Beijing, China -- American sprinter Tyson Gay turned in a successful Olympic debut as he won his heat in the men's 100 meters Friday at the Beijing Games.

Gay, the defending world champion at both the 100- and 200-meter distances, won the fifth out of 10 heats in the 100 on the first day of track and field competition at Beijing National Stadium. He finished with a comfortable time of 10.22 seconds, tying him for the seventh-fastest run of the day.

The 26-year-old Gay said last week that he was "fully recovered" from a hamstring injury suffered last month at the U.S. Track and Field trials and that appeared to be the case on Friday. Gay had injured his left leg in the quarterfinals of the 200 at the trials, keeping him from qualifying for that event in Beijing.

The American sprinter is expected to have some serious competition for gold in the 100 at the Summer Games from Jamaicans Asafa Powell and Usain Bolt. Powell held the world record in the event for three years before Bolt broke the mark with a blazing 9.72 run to defeat Gay in New York City on May 31. Bolt won heat 1 on Friday with a time of 10.20 seconds and Powell took the second heat in 10.16 seconds.

Tyrone Edgar of Great Britain had the fastest time in the 100m heats, winning the sixth heat in 10.13 seconds. Americans Darvis Patton and Walter Dix also qualified for the next round.

American thrower Adam Nelson advanced to Friday evening's finals of the men's shot put by finishing second in the morning session with a toss of 20.56 meters. Nelson won a silver medal in the shot put at both the Sydney and Athens Games.

"Tonight is when the show starts," said Nelson. "I'll try to conserve my energy till then."

Poland's Tomasz Majewski finished first in the morning with a throw of 21.04 meters. Christian Cantwell and Reese Hoffa of the U.S. also moved on to the medal stage with the fourth and sixth best throws, respectively.

Qualifying for the women's 800m and the men's hammer throw also took place Friday morning as did competition in the women's heptathalon. Hazel Clark-Riley, Alice Schmidt and Nicole Teter all failed to move on in the 800 for the U.S.

In addition to the final round of men's shot put, the women will also compete for a medal in the 10,000m. Shalane Flanagan of the U.S. is expected to challenge for gold in the distance event.