Core training questions plz help me with your input!!!!!!

[bostonceltics11]

Okay here's the deal I have been working out consistently for about two months now and have been pleased with my progress so far. However one issue remains to bother me and this is the fact that I believe I have a hard time working my abs to their limit or at least I think thats the problem. My questions that I would like some input on are these, whenever I work out say chest or legs the next day DOMS sets in for my muscles, no suprise, however the day after my ab workout I feel no soreness why? Obvoiulsly I have not been training long enough to have built up so much conditioning that they wouldn't get sore anymore. When I do my ab workout routine which is listed below I can feel a strong contraction, making sure I exhale during the concentric phase to get a good contraction and it will burn by the time I am done with the set. One question when I do crunches at first I can lift my shoulders off the ground around 5 inches(estimation) for maybe 15 reps but then it decreases as reps continue to maybe one inch off the ground, so when you do crunches do you continue to rep it out even if your only lifting your shoulders slightly off the ground? I really appreciate anyone who helps me with my questions. Thanks in advance.

Crunches 3 sets all to failure
Oblique side bends 3 sets 15-20 reps, just to note my obliques do get sore after w.o)
plank 1 set for 2:30 min(try to inrease every w.o by 5s)
reverse crunch 3 set 10-12r

[DTaylor1988]

Try adding weight to your crunches, and it depends on what sort of crunch as I put a dumbell overhead and crunch that way and it kills, if your doing just a normal crunch (IMO It wont benefit you much). Try doing other ab exercises such as hanging leg raises, dragonflys, jacknife etc. Also include deadlifts and squats as these exericses will smash your core!