Chris Hemsworth has joked his muscles are the work of CGI.

The 33-year-old actor has become known for his role as Thor in the Marvel film series of the same name, as well as the 'Avengers' ensemble movie series, and although he has to be fighting fit for his part, the hunk has teased that he's actually ''400 pounds.''

Asked by E! News if he packs on more muscle for every movie, Chris joked: ''No, the special effects get better. I'm about 400 pounds - you just can't tell.''

Although his muscles are impressive, Chris recently admitted he has a ''healthy rivalry'' with his young brother and fellow actor Liam when it comes to staying in shape.

When asked if he and the 'Hunger Games' star are competitive, Chris said: ''Yeah, in a fun way, you know? I feel like we've always been. People try to pair us off like there's this vicious competitiveness, and, 'Arghhh! You got that part and I didn't,' and stuff which isn't the case. Get us at home, playing cricket or football or surfing or something and, yeah, there's a great rivalry there - a very healthy one.''

And Liam - who is in a relationship with Miley Cyrus - previously admitted he and the 'Thor: Ragnarok' star, along with their eldest brother Luke, 35, are all incredibly ''competitive''.

He said: ''I was the youngest, so I was never really anywhere near their physicality. If they wanted to beat me up, they would. But I idolised them. As a kid, I followed them into anything and wanted to do whatever they were doing. And it was always competitive.

''I went and watched [Chris] on set one day and I clearly remember something snapping in my mind. It was like, 'Yeah, I want to do this.' It was definitely the goal. Before I even started working on 'Neighbours' in Australia, I was already thinking about Los Angeles.''