Covering the December issue of Women's Health UK, the actress said she was "entirely self-regimented" in her workout schedule and talked about completing the 2014 London Marathon in a little over 3 hours and 50 minutes.
"I place high demands on myself," said Dormer of her running times. "After all, if you want to do something, do it properly, else what’s the point?"
In addition to running, the actress said she also tries to fit in yoga whenever she can.
"Whichever city in the world I’m dropped in for shooting or promotion, I’ll find somewhere close by," said Dormer. "For me, I’ve had to shift around what I do over the years to find the nearest place.”
In a March 2015 issue of Self magazine, Dormer added that eating well also keeps her healthy, which is why she juices.
"When you have early calls, you don’t necessarily want to eat first thing in the morning," she said. "But you have such long days that if you don’t, you really fall down from it. So, juicing before and eating later is, for me, a good nutritional compromise."
U.K. readers, be sure to pick up a copy of the full interview in the December issue of Women's Health UK when it hits newsstands Nov. 5.
Also on HuffPost: