It seems that everyone's trying to get that six pack - to see those ab muscles bulging from your stomach like those models in Men's Health. Here's what I've read about the best ways to build your abs and burn the fat that hides them...
1. Do crunches - you can do crunches everyday when you wake up, 20, 30 50, whatever seems reasonable to you.
2. Do situps - similar to crunches, but with a more full range of motion, situps help to work the upper abs and obliques, try not to rest at the top but go just to the point that the tension in your stomach starts to subside and then go back down.
3. Leg lifts - leg lifts are a great way to work the lower abs. Just lie on your back and lift both straight legs 6 - 10 inches off the ground and hold for 5 - 10 seconds each. Bring your legs down slowly to really use the resistance.
4. Cardio - at the end of the day, your six pack needs to be revealed more than built. Do exercises that get your heart rate up and burn fat in your stomach, that's the only way you'll be able to see those ab muscles shining through.
5. More cardio! - see 4. You won't be able to see your ab muscles with a layer of fat on top of them, so get running, biking, walking, swimming, play sports - whatever form of cardio exercise works for you.
Don't forget to talk about the importance of nutrition and proper hydration as well as the exercises you mentioned to achieving 'six pack abs'. The American Council on Exercise commissioned a study to analyze the effectiveness of abdominal exercises. Although the crunch and sit ups were listed, they ranked rather low on the list, unless incorporated with a stability ball. Adding a stability ball to those exercises increases the number of motor units recruit in the abdominal area, hence firing more muscles fibers, ending up with more ab work. Also, the bicycle maneuver and 'captain's chair' exercise were also ranked high on the effective ab list. For a full text, check out the
www.acefitness.org web site.
Of course any action performed without integrity of movement drops off in efficacy. Translation: if you are not focused on your form then you're likely working some other muscle - or god forbid the secondary movement structure of tendons and ligaments.
One more little thing to remember is that genetics plays a part in having fabulous abs....some of us did not have the ripped 6-pack abs gene passed on from our parents. Remembering this cuts down on my frustration as I continue to work my core as best I can knowing that I may or may not end up with the perfect sculpted abs like in the magazine!
And don't forget to tighten those abs often during cardio. My kickboxing instructor reminds me of this during boxing by giving me a slight punch in the stomach. He's brutal, but I'm seeing results. I believe though that you pretty much have to get your body fat down to nearly the single digits before you can see your six pack.