You might wonder why there are times when your serve is really fast in Wii Sports Tennis. You try to sling your arm as hard as you can, but just can’t reproduce it. Well actually, the serve speed has nothing to do with your arm movement.
You have to time it just right so that when the ball is tossed in the air that it is hit it at the very top of the toss. If you make contact with the ball right at the top, even just a slow flick of the wrist will hit it really hard it to the other side.