By BRENT STUBBS

Chief Sports Editor

bstubbs@tribunemedia.net

TOKYO, Japan: Printassia Johnson's switch from the sprints to the quarter-mile this year got her to the 20th World Championships in the 400 metres.

She advanced to the semifinal with a personal best of 50.53 in the heats, but struggled in the final on Tuesday at the Japan National Stadium.

Johnson, 31, attempted to get into the final, but her time of 50.81 seconds was good enough for sixth place in the second of three heats.

The top three finishers in the three heats combined and the next two fastest losers advanced to the final. Johnson ended up at number 17 in the world.

Salwa Ed Naser of Bahrain won the wheat in 49.47 for the fourth fastest qualifying time. American 400m hurdles record holder Syney Mclaughlin-Levrone, who made the switch to the 400m, had the fastest qualifying time of 48.9.

Despite not advancing to the final, Johnson said she's just pleased to make her first World Championship team in the 400m, but she's still not sure it if she enjoys it more than she does the sprints.