Bigger Balls May Slow Tennis Matches

Sept. 20, 2000 -- When Pete Sampras finishes off his opponents, he often does so in an efficient, rather uninteresting manner — he serves another ace.

Even Sampras admits his dominance can make his games somewhat clinical. “There was nothing dramatic about the match,” he told reporters after soundly defeating Martin Damm in this year’s U.S. Open.

Sampras’ blazing serves are exactly what the International Tennis Foundation (ITF) is hoping to tone down. Some believe the best way to increase exchanges and cut down the number of aces is to use a bigger ball. And new results from scientific studies in England suggest a new ball, which is 6 percent larger, has just that effect.

More Sweat Per Point

“The number of shots per point increased dramatically,” says Sean Mitchell, a sports technologist from Loughborough University in England who conducted tests on the new ball for the ITF. “We took that to mean that players were still matched the same, but they had to put more effort into each point because the serve was less dominant.”

The Loughborough study, which evaluated four men and four women college players, showed an overall increase in rallies among all the players when using the larger ball. And among the men in particular, the number of shots per point increased even more markedly, by 25 percent.

The oversized ball is 2.79 inches in diameter, compared with the conventional ball’s 2.63 diameter — about the difference between an apple and an orange. To make up for the larger size, the skin of the ball is slightly thinner so both balls weigh exactly the same. While thinner, the larger ball’s rubber covering is also slightly firmer, so each ball travels at the same rate from the racket. Where the balls differ is how fast they sail through the air and how they bounce once they strike the other side.

“The physics is simple, really,” says Steven Haake, a mechanical engineer at Sheffield University who studied the new ball’s movement. “The larger ball slows down in the air because it’s larger and has more drag.”

Haake explained the ball’s size also makes it bounce from the court at a steeper angle. That’s because the larger surface area of the ball causes it to compress more on the bounce and more forward energy is absorbed. Put together, the effects of the larger ball mean an opponent has more time to react to a shot or serve and must put more energy into each hit to make the ball travel fast and far.

Tennis Elbows

Researchers are still number crunching results from recent United States Tennis Association tests at the University of San Francisco. But Duane Knudson, an exercise scientist from California State University in Chico reports, “Many subjects thought the ball ‘felt’ heavier, even though the mass of the ball is the same … ”

That ‘heavier ball’ perception is a little worrisome to trainers, since players might be inclined to hit the ball harder each time to make it travel further and faster. Hitting the ball hard over a long time can lead to muscle strain or a condition known as tennis elbow.

To test for muscle strain in the Loughborough study, Mitchell and his colleague Mike Caine had each player perform grip tests and evaluate their muscle soreness after each day’s session.

The players performed drills and played in matches for four days straight. On the first and third days, they used standard sized balls and on the second and fourth days, they played with the larger ball. If the ball were adding more strain, the expectation was the players would feel more soreness and their grips would weaken on the second and fourth days. Mitchell said they noticed no difference.

But Will They Like It?

Even if tests prove the oversized ball has the desired effect on the game, how players would feel about playing with a larger ball is less clear.

Wimbledon tournament officials still resist the early 1970s’ change from white to yellow tennis balls. Many decried oversized rackets when they were introduced in the mid-1970s, saying they made hitting the ball too easy. And, most recently, people have been perplexed by the new purple courts at the Canadian Tennis Masters.

So far, it seems players have similarly ambiguous feelings about the new ball. Among the eight college players tested in the recent studies at Loughborough University, six said they preferred the new ball, one remained neutral and one said she strongly preferred the standard ball. Mitchell points out that the person who favored the standard sized ball was also a very strong server.

“She may have expected to win more easily,” he says.

When the ball was introduced at four Davis Cup matches among fourth level players, it had less than glowing reviews. As Paul Rose, a project technologist for the ITF, reports, the Davis Cup players “had a mixed reaction.”

Mixed feelings aside, Rose is fairly confident the ball will eventually make its way into professional tennis.

“I’d say there’s a real possibility the ball will be introduced,” he says. “If you’re the number one seed, you’re still going to win matches. It will just make the game more interesting for spectators.”

The larger balls, which are newly available from tennis ball manufacturers, Wilson and Penn, may have a bigger effect among casual players. Haake calculates the new balls give professional players about 10 percent more time to respond to a shot. For recreational players with slower serves and shots, that extra reaction time doubles.

“I’m a player who is not terribly fast, slick or clever,” says Haake. “So for everyday players like me, it can be a great learning tool.”