Instructions
Lie with your back on a flat padded bench, with your arms and hands behind your head, grasping the end of the bench. Keeping your core braced, bring your legs up so that they are raised 90 degrees to your body. Raise your glutes off the bench, moving your legs up higher above you until you are supporting yourself through your hands and upper back. Return your glutes back down to the bench and with control, lower your legs down, keeping your core braced throughout the whole movement. Repeat for the desired number of repetitions.
Tips
Do not allow your back to arch when lowering your legs down towards the bench. If it does arch, it means that you have lost the ability to keep your core braced and as such you are better off not going as low. Only lower as far as you can maintain a strong brace. You can also perform this exercise on the floor, with your hands by your sides.