If you're anything like me, people know you're into fitness and ask you fitness-related questions.
The one I get asked the most is about abs. How do I get good abs? This is usually followed by a description of some insane number of crunches they do ("I do 200 swiss ball crunches every day...") or heard they should do ("That guy in that movie says he does 1,000 a day, is that good?")
The goal, as always, is to improve "the core" and get the coveted 6-pack of abs.
My answers usually revolve around four things:
Spot-reduction is a myth. You can't "burn off" abdominal fat with crunches. Well, you can, but doing crunches will burn off only as much fat as is required to fuel the exercise, and it won't preferentially burn fat from the abs. You'll burn more fat off your abs doing chinups and pushups and squats, because that'll burn more fat overall. Your body chooses the order in which in burns fat reserves, and you can't influence that with exercise selection. You can only work hard enough to make it scrounge it all up. Crunches won't do that, they aren't that demanding on the body!
Check out the very first myth discussed on EXRX. Read the rest while you're there!
High reps isn't the answer. Anything you can do 200 times doesn't take too much effort for each rep. So you've long since reached the point of dimishing returns. When 10 reps of an exercise is hard, getting an 11th rep means you've made a 10% increase in effort. Getting to 20 is a 100% increase. When you're doing 200 and want to get that 10% jump, it takes 20 more reps, and 100% takes 400 reps. As you go, each of those reps requires less and less effort. So you can't high-rep yourself into strong, lean abs.
You can't out-train a bad diet. If you're eating poorly - insufficient food, insufficient nutrition (not enough food in your food), too much junk food, etc. - no amount of exercise will overcome it. You'll either run down from fatigue (insufficient nutrition) or keep fat on even as you try to burn it off exercising (too much junk). Your diet has to be in order for you to see your abs. If you have to, do Atkins, or The Zone, or go Paleo...or just learn to cook and eat plenty of meat, fruit, and veggies. Find something healthy that works for you. But you can't eat whatever you want whenever you want to, and expect to train hard to overcome it. Like computers, GIGO - garbage in, garbage out. Learn to eat real food in proper amounts.
Crunches aren't the end-all, be-all of exercises. Seriously. It's a short-range exercise for a small muscle group. And important one, sure, but there is a reason workouts on most serious programs start with squats and bench presses and chinups, and end with some ab work. They don't start with abs and then get to squats later if you have time. The ab work is the bonus work. Those exercises build muscle, and make systemic demands that burn fat. That's how you'll get those abs.
And if you really want to do direct ab work, have at it. But crunches aren't your only answer. Check out this article by Anthony Renna on Strengthcoach.com - "No More Sit-Ups and Crunches" or this one on Stronglifts.com on Reverse Crunches. That's just a start! There are lots of options for increasing your ab strength.