Justin Theroux is ''hitting the gym hard'' following his split from Jennifer Aniston.

The 'Leftovers' star has been busy working out after ending his relationship with the 'Friends' actress.

A source told Entertainment Tonight: ''Justin has been hitting the gym hard since the split. He's been working out for over an hour every day at Gotham Gym. Boxing is a big part of his workout routine. He loves working out. Not only is it great to get ripped, but it's a good way to clear his mind.

''He's always in a better mood after a workout. He's always been in good shape but is more committed to a consistent regime. When he was with Jen they took cars everywhere, which he hated. Even in the cold weather, Justin's been biking everywhere. He's totally back in his element now.''

However, Justin has ''stopped caring'' what people think of him as he believes the person he is when he's in the spotlight is a different ''avatar'' to who he is when he's away from the cameras.

He said: ''Well, that avatar is not me. So, in that sense, I don't lose any sleep over it. I've stopped caring about what other people think of me. It's also minimised over the years.

''I just keep working, which is the only thing you can do. So, when someone I've never met in my life comes up to me and asks me a personal question, I say 'I don't know what you're talking about.' And you know, I'm sorry, but I really don't.''