Elsa Pataky doesn't tell Chris Hemsworth he's ''beautiful'' because she doesn't want him to get ''cocky''.

The 38-year-old beauty jokes with her husband - who was named Sexiest Man Alive by PEOPLE magazine last year - that she has also received plenty of similar plaudits in her native Spain in an attempt to make sure the Hollywood hunk doesn't get a big ego.

She told Women's Health magazine: ''It's funny when it's your husband. For me, sexy is the inside of someone.

''Of course I think he's beautiful and fit, but I will never tell him that because he will get too, how do you say, 'Cocky?' He'll be like, 'What do you think of that?'

''I'll say, 'Well, I've been the sexiest woman in Spain for a lot of years.' It's all just a joke, though.''

Elsa - who has three kids with Chris, India, two, and 11-month-old twin sons Tristan and Sasha - also likes to compete with her husband about who can get into the best shape.

She added: ''He'll hold the pads for me, although I won't for him as he'd smash me into the wall.

''When he was training for 'Thor', he came home with this bodyfat measurer - you know, where you clip the parts where you accumulate fat?

''So it became a competition between us. If I had some fat somewhere I'd be like, 'Grr, I'm working that part.' It's fun, it's just like a challenge, for no other reason that I like to challenge myself.''

The full interview with Elsa Pataky is in the April issue of Women's Health - on sale Thursday 5 March.