True that movements like squats, DL's, overhead pressing and even curls & lateral raises recruit the Abs (chins/pullups also affect the Abs strongly), but the full potential of the Ab's themselves is not met if only relying on the secondary affects of these exercises. Also the important obliques will need consideration. This is all accomplished through direct Ab work. Most all Pl'ers & Olympic lifters understand this. Not talking about any marathon style sit ups, leg raises, etc, with endless reps. Treat the Ab exercises within the range of 6 to 10 reps, with perhaps 2 to 3 sets max. With progressive heavier weight each workout, just like any other body part.
The important counter balance to the Abs is a matching strong lower back. Can't have one without the other if full potential, in strength & development, is the goal. Can be very good insurance against injury and keeping the lower back in a healthy state. Hyper extensions, GM'ings, Romanian DL's may prove worth the time invested in them. These selective exercises have also help many men increase their squatting and Dl abilities very well, when a sticking point was reached. As well as having a noticeable effect on their overhead lifting. With improve Ab & lower back strength, it's like have a built in lifting belt 24/7.
Yev33 mentioned the Ab wheel , which is one of the better pieces of equipment to work the full lower & upper Ab's. Other than a Plank, which may be a little advance for some. . Might also try holding a bar above the head (as in the BP) in the start of a situp position and do your situps or crunches with the added resistance that way. Rope Ab work is also very good. Good Luck.
Funk51: Yes, a picture is indeed worth a thousand words.
