Josh at bat
We all know Alex Rodriguez has had a rough year, but you can still learn from studying him in his prime, even about cello playing. This article made the front page of the New York Times in the spring of 2007. I keep this graphic from it taped to the wall outside my studio. Regardless of how you might feel about baseball, it is worth looking at some of the physical parallels between the motion and efficient body movement required to swing a baseball bat and that which is required to pull a cello bow across a string in either direction, or move the left hand up and down the fingerboard. The principle of rotating around a stationary spine was revelatory for me as a cellist, and has helped me be much more solidly planted while dealing with both bow-arm movement and left hand / arm movement. Keeping my head stationary was one of the first suggestions I ever heard from Harvey Shapiro (himself a baseball fan, years later we watched on his TV as the New York Mets won the 1986 World Series final game).
A web page devoted to the subject of rotational hitting can be found here.