Cos it's body weight transference and timing. A lot of tennis players just use their arms, Mary really swung fast and transferred her body weight at the same time. Difficult to teach and only a few players can do it really well!
@@cupidslover3 it's not difficult to teach. You don't need a big swing to hit hard. Bigger swings leave room for mistiming the ball. If you teach a player to use short compact swings they'd use their body transfer. It's not hard to teach everyone on the prociruit does it
