No, you can do abs anytime you want. I actually superset them at the beginning of my workouts--i.e. if I'm doing biceps I'll do a set of bicep curls & then a set of crunches, curls, crunches, etc.
I took a class on abs some years ago that debunked many myths about ab workouts. As we all know, the number one way to get a six pack is cardio, cardio, cardio.
However, one of the myths they discussed was the working abs every day w/sets of 100+ reps to "shrink the muscle." The instructor said abs should be worked just like any other muscle, and that weights should be used.
I've been weight training for 16 years as of next March & have tried pretty much every ab w/o there is. I took this lady's advice & started using weights. Now I do abs twice a week. I do 4 sets of 15 crunches w/a 45 lb plate on my head (I know, it sounds uncomfortable but really once you get the movement down you can really feel the muscle working), and 4 sets of cable crunches w/about 100 lbs. I started this w/o about 4 years ago, I do have a six pack now & my abs have never looked better.
