Hey Blueanna,
You should only work your abs as often as you would resistance train any other part of your body, preferably two to three times a week. Remember, when you train a muscle you are actually breaking down those fibers and they need time to regenerate and hopefully comeback stronger and better than ever. Studies show that this takes anywhere from 48 to 72 hours depending on the intensity of the training. Keep in mind however the only way to acheive that "toned" appearance is losing bodyfat and adding a little muscle mass. For more help on those topics check out my articles on "The Truth About Weight Loss" and "More Muscle, Less Myth".
Thanks for the question,
Brent Brookbush NASM, NSCA, IFPA CPT & ACSM H/FI
