This one is a toughie at first to coordinate, but hits all the major muscle groups in one powerful move. Lie down, back to the mat, with knees bent. Hold a medicine ball on the ground with arms fully extended overhead. Pull the knees into the chest, preparing to use the weight of the ball (and the strength of your core!) to help catapult you to a controlled squat position, then standing. Next, slowly lower back into a squat, and ease back to the floor, butt first before lying back down. Don’t get too comfy though: The goal is to rock and roll for 10-12 reps.