Arnold Schwarzenegger's son Joseph Baena shows off abs as he undertakes grueling gym workout in LA

Arnold Schwarzenegger's son Joseph Baena showed off his muscled physique in a gym selfie he posted on social media Tuesday. 

The Pepperdine University graduate, 23, was shirtless with black athletic pants and a grey beanie cap with checkerboard pattern Vans slip-ons.

Joseph, who is Arnold's son with his one-time housekeeper-turned-mistress Mildred Baena, added the caption 'Feelin nuts today' as he posed with his manager in a gym setting, flexing his massive arm at one point.