A standard crunch is the basic form of this exercise and is the foundation for building a stronger core. Lie on your back and carry your legs up to your body at a right angle – bend your legs at your knees. Put your hands behind your head so your arms are bent into a “V” shape. Then use your abdominal muscles to lift your head and shoulders from the floor to the ceiling.
If you want to do the most advanced movement, turn a crunch into a sit-up and take your upper body until you are seated.