Ronda Rousey refused to shave her head for 'Mile 22' because she has an endorsement deal with a hair-care firm.

The 31-year-old star has revealed that director Peter Berg was eager for her to shave off her glamorous blonde locks ahead of filming the new movie, but Ronda insisted she wouldn't because she has a deal with Pantene.

She told Collider: ''On one of our first days on set, we were just kind of getting a feel for everything and they were like, 'OK guys, we're just going to set everything on fire.'

''That was basically what it was. It wasn't like, 'Oh, there's going to be a fire over here...' There's just fire everywhere. And I just had a Pantene endorsement, and Pete already wanted to shave my head for this movie. Let's get that straight. He wanted to shave my head, it was the one thing he was super on.

''He was like, 'I want your head shaved, gone.' And I was like, 'Pete, I've got a Pantene deal - you can't shave my head.' So on the first day of shooting, there's fire everywhere and I'm like, 'This is just because he wanted my head bald and he's going to try and burn all of my hair off today.'''

Meanwhile, Ronda - who joined the WWE earlier this year - recently insisted that wrestling is tougher than acting.

The former mixed martial arts star - who appears alongside Mark Wahlberg in 'Mile 22' - admitted that performing in front of a live audience in an arena, where there are so many more variables, is much tougher than working on a movie set.

She said: ''It's very different in that you only get one shot. Everything is live so people aren't going to reset the shot for every scene, so you need to be very aware of where the cameras are at all times to make sure they're catching what's going on.''