The current world record holder of the 400 m sprint race is Michael Johnson, USA. The record has been broken August 26, 1999 in Seville, Spain. Johnson ran 43.18s.
Michael Johnson speed (average):
9.2635 m/s, 33.3486 km/h, 20.7219 mph, 10.1307 yd/s
The current men's world record is held by Wayde van Niekerk, with a time of 43.03 seconds; van Niekerk is also the reigning world and Olympic champion.