Why this trainer says smashing medicine balls like Karlie Kloss is a seriously good way to tone your total body

Karlie Kloss is never one to disappoint when it comes to major fitness inspo. Case in point: This footage of the model smiling and slamming around a medicine ball at The DogPound, a fave workout spot for runway walkers in New York City. The former Victoria’s Secret Angel certainly looks to be having a good time. But what *exactly* is she doing and why? To find out, I contacted one of the studio’s trainers, Lucca De Oliveira, and asked him to break down the move, which is technically called a “med ball slam.”

If you’re looking to up your fitness game with an exercise that can challenge multiple muscle groups and double as a cardio sesh, then this may be your new go-to. “It’s a full-body motion that engages your shoulders, back, triceps, glutes, quads, and calves, but most importantly, teaches people to transfer energy via their core. With the right intensity and rep range, med ball slams can have a great cardio element, too,” De Oliveira says.

“It’s a full-body motion that engages your shoulders, back, triceps, glutes, quads, and calves, but most importantly, teaches people to transfer energy via their core.”

To try the move on your own, De Oliveira says to start with a 10–30 lb. medicine ball, depending on how much weight you’re comfortable lifting. Not sure where to start? “Modify the weight of the ball based on the goal of the movement: strength, endurance, or fat loss [heavy for muscle building, medium for conditioning, and light for cardio]. By continuously connecting the power of your upper and lower body in a repeated motion, med ball slams will leave you drenched,” he says.

Once you select your weight, you can begin the exercise: “Find an area where a full swing of your arms won’t cause any damage. Start in a standing position with your knees slightly bent, looking down at the ball. With bent knees, hold the med ball at your waist in front of you. In a synchronized motion, bring the ball above your head as you rise up onto your toes. While slamming the ball onto the floor as hard as possible, contract your abs and drive your chest down. (Don’t bend over.) Pick the ball up and continue the movement until fatigued,” De Oliveira explains.

Whether you’re looking to switch up your gym routine or get your own Insta-worthy boomerang to post, one thing’s for sure: You’ll feel this one tomorrow.

To find out how else Karlie Kloss fuels her busy days, check out her go-to healthy breakfast—plus, how the supermodel curbs her sugar cravings.