She was crowned Britain’s women’s champion Spartan Race obstacle runner for 2013 just a few weeks ago.

And now Ipswich nurse Katie Keeble is taking on the biggest physical challenge of her life – a fearsome, military-style assault course nicknamed “The Beast”.

The fitness enthusiast will join thousands of super-fit obstacle racers from across Europe, America, Australia and the UK to take part in one of the toughest sports events in the world on Saturday.

The Spartan Race “Beast”, a 25km cross-country endurance challenge, is the climax of the 2013 obstacle racing season, and takes place in Pippingford Park, Nutley, near Uckfield in East Sussex.

The 31-year-old Ipswich Hospital nurse became the UK women’s champion Spartan Race obstacle runner at The Spartan Super Sprint race at the West Midlands Water Ski Centre in September.

But she has been training hard for “The Beast” for months, getting up at 4.30am to go running before work. She also cycles to and from work seven miles a day, and crams in a strength training session after she clocks off her nursing shift. At weekends, she runs 12 miles off-road.

“I took up running when I was 21 to get fit,” she said. “You become addicted to the endorphins and when my friends one day said come and do a Spartan Race, I found it quite easy.

“I love getting dirty and muddy. Mud running is such fun and it amuses me when I’m running round covered in mud because I know the next day, I’ll be sterile and scrubbed down for my job. Being spotlessly clean is essential to my role in theatre.”

Asked about Saturday’s “Beast” challenge, she added: “I’m really looking forward to The Beast. I have trained hard and I feel ready.”

Called “The Beast” because of its fearsome, military-style course, the strictly-timed race, set to attract 4,000 runners and 2,000 spectators, forces competitors to conquer 75 obstacles.

These include 50-foot-long ‘monkey bar’ straddles over water, 25-foot-high rope climbs above a lake, clambering through 20-foot-long, semi-submerged ditches and drainage tunnels, and the notoriously tough ‘Atlas Stone Lift’.

“The Beast”, launched by Spartan Race last year, attracted 2,500 runners in 2012, and its increased popularity is part of a worldwide boom in popularity of obstacle racing, according to Richard Lee, the UK Director of Spartan Race.

“Last year more people did a Spartan Race than have ever run the London Marathon,” he said.

“The UK obstacle course racing scene is about to get very serious.

“The statistics of Spartan’s growth over the last five years tell the story: 1,000 Spartans lined up in 2010 to compete at our first UK race, this year an estimated 40,000 competitors will run one.

“Worldwide, around 1.5 million people will run a Spartan event this year.”