Most tennis players tend to develop a shift toward their dominant side. I serve left handed and am starting to notice that I have more tension on my back on that side. While I am no Quasimodo, I can feel a difference in the thickness of the muscle. I am not weight training right now and am satisfied w/ overall strength. Reality is that tennis and aerobics are more important. However, I would like to excercise to maintain body balance. I want to play tennis many years; so I must invest some care here before it leads to overstrain. Does anyone have any experience w/ this?