Compared to glamour stadium events such as the 100m, the marathon is not the most sexy of the Olympics's athletics events.

Gruelling, oft-times solitary, painful, long — it's a challenging test of endurance that demands plenty and gives precious little in return.

There is an argument though, that it is one of the most important events on the program.

The marathon is, of course, indisputably one of the Games's toughest tests — and this Paris course is up there with one of the toughest ever run at a Games.

Typically, marathons are run over fairly flat courses: at the Tokyo Games, where the marathon was held in Sapporo, the route consisted of just 108m elevation gain over the entire distance. 

The course in Rio five years earlier had even less — it was essentially pancake-flat.

In fact, four of the six world marathon majors have elevation gains of 75m or less — Tokyo (60m), Berlin (73m), Chicago (74m) and London (75m) — while the other two — New York (246m) and Boston (248m) — are slightly more lumpy.

In Paris though, the race goes up a staggering 436m over the 42.195km distance, mostly in a brutal middle section from 14km in.

In short, don't expect the race to be quick.

Marathon myths and legends

The marathon was invented to headline the first Olympic Games in Athens in 1896, playing on the storied myth of Pheidippides who ran 26 miles or thereabouts from Marathon to Athens to deliver news of a famous Greek victory over the Persians.

It was Baron de Coubertin's friend Michel Bréal who suggested the marathon would be an event suitable to headline the Olympic revival, based on his enjoyment of a 1879-published poem by Robert Browning. 

That poem vividly speaks of the bliss Pheidippides experienced in the joy of his blood bursting his heart — a feeling many marathon runners may be familiar with.

Marathons were not standardised in length until shortly before the 1924 Games in Paris — the term Marathon essentially referred to a "long run".