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Los Angeles - Justin Bieber wowed fans by posting two shirtless selfies on Instagram.
The 21-year-old showed off his muscular physique in two snaps he shared on the social networking site, revealing he is "back in the gym".
In the picture, Justin is seen flexing his muscles while wearing just a towel slung around his waist
The Sorry hitmaker has obviously been working hard over the past few weeks as the results clear to see!
In January 2015, Justin was signed up as the new face of Calvin Klein underwear, and has since posed in several steamy campaigns.
His personal trainer Patrick Nilsson previously revealed he had worked hard to maintain the body he needed for the shots.
He told HollywoodLife.com: "He has put on 20 pounds of muscle and he's still working on it. It's a work in progress.
"We want to put on at least 15 pounds, he's going to get even bigger, that's the plan."
It's not just exercise though that Justin has been using to bulk up - he has also been sticking to a rigid diet.
He said: "Justin has at least one green juice every day. He usually starts the day with one, he gets them delivered and he stocks his fridge with them. He hated them at first and the way they taste but he loves them now, he loves how they make him feel.
"It's the same way with coffee, it tastes bad at first but then you get addicted to it and you start to love the way it tastes, it's the same with green juice. Justin has one every morning now."
