http://AskTheTrainer.com Personal Trainer Mike Behnken, MS, NASM-CPT-PES, CSCS Here is a great way to increase the difficulty tremendously of a stability ball plank. Position yourself enough distance away from the door or whatever you have the tube attached to so you will encounter resistance while you perform the plank. If you cannot maintain core stabilization meaning your torso is not completely stable, without any movement, DO NOT perform this exercise. There is no point to perform any advanced core stabilization exercises if your core is not strong enough or trained enough. There are no secrets in fitness, bodybuilding or exercise, just science. Neither this nor any core, abdominal, or obliques exercise will get you 6pack abs or a six pack abdominal washboard ab look by itself. Learn to eat right for a lifetime of good health and results from your exercise program. http://AskTheTrainer.com/why-nutrition-is-so-important.html