Justin Bieber Arm Wrestles Shirtless -- Watch!

Justin Bieber has been hitting the gym!
The 23-year-old singer took to Instagram on Saturday to show off his late-night activities: shirtless arm wrestling!

The Biebs also gave fans a close up of his game face with a few silly selfies.

On Friday, Beiber debuted a new tattoo, reflecting on his past mistakes and explaining that he wants to "work everyday to be BETTER AT 70."
See more in the video below.