Crunches are much more effective than regular sit-ups because they specifically target your upper abdominal muscles rather than your hip muscles. If you're not used to them, they can cause soreness a day or two later, but it's a 'cool' soreness. A badge of honor.
Sylvester StalloneDon't be gullible, use life before it uses you. Understand there are no free lunches, and for every action you take, there's a reaction.
Sylvester Stallone