Joseph Baena's channeling his inner Mr. Universe ... with a weightlifting routine that would make his old man proud.
Arnold Schwarzenegger's son was at the gym Wednesday, and flaunted his muscles in a short vid of himself jacking up 120 lb. dumbbells on the incline press ... 4 times.
Baena doesn't quite have the bodybuilder bod yet ... but he's getting there. He's looking even more shredded than when we saw him with his smokin' hot GF around the Fourth of July.
And, speaking of Mr.