SCULPT THE SIX-PACK you’ve always wanted using these core-centric moves from Firdose Khan, head trainer at Nine Innovations athlete training facility in Houston, who’s helped whip the U.S. national soccerteam and the Argentina rugby squad into shape.

1. Overhead side-to-side slam

Lift a non­-bouncy medicine ball overhead, pivot to one side, and throw the ball to the floor. Pick the ball up and alternate sides—that’s one rep. Perform for reps.

Pro tip: “Keep your chest up as you slam the ball as hard as you can,” Khan says.