EXCLUSIVE PHOTOS - Justin Bieber Works Out In His Underwear

We guess it has been hot in California lately!

Justin Bieber is back from his troublemaking South American trip, and we caught the pop star working out at his Calabasas mansion in nothing but his boxers!

The Biebs was walking on the treadmill with no shoes or shirt, and we're not sure this is this is the most efficient way to exercise! The Canadian sensation has been looking a lot more buff lately, though, so who's to say this isn't his fitness secret?!

The chart topper was probably blowing off some steam in the wake of his latest scandal, which occurred when he accidentally swept the Argentinian flag off stage when he mistook it for a fan's t-shirt.

"People throw stuff on my stage all show and I get it to the stage hands to get off so no one got hurt. That video I saw a bra and thought it was a shirt. I'm being told by my team it was a shirt but even if it was a flag I would never do anything to disrespect Argentina or the people of Argentina or the fans. I'm so sorry for anyone who took my actions the wrong way and I hope you can forgive this mistake," he tweeted to his 47 million followers.

Lookin' ripped JB!