Talk about the ultimate flex ... Giancarlo Stanton showed off ALL of his muscles in front of smokin' hot model Adriana Lima -- BY BENCH PRESSING HER!!!
The video of the Yankees superstar in the gym is insane ... he laid down on his back, grabbed Lima by the legs and the armpit -- and benched her AT LEAST 4 times!!!
It's unclear why a normal barbell and plates weren't enough for the outfielder ... but Lima sure seemed to dig it -- the supermodel was smiling the whole time!!
Of course, the feat ain't exactly tough for Stanton .