3B SWISS-BALL BACK EXTENSION Hold a medicine ball and lie facedown on a Swiss ball, positioning your hips on the center of the ball. Hook your feet under something sturdy (such as the leg station of a bench, as shown here) and, keeping your torso straight, allow your body to angle toward the floor. Hold the medicine ball out in front of you . Now contract your glutes and hamstrings to raise your body up as high as you can . Lower yourself back to the starting position. That's one rep.