The player generates the data and owns almost none of it

Tracking systems turn every training session into a licensable asset, and the athlete is rarely a party to the licence.

Every stride a professional takes inside a stadium is captured by a camera array or a vest, converted into a feed, and sold to somebody. Broadcasters buy it for graphics. Betting operators buy it for in-play pricing. Recruitment departments buy it to value players. The person producing it usually gets a copy on request, if that.

The commercial structure is worth spelling out. A league signs an official tracking partner. The partner installs the hardware at every venue, and in exchange receives the right to distribute the resulting data. Clubs get access to their own numbers as part of the arrangement. Downstream, the same data flows to media rights holders and to the wagering market, which is where the real money is, because in-play betting needs low-latency truth and is willing to pay for it.

Players sit outside that chain. Their collective agreements were written when data meant a scoresheet. Some player associations have started pushing back, arguing that biometric output is personal data and that consent for medical monitoring is not consent for commercial distribution. They are right, and the pushback has been slow because the parties who benefit are the same parties who administer the sport.

The practical harm is not abstract. A fatigue profile that shows a player declining in the back third of a season is a negotiating instrument. A club that holds it and a buying club that does not are not trading on equal information. Meanwhile a betting market with access to real-time positional data prices a match more accurately than any spectator can, and the raw material for that edge came out of somebody's hamstring.

I do not think the answer is banning it. The answer is a licence, with a fee, negotiated collectively, the way image rights were eventually handled after decades of clubs assuming they owned faces as well as contracts.

There is a self-interested argument for clubs too. Data an athlete does not control is data an athlete has no reason to trust, and monitoring compliance falls apart the moment players suspect the vest is working for the contract department rather than the medical room.

Ask who signs the data agreement. In almost every league on earth the answer is: not the people wearing the sensors.