LONDON, England -- Olympic champion Melaine Walker is hoping for a better run in today's semi-finals of the women's 400m hurdles at Olympic Park after what she described as "a

flat run" in yesterday's opening rounds.

Walker, the Olympic record holder who said she had not expected to run that hard, was second in her heat in 54.78 seconds behind Great Britain's Perri Shakes-Drayton (54.62 seconds) as all three Jamaicans, including Kaliese Spencer and Nickesha Wilson advanced to today's round.

"The instructions were to run the first three hurdles (hard) and get control and then run the last three," Walker explained, but said the pressure from the

Briton in front of her home crowd caused her to change race plans.

"I did not want to run this too hard, but in competition people will push you

and you need to respond and I did just that."

Retaining her title would mean a lot, she said, but was quick to add that the

focus was on getting through each round.

Spencer, who was fourth in Beijing, looked comfortable in her heat, placing second in a season-best 54.02 seconds to Russia's Natalya Antyukh, who ran 53.90 seconds. She later said she was happy with her time and said the season's best came at the right time as she was looking for better today.

Wilson was also second in her heat in 55.53 seconds to American Georganne Moline's 54.31.