U.S. Open Ball Bounce (Ball/Court Interaction) (Page 1)

One of the major sources of the heavy spin generated in pro tennis is actually completely unrelated to the players. This is the bounce of the ball on the court. This collision lasts only about 1/250 of a second, but radically alters the speed, direction, and spin on the tennis ball.

Investigating how the ball bounce affects the flight of the ball is a major focus of our research project. At the USTA training center at Key Biscayne, Florida, the team spent 5 days filming the ball bounce in controlled conditions on the major court surfaces in tennis, hard courts, grass courts, and both types of clay courts.

During the Open filming however, our team also collected significant data about the influence of the ball bounce on spin at the highest levels of pro tennis. Specifically our camera was able to record over 60 incidents in which it was possible to measure the spin before the bounce and after the bounce, as well as the spin on the players hit that followed. The results showed how in all but a tiny number of cases, the bounces added significant additional topspin to the flight of the shot.

In the case of balls that approached the bounce with topspin, the results were quite similar for both the men and the women. In both cases the bounce added over 2000rpm of topspin to the shot. This included balls hit to players including Pete Sampras, Andre Agassi, Michael Chang, Venus Williams, Anna Kournikova, and Martina Hingis. For the men, 31 incidents averaged 1324rpm before the bounce, and 3355rpm after the bounce and before the hit. For the women, 21 incidents had an average spin of 995rpm before the bounce and 3129rpm after the bounce.

The data also showed that on average, the amount of topspin on the ball after the bounce was actually much greater than that generated by the players themselves. We noted above that only Sergi Bruguera's forehand was hit with topspin in excess of 3000rpm, with the majority of players hitting far less average spin.

Our ball bounce data showed that, for the men, the average spin rate of 3355rpm after the bounce and before the hit was slightly faster than Bruguera's average forehand. Although the players were hitting a ball spinning over 3000rpm after the bounce, the actual spin they generated on their own outgoing shots was on average less than half than the oncoming spin, an average of 1619rpm.

Men: Oncoming Balls with Topspin Before Bounce

Number of Incidents	Avg Topspin Pre Bounce	Avg Topspin After Bounce	Avg Topspin On Hit
31	1324rpm	3355rpm	1619rpm

Average Topspin Gained After Bounce: 2031
Average Topspin Lost After Hit: 736

For the women, the ball after the bounce was spinning at an average rate 3129rpm before the hit. The average spin the women players generated after hitting this ball an average of 1128rpm.

Women: Oncoming Balls with Topspin Before Bounce

Number of Incidents	Avg Topspin Pre Bounce	Avg Topspin After Bounce	Avg Topspin On Hit
21	995rpm	3129rpm	1128rpm

Average Topspin Gained After Bounce: 2134
Average Topspin Lost After Hit: 2001