I've experimented with myriad abdominal regimens to burn off the fat and expose some rock-hard muscle in my middle. No matter what I try, though, I'm still not getting it done. What's your advice?
The wording of this question makes it abundantly clear your lack of progress is based on misinformation. You can't "burn off the fat" of your abdominal region via exercise. There's no way to spot reduce, despite what those cheesy infomercials would lead one to believe. Targeted abdominal training can help you build rock-hard muscles in your midsection, but the plain truth is that the best route for burning fat is through diet and cardio.
The first thing you must realize about ab development is how much they come into play when working other bodyparts. When you try to do any heavy multijoint exercise--bench presses, deadlifts or squats, for instance--the first thing you must do is contract your abs to provide the necessary support for the lift. That tendency to work abs on heavy-lifting days means that there's no reason to go overboard on marathon ab workouts.
I don't see the point in doing abdominal exercises every day, as I'm already stressing those muscles on leg, chest and back days. Training abs every day is just another way that bodybuilders get manipulated into thinking that overtraining equals success. Genetic limitations and diet will dictate whether or not you are able to build a four-pack, six-pack, eight-pack or none of the above.
Now, let's break it down and simplify the ab-training process. I recommend doing forward and reverse crunches: three sets of 20-25 reps for the former and three sets of 12-15 reps for the latter. Hit both of these exercises in two sessions per week if you are under pressure to see results, or one day per week if you are in a size-building mode for your other bodyparts.
My view--and many so-called experts might take exception to this--is to avoid doing situps and leg raises, as they stress hip flexors rather than abs and place too much pressure on the lumbar region.
Many hardcore types do crunches with a 45-pound plate on the chest to up the ante of resistance and to intensify the stress on the abdominals. I'm not against crunching with some plates if you are flying to make inroads en route to creating a well-chiseled midsection; however, once you see real progress and can state categorically that the abs are in, stay consistent with a program that maintains the solid condition that you've strived so hard to achieve.
As to proper technique on the crunches, I preach that just a few inches go a long way toward a successful contraction. All you are trying to do in the movement is to bring your chest and rib cage toward your pubic bone. Don't pull on the back of your neck as you crunch forward. All stress comes into play in that one targeted area between pubis and lower chest. Hold and squeeze for a complete contraction and repeat for the desired number of repetitions.
Reverse crunches are a challenge to perform precisely, but practice will make perfect if you are dedicated to seeing your abs in the near future. I lie on the floor, cross my ankles and bend my legs. Then I crunch my hips toward my chest. Once I feel a contraction, I hold it for a count of three. The intensity of the contraction dictates fewer reps (12-15) and total concentration on completing the job at hand.
Quite honestly, these two ab killers are all you need to hit serratus, upper and lower abs. Throw a twisting movement in on the crunches to tweak the serratus, but above all keep things simple and you'll have abs that are clear as a bell in less time than you thought possible.