When you spend as much time as I do around batting cages, one of the things you’re bound to hear is a coach telling a hitter about the importance of keeping his/her head steady. What the coach means by this is that you should set your body in a position, and then the head should stay there throughout the entire swing.

The rationale is that if the head is moving then the eyes are moving, and it’s too hard to see the ball that way.