I'm coaching a player who swings their racket back and forth in time with their run when moving to reach shots, and it impairs their ability to prepare for the shot. I teach players to start moving their racket back as early as possible and to time it so it's a continuous movement into their forward swing. If it's a really difficult short or wide ball they might be better off swinging their arms so they can run faster, but that's not the problem here. However, I watched some video of Serena playing and she seems to favour swinging the racket left and right more often than other players when running for backhands. I think it's just a style thing particular to Serena. Any thoughts?