Nina Dobrev is working hard for her killer bod.

For her latest fitness challenge, the Vampire Diaries star got down and dirty at the Spartan Run in Atlanta, pushing her body to the limit during the super hard obstacle course-that clearly involves some dirt. "I cant say I didnt see the signs," Nina posted on Instagram, along with a muddy shot of herself covered in mud. "Literally and figuratively. Haha. I was warned. Most challenging physical/mental accomplishment of my life."

To just give you a run down of exactly what Nina had to do during the challenge, here's what is involved: Fire, water, mud and barbed wire and every crazy obstacle that's thrown your way within those conditions-you know no specifics before heading in. "SPARTA!!!! #TeamJones #KilledIt Sunday. 5k ObstacleCourse Mud Run Race-Climbing Walls,Ropes,Barb Wire,Fire,IceWater etc.. #MusclesScreaming," Nina also wrote.

Have you ever done a Spartan race? Would you? Tell us in the comments.

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