You may find this exercise listed on your strength routines. And it's one that many athletes find puzzling. Here's how to do it.
Shake up the ab routine with this simple yet effective crunch.
Lie on the ground with your feet flat on the floor. Place hands gently behind your head. Engage your core - a quick cough can help you achieve this - and make a small circle with your torso first to one side. Bring your torso through the middle and then come down the other side. Once you've completed those repetitions, repeat to the other side.
This does not need to be a big motion to be effective but your shoulders should come up off the ground. Work to make even circles both ways which can highlight stiffness or limited mobility in your back. Do not yank on your head and keep your shoulders and neck relaxed.
This will work all of your abs!
As always, if you find this exercise uncomfortable or painful. Stop and ask for alternatives.