I am a firm believer that the world would be a better place if everyone was able to admit when they are Wrong!! After some research, one of my first posts on The Multidisciplinary Workout, which focused on Ab Workouts, was not necissarily the best advice...
I recommended 4 different Ab Exercises to be repeat once maybe twice; I will now admit this is not the most efficient workout because Abs are Fast Twitch Muscles ie they fire strong and will get exhausted fast. Therefore for Fast Twitch Muscles it is more efficient to perform aggressive exercises than multiple sets at a lighter weight.
Back to Abs the best practice is subjective, especially when using your self weight but note that 100s of sloppy sit ups will not get you 6 pack abs. Personally I still stick to my core core lift of Super Crunches, squeezing at the top to emphasize the resistance. I also found a great new exercise, Side Plank with a Knee Tuck. No more than 20 slow reps and repeat... but maybe repeat the next day :)
It's hard to confirm exactly which muscles are Fast Twitch vs Slow Twitch as everyone is different. Sprinters will typically have a higher percentage of Fast Twitch Muscles compared to Distance Runners. If you want Size & Power check out these Tips for you body to develop Fast Twitch Muscles. If you're like me, a non specific athlete, and just want to be as efficient as possible in the gym heres one rule of thumb: Fast Twitch Muscle are likely pull muscles ie Biceps, Lats, & Hamstrings therefore respond better to less reps with heavier weight.
For the athlete seeking Muscle Tone & Endurance; check out guide to Slow Twitch Muscles!