This article originally appeared in Well+Good.

Because I’ve (shamefully) never watched Buffy the Vampire Slayer (and yet I am about to speak enthusiastically about Sarah Michelle Gellar’s workout), I decided to take a crash course by cueing up a montage of the hit show’s opening credits on YouTube. I learned that Buffy Summers (Gellar) is the dictionary definition of a badass. Buffy slays indeed. And if her workout of choice is any indication, she treats her real-life workout sessions a lot like kicking demon booty.

Gellar, co-founder of Foodstirs baking company, tells Well+Good that her exercise of choice is Platefit, a 27-minute high-intensity interval training workout performed on a device called a Power Plate, which claims to “challenge you, strengthen you, and renew you” by moving in three directions at once (left to right, front to back, up and down). “The vibration activates your muscle reflexes, and during our workout classes, muscles are contracting 30 to 40 times per second,” says the website. Basically, the machine creates an instability that’s not dissimilar from the one you may experience on a Pilates reformer. Feeling slightly off balance means your muscles really have to get to work.