Caen, France ? Tom Boonen built his overall lead in the Tour de France by finishing second in the fifth stage Thursday, although the Belgian world champion is feeling the strain of wearing the yellow jersey.

He was runner-up to Spain’s Oscar Freire, the three-time former world champion who prevailed in a closing sprint.

Boonen increased his lead by earning bonus time, and he will be the front-runner for the third straight day during today’s sixth stage. But the yellow jersey, he said, felt “more heavy” because “I’m not supposed to wear it.”

Freire also benefited from bonus time, jumping from 20th to third overall. World time-trial champion Michael Rogers of Australia is still second, 13 seconds behind Boonen, with Freire another four seconds back. George Hincapie of the United States slipped from third to fourth, also 17 seconds behind Boonen.

Freire, of the Rabobank squad, accelerated sharply in the last 300 yards, sprinting up the right side of the finishing straightaway for his second stage victory in three Tours.

The Pack, with overall leader Tom boonen second from left, rides through the town of Blangy-Le-Chateau during the fifth stage of the Tour de France. Oscar Freire of Spain won the stage Thursday, while Boonen held on to the yellow jersey.

“It wasn’t the way that I’m used to sprinting. I usually stay in other riders’ wheels and wait until the last second,” he said. But this time “what I needed to do was to take the initiative. … That is what I did.”

All 172 remaining riders started the mostly flat, 140-mile route from Beauvais, north of Paris. There were several crashes along the route, but all riders finished.

For all his success so far, Boonen has not displayed the explosive form he showed on the past two Tours, when he won four stages.

He said defending the lead has drained him. His goal is not to succeed seven-time champion Lance Armstrong as the winner when the race ends in Paris on July 23. Rather, he wants to win more stages and the green jersey, which goes to Tour’s best sprinter.

In that category, Boonen is one point behind Australia’s Robbie McEwen, who won the green jersey in 2002 and 2004.

Although Boonen has won smaller stage races and the treacherous Paris-Roubaix, the “queen of the classics” that dates to 1896. But he still sees himself as a sprint stage winner at the Tour, not a contender for the overall title.

“It’s something I have to work for very hard because I’m not the kind of rider to wear yellow,” he said. “It’s been causing a lot of strain but I’m close to the green and I’m wearing the yellow.”