Side bends are commonly used to work the oblique muscles. The obliques are located on the lateral aspect of the "six pack" portion of the abs. They are involved in all abdominal contractions to some degree. Side bends are unique in that they do not isolate the obliques completely. Lateral flexion (bending the torso sideways) is caused in part by the action of the quadratus lumborum, which is a part of the lower back. Instructions for side bends with resistance tubing are listed below:

Begin by securing the resistance tube under your shoe. Ensure that there is enough tension in the tubing. Grasp the resistance tubing in one hand and stand up straight with your feet together. Slowly bend your torso sideways on the same side as the resistance tubing. Then bend to the opposite side, approximately 10 to 15 degrees past the upright position. As you are performing this exercise, be sure to maintain a stomach vacuum (suck in the abs) and keep your chest lifted high.