As we have demonstrated, it is possible to obtain ball speeds of over 80mph from a lead off ball. In the video below the player illustrates a standing forehand which is the maximum stability possible. Recall that stability refers to how small errors in the stroke path are magnified into large errors in ball speed and placement. In a stable stroke, the errors in the racquet movement are so small that the maximum ball speed and accuracy are obtained. As seen in the figure, the radar reading of the ball speed is 81mph. Movement will in general reduce ball speed because the instability of movement will result in misalignments in position and balance which, at high speeds, become amplified into significant errors in speed and placement. Theoretically, forward movement should increase ball speed. However, if the movement is even slightly unbalanced the quality of the contact will be reduced and the balls speed and placement will be affected proportionally.

Perfect Stability

In the two illustrations below we show the differences in the stability of two professional players. On the left, the player is leaping into the air to hit her backhand. Radar data showed that the resulting ball was just about 60mph, a marginal speed at the professional level. In contrast, the player on the right achieves excellent stability. Note how her balance is firmly controlled from the front foot. For five frames (1/6 of a second, which is a long time during the stroke) her front foot does not move, demonstrating exceptional balance.

The final frame before the strike	The final frame before the strike.

It is a common mistake to think that hitting while jumping in the air is a good idea because one sees it on TV frequently. After all, the player player on the left does make contact with the ball. What contradicts this is that the radar measurements show that there is a significant loss of ball speed that is undetectable to the human eye. This loss of ball speed gives the opponent a significant advantage in that the ball is too slow and will fall short. In the case above left, the ball falls near the service line. These two illustrations were characteristic of the players matches (they were not playing each other) The outcome of the matches was a loss for the player in the illustration on the left and a win for the player on the right.