By Jennifer Davis
Updated Jan 08, 2016 @ 12:00 pm
"We Are Your Friends" - European Premiere - Red Carpet Arrivals
Credit: Anthony Harvey/Getty Images

It's no secret that Zac Efron looks crazy hot with his shirt off, but his Dirty Grandpa co-star Robert De Niro may be giving him a run for his money. Efron posted a new promo photo from their upcoming movie, and the 72-year-old actor not only showed off his impressive physique, but he also wowed us with his strength.

"No joke Robert De Niro is low key as strong as The Rock," Efron captioned the snap (below). "First time I saw him shirtless he did over 25 pull-ups in a row and I couldn't help but be entranced by his rippling back muscles. This picture is real by the way. Like he actually did that. #DirtyGrandpa January 22!"

In their upcoming film, Efron plays De Niro's grandson, who is tricked into driving to Daytona Beach just before he’s about to get married. Catch them ham it up shirtless when the film hits theaters Friday, Jan. 22.