BEIJING — Jamaican sprinter Usain Bolt left no doubt again as to who is the world's fastest man Wednesday, breaking a 12-year-old world record in the 200-meter dash and winning his second Olympic gold medal.

Bolt had already set a world record and won gold in the 100 in these Olympics. This time he beat the entire field by more than half a second and ran hard all the way through the line for a time of 19.30 seconds, which barely eclipsed the 19.32 American Michael Johnson posted in the 1996 Olympics in Atlanta.

"I blew my mind," Bolt said, "and I blew the world's mind."

Bolt, who turns 22 Thursday, is a 6-foot-5 sprinter who is doing to records what Randy Moss does to NFL cornerbacks. Said U.S. track legend Renaldo Nehemiah after watching the race: "He's got the same tempo as the shorter guys, as well as a 9-foot-plus stride. It's ridiculous."

Said sprinter Kim Collins of St. Kitts and Nevis, who finished sixth in the 200: "He takes one stride and I have to take 2 ½ just to keep up. I mean, how fast can a human being go?"

American Shawn Crawford took the silver medal and American Walter Dix the bronze. They moved up from fourth and fifth place, respectively, after two other sprinters were disqualified for running out of their lanes.

While Bolt showboated and coasted for much of the last 20 meters in the 100, he obviously wanted this world record more.

"The 200 means a lot more to me," Bolt said. "It's been my favorite event since I was 15."

As he had before the 100 final, Bolt spent the day sleeping, warming up lightly and eating two separate meals that consisted of nothing but chicken nuggets.

Running in Lane 4, right next to Crawford, Bolt ran a dazzling first half of the race. "That's really where he set the record, in that first 100," Nehemiah said.

Johnson had predicted before the race to reporters that Bolt wouldn't break the 200 record Johnson had set in the 1996 Olympics, but he was wrong. After Bolt finished and realized he had broken the mark, he fell straight on his back. Then he got up and did a victory lap that included one of his signature Jamaican dances.

Bolt still has one more race in these Olympics - the 4x100 relay, in which the Jamaicans figure to battle the Americans for the gold medal.

First, though, he said he wants to celebrate his birthday and his unprecedented double - not even Carl Lewis or Jesse Owens broke both the 100 and 200 world-record marks in a single Olympics.