BEIJING - Tyson Gay burst out of the blocks, accelerated to the lead then coasted to the finish.

If there was any twinge of pain in his hamstring, it didn't show.

If he is anything other than healthy, he didn't say.

Racing for the first time since crumpling to the track six weeks ago, America's fastest sprinter enjoyed an uneventful debut at the Beijing Games, coasting to the finish Friday to win his preliminary heat in 10.22 seconds.

"It feels good," Gay said, referring to the left leg that has had the track world wondering. "I felt a little sluggish the first round, but my body is woke up now."

World record-holder Usain Bolt and fellow Jamaican Asafa Powell also advanced comfortably, winning their heats.

And with that, track and field was finally under way at these Olympics.

The quarterfinals were set for later Friday. All three are expected to make Saturday's final _ perhaps the most highly anticipated event of the 10-day track and field meet at the Bird's Nest.

Bolt, Powell and Gay are owners of the eight fastest times ever.

Blue skies and wispy white clouds welcomed the runners as they started the day in the 91,000-seat stadium, with the temperature around 80 degrees. Air quality has been a major issue for months, but an overnight rainstorm cleared the air. It was the first nonhazy day in Beijing since the games began.

Entering the day there was concern about Gay's status, though he has been assuring everyone in Beijing he's fine. Rounding the first corner of the 200 at the Olympic trials, the 100 and 200 world champion pulled up, then sprawled out. He needed to be carted off the track _ hardly perfect preparation for his first Olympics.

Gay pulled out of a race in London last month, then skipped the American training camp in Dalian, China, choosing to come directly to Beijing to march in last week's opening ceremony and work out at the U.S. training facility.

Lining up in Lane 2 for his first race since the injury, he got off to a decent start, then pulled ahead about halfway through.

Bolt also turned the first race of his first Olympics into a nonevent. He got off to a bad start and was in last place about 10 strides in, but passed everybody and was jogging when he crossed first, in 10.20.

It was just the kind of energy-saving start everyone expected from the 21-year-old sprinter, who set the world record of 9.72 in a blowout win over Gay on May 31 in New York.

Bolt needs to go easy because he'll be trying for two individual medals. Even though he holds the 100 record, the 200 has been his better race, and it starts Monday. After some hemming and hawing he committed to running the 100, a race he started taking seriously only this year.

"Tonight, tonight, tonight," Bolt said as he hustled through the interview area to get ready for the later heats.

Powell simply gave a thumbs up after winning his heat in 10.16. He held the world record for three years until Bolt broke it.

Powell has overcome a chest injury that sidelined him for much of the season, but insists that's healed and what fans are most interested in is how he responds to pressure. Never known as a big-race performer, he finished fifth at the Athens Olympics and third at last year's world championships, pulling up at the end.

Americans Darvis Patton and Walter Dix also advanced. Dix qualified for the U.S. team in the 200 and it is he, not Gay, who has a chance at two individual medals.

"I felt controlled, good start, did exactly what I wanted to do in that race," Dix said after finishing third, in 10.35.

Dix was set to run in the second-round heat with Powell, while Patton was placed in the same race with Gay. On Saturday, the final 16 go in the semifinals, with the final set later the same day.

The fastest time of the morning was 10.13, run by Tyrone Edgar of Britain.

The first track and field medals were to be handed out later Friday in the shot put, and Americans Reese Hoffa, Christian Cantwell and Adam Nelson all made it through to preserve the possibility of a sweep.

The 315-pound Hoffa has put out the tantalizing prospect of a gymnastics celebration _ a roundoff back tuck _ if he wins gold in the evening session.

His plans for the midday break?

"Probably play a few video games," he said. "Something like with the Wii, where you don't have to push buttons."

Nelson, meanwhile, was heading straight to physical therapy. He has sore ribs after hurting himself in training Monday. The two-time Olympic silver medalist said he'll tough it out.

"It's a case of mind over matter," Nelson said. "If I breathe or turn the wrong way, it bothers me."