Rebecca Ferguson found making Mission: Impossible 5' similar to being in labour.
The 33-year-old actress made her debut in the action franchise as assassin Ilsa Faust and admitted she needed to do a lot to get in shape for the role, but has found it much easier to reprise the part for the upcoming next instalment of the series.
She said: "[The first one was] like going through labour, it was exciting, it was new, it was so goddamn painful.
"This time I've kept up my fitness so it's not so hard.
"I could now practically sleep on the Pilates reformer, I love it so much."
During term time, Rebecca's 10-year-old son, Isaac, lives with his father - who she split from some time ago - in Sweden and she is thankful they have been able to make it work for her to travel with her work.
Rebecca - who has a new, unnamed, English partner, who is not in the film industry - said: "We make it work. It could be so hard, but it's not because everyone gets on and supports each other."
The actress can next be seen on screen in 'The Snowman', which she began working on in Norway as soon as filming wrapped on 'The Girl on the Train' in the US, but she insists her workload isn't that tough, especially because she enjoyed working with co-star Michael Fassbender on the horror.
She said: "I wouldn't worry too much about my workload. After all, I had four months with Michael."
She has also been working on 'The Greatest Showman' with Hugh Jackman and Zac Efron but was initially unconvinced by the project when director Michael Gracy arrived at her house carrying a television set.
She recalled to Britain's Vogue magazine: "Did I want, then, to do a musical? Hell no."
However, after the filmmaker showed his video montage, she felt "electrified" and jumped at the chance to be involved.