Antonio Brown has missed practice time with his new team for reasons stemming from cryotherapy to a grievance over his helmet. (Eric Risberg/AP, file)

An arbitrator heard arguments Friday regarding a grievance filed by Oakland Raiders wide receiver Antonio Brown against the NFL over Brown’s nonapproved helmet, according to multiple people familiar with the situation.

No immediate ruling was made during Friday’s hearing, according to those people, who spoke on the condition of anonymity for that reason. The NFL declined to comment, and Brown’s representatives did not respond to a request for comment.

Brown has not been practicing lately because of ailing feet, an injury reportedly caused or aggravated when Brown failed to wear proper footwear at a cryotherapy treatment. There also have been reports about communication issues between Brown and the Raiders, and now his displeasure with the league’s helmet rules further complicates his playing status. ESPN reported that Brown told the Raiders he would not play football again unless he’s permitted to wear his preferred helmet.

Brown wants to continue wearing the helmet even though the model was discontinued by the manufacturer and it is not certified by the national governing body, the National Operating Committee on Standards for Athletic Equipment (NOCSAE), because it is more than 10 years old, according to those people familiar with the case.

NOCSAE said it does not have a rule that no helmet older than 10 years can be worn, but the National Athletic Equipment Reconditioners Association (NAERA) does not permit recertification of helmets 10 years old or older.

The league announced in April that the 32 players who ended last season wearing helmet models not approved by the NFL and the NFL Players Association would not have the option to continuing to wear those helmets. The grandfather clause allowing players to wear banned helmet models expired after last season, the league said.

“The prohibited helmets will not be allowed in the locker room,” Jeff Miller, the NFL’s executive vice president of health and safety initiatives, said in April. “A player will not be allowed on the field [wearing a banned helmet].”

Friday’s hearing continues the strange saga of Brown’s first year with the Raiders. He is among the league’s most productive wide receivers but was traded from the Pittsburgh Steelers in the offseason. Brown had become increasingly disgruntled in Pittsburgh and requested a trade, apparently in part because of a clash with quarterback Ben Roethlisberger.

The league and the NFLPA are in their fifth year of testing various helmet models to study how they withstand impact. The NFL and the players’ union compile the testing results, rank the helmets and produce a poster in which helmet models are categorized as green, yellow or red. The green category is for the helmet models that performed the best in the lab testing. The prohibited helmet models are placed in the red category.

New England Patriots quarterback Tom Brady and Green Bay Packers quarterback Aaron Rodgers also are among the players being forced to switch helmet models this season.

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