Ask a bodybuilder how to shock your abdominals, and he'll likely say Boo! because the last thing he'll think you mean by "shock" is shock sets.
Since the day they were invented, shock sets have been used almost exclusively for showoff muscles such as arms, chest and legs, bodyparts that expand with boastful prominence and bursting vascularity when hit extra hard with furious reps. In other words, the litmus test for shock sets was that they had to produce visible results instantly. Unfortunately, the midsection, being a two-dimensional plane of muscles, displays no discernible change after it's pumped, so bodybuilders have dismissed shock sets for abs as a waste of time.
Your midsection, however, is a bodypart like any other bodypart in that, if taken for granted and neglected even slightly, it will not develop the quality of other muscles that are trained with more intensity. In fact, it is such a complex of difficult-to-reach muscles that it actually requires more merciless and comprehensive stress than other bodyparts.
Because abs and obliques are both located in the midsection, most people assume they are part of the same bodypart, but I approach them as separate bodyparts. Not only are they located in different areas of the body, but they perform different functions: the abs bending you forward and backward, and the obliques bending you side to side. For these reasons, they need to be trained with equal focus. Never make the mistake of thinking an abdominal exercise can adequately work your obliques or vice versa.
Abs and obliques are compact muscle groups, the functions of which are not directly tied to the movement of limbs. Therefore, they can be trained following a larger bodypart workout without a significant loss of their own power. The converse, However, does not hold: Training them first could sap energy (even if a small amount) from the stabilizing strength of the body and thus limit the workout of a larger bodypart that is more dependent upon energy resources.
It's easy to rationalize your way out of working abs and obliques by saying, "They're used all the time, anyway, to support my squats, standing curls and shoulder work." In order to build quality into any muscle, however, it must be trained with specific exercises, sets, reps and intensity; if that muscle is stubborn in its response and, in the case of abs, difficult to reach, you have to go above and beyond, shocking them into growth and shocking you out of your complacency. I shock my abs and obliques twice a week during the offseason and every other day precontest. The technique I use is giant sets: I run through four different exercises in a row, three times each. The first three exercises are abdominal movements, each of which is crunched for 30 reps per set. The fourth is for obliques, and that one gets 150 reps per set. The total: 720 reps, all nonstop, all of which tie my torso in a knot. Here's how it goes.
HANGING KNEE RAISES
This is the best combination movement I know for not only warming up the abs and stretching the entire body, but also for generating a hot-poker burn in the lower abs and serratus. However, don't make the mistake of thinking you can simply pump your knees up and down and be done with it; that will do you more harm than good. Remember that the principle behind all abdominal and serratus exercises is to contract the muscles, or shorten the distance between your sternum and your pelvis. As you hang from an overhead bar, your body should be straight and your abs should be tensed. Never arch backward. As you raise your knees all the way to your chest, curl your body together. At maximum contraction, crimp your ab muscles for a good peaking burn, then keep them tight as you lower your legs. This latter technique is absolutely essential to prevent your body from swinging. If you detect the slightest swing when your legs reach bottom, you are not keeping your abs tight enough.
Without rest, I go immediately into a set of decline crunches, with my hands behind my head. I currently do 30 reps, but used to do them for 30 minutes nonstop, followed by another 30 minutes of nonstop leg raises. At this stage of my development, that would be overtraining, but it nonetheless built my superior foundation for abs and gave me a permanent advantage over other pros. Before I even start this movement, I tense my abs to prevent my pelvis from rotating inward against my spine. Again, I never arch backward, and I try to bring my head all the way up between my knees. The return is also tight and contracted, as is the transition from one rep to the next.
SEATED REVERSE CRUNCHES
Again without rest, I go next to a flat bench, sit on the edge, grasp the pad for stability and squeeze out 30 reps of reverse crunches. I'm careful not to go all the way down or all the way up on these, staying instead in the arc of maximum contraction for my abdominal muscles. It's important not to pump with the legs or lift the hips; that only removes stress from the abdominals.
Now it's time for the obliques and serratus. Holding a stick or bar behind my shoulders, I stand with my feet about shoulder-width apart and twist 150 times to each side, as far as I can go, very deliberate, neither too fast nor too slow but still with a good enough pace to torque my torso. My feet and hips remain perfectly in place; if they move, the twisting action will be released. To ensure that I'm hitting every oblique and serratus muscle in my torso, I constantly change the angle of my body as I twist: standing upright, then bent to one side, then working my way to the other side, then bent all the way forward, and so on. If, when I'm finished, my midsection burns as though I've been cut in half, then I know I've had a proper shock workout
No bodypart is more affected by nutrition than the midsection, because no other bodypart contains such delicate detail. The slightest film of bodyfat can obliterate nearly all of the quality that resulted from your great investment of effort and time, so watch your diet. The thinner your skin, the more your abs will show.