Player unions representing athletes from the NBA, NFL, MLB, NHL, and MLS have submitted a letter to the Commodity Futures Trading Commission requesting a ban on certain types of sports betting markets.

The unions are specifically calling for prohibition of prediction market platforms that allow users to bet on a player's underperformance or injury, according to Sports Business Journal. These betting options, commonly referred to as "unders," allow gamblers to wager that a player will perform below certain statistical thresholds or suffer injuries.

In their letter to the CFTC, the unions emphasized the need for "appropriate regulations" to protect athletes from these types of betting markets. The request represents a coordinated effort across multiple major professional sports leagues to address concerns about gambling markets that could potentially incentivize harm to players.

The petition comes as sports betting continues to expand across the United States following the Supreme Court's 2018 decision striking down the federal ban on sports gambling. Prediction markets and various forms of sports wagering have proliferated in recent years, prompting increased scrutiny from leagues and player organizations regarding the potential impacts on athlete welfare and game integrity.