Mine is my leg position. I used to sit ahead of the vertical, but I've gotten better about sitting back. Now that my upper body is better, my lower legs are slipping forward into the chair position. It's SO frustrating. I can't even stand watching myself on video because I hate it so much. I tend to turn my heels in, too. And I have trouble keeping my weight down in my heels. As much as my trainer hounds me and as hard as I work at it, I'm still not a solid rider yet. Ugh.