The origins of long-distance running are uncertain although it is widely speculated that early hominins did it in order to chase and kill prey.

Christopher McDougall’s 2009 book Born to Run takes this persistence hunting hypothesis a step further by suggesting that much of early human activity was shaped by this particular action of bipedal running. The book goes on track down the Tarahumara Indians of Mexico, a tribe of legendary long-distance runners who could go on running for hundreds of miles without a break.

On Monday, tired of wowing us all with his legendary Old Spice ads, fitness enthusiast Milind Soman went on to complete a gruelling, 517.5-kilometre race over three days – a combination of swimming, bicycle riding and running.

Though not strictly an ultramarathon, Soman did have to run 84 kilometres, which he did barefoot. Technically speaking, any race longer than the standard marathon distance of 42.195 kilometres and run on foot is considered an ultramarathon.

These are some of the toughest races in the ultramarathon calendar:

Spartathlon

In 490 BC, when the Persians invaded Greece, Pheidippides, a messenger was sent to Sparta to seek help. He covered the distance of nearly 246 kilometres in a day and a half. Later, he would collapse and die on his way to Athens from Marathon, while delivering a message of victory.

Not only did Pheidippides’s exploits inspire Baron Pierre de Coubertin to set up the modern marathon race, but also one of the world’s most famous ultramarathons, started by five British RAF officers in 1982.

Starting from Athens, what makes this race one of the most difficult is that competitors have 75 checkpoints en route to Sparta and they must make sure they make it to each within a specified time limit or risk being pulled out of the race.

When Leonidas said, “This is Sparta!,” he certainly wasn’t kidding.

Yukon Arctic Ultra

Frostbite, hallucination, panic and severe distress – no, this isn’t an episode of Man vs Wild in the Alps but the experiences of those that are brave enough to participate in the Yukon Arctic Ultra.

A little over 690 kilometres starting from Whitehorse, the capital of the Yukon territory in Canada, athletes finish up at Dawson City braving extreme conditions with temperatures sometimes plummeting to -50 degrees Celsius.

The official website doesn’t try to paint a rosy picture either: “Situations which under normal circumstances don’t cause any problems can become absolutely life threatening in the dead of winter in the Yukon.”

This is one survival course even Bear Grylls would think twice about.

Barkley Marathon

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Well, if you thought that the Spartathlon was madness, the Barkley Marathon takes the definition of insanity and blows it into smithereens. Before you even start thinking about it, know this – only 14 men have finished the race in its 30-year history!

The race, held in the Cumberland Mountains, Tennessee, is 100 miles long, consisting of five 20-mile loops. Finishers have stated that it might actually be more than 130 miles or so.

Race director and creator Gary Cantrell is known to not allow GPS or cellphones, and runners will have to navigate the unmarked trail using a series of printed instructions handed out to them. A compass isn’t of much help either. Not only that, Cantrell will not even reveal the start time or the entry criteria.

Most runners are known to give up after the first loop or get lost in the woods. Most runners and finishers like to maintain its secrecy, unlike big-money, glitzy marathons but that might be difficult to do after a 2014 documentary called ‘The race that eats its young’ was released on Netflix.

The best thing about the race: the entry fee is a mere $1.60. But be careful, you have been warned!

Trans Atlas Marathon

Spread across the Atlas Mountains of Morocco, runners race across 177 miles in Berber country spread across a variety of terrains, often coming across gravel-filled paths cutting across almost 50,000 feet of elevation change.

Running through the mountains, this race is unique for the variety of conditions that ultramarathoners have to endure on their way – one can find heat, strong winds, hail and fog on this course.

In 2016, the top ten finishers were all Moroccans and finishing times ranged from 28 hours to a maximum of 80 hours taken to complete six tough, physically exhausting, punishing stages of the race.

In recent years, the race has become so famous that racers have stated that it is more demanding than its more illustrious counterpart – the Marathon des Sables held in Morocco.

Ice Ultra

The race’s name says it all – it has been described as “an adventure across Europe’s remaining wilderness”.

Set in the fancily-name region of Lapland in Sweden, racers dash across 230 kilometres of ice-covered hell with nightime temperatures dropping to as low as minus-30 degrees Celsius. It is also a self-sufficient race, which means that participants will have to carry all their gear themselves and nothing is provided to them at designated checkpoints.

Add to this the fact that terrains consist of “Snow Fields, Mountain Tundras, Ice Forests and Frozen Lakes” and the setting’s not too dissimilar to that of a fantasy novel’s, except the fact that this time the pain is real, very much real.

Split across five stages, runners are expected to run pretty much in darkness, aided only by a torch. The only hitch, the entry fee of $2000 is a bit steep but worth it if you can cover yourself in ice-cold glory.