This is beyond unreal. The soreness that is in my abdominals is unmatched from any number of crunches or situps I have ever done.
So let me give you some back story. I'm learning how to breakdance and I'm practicing a few moves with my friends. We have some mats so we try doing some one-handed tricks, namely the valdez. This is how the valdez works. You put your hand behind you on the ground so that you are facing upwards and your hips are pointed toward the ceiling. In one motion, you push off with your legs and tighten up your arm as your legs fly backwards. As they arch backwards, you land with your feet first and that's it. Here is a video since words can't really describe it. (http://youtube.com/watch?v=U4Jq7ctY5L0
Unbeknownst to me, I did about 15-20 of these, trying to perfect it and trying to get the movement down as slow as possible. The next day, my abs felt like the were broken. Obliques (particularly my left side) were ridiculously tight. The rest of my abdominals felt as though they were put through the grinder.
Also note that I had been training my abdominals for at least a few months.
So, to the exrx community, I don't ask that you do a valdez (though if you want, it's really fun to do). What I ask of you is tell me why it works the abdominals so well. In the descriptions for abdominal excercises, "Rectus Abdominis and Obliques only contract dynamically if actual waist flexion occurs. With no waist flexion, Rectus Abdominis and External Oblique will only act to stabilize the pelvis and waist during hip flexion. It may be necessary to completely flex the hips before waist flexion is possible. " When I do valdez's, I do not see any contraction. In fact, it stretches initially and then goes back to a neutral position. If that is so, why does it work my abdominals so well?