Lie on your back with knees bent and feet up at 90 degrees. Bend your elbows and place your hands behind the head to support it. Keep the elbows out to the side and don't bring them forward at any point.

Simultaneously, lift your upper body till the shoulder blades come off the floor and raise your hips lifting them off the floor, drawing your knees towards the chest. Squeeze the whole abdominal muscle hard, pressing the navel down to the spine.