@aaronwilliamson / Instagram 1 / 3
@aaronwilliamson / Instagram 1 / 3

Welcome to the gun show! JK Simmons is really, really getting ready for his role as the muscular Commissioner Gordon in the "Justice League."

The actor and Farmers Insurance pitchman looks absolutely jacked in several photos taken by his trainer, Aaron Williamson.

Aaron, a former Marine, has reportedly trained Zac Efron in the past and works out with Dwayne "The Rock" Johnson, so he knows about Hollywood life. But, those guys are relatively young.

JK is 61 years old and his body is a muscular masterpiece.

"Every time we train together I forget he's 61 years old. So much respect for this guy," Aaron captioned an Instagam snap of the actor doing bicep curls.

Several weeks ago, Aaron showed another image of his famous client.

"Saturday morning, 61 years old & making the young generation jealous. This is what dedication looks like. #JKSimmons," he said of a photo of JK's arms looking ridiculously shredded.

In speaking to TMZ about the pics and JK's super fit body, Aaron said he wasn't quite sure that JK's ripped physique is for "Justice League."

"He's just a really good friend of mine and he's been training now for a couple of years and he's just kind of wanted to adopt this new lifestyle and see what he could do with his physique," Aaron said. "He's feeling better about the way his training has progressed."

Aaron, who has been featured in many national magazines and websites, said JK is doing what he refers to as "blood volume training."

"Basically you're trying to hit the muscle from as many different angles as you can," he said. "You're trying to flush it with as much blood as you can and what ends up happening is the muscle is gonna look more defined and more ripped without having to lift heavy, heavy weights, and it's easier on the joints, it's easier on the ligaments and you can actually get in shape faster that way.

Of JK, he told TMZ, "He's the most natural guy I've ever trained," adding that the actor shuns even basic supplements.

Considering his bod, Aaron added, "I know he would be interested to do a role where he's able to kind of showcase his guns a little bit."