We love getting behind-the-scenes glimpses of our fave hot guys' crazy workout sessions! Justin Bieber Instagrammed gym selfies along with an intense collage of himself working out — and we have to say, he's looking totally buff! He really has been putting more time in the gym recently, lifting weights and working on his abs – and it's definitely paying off.
Justin's not the only hot star who spends countless hours breaking a sweat — and making it look good! – Harry Styles, Cody Simpson, Colton Haynes and Austin Mahone all regularly share super hot pictures of themselves exercising.
We rounded up pics of some of the hottest guys working on their fitness, so you can decide whose gym sesh is most impressive! Click through the gallery above to check them out!