Doutzen Kroes keeps fit by doing ballet.

The Victoria's Secret model believes dance is one of the best forms of exercise for giving her a catwalk-ready body, and has regular sessions with the teacher who whipped Natalie Portman into shape for her role in 'Black Swan'.

Doutzen said: ''I work out three or four times a week. I do a mix of boxing at a gym in New York and ballet with Mary Helen Bowers, who runs Ballet Beautiful and helped get Natalie Portman in shape for 'Black Swan'.

''It's tough because it focuses on specific areas including the inner and outer thighs, butt and abdominal area and arms. Every morning after a workout with her, I feel so sore in places I didn't know I had, so it really works and I enjoy it.

''I also think that working out with a woman makes a difference as she understands what I want to look like. Men see things differently.''

The Dutch beauty - who has two-year-old son Phyllon - says becoming a mother has forced her to take better care of her body, so she has to watch what she eats and work out more often.

Doutzen told Britain's HELLO! magazine: ''When you're younger you think you know everything, but I know my body better now than 10 years ago. I run around like crazy since I had my son, but I'm lucky and have good genes so my stomach has never been a problem area.

''However, I know I have to work out and eat healthily now.''