The truth is, it's not about how many repititions of an exercise you do; it's about how well you hold the form and what kind of exercise you do. Heck, you could probably do 1,000 sit ups a day and still have some extra flab on your belly. That's because sit ups only tone the upper portion of your core, making the rest liable to grow chub.
Check out this video to learn how to do ab twists, a move that works both your obliques and lower abs.
Many people strive to get that perfect 6 or even 8 pack to show them off. Many people tend to make the mistake of only doing one type of workout to get those great looking abs. They fail to realize it is more than just the conventional sit-up. There are many more muscles in the abdominal area and the obliques are one of the other primary muscles in this region. This is why we created this video on how to do the ab twist to work those obliques!
Step 1: Lie on the ground on your backside (you can use a mat to make it more comfortable). Now extend your legs straight out and upward with your hands placed at your sides at the level of your shoulders for stability.
Step 2: Now try to keep your upper body stable and begin to roll your legs downward to one side bringing your feet near the floor. Be sure to keep both legs together.
Step 3: Bring your legs back up to starting position and repeat the same steps but to the opposite side. Then, return to the starting position and repeat.