Threat to Marsh's Olympic medal hopes

Michael Marsh, the Olympic 200 metres gold medallist, is fighting against a thyroid condition as he prepares for a showdown with the world champion, Michael Johnson, in the United States Olympic trials, which begin in Atlanta tomorrow.

"A lot of time the chemical balance of my body isn't right, and I get cramps," Marsh said in Houston yesterday. "It is getting better, and I don't think it's gonna keep me off the team or anything. It's just something I have to keep a hold on."

Marsh, hoping to make the US team in the 100 and 200m, already has been affected by the condition once during a race in the Olympic stadium.

Marsh was ahead of Johnson through the turn of the 200m race at the Atlanta Grand Prix on 18 May when he felt his right leg cramping. "It was a very slight cramp, but it made me pause between 80 and 100 metres, coming off the turn, and I wasn't able to concentrate on running," Marsh said.

Johnson went on to win the race in 19.83sec, the fastest time in the world this year, with Marsh coming in second in 19.88.

Doctors have told Marsh that the "hypo-thyroid'' condition is a common problem caused most often by severe physical stress.