Cardinals superstar David Johnson's out to prove he's back ... and he's doing so by throwing nearly half a thousand pounds ON his back!
The stud RB put 495 pounds on the barbell Wednesday and squatted it ... THREE TIMES!!
FYI -- Johnson missed 15 games last season 'cause of a wrist injury he suffered in Week 1 ... but, clearly, dude's no worse for wear heading into this season.
We know what you're thinking ... not THAT impressed, especially since Rams star Aaron Donald just BENCHED that last month.