Blake Lively used daughters 'as weights' during 5am workouts for The Rhythm Section

Blake Lively had to get extremely fit for her upcoming role in The Rhythm Section - and had a very gruelling filming schedule too.

But the actress found a unique way of fitting in her filiming and workouts around being a mum to her and her husband Ryan Reynolds' then two daughters, James, five and Inez, three.

Blake has revealed she would wake up at 5am every morning during the eight months she was filming, and wake up the girls too, including them in her exercises.

Speaking on Vanity Fair's YouTube channel, she said: "I woke up at 5 am, but mostly because I was doing mama duty with my girls.

"Have breakfast with them, hang out with them, work out with them, 'cause I didn't want to to wake up any earlier. I'm not Dwayne 'The Rock' Johnson. I had to just get some sleep."

She continued: "So I would sort of use them as weights. Instead of wearing a weight vest, I got to wear my children."

Blake then explained how she would then have an hour's drive to work, and get home around 9pm to put her kids to bed - and often fall asleep in there herself, due to her busy day.

But Ryan would come in and wake her up to get her in her own bed.

She said: "My kids had, like, a pack-and-play, almost like a crib, and I would crawl in there and sing them to sleep.

"Usually I'd fall asleep in there. Almost every single night I'd fall asleep in there. And then my husband would usually come in and be like, 'Hey, you're safe now. You can come to bed.'"

Since filming wrapped on The Rhythm Section, Ryan and Blake have welcomed a third daughter - whose name is yet to be revealed - and Blake confessed having three children who were aged four and under all at once was a lot to handle.

She said: "It's like going from two to 3,000! We have so many children. It's pretty crazy. We're outnumbered. It's a lot.

"People say that from two to three, it's the same, it's kind of easy. Those people do not have three kids. It is crazy."