Somewhere, recently, on this forum, I read about someone's PT or trainer recommending that she do planks with her elbows on an exercise ball. She moves the ball around & from side to side while in the plank position. The exercise is supposed to mimic our upper body action on the bike. I tried to find the original thread to no avail. Anyway, I'm here to report that this is an EVIL exercise So evil, in fact, that it's going to become a regular part of my workout routine