UF Research Shows Larger Tennis Balls Do Not Harm Players

April 23, 2003

GAINESVILLE, Fla. — Larger tennis balls may slow the game and make it more spectator-friendly, but they won’t increase the likelihood of injuries that many athletes fear, according to new University of Florida research.

The study disproves a common worry among athletes that using larger balls will result in more stress-related injuries, such as tennis elbow. Each year, more than 78,000 tennis-related injuries are treated in hospitals, doctor’s offices and clinics throughout the United States, according to the American Academy of Orthopaedic Surgeons.

In addition, the study found the larger balls had no effect on participants’ reaction times.

Athletes have been afraid the larger balls would cause more racquet vibration and force adjustments to their strokes that could damage their arms. However, the study found no evidence to support this concern, said John Chow, a UF associate professor of biomechanics and an author of the report published in a special March tennis edition of the Journal of Science and Medicine in Sport.

Instead, Chow said, the larger balls have many practical applications, especially to recreational players.

“One of the targets in terms of marketing is to average players,” he said. “Recreational players can keep the larger balls in play longer. They have more time to react to the ball because it travels in the air longer.”

As a result of longer, more powerful racquets being developed that decreased interaction between players, the International Tennis Federation – the governing body responsible for developing the game’s rules – sanctioned in 1999 the use of balls 6 percent larger than the standard variety on a trial basis in order to slow down the game and make it more interesting for spectators.

“Because of the power serve, there are fewer ground strokes, and it is less interesting for spectators because they just see serve after serve,” Chow said.

Two major tennis ball manufacturers, Penn and Wilson, subsequently issued larger balls, which have greater air resistance and so take longer to reach the other side of the net allowing players more time to react, Chow said. The new balls are about a half-centimeter larger at .432 centimeter. The Penn ball also is slightly heavier – 2 grams – than a standard ball.

Use of the larger balls has been slow to catch on, however, because they currently are not promoted heavily at any level of the game, Chow said.

Both sizes are now recognized in the rules of tennis, but the federation can make recommendations only about which ball should be used on which surface, said Stuart Miller, technical manager at the group’s headquarters in Roehampton, England. Tournament directors must make the final decisions on which size ball to use.

The UF study involved 29 beginning to intermediate tennis players who performed volleys under 18 experimental variables, such as ball size and serving speed. The variables were intended to determine the effect of ball size on reaction time, movement time, and the vibration and acceleration of the racquet during impact.

Nine women and 20 men ages 21 to 36 each performed two trial strokes per experimental variable. A machine delivered the ball from the opposite side of the court and was obstructed by a screen so participants could not see which angle the ball was coming from until it was released.

This study concentrated solely on the effect larger balls had on players who performed volleys, or intercepted the ball as it came over the net rather than after it hit the ground.

The study found ball size had no effect on participants’ reaction times and did not increase stress-related injuries. The standard-sized ball actually was found to cause greater racquet vibration than the larger ball, but Chow said the difference was not significant.

Although the larger balls won’t result in more injuries, there are other implications to consider, Chow said.

“In terms of disadvantages, it feels different when you hit an oversized ball,” he said. “Whether you like it or not, it is going to be a difference.”

Also, a change in ball size affects many areas of the tennis industry that depend on ball size, such as women’s bloomers that have pockets designed for standard-size balls, and ball machines and ball-retrieval devices that don’t allow for an increase in ball size, Chow said.

The study, which was supported in part by a grant from the United States Tennis Association, did not control for ball speed at impact or contact location on the racquet face. Future studies should account for these variables as well as different material properties of the ball, such as internal pressurization or felt covering and their effects on players, Chow said.

While the UF study looked at the larger balls’ effects on volley strokes, Duane Knudson, an associate professor of physical education and exercise science at California State University at Chico, found results similar in his research examining their effect on forehand strokes.

“We concluded that the larger ball poses no physically significant risk to tennis players beyond what they normally experience day to day due to wind or other environmental factors,” Knudson said.