Medicine Ball Russian Twist Show Video Show All Exercises     Primary Muscle Group: Abdominal Obliques Muscle Groups Worked in This Exercise: Obliques and Lower Back Preparation: Start out sitting on the floor, knees bent, and feet flat on the floor. Hold the core ball at chest level, elbows out and shoulders down. The core ball is similar to a medicine ball (weighted ball), except it has handles on either side of the ball for functional uses. Make sure the chest is up and back is straight. Breathing: Breath out on the contraction of the muscle and breath back in on the way back to the start position. Execution: Begin by rotating to one side and then directly to the other. Do not stop in the center. Make sure that you rotate at the trunk, keeping the ball in front of the chest at all times. Rotate slow and continuously. If at any time the lower back begins to hurt, stop and readjust the position, keeping your chest out. Here are a few suggested alternative exercises: Ab Crunch Obliques Ball Crunch Traditional Dumbbell Side Bends Lateral Bend with Barbell