If you spotted Halle Berry working out with a heavy black bag wrapped around her shoulders on Instagram, you may have wondered what in the world she’s doing. Unlike kettlebells and dumbbells, the crescent-shaped piece of equipment definitely isn’t something you see every day.  But a Bulgarian bag workout has been a top training tool for wrestlers and Olympic athletes for years. And if Berry has anything to do with it, you might consider Bulgarian bags integrated into your next workout.

“Peter [Thomas] recently introduced me to Bulgarian bags and I’m hooked,” Berry wrote on Instagram. “We’ve used these bags for strength training, cardio, plyometrics—you name it.”

Originally created by a wrestling coach as a way for his team to build up their strength, each Bulgarian bag is filled with sand weighing up to 50 pounds. And because of the shape and different handle options, they’re incredibly versatile.

Basically, even a quickie session with a Bulgarian bag is going to leave you pleasantly sore. It’s something that can work your entire body as you’re swinging and carrying it around. If you want to try it out for yourself, you can grab one on Amazon (you just need to fill it with sand yourself) or DIY one on the cheap with an inner tube, duct tape, and some aquarium rock or rubber mulch. When you’re ready to sweat, start with a few of the exercises Berry’s trainer, Peter Lee Thomas, did with her: squats, lateral lunges, and rotational swings. You’ll see those muscles popping in no time.

This is the 10-minute beach workout Halle Berry’s trainer swears by. Or, try a 15-minute workout from Rhianna’s trainer.