Lay flat on your back as if doing a crunch. Lift your legs up with the upper leg being parallel to the floor but not resting on it.
Start the exercise just like a normal crunch whereby you lift your upper shoulders off the floor but in a twisting motion. Performa a "one shoulder at a time" crunch and in a bicycle fashion, bring the left knee and your right shoulder off the floor towards the centre of your body. Next repetition, switch your crunch so that your left shoulder and your right knee come closer together.
Tip: Remember to slowly but deliberately lift your shoulder off the floor and focus on the abdominal muscle doing the work. Don't aim to get your shoulder off the ground as much as possible but to feel the abdominal contraction. You should not focus on bringing the shoulder up with any other muscle group such as the neck and shoulder.