Kerron Clement has broken indoor world record for the 400m

Clement has already won world junior championship medals

The 19-year-old was competing for the University of Florida at the National Collegiate Athletic Association indoor championships in Arkansas.

Clement, who is the world junior 400m hurdles champion, clocked a time of 44.57 seconds, as opposed to Johnson's time of 44.63 seconds.

University of Arkansas' Terry Gatson came second in 45.29 seconds.

It was the second big success in a week for the teenager, who had helped his university team set a new NCAA 4x400m relay record the previous weekend.

"I can't describe how I feel," he said aftewards.

"When I crossed the line, I wanted to cry, that was my first reaction" he said. "It was so overwhelming - breaking Michael Johnson's record. I guess it's mine now."

Congratulations Kerron from SCMT!