Carlos Alcaraz, Jannik Sinner and Aryna Sabalenka are among several players banned from using wearable fitness trackers. But why are they banned at Grand Slams?
Sabalenka and several top players have been seen wearing a fitness tracker on their wrist, a device which has been approved by the International Tennis Federation (ITF).
But while the wearable trackers can be worn at most tournaments on the men's and women's tours, they have not been cleared for use by the organisers of the Grand Slams.
In other elite high-intensity sports, such as football and rugby union, data and fitness tracking are used to identify when players are in the "red zone" and could be more susceptible to injury without sufficient recovery.
"The reason why I was wearing that on court, because we received the email that we got approval from the ITF to wear this device," Sabalenka said.
"The whole year we are wearing - on WTA tournaments, all the tournaments I play. It's just for tracking my health," she added.
"I don't understand why Grand Slams have not allowed us to wear it. I really hope that they will reconsider the decision and let their players track their health monitor."
The ATP, which governs the men's tour but not the Grand Slams, approved players using the technology during matches in 2024.
A statement from then chief sporting officer Ross Hutchins said the technology was a "big step forward in our push to optimise player performance and prevent injury".
Women's players have been allowed to use them by the WTA since 2021.
But health analytical devices - known as wearables - are not currently permitted at Grand Slam tournaments.
Tennis Australia said organisers were discussing the issue although the tournament already uses high-tech cameras to provide players with data such as distance covered, changes of direction and sprints to measure load.
"Wearables are currently not permitted at Grand Slams," the governing body said. "The Australian Open is involved in ongoing discussions on how this situation could change."
Top seed Alcaraz was asked to remove the tracker he was wearing under his sweatband ahead of his fourth-round victory over Tommy Paul.
Defending champion Sinner, who struggled with the extreme heat during his third-round win, said his team had wanted to collect performance data with the tracker to improve training sessions.
"There is certain data what we would like to track a little bit on court," Sinner said.
"It's not for the live thing. It's more about [what] you can see after the match. These are data we would like to use also in practice sessions, because from that you can practice on with the heart rate, how much calories you burn, all these kind of things."
The former world No 1 was asked to remove his device ahead of his fourth-round match against Luciano Darderi.
"The umpire asked me straight away if this is the tracker," said the Italian. "I said, 'Yes'. He said, 'Remove'.
"It's fine. There are other things we could use (like) the vest but it's a bit uncomfortable for me. You feel like you have something on the shoulders.
"But rules are rules. I understand. I won't use it again."
Whoop's fitness tracker is waterproof and designed to be worn 24/7, making it a must-have for professional athletes and their teams, who use it to track everything from heart rate variability to sleep stages, skin temperature, blood oxygenation, and even detect illness.
This data can then be synced via Bluetooth and read by a coach using a paired mobile device.
It's been worn by top-flight athletes like Cristiano Ronaldo, LeBron James and Rory McIlroy.
Whoop CEO Will Ahmed said the devices did not pose a safety risk and that it was "crazy" to be depriving athletes of their health data.
"We will fight this so athletes can have the data they need," he wrote on X.
Watch the ATP and WTA Tours, live on Your Site or and the , giving Your Site customers access to over 50 per cent more live sport this year at no extra cost.
