J.K. Simmons buffs up for 'Justice League' role

LOS ANGELES, June 8 (UPI) -- J.K. Simmons is seriously buffing up for Justice League.

Fans were shocked to see the 61-year-old actor looking extremely muscular in a new photo that personal trainer Aaron Williamson shared on Instagram.

"Every time we train together I forget he's 61 years old. So much respect for this guy. #JKSimmons #OldManCranking," the fitness expert wrote.

Williamson, who served as a trainer on G.I. Joe: Retaliation and Terminator Genisys, has worked with Simmons on several occasions. He expressed admiration for the actor in April, writing, "This is what dedication looks like."

Simmons will play Commissioner James Gordon in Justice League, which opens Nov. 17, 2017. Pat Hingle, Gary Oldman and Ben McKenzie are among the actors who previously played the character in movies and TV.

"I can't say that I don't have some impression of that character in my head that's based on what I saw, but I'm not planning on going back and watching any of the other films," Simmons told Collider in April.

"I'm just planning on learning as much as I can about him through the comics and getting my feet wet in the first movie, and then hopefully continuing on from there," he revealed.

J.K. Simmons during a workout with personal trainer Aaron Williamson. Photo by Aaron Williamson/Instagram

Justice League will co-star Ben Affleck as Batman, Henry Cavill as Superman and Gal Gadot as Wonder Woman. Simmons is no stranger to the comics universe, having played J. Jonah Jameson in Spider-Man and its sequels.