What's your opinion on weighted abdominal exercises? I usually get a good "burn" from holding a weight plate while doing inclined crunches or using a weight resistance machine for abs. Will this cause my abs to become more noticeable or will they become thicker?

I like weighted abdominal exercises. But, when you start to use weight you really should cycle your exercises for the best affect. This means that just as you would not want to train your biceps everyday, you will not want to do heavily weighted ab movements everyday. Most people can however, perform the non-weighted ab exercises on a daily basis. The abdominal muscle group will respond to weighted exercises by becoming more developed. If you are not dieting, doing cardio etc., this development will appear as a thickening of your ab area. This is simply because you will be developing muscle underneath the fat layer. However, if you are dieting and doing a little cardio you will start to reduce your bodyfat and then, your ab muscle will become much more noticeable!