How fast does Usain Bolt run?
Bolt holds both the 100m and 200m world records - 9.58 and 19.19 seconds respectively - and the last three Olympic titles in each event.
Since automatic timing became mandatory, he is regarded as the fastest human ever timed with his world records.
Usain Bolt celebrates breaking the 200m world record for the first time, at Beijing 2008
Image credit: Reuters
How is Bolt the fastest recorded human ever?
The fastest recorded human footspeed was recorded between 60 and 80m in Bolt's world record 9.58-second 100m final in Berlin in 2009.
Bolt was clocked at 44.72km/h, which is 27.8mph.
The Jamaican covered the distance between 60-80m in a time of just 1.61 seconds.
Is Bolt's 100m world record really the fastest ever?
Officially, yes. But the unpopular answer is 'no' because of a very wind-assisted run from Bolt's rival Justin Gatlin in 2011.
The controversial American ran the 100m in 9.45 seconds - the fastest time recorded for a human at that distance - smashing Bolt's world record by 0.13 seconds.
However, Gatlin - who has twice been banned from competing for drug-related offences - was being helped along by a huge 20 metres-per-second tail wind as part of a Japanese game show, so the time did not count.
Still, no one has ever been recorded running faster from a stationary start on a flat surface - hence the smug grin from Gatlin as he posed by the clock.
Is the 100m even the fastest event though?
On average, the 200m usually sees faster running speeds recorded due to athletes not having to react and accelerate for as much of the race.
For example, when Bolt broke both the 100m and 200m world records at the 2008 Beijing Olympics, his 200m time was 19.30 - less than twice the time of his 100m of 9.69 seconds.
But the fastest recorded times come in the 4x100m relay with the 'anchor' leg runner able to accelerate before even receiving the baton and run through the line.
Bolt's 'anchor' leg at the 2014 Commonwealth Games in Glasgow was timed at a staggering 8.65 seconds. Jamaica won, obviously.
Usain Bolt with his Jamaica team-mates at the Commonwealth Games in Glasgow in 2014
Image credit: Reuters
How does Bolt's time compare to land animals?
According to the American Museum of Natural History, Bolt's top recorded speed of 27.8mph over 100m does not compare too favourably:
Cheetah - 70mph
Antelope - 61mph
Lion - 50mph
Elk - 45mph
Greyhound - 39mph
Wart hog - 30mph
Grizzly bear - 30mph
Domestic cat - 30mph
Remember when rugby star Bryan Habana took on a cheetah in a race? Even with a 50m head start it didn't go too well...