After crossing the finish and hugging his team supporters, a joyful Martin dropped to the road on his back and gave a wide smile.
"It was really emotional for me," he said. "The last years gave me a lot of experience. I had to work with the pressure and to use the pressure as more motivation."
The only uphill section of the course was a mild two-kilometer (1.24 mile) stretch shortly after the start. That made it ideal for TT specialists capable of maintaining their aerodynamic position crouched over their handlebars for more than an hour at full speed.
Conditions were perfect, with the course bathed in Tuscan sunshine, and fans came out in large numbers as the route took riders past Florence's historic monuments like the Duomo cathedral.
Vasil Kiryienka of Belarus finished fourth and Taylor Phinney, the American who finished second last year, was fifth.
Martin has now won nine of 12 individual time trials this year, including one at the Tour de France. He also powered Omega Pharma-Quick Step to victory on Sunday in the team time trial at worlds in another title defense.
Martin said he examined the course for the first time just last week. Since it was mostly flat and straight, the toughest thing was to develop a race strategy.
This time trial was about 10-15 minutes longer than at previous worlds.
The most technical section came just before the finish, with a series of sharp turns along Florence's medieval streets.
Martin trailed Cancellara at the first checkpoint but seemed to grow stronger as the race progressed. By the time he reached the historic center, the German rider was pretty confident he would win.
"The old town was nice but I was more focused not to crash. You really needed to concentrate after one hour on the limit," Martin said. "I almost didn't feel the pain anymore."
Martin's average speed was 52.911 kph (32.88 mph).
For Wiggins, the silver medal capped a somewhat disappointing year.
In 2012, Wiggins became the first British rider to win the Tour de France but he missed this year's race due to injury and illness after also withdrawing from the Giro d'Italia midway through.
Wiggins won the Tour of Britain earlier this week in a sign of improved form but Chris Froome, this year's Tour de France winner, will lead Britain's team in Sunday's road race.
"I feel pretty relieved now that it's over," Wiggins said. "I'm pretty satisfied to come away with the silver medal. There's not that much more I could have done. I was just beaten by a better bike rider today."
Cancellara entered the worlds with the aim of challenging for gold in three events, but his RadioShack team finished only fifth in the TTT. Still, Cancellara will be among the favorites for the road race, an event he has never won at the worlds.
With no races on Thursday, the next events are the junior women and under-23 men's road races on Friday.
Also on Friday is the UCI presidential election, with British Cycling president Brian Cookson running against incumbent Pat McQuaid.
The worlds conclude on Sunday with the featured road race over a 272-kilometer (169-mile) route that starts in Lucca near the coast and ends with 10 laps of a hilly circuit in and around Florence.
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