All-conquering Jamaican sprinter Usain Bolt has ruled out an assault on the 400m record until after the 2012 Olympics.
The 23-year-old Olympic and world 100m and 200m champion has been challenged by Michael Johnson to change events.
American Johnson, who retired in 2001, still holds the 400m world record of 43.18s but it appears there is little prospect of Bolt going for it in the immediate future.
"The 400m is painful! I think it is somewhere in the future but hopefully after 2012," he said.