Begin by lying on the floor and positioning the arms in the desired position; for increased difficulty the arms can be positioned overhead with hands on the floor. Place the feet on each side of the Swiss ball and contract the abdominals to flatten the low back into the floor; do not allow the low back to hyperextend (i.e. arch off the floor) during the movement. Slowly begin the rotation at the hip joints so that the right foot is raised above the level of the left foot, then switch so that the left foot is raised above the level of the right foot. Continue to swivel at the hips focusing on achieving a total of 90 seconds of continuous movement per set.