3 May 2017
24 Mar 2017
15 Aug 2016
27 Aug 2015
If you want the glory of a fast time, don't go on the first leg.
Most indoor performers will improve outdoors, but it might be the slowest 400m runners who have the most to gain.
Pierre-Jean Vazel breaks down the South African's race in Rio.
See how the South African's world championship run in Beijing compares to Johnson's world record.