She was so exhausted she slumped to the ground after finishing the race which is inspired by a famous prison escape.

The course, at Frozen Head State Park, changes every year but covers 100 miles involving 60,000ft of climb and descent - about twice the height of the Mount Everest.

Only 20 people have ever made it to the end of the race within the allotted 60 hours since it was extended to 100 miles in 1989.

The idea for the race came when they heard about the 1977 escape of James Earl Ray, the assassin of Martin Luther King Jr, from nearby Brushy Mountain State Penitentiary.

Prospective runners must write a “Why I should be allowed to run in the Barkley” essay along with a $1.60 (£1.27) entrance fee and if successful get a letter of condolence.

Competitors must find between nine and 14 books along the course (the exact number varies each year) before removing the page corresponding to their race number from each book as proof of completion.