Make sure that your head, legs and bottom are all in contact with the floor. Engage your stomach muscles and grasp the sides. Slowly lift your legs to a 90-degree angle, keeping your legs straight and not bending at the knees. Pause for a second then slowly lower the legs back down.
If you choose to have your hands out to the side of your body, concentrate on keeping your lower back pressed to the floor. Contract your abs and keep them tight throughout the exercise. Lift your legs off the ground about 6 inches. Lift your head and shoulders slightly off the ground.