Jon Gruden's son is a competitive powerlifter -- he's jacked as hell -- and tells TMZ Sports his best numbers on the bench, squat and deadlift are CRAZY impressive.
23-year-old Deuce Gruden is currently in Belarus where he took 1st place in the junior 183-pound weight class at the International Powerlifting Federation Classic.
Deuce -- who's an assistant coach with the Washington Redskins -- says he credits his famous father for helping him become a world-class lifter ... and then he busted out the number.
Deuce also told us about Jon's workout routine these days -- and the numbers ain't too bad for a 53-year-old non-professional athlete.