Erriyon Knighton became the fourth-fastest man over 200m as he clocked 19.49 seconds at the LSU Invitational.
The American, 18, broke his under-20 world record by 0.35 seconds in Baton Rouge, Louisiana.
Only world record holder Usain Bolt (19.19), fellow Jamaican Yohan Blake (19.26) and American Michael Johnson (19.32) have ever set faster times.
Knighton’s mark is the eighth-fastest 200m time overall and the quickest since Bolt won the 2012 Olympics final.
Bolt beat 19.5 seconds on four occasions, doing so for the first time aged 21, while Blake has done it twice and Johnson did it once in setting the then-world record at the 1996 Olympics in Atlanta. BBC