The Vail Pass Half Marathon
Whist a half marathon is 13.1 miles worth of child's play compared with some of endurance events on this list, stick that run 10,662 feet above sea level where there is roughly 21 per cent less oxygen and it quickly becomes a throat burning battle of the fittest.
One aspect of the annual Teva Mountain Games, hosted by the outdoor footwear company, a further 2,900 feet of elevation to tackle during the run, oxygen starved muscles become lead weights to drag you up the side of a snowy mountain. Oh, and did we mention the possibility of altitude sickness, nose bleeds and lung busting shortness of breath before you even cross the start line?
The Badwater Ultramaraton
Around 70 competitors and their sled dogs enter “The Last Great Race on Earth” every year to take on the dangers of the Alaskan tundra. The 10-day trail takes them from jagged mountain passes down through frozen rivers and lakes, forcing them to confront wind-chill temperatures of -70˚C, blinding snowstorms and treacherous tracks. At least 109 dogs have succumbed to the grueling conditions since its advent in 1973. No humans have died, but there's always a first time.
The Crocodile Trophy
Taking saddle soars to new levels of dusty heat exhaustion this nine day endurance monster sees its personal wellbeing bereft participants attempt to cover 1,400 km of Australian outback with a mountain bike and a quickly emptied water bottle.
Adding to the damning motivation killers of muscle fatigue, cramp and the largely barren surroundings, daily bouts of combating the sweltering, dehydrating and hallucination educing heat can be halted only by the odd trip to muddied water holes and questionable looking ponds.
The Iditarod Trail
As if 135 miles of road running through Death Valley to Mount Whitney, California, wasn't enough, this nightmarish hell-ride of a marathon is run in mid-July. That means temperatures of up to 55˚C – that's so hot that if you don't run on the white lines, the tarmac may actually melt your shoes. Along the way you'll take in such welcoming-sounding sights as Furnace Creek, Devil's Cornfield and Devil's Golf Course. Bills itself as “the world's toughest foot race” – you'd better get in training…
This 10- to 12-mile obstacle course designed by the British Special Forces breaks you with fire, electricity, ice water and a million other things. The self-billed “toughest event on the planet” is hardcore, but you don't need to be in peak condition to compete, just willing to get messy. In 20 locations worldwide, 7,000 “Tough Mudders” take on huge walls, claustrophobic tunnels, mud-crawls and more on any given weekend, and you're greeted with a beer and a party at the finish line.