Calvin Harris Works Out with NFL Player ... Beast In the Gym

Calvin Harris works out like a real-life pro athlete ... so says Minnesota Vikings safety Antone Exum, who says the DJ blew him away during a Thursday gym sesh.

Exum and Harris were puttin' in work at Heart & Hustle in L.A. -- a pretty elite gym where tons of pro athletes and big stars go to get swole.

Harris was such an animal during the workout, Exum didn't realize he wasn't a pro jock -- and when he figured out who he was, he raced after Calvin to introduce himself.

By the way, Harris is pretty ripped -- and Taylor Swift used to post pics of his impressive physique on her social media before that whole thing crashed and burned.

Her loss, Tinashe's gain (allegedly).