While the thresholds for rotational force are the same for both male and female players at 4,500 radians, an acceleration alert is triggered at 75G for men and 65G for women.

It is believed that women are more susceptible to concussion as their game contains fewer head acceleration events, but a similar rate of concussion to the men’s game.

Instrumented mouthguards, which were first used in the international game in WXV in 2023, are not mandatory.

Some players have medical reasons for not wearing them, while others have concerns over the use of their data or a Bluetooth unit within their mouth.

However World Rugby says there has been “full opt-in” from players set to compete at the 2025 Rugby World Cup, with two players willing to wear the mouthguards, but unable to do so due to dental braces.

The tournament begins on Fridayc, 22 August, when hosts England take on the United States.