HOW: Start in a standing position while holding a medball with both hands. Move the ball to one side and then bring it up overhead and slam it to the ground on the opposite side. This rainbow motion can be repeated on both sides for the prescribed amount of reps.
FEEL: You should feel your core and arm muscles working them most. You should also feel you hip muscles working as you slightly twist them to each side.
COMPENSATION: Keep your feet stable, don’t move them as you slam the ball from one side to the other.