Starting Position: Stand holding a medicine ball with your feet hip-width apart. Hold the ball relatively close to your body slightly below chest height. Position your hands at the midline of your body. Engage your abdominal / core muscles to brace your torso. Keep the torso upright. Pull your shoulder blades down and back without arching your low back.
Movement: Exhale and slowly rotate your torso in one direction, keeping your upper arms at your sides, elbows bent and hands positioned at the midline of your body. Your head, chest and torso should all move together. Avoid leaning your torso in the direction of your movement. Hold this end position briefly before turning to rotate in the opposite direction.
Exercise Variation: To increase the exercise intensity, fully extend your arms to shoulder height and keep your arms in this position throughout the exercise. The longer lever increases the loading on the spine, requiring the core muscles to work harder.
Engage your abdominal / core muscles throughout this exercise to stabilize and protect your spine.