Outdoor endurance events like ‘Tough Mudder’ have seen a meteoric rise in popularity over the past few years. We examine how the obstacle racing craze has developed and take a look at five of the world’s toughest outdoor challenges that push the human body to its absolute limits.

The evolution of assault courses

Assault courses have been used by armed forces across the globe for decades, as a method of physical training and a way to school recruits in the tactical movement required for combat.

In 1987, former Grenadier Guards trained soldier Billy Wilson opened obstacle courses up to the public, launching ‘Tough Guy’ – an eight mile cross-country run followed by a course consisting of slalom hills, ditches, jumps, freezing water pools and fire pits.

The 76 year-old recently revealed the inspiration behind Tough Guy to Saga Magazine, saying “I saw people sitting on buses in the early Seventies, day after day, looking miserable, and I thought: I need to get those people off those buses, and out in the fresh air.

“So I set up jogging exercises in the park and encouraged people to jump fences, which was unheard of in those days. Those small fences grew into vast obstacles, and Tough Guy was born.”

Why put yourself through it?

Over the past five years, Tough Guy has spawned many copycat events, each claiming to test the mettle of even the hardest of competitors. But why are they so popular? Tough Guy claims that its participants experience “the addictiveness of fear”.

Will Dean and Guy Livingstone – founders of the world’s biggest endurance event company “Tough Mudder” that started in 2010 – argue that people are simply bored of the traditional marathon.

Livingstone told Inc.com: “Marathons are terribly run. For us that was just a huge, huge opportunity. We’re offering a product to people who are athletically minded but don’t want that competitive aspect,”

Dean adds: “Running’s a bit boring. In what other sport do you have to listen to music to make it passable? I wanted to make something that was Ironman-meets-Burning Man, a test of all-around fitness, but in this fun, slightly quirky environment.”

Five of the world’s toughest events

1. The Spartan Race

Described by ESPN as “a true test of will”, the Spartan Race is held in 15 countries and offers events from 1 mile to marathon distances. Obstacles include fire jumps, barbed wire crawls and a spear throw. Voted Outside Magazine’s Best Obstacle Race of 2012.

2. Superhero Scramble

“It’s not just a race, it’s an adventure!” Held in over 20 American locations, the Superhero Scramble encourages competitors to dress up in superhero costumes as they complete a course between 4 and 13 miles with up to 30 obstacles.

3. Warrior Dash

This 5k mud run with around 12 obstacles is seen as one of the “sprints” of obstacle races. Warrior Dash began in Joliet, Illinois with 2,000 participants in 2009 and has since spread to six countries across four continents.

4. Men’s Health Survival of the Fittest

This comprises a run of at least 10k together with an urban assault course in one of five UK cities. Open to men, women and teams, the courses include slippery walls, water obstacles, a parkour zone, an 8 foot wall and hay bale scrambles.

5. GORUCK Challenge

Lasting anywhere from 4 hours to 4 days, the GORUCK Challenge tests physical and mental boundaries. It’s designed to mirror Special Operations training where an experienced Cadre challenges, teaches, and inspires small teams to do more than they ever thought possible.