But did China really steal Sinner's brain data?

A US report has put the spotlight on BrainCo, the company that produces the FocusCalm EEG headband, adopted by high-level athletes, including tennis player Jannik Sinner, for mental training.

The investigation, published by Hunterbrook Media —an investigative media outlet that operates alongside a hedge fund—and journalist and podcaster Pablo Torre, examines the company's origins, funding, and data management practices, raising questions about possible ties to Chinese government agencies. BrainCo has denied the main allegations, emphasizing its commitment to protecting user privacy.

Founded in 2015 at Harvard University's Innovation Labs by Bicheng Han, a former Harvard PhD student and teaching assistant, BrainCo initially presented itself as an American neurotechnology startup staffed by scientists from Harvard and MIT. The company developed FocusCalm, a wearable headband costing around $300 that uses electroencephalography (EEG) sensors to measure brainwaves and provide feedback on levels of concentration and calm, inspired by NASA technologies. The device, promoted for sports performance and education, has reportedly been used by over 20 NCAA basketball teams and Olympic organizations, as well as by tennis players like Jannik Sinner.

Sinner, currently ranked No. 2 in the world in men's tennis, reportedly used FocusCalm as part of his training program under the supervision of Dr. Riccardo Ceccarelli of Formula Medicine, a performance coaching firm. Ceccarelli introduced the headband to help Sinner and other elite athletes—such as skier Mikaela Shiffrin, Formula 1 driver Charles Leclerc, and players from Manchester City and the Italian Olympic teams—regulate their mental states during their training sessions. Former NFL player Logan Ryan has also publicly praised the product for its role in mental conditioning.

Hunterbrook Media's six-month investigation revealed that BrainCo moved its headquarters to Hangzhou, China, around 2017, and has since received tens of millions of dollars from sources linked to the Chinese government, including investment funds in Zhejiang province and China Electronics Corp. (CEC), a state-owned military contractor under US sanctions. Additional ties include collaborations with at least three universities reportedly involved in Chinese military research. BrainCo has also partnered with Unitree Robotics, a Chinese humanoid manufacturing company linked to the People's Liberation Army.

One of the main concerns is how the data collected by FocusCalm is handled. The device detects EEG brainwaves, which are processed by artificial intelligence algorithms, including in the cloud, according to BrainCo's privacy policy, patents, and developer documentation.

The investigation highlighted how Chinese national security laws require companies to share data with authorities upon request. This raises concerns about the potential use of neural data from U.S. and international users, including athletes and students.

In response to Hunterbrook Media's investigation, BrainCo stated that EEG data is "deleted from the app after each use" and denied military collaboration, saying it has implemented compliance measures to prevent prohibited applications. According to a former BrainCo executive interviewed by Hunterbrook Media, the company's headbands—which the company claims can read brainwaves—may not have worked as well as advertised.

BrainCo claims the report contains “incorrect bias” and “unfounded speculation,” and declined to comment on its ties to sanctioned entities or any data-sharing obligations.

Neither Sinner nor his representatives have yet made any public statements on the matter.