No, it is not neccesary BUT...you NEED ONE! How's that for an answer? All the moves can be done without one but if you can afford one, you will be using way more muscles as the idea of their use is stabilization. I LOVE the way Cathe incorporated ABS this time on the ball. And, wait til you see her biceps done with the ball. Ouch, had to lower from what Cathe used! You can pick a ball up fairly cheap at places like WalMart, TJ Maxx, Marshall's and such. But, like I said, one is not neccesary.
Your-Friend-In-Fitness, DebbieH http://www.handykult.de/plaudersmilies.de/wavey.gif[/img] If You Get The Choice To Sit It Out Or Dance...I Hope You DANCE!!!