One secret to Lady Gaga's killer abs is this killer exercise sequence: Harley starts her on a basic crunch and modifies that into reverse crunches, ending with a double crunch.
To do a reverse crunch and a double crunch:
•Lie on your back on the floor. Place your hands on the floor beside you.
•Bring the knees in toward the chest with your feet together.
•Use your abs to slowly curl the hips off the floor and into your chest; now slowly lower them back to the starting position to complete one.
•Do two sets of 25. Don't swing your legs to create momentum; use your abs — after all this is an ab exercise.
Double the return on your efforts adding an upper abdominal curl while you curl up your pelvis. This will work your upper abs as well as your lower abs. Go slowly and feel as if you are curving around your belly button from both the top and the bottom of your spine.