While racket manufacturers compete to bring the latest technologies to the sport, all rackets, must comply with specifications set out in the ITF Rules of Tennis.
These rules legislate for factors such as maximum racket dimensions as well as stringing patterns. Manufacturers wanting to ensure their rackets conform to the Rules of Tennis submit them to the ITF where they are reviewed and tested for performance and spin.
“We get the odd racket come in on a conformity issue and matters like that go to the technical commission,” explains ITF sports engineer James Spurr. “The commission is a group of people representing the tennis playing community and experts from academia. We have a lab to do lots of testing and we present data to back up any decisions that are made concerning any product.”
To test the performance of a racket the ITF use a machine known as MYO (a Greek word meaning muscle), which measures the maximum power a racket can generate. “It is quite a big machine that spins a racket around at a rate of knots and hits a ball,” says Spurr.
“We can load a racket and recreate a serve as the ball dropper, with very impressive timing, drops the ball and the racket comes round and hits it at a certain point on the string bed and we measure the speed of the ball off the racket. That’s our racket power because that’s what the players perceive as racket power. We measure racket power down the face of the racket and build up a racket profile. We have done that for lots of off the shelf rackets so we have a large database of power figures and if something new comes out we have the benchmark tests to compare it against.”
The ITF also tests rackets for spin using a rig where a racket head is clamped and balls are fired in at the heads from different angles. The engineers then measure the amount of spin produced by the rackets as the ball bounces away. “We have done lots of testing with lots of different strings and patterns and rackets, because some rackets have subtly different methods of suspending the strings in the frame,” explains Spurr.
“We have benchmark values for products available on the market and we can compare new systems against that data and assess whether something produces a lot more spin, more than we are comfortable with maybe. The idea is that with the data the technical commission can make more informed decisions about conformity issues.”
Although the ITF does not currently operate any form of official approval or endorsement system for tennis rackets it once stepped in to ban a racket innovation. The spaghetti racket, also known as the double-strung racquet, came into fashion in the late 1970s and helped players created massive amounts of spin on the ball. The secret behind the spin was extra string wrapped around the racket’s cross strings and Guillermo Vilas’ saw his 53-match winning streak on clay ended in 1977 by a player with a spaghetti racket. A year later the ITF banned the double-stringing technique and created new rules prohibiting anything similar in the future.
There are plans in the pipeline for the ITF to develop another test for rackets to measure their control, which could enable them to provide classifications for players. “We would then have the three specific tests to give rackets a classification,” says Spurr. “It wouldn’t be approval, because that implies one is good or bad, more a classification to say racket A is high powered and low control or racket B is medium spin but low power. The idea is then we can offer that service to manufacturers and the wider tennis playing community will have a scale they can compare all the different rackets to.
“It is a daunting thing to go into a shop and buy a new racket and you have a choice of hundreds, all with pro and cons and it depends on your ability and playing style. The idea is to have that independent verification of performance and properties to improve consumer choice and that sort of thing.”