There's no two ways about it, running a sub-two-hour marathon would be the biggest achievement in athletics history.
Across track, field and roading running, there are a number of barriers that inspire athletes to set world records and push human athleticism into territories never seen before. Jim Hines will always endure as the first man to break 10 seconds over 100 metres on the electric 'Night of Speed' and Bob Beamon famously leaped over 29 feet in the long jump at the very same Olympics.
There are numerous examples and many have yet to be broken, but nothing compares to the challenge of trying to run 26.2 miles in less than 120 minutes. The sub-two-hour marathon has become such a mythic proposition in athletics that it's sometimes easy to forget just how improbable such an achievement really is, but recent years show it could soon be a reality.
Just this month at the Dubai marathon, Herpassa Negassa joined the top 10 marathon runners in history and winner Getaneh Molla elevated himself to sixth place on - and we're not kidding you here - his debut over the distance. In fact, the 17 fastest marathon runs have all been posted over the last decade, proving that the queue behind two hours is becoming more populated than ever.
But when it comes to running the marathon, nobody can touch Eliud Kipchoge. The legendary Kenyan is at the cutting edge of athletic achievement and his astonishing time of 2:01:39 at last year's Berlin event had everybody in the sport dreaming. Could he really become the first athlete to dip under two hours?
The great Eliud Kipchoge
Kipchoge has actually run faster than the aforementioned world-record, but his time at Nike's specialist 'Breaking2' event was invalidated by the IAAF because of their illegal use of pacemakers. Nevertheless, the fact he crossed the line just 25 seconds away from history, shows the 34-year-old is getting closer and closer.
To put these astonishing times into perspective, the best way is to break down the marathon distance and evaluate segments of the race that are more compatible with the good old 'Sunday run.' As noted by the Guardian, Kipchoge ran the opening 5 kilometres - the distance of a park run - in a blistering time of 14 minutes 24 seconds.
Not good enough? Well, the Olympic champion took the unorthodox decision to run the second half of his race faster than the first, clocking 60:34 while his rival athletes were beginning to fade away. That's a half-marathon time which has only been bettered by two British athletes in history and Kipchoge came into it with a 13 mile 'warm-up.'
What makes Kipchoge special?
That's all well and good, but the times are so remarkable to come within one minute of the barrier, that it makes you wonder whether pushing that extra one per cent is really possible.
The time demands would require the athlete to run one of the 50 fastest half-marathons in history, twice in a row. Even if you boil down the challenge to each mile, they would have to sustain a pace that would have bagged them the world-record in the 19th Century, 26 times over and with an extra 352 yards for good luck.
There can be no doubting that Kipchoge is athletics' best bet. After all, he holds the world-record by a comfortable one minute and 19 seconds and the duo of Lelisa Desisa and Zersenay Tadese simply couldn't keep up with him around Monza.
Yet his complete dominance over the distance doesn't necessarily give him an advantage, with the role of pacemakers proving crucial in any world record attempt beyond 400 metres. New athletes can't join halfway through a race and due to the gruelling challenge of holding stride with Kipchoge, the Kenyan was forced to run the final 11 miles of his world-record by himself.
Scientists have been keen to point out that - believe it or not - Kipchoge doesn't necessarily have anything 'superhuman' about his physiology. It's been implied that the world-record holder might not be the most exceptional when it comes to VO2max, somebody's maximum oxygen intake during intense exercise.
The key to sub-two hours
Instead, it seems that lactate threshold and running economy are the secret to Kipchoge's success and that should be cause for optimism as far as the next generation of runners are concerned. Experts like Michael Joyner have also highlighted mental aspects, such as the teachable ability to sustain relaxation and focus throughout punishing exertion.
Environmental impacts also play a key role in making Kipchoge and his main competitors so incredible over the longest of distances. It's no secret that the vast majority of elite marathon runners come from east Africa with Kenya and Ethiopia proving the most successful nations of all.
Kipchoge has admitted to running approximately 20 kilometres a day during his childhood, allowing him to build up incredible fitness and stamina into his professional career. Marry that to the fact Kenya straddles the east African rift and you have extraordinary altitude, allowing athletes to stimulate lung growth throughout their youth.
The source of these elite athletes are often astonishingly concentrated. The most famous example is the small Kenyan village of Iten, home to the Kalenjin tribe who - despite totalling just 0.6% of the world's population - are always in the top 80-90% of distance runners at any given time.
That's the 'recipe' and there's no questioning that Kipchoge has been in the form of his life in recent years. However, excluding any illegal settings such as those constructed by Nike, it sadly seems unlikely that the world's greatest marathon runner will topple the biggest barrier in all of sport.
Can Kipchoge do it?
Time is ticking for an athlete now deep into his thirties and shaving almost two minutes off his time proves a daunting task, even over a faster route such as the Berlin marathon. Kipchoge would have to call upon remarkable mental strength to run how no human has done before and in complete isolation for almost an hour.
If the ideal circumstances of Nike's experiment could be replicated, then shaving 'just' one second off each mile would certainly be possible for the Kenyan. But the limitations of IAAF regulations could be the difference between Kipchoge making history and being able to set an official, undisputed world-record in the process.
Yet, if Kipchoge can't succeed, it seems unlikely that any of his competitors will do either. As much as British fans would love to see Sir Mo Farah make the breakthrough, his Kenyan adversary has been beaten just once at a World Marathon Major and that came over half-a-decade ago.
Sports scientist Dr Ross Tucker gives one of the more conservative estimates on the feat, predicting it will be broken within the next 15-20 years. Meanwhile, the aforementioned Joyner actually forecasts that the physiological limit is around 1:58:00, suggesting that athletes could push even further into the impossible.
Fans will have to keep their fingers crossed that the right conditions collide with the right race and the technology of trainers in particular continue to improve. Advancements like the Nike Vaporfly 4% - even donned by Adidas athlete Negassa this month - could do enough to give up-and-coming athletes that extra boost.
So, there's every reason to suggest that the 'next Kipchoge' could bring the sporting world to a standstill in the not too distant future. With the current Olympic champion providing a quantum leap in the progress of marathon running, it's inevitable that the following pack will close the gap and stride their way into the unchartered territory of human achievement.
We hope we're wrong, we really do, but even the omnipotent Kipchoge is human. Just.
Do you think Kipchoge can run a sub-two-hour marathon? Have your say in the comments section below.