Per Wikipedia:
the contestants allege that they did not get paid adequately for their work, oftentimes not getting paid at all. Contestants have also said they have not yet received promised prizes and compensation money. Contestants further said that they did not receive adequate amounts of food or medical care throughout the course of the show, despite many participants becoming injured.Contestants also stated that they had their phones and other personal belongings taken away from them prior to arriving to the stadium to film.
The complaint also alleged that contestants were made to provide false information and were misclassified as volunteers rather than employees to allow the production to obtain Nevada tax credits and avoid other taxes. In addition, the plaintiffs alleged that they were told that the competition would involve 1,000 participants, which was later revealed to them to mean 1,000 on the televised show out of an initial 2,000 participants.
As a result of the conditions they faced, contestants alleged that the conduct of the production companies and staff caused them "serious emotional distress"