Natalie Dormer talks being in 'the best cardiovascular shape' of her life

NEW YORK, March 26 (UPI) -- Natalie Dormer has had to work hard to be able to run in heavy armor in the Hunger Games: Mockingjay films and to rock this tight cosets from Game Of Thrones.

The 33-year-old actress opened up about her fitness routine during filming and how she managed to fit it all in thanks to midday naps and green juices in the April issue of Self magazine.

"In Mockingjay – Part 2, I'm basically running around in heavy armor while carrying a semiautomatic rifle," Dormer said. "I don't know how I would have kept up with [costars] Liam Hemsworth or Sam Claflin if I hadn't been in the best cardiovascular shape of my life."

Dormer's workout schedule featured early morning runs on Atlanta's hilly streets -- where Mockingjay was shot -- and hour-long interval workouts at night after 12-hour shoots.

"I actually look back on it now and think, '[Expletive] hell, how did I do that?'" says Dormer, who also trained for the London Marathon in April 2014.

Her role as Margaery Tyrell in GOT has also encouraged the British star to stay fit.

"Being strapped into a corset with this long flowing skirt immediately changes the way you look in the mirror," she told the magazine. "My way into Margaery is actually quite physical."