Tyson Gay - File

California (AP)

A knee injury cost sprinter Tyson Gay six weeks of training at the beginning of the year, and with the 2009 season starting soon, the American record holder still hasn't set his schedule.

He is aiming to be 100 per cent fit for the World Championships in August, which could be his next chance to line up with three-time Olympic gold medallist and world record-holder Usain Bolt.

Gay said he hurt his left knee while training last November, trying to get in shape after a disappointing Beijing Olympics in which he didn't win a medal and didn't even make the finals in his signature event, the 100 metres.

"The first week of training, I think I was going too hard," Gay said this week. "I felt good the first week. We were doing great and I was going hard. But probably too hard for the first week. It was just a mistake I made knowing it was a big year, trying to step it up when I just should have relaxed and eased into it."

The injury means it will be at least a few more months before he's completely healthy, and that will mark the first time since he was in the starting blocks of the US Olympic trials in the 200 preliminaries. As he entered the first turn, he sprawled to the track, victim of a hamstring injury that essentially ruined his season.