The four-times world sprint hurdling champion, Allen Johnson, has called an end to his remarkable career, after years of defying his age in one of track's most demanding disciplines.
The 39-year-old American says it's just come to the point where his body can no longer handle the demands of the sport.
Johnson says the older he gets the more often he gets injured, and he has to take more time off to recover and get back in shape.
Johnson set his personal best of 12.92 seconds in the 110 metre hurdles in 1996, the year he also won gold at the Atlanta Olympics.
In that event last year, Johnson still ranked among the world's top 40 with a best of 13.43 seconds.
Johnson says he's going to miss competing, but might get into coaching to give something back to the sport.