Originally Posted by sweet_scientist
If you do other exercises (i.e. working out your other body parts) then once a week will do. The key is to blast them though, not simply go through the motions.
Abdominals are muscles that recover quicker than other muscles, so don't take long rests between sets. Hit em hard and fast whilst you're carrying weights as I suggested.
Also, the key is not to do many sit ups but to do sit ups with a lot of resistance because that's what puts on muscle.
Same with something like benching for example. You don't get a big chest by doing sets with countless repetitions. You get it doing sets a low amount of reps with heavy-ass weights that tax you.
I'd say, if you do about 12 sets of about 12-15 reps (mixing in about 3 sets of standard crunches, 3 sets of crunches with your legs raised to work the lower abs in particular (see American Psycho for leg positioning, lol,) and about 3 sets whilst lying on your left and right sides to work your obliques, your abs will be mint.
Oh and **** that junk food off
12 sets of 12-15 reps sounds a bit light though. Someone told me that you know you are doing them well if you can feel a good burn in your abs, and it takes me about 50 or 60 reps to finally feel them. I'll give it a try though.
Oh and i agree about the weights, when i was taking the weigh protein and lifting at the same time, i use to only do about 10-15 reps in 3 sets and my chest was huge on my small body frame.
:EDIT: i forgot that the reps were including weights as well so 10-15 will probably be all i can do. More weight, the harder it is to do the sit up..