Blake Lively reveals her 13-hour workouts for 'The Shallows'

Blake Lively wasn't messing around when she signed on for The Shallows, and the actress revealed just how grueling her fitness routine was on set. The 28-year-old took her routine to a whole new level to get in shape for the action-packed thriller, on which she set to work just months after welcoming her baby daughter James with husband Ryan Reynolds.

TAP TO VIEW GALLERYBlake Lively at The Shallows promo Blake Lively has spoken about her gruelling routine during The Shallows

"I was working out 13 hours a day because shooting was working out," the former Gossip Girl star told Entertainment Tonight. "It was neat to be able to do that, and it was neat to have that challenge after having a baby, because you think your body is so different – you think no matter what, it's never totally [going to] be the same."

In the film, Blake stars as a student who becomes stranded on a giant rock, 200 yards from shore, with a great white shark lurking in the water ready to attack. Therefore, it comes as no surprise that her training involved a lot of swimming, which the star credited for helping her to get "stronger and more fit".

The Shallows The actress did a lot of swimming while filming the action-packed thriller

"Being in waves like that, swimming like that, doing such long takes like that all the time, I became so much stronger and more fit by the end of production," she explained, crediting her "amazing trainer" Don Saladino for helping her to get in shape "in the most healthy way".

Blake also revealed that husband Ryan encouraged her to take on the challenge. "He was very kind and generous to read the script," she said. "I was really sick and I was working, and so he read it and he was like, 'Aww, the action is amazing.'"

Blake Lively and Ryan Reynolds Blake and Ryan are expecting their second child together

However, the blonde beauty confessed that Ryan warned her that it would be a demanding role to take on, telling her: "Be prepared, this movie is a physical challenge, it is an athletic event. It was like training for a marathon."

As she promotes the thriller which is out later this month, Blake will no doubt also be making the most of her downtime, following the news that she and Ryan are expecting their second child together.

The couple are said to be over the moon as they prepare to welcome the new arrival, as a source told People: "Blake is absolutely thrilled and so is Ryan."

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