Usain Bolt's 100m world record is just under which time?

9.6 seconds - 9.58, set in Berlin in 2009, which has stood for over fifteen years and shows no sign of going. He also holds the 200m record at 19.19 from the same championships, and the margin by which he broke his own records was unusual enough to make statisticians uncomfortable.

He should not have been a sprinter by the sport's own conventional wisdom. At 1.95 metres he was thought too tall - long limbs mean a slower start, and Bolt's reaction times and first thirty metres were routinely among the worst in the field. What the height bought him was stride length: he covered the 100 metres in about 41 strides where his rivals took 44 or 45, so he was losing the start and winning by needing fewer steps.

The physiological ceiling is genuinely unknown. Analyses of the record progression suggest we are close to a limit somewhere in the 9.4s, set by how much force a leg can put into the ground in the fraction of a second the foot is down - the constraint is not leg speed but ground contact force. Bolt's 9.58 also included a deceleration phase; nobody has yet run the whole distance at their own peak.