How the marathon distance was determined

 By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

30 October 2011

Today is Nairobi Marathon Day and by the time you read this, some of the athletes will have completed the full 42.195km distance! For me, the four-point-something kilometre Family Fun Run will be enough.

Still, the question that keeps coming up is why the Marathon distance is such an awkward figure – why not round it to something like exactly 40km, or even 50km? Could it be a conversion from imperial to metric units? Let’s find out.

The Imperial System of inches, feet, yards, miles etc has an exact conversion factor into the metric units of millimetres, centimetres, metres, kilometres etc. It starts by defining one inch as 25.4mm exactly.

Now 12 inches make a foot; three feet are a yard; and 1,760yards make a mile. Therefore, one mile is 1,760 x 3 x 12 = 63,360inches. Converting this to millimetres yields 1,609,344mm (63,360 x 25.4)

The metric system is a lot more convenient because the factors are in multiples of ten. Thus, for example, there are 1,000mm in one metre and 1,000m in one kilometre; that is 1km has one million millimetres (1,000 x 1,000). Therefore it is very easy to see that one mile is equivalent to 1.609344km – no one needs a calculator to divide by one million!

To convert the 42.195km marathon distance to miles, we divide it by 1.609344. It is important to retain all the decimal places at this stage. That way, if the metric value was obtained from an exact imperial quantity, we should get “nice round” answer.

Now take out your calculator and do the division…. Mine gives 26.21875745645 miles! Or 26miles; 385.0131yards. Clearly, not a round figure.

I did some digging and found that the distance was intended to be approximately equal to that from the town of Marathon, Greece, to Athens. Legend has it that in 490BC, a military messenger was sent from this town to the capital to announce that the Greek army hard defeated the much stronger Persians. He collapsed and died of exhaustion after making the announcement! The most probable route that the messenger took is about 25 miles long.

The first marathon race was run in Athens in 1896 during the first meeting of the Modern Olympics. The distance for that event was about 25miles (40km). It was not until 1924 that a standard length was fixed for all marathons. This is the 42.195km that we use today.

That distance itself was arrived at rather arbitrarily during the 1908 Olympics in London. It started off as 25miles exactly, but due to public protests about the route and the need to give spectators a good view of the athletes during the final lap in the stadium it was adjusted to 26miles, 385yards. This was later standardised in the metric system of units as 42.195km.

However, the International Amateur Athletic Federation (IAAF) rules state that the distance should be “at least” 42.195km. Taking advantage of this, race organisers usually add one metre after every kilometre just to hedge against planning a route that is too short. So don’t be surprised if today’s race is 42.237km.