I would like to make my shoulders more well developed and specifically more flexible for tennis. I am wanting this to contribute to increasing the height of my elbow on my racquet drop in my serve. What are some exercises and stretches that will accomplish this? Also, Pete Sampras' shoulder was supposedly more well developed than most pitchers', and he could touch his elbows together behind his back. Sampras was obviously an amazing natural athlete, but is this sort of flexibility impossible to reach for most people?