1) Lie on your back with your thighs vertical but knees slightly bent. Place your palms on the floor beside you and have your head and shoulders off the ground. Bracing through your abs, slowly lower your legs towards the ground. Maintain a small arch in your back throughout this exercise.
2) Go as low as you can control and then slowly raise back to vertical. As soon as you reach vertical, raise your tailbone off the ground and move your feet up above your head and crunch your abs. Control the down phase so that your hips don’t crash back to the ground. Lightly touch your backside to the ground and then start your next leg lower.
3) Avoid over-arching or completely flattening your back and be careful of using momentum on the up phase of this exercise. Wiggle your toes and relax your feet to ensure your abs are dominant otherwise your quads and your hip flexes will take over.