Cardio weightlifting can save you *major* time in the gym—and who doesn’t want that?

Pretty much all my life, my workouts have stayed relatively the same: run for about three miles, then throw in some impromptu strength training at the end. Of course, I’ve been to countless boutique fitness classes over the years (from cycling to HIIT to Pilates to yoga), but the real meat and potatoes of my personal fitness regimen has been all about logging time and miles on the treadmill, day in and day out. So, my mind was blown when celebrity trainer Ngo Okafor put everything I knew about cardio to the test.

Upon entering his Iconoclast Fitness studio in New York’s Flatiron neighborhood, I was ready to be thrown into the lion’s den, so to speak. I got right down to business with 20 goblet squats using a kettlebell—not starting on a cardio machine like I’m so used to doing. More weights were lifted, some intense ab work was done, and then came the cardio round. Okafor’s weapon of choice for me? The bike.

It was only three minutes long, and consisted of one minute of speed (over 100 RPMs), one minute of high resistance while standing up, and then another of speed. That’s it. Sure, it was still really challenging and I was totally out of breath, to be fair—but only for three minutes.

“While used in conjunction with lifting weights, a three-minute cardio burst is the ideal length of time to a spike in the client’s heart rate without completely exhausting them.” —Ngo Okafor

As someone who’s used to atleast 30 minutes of cardio straight-through, I was shocked at the brevity of this circuit. “I’ve discovered that while used in conjunction with lifting weights, a three-minute cardio burst is the ideal length of time to a spike in the client’s heart rate without completely exhausting them,” says Okafor. “Completely exhausting a client with a cardio burst creates a situation where the client would require a lot more recovery time between sets. Extending the recovery time can cause some clients to lose focus or get cold, which ultimately could ruin the workout and the experience. The extended recovery time also could lower the heart rate to a point where the client doesn’t burn as many calories as the workout originally was designed to burn.” Aha.

I proceeded to go through the same strength training routine that I started with, 20 reps on each move. We did three rounds total, which means three rounds of that cardio circuit (which only got harder, by the way). The thing is, despite the “cardio” part being only three minutes at a time, my heart was pounding and I was practically out of breath throughout that whole hour of working out. Like, I’m sure my heart rate throughout even the strength training part was akin to what it is when I run on the treadmill.

“Studies have shown that although you could burn a ton of calories from doing cardio alone, once you stop the cardio endeavor and your heart rate slows, you stop burning calories,” Okafor tells me. “However, utilizing circuits while lifting weights raises your heart rate during the activity and continues to burn calories even when you stop, because the human body requires energy to build and repair muscle. And this energy recruitment burns calories.”

While weight lifting isn’t considered traditional cardio, your heart is still seriously pumping as you’re working that strength. And so, with a well-planned-out circuit that alternates between strength training and short cardio bursts, you can scratch that trudging through a half hour on a treadmill off the list—and instead, have a more fast-paced (and less boring) workout sesh that leaves you panting even harder.

If you’re starting out with weights, here’s why trainer Jason Walsh says to start strength training just twice a week. And this is a Victoria’s Secret trainer’s at-home strength exercise advice.