The Oscar winner shocked fans earlier this month (Jun16) when pictures featuring his bulging biceps while working out at the gym surfaced online.

People were quick to speculate his fitness regime is connected to his upcoming role as Jim Gordon in DC Comics' Justice League, but the 61-year-old has revealed that's not the case.

"This is all coincidental," he told Business Insider. "I'm not going to mess with something that iconic."

Instead, J.K.'s impressive muscles are down to a health kick the actor has been on since 2009, having yo-yo'ed in weight for different roles, including TV prison drama Oz.

"After the second and final time that I got hugely fat in my life and when I lost that weight six or seven years ago, I pretty much decided that I was going to stay in decent shape for the rest of my life," he explained. "I was not in good shape at all. I was overweight and soft and here I am playing the head of the Aryan Brotherhood in this maximum-security prison in the first-ever HBO original drama and I was watching the first season when it came out and I just thought, 'Wow, I don't believe this guy at all. I have to get my a** to the gym and be a believable hard-a**."

J.K. had hit 250 pounds at that time, and decided to turn things around and work with trainer Dana Perry to build muscle and get in shape.

"I've gone back and forth with fine-tuning the kind of conditioning I'm doing," he added. "Sometimes trying to shed weight and getting leaner and sometimes trying to pack on a little more muscle."

His most recent workout pictures came from his fitness sessions with Dana and Aaron Williamson, the on-set trainer for Terminator Genisys.

"I just had free time to go to the gym, so I started training with him," he continued.

It was down to Aaron, who also trains Zac Efron and Dwayne Johnson, for posting the viral photos of J.K.'s bulging biceps as he lifted weights, captioning them, "Every time we train together I forget he's 61 years old. So much respect for this guy #OldManCranking".