Former world champion Tyson Gay equalled the second fastest 100 metres time ever on Sunday when he clocked 9.69 seconds at the Shanghai Golden Grand Prix.
Gay's time equalled the world record set by Jamaican Usain Bolt when he won the 100 metres final at last year's Beijing Olympics.
Bolt reduced his mark to 9.58 seconds at this year's Berlin world championships with Gay second in 9.71.
Gay, who has been suffering from a strained groin, told reporters he would be more motivated to challenge Bolt's world record when he was fully fit.
"I'm not too motivated because I've not been fully healthy ...I ran my run so well even though my groin hurts," he said.
Gay's team mate Carmelita Jeter overtook Marion Jones as the world's second fastest women over 100 metres when she clocked 10.64 seconds. Only the late Florence Griffith-Joyner has run faster.
"I started well today and the track was comfortable," the 29-year-old said. "(Griffith-Joyner's record of 10.49) was a great record. I am now closer to it."
The biggest cheer of the night came when former world and Olympic champion Liu Xiang looked to have edged Terrence Trammell in his first 110 metres hurdles race in more than a year.
However, the American was given the victory with both men clocking 13.15 seconds.
"I didn't expect I could run so fast...but once I stepped on the track I could not hold back," said China's Liu, who thumped his chest and collapsed on the track after the finish.
"I felt like I had been infused by an enthusiastic spirit." Liu hobbled out of the Olympics last year due to an Achilles injury.
The 26-year-old looked in surprisingly good form before his exuberant home crowd, even though the 25,000 spectators measured far fewer than the previous full houses at the cavernous Shanghai Stadium.
"He was inspired by the crowd," said Liu's coach Sun Haiping. "And the wind, the rivalry with Trammell, all the factors were positive. But I am a bit concerned about the possible reaction on his foot."
Russian Yelena Isinbayeva failed in three attempts to improve her own pole vault world record of 5.06 metres.