This ab roller consists of wheel with handles on either side. To use it, you start in a kneeling position, grasping the handles and placing the wheel on the floor in front of you. From there, you roll the wheel forward while keeping your core engaged and your back straight. As you roll forward, you extend your body until you are almost parallel to the floor, and then you roll the wheel back to the starting position. The primary muscles targeted by the ab roller are the abs, but it also engages the muscles in the shoulders, arms, and hips.