The double crunch is a great twist in the regular crunch because it works both your lower and upper abdominal muscles as well as obliques. The movement of rolling the spine upward allows for deep muscle movement and helps give you that flat stomach you always wanted!

1) Lay on your back with your knees bent as if doing a normal crunch. Cross your feet at the ankles or keep them shoulder width apart, whichever way is most comfortable.

2) To support your neck, place your fingers behind your head with your elbows open to the sides.

3) Exhale as you curl your legs toward your chest and lift your shoulders slightly off the floor. You should always exhale during an exercise when your muscles are working their hardest. Really concentrate on your ab muscles as you contract. Keep your movements slow and controlled for the best results.

4) Bring your legs and shoulders back down. Do at least 3 sets of 10 to 12 reps.

Read more: How to Do Double Crunches | eHow.com