“Everybody will be able to tell when a player has sustained a big head impact,” said Dr Lindsay Starling, the science and medical manager for World Rugby. “It will create awareness in the stands and for fans at home, as well as for the players and officials. It should mean that there is absolutely no delay in a player being pulled off for a HIA [head injury assessment]. Ultimately, this just helps to tell the story.” The English Premiership and the United Rugby Championship will be among the competitions to follow the 2025 World Cup in showcasing the LED mouthguards, which have been developed by Prevent Biometrics and are installed with an accelerometer and a gyroscope to measure linear and rotational force. After years of gathering data, scientists have set the threshold for an alert at 75Gs (g-force) for men and 65Gs, or 4,500 radians (measuring how fast something is rotating) per second, for either gender. These are categorised as the 99th percentile of collisions. Wallaby Carlo Tizzano suffered a blow of just over 54Gs of force when he was struck by British and Irish Lions breakaway Jac Morgan during the second Test of the recent series.