Kristen Stewart and Robert Pattinson had to work out

The real-life couple`s alter egos Bella Swan and Edward Cullen get intimate in a scene in the final installment in the vampire franchise and realised at the last minute that their fans wouldn`t want to see them looking out of shape.

Kristen said: "I know I`m tiny and s**t. I did `On the Road` right before `Breaking Dawn` and I definitely did hang out a little bit.

"Then when I was doing prep for `Breaking Dawn; I suddenly realised, `This is so not `On the Road`. People definitely want to see you looking trim.`

"Usually, we`re all making fun of Taylor Lautner for working out so often, and then suddenly me and Rob were like, `S**t` and running around the block while Taylor laughed at us."

Kristen also admitted she was put in "total lock down" so no one could catch a glimpse of her character`s wedding dress in the final movie, but she can`t wait for fans to see the scene.

She added in an interview with Britain`s Glamour magazine: "I had to be so shrouded in secrecy the entire two days of filming. It was crazy. I was on full lockdown, as if I was wearing millions of dollars worth of diamonds, but it was just a dress.

"I think the dress is beautiful and I`m so excited for the wedding to be revealed. It was one of those moments you go, `This is something to remember.` And you want to put yourself in the experience so it doesn`t mass you by."

sections: Celebrities