Scarlett Johansson stays in shape through martial arts.

The 'Avengers Assemble' actress has been working hard to get back into shape to play the Scarlett Widow in the superhero sequel with a combination of martial arts.

A source told the US edition of OK! magazine: ''Scarlett really got into martial arts. She has also logged a lot of time toning her muscles in the gym. She likes to mix up her workouts with circuits and resistance training.''

Scarlett has also changed her diet.

The insider said: ''She's a grazer. She will have between six and eight small meals a day.''

All Scarlett's training should also pay off for further movie roles, as she has already signed up for another action movie, 'Lucy'. The star will play a woman forced to become a drug mule, but upon ingesting the drug, she develops super strength, as well as the ability to absorb knowledge instantly and move objects with her mind in the Luc Besson film.