day), which helps you zone out and stop focusing on what the person next to you is doing.

With the heart rate results shown on monitors throughout the room, I thought it’d be a lot more competitive — and embarrassing for people like me, who aren’t exactly fitness buffs. Or even casual gym-goers. But, since everyone’s monitors are connected to nicknames (and some members don’t buy the monitor, so their results don’t show up), you can’t tell who’s who. Plus, within minutes of starting the workout, you’re sweating so hard you don’t care who’s doing what. You’re focusing on yourself, and just getting it done.

The one thought running through my mind nonstop:

“Am I doing this right?” (Thankfully, an instructor routinely stopped by to correct my form and explain what the heck I was supposed to be doing.)

The Verdict:

After taking four classes, I can honestly say that (1) half the time, I dread going, just like I dread any workout; but (2), I feel better than I ever have after any workout afterward. It’s such a good balance of strength training and cardio that I really feel like I’ve gotten a lot out of that hour, and I’m ready to take on the world. It’s the kind of post-workout high I’ve heard

However, classes are so expensive it’s hard for me to justify this long-term. My company offers a $300-a-year wellness reimbursement, where they’ll provide that much toward a gym membership. Since Planet Fitness and other, cheaper programs haven’t worked too well for me, I decided to give this a try. At the basic package level, that $300 only paid for four months’ worth of classes. And that’s just four classes a month! Crunch, Equinox, and spin class devotees may be used to those costs, but for me, it’s a bit too much.