Aska Cambridge ran a wind-assisted 9.98-second 100 meters on Saturday during a qualifying heat at a meet in Florida.
The 23-year-old Cambridge, who anchored Japan's silver medal-winning 4x100-meter Olympic relay team last summer in Rio de Janeiro, is competing for the first time this season. Because of the 5.1 meters-per-second tail wind, the time will not count as his personal best.
"I still think it's OK to be happy about running under 10 seconds," Cambridge said of his heat at the NTC/Pure Athletics Spring Invitational. "It didn't feel like I was running that fast. If I can refine my form, I think I can really do it (officially).
Records from races with tail winds of 2 mps or more do not qualify as official records.
"It's just my first event and I wasn't sharp. My starts are still not there, and I'm not building speed in the first part of the race. There were many things that need fixing," said Cambridge, who started poorly in the final.
"Because of the strong wind, my mechanics were all over the place. These two races (today) drove home the need to improve in all areas. I want to lean forward a little more so I can accelerate smoothly."
The next big challenge for Cambridge will be July's world athletics championships.
"First I need to clear the qualifying standard of 10.12 seconds to earn a spot in the worlds, then I want to aim for a time under 10 seconds," he said. "I want to make it to the final at the worlds."
Yoshihide Kiryu, who shared the silver medal with Cambridge by running the second leg in Rio, has also broken the 10-second barrier with strong tail winds. Kiryu ran 9.87 seconds with 3.3 mps tail wind two years ago in a meet in Texas.