SHUNDE, South China - In a fight against high temperature and morning finals, Chinese veteran swimmer Zhou Yafei failed to defend her title at the women's 100 meters butterfly heat on the opening day of the Chinese Spring National Championships here on Tuesday.

The seven-day national meet is testing the morning finals schedule just like the Beijing Olympic Games by starting finals at 10am but holding heats at 3pm local time.

Under 37 centigrade at the Shunde outdoor pool, Zhou finished one minute 1.48 seconds for her 100m butterfly heat, a far cry from her own Asian record of 58.20 seconds.

Jiao Liuyang, fourth place finisher at the Melbourne world championships over 200m butterfly, touched first in 59.72 seconds.

Zhou said:"I underestimated my rivals. I thought I could enter the final by using 70 percent of my strength. I was wrong."

Yang Yu, medalist in the women's 200m freestyle at 2001 and 2003 world championships, also suffered an unexpected defeat in her trade-mark event by finishing 10th in 2:02.43. Pang Jiaying topped the heats with 2:00.71.

In the men's 100m butterfly, Wu Peng, world 200m butterfly silver medalist in Melbourne, swam third fastest in 53.68 while Wang Dong and Lin Lejun finished in 53.47 and 53.49 respectively.

Liu Weijia qualified first for the men's 400m individual medley in 4:24.34.

The national meet attracts 416 swimmers to compete in 32 events.There will be five finals on stake on Wednesday morning.