Chris Hemsworth spent ''four or five months'' preparing to become Thor.

The 31-year-old hunk, who stars as the comic book hero in 'The Avengers: Age of Ultron', has revealed the lengths he goes to in order to fulfil the iconic role.

Chris - who's reunited with the likes of Robert Downey Jr., Chris Evans and Mark Ruffalo for the new movie - explained: ''[Preparing] is a good four or five months of all the boring activities, lifting weights and eating lots and lots of protein.

''But, you know, doing it with the rest of the cast makes it a little easier, we're all in there together.''

Chris thinks the new Marvel film is a bigger, more spectacular improvement on the 2012 original.

He said: ''It felt so big that you lose any real context. There were so many different fight scenes and so many special effects ... you put your trust in Joss and Marvel to put it all together. We sort of knew it would be even bigger than the first one, which was scary, and it was.''

The Australian actor also said it was nice to reunite with his fellow Avengers, who he considers to be friends.

He admitted: ''The first film felt like the first day of school, full of nervous energy as we got to know one another. This one was like a high school reunion. We've all become great friends.''