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It's 8 a.m. on a Sunday morning and I'm in pain in New Orleans. Not morning-after-a-night-in-the-French Quarter type of pain, but knee pain.

Together with 15,000 other runners, I'm winding through streets that have been closed for the Rock 'n' Roll Mardi Gras Marathon and Half Marathon. And like 70 percent of the others, I've traveled here from out of town to do so.

Runners have always traveled to race. The Boston Marathon has attracted international participants for more than a century. In recent years, however, the concept of destination running "didn't just evolve, it exploded," said Robert Pozo, president of Continental Event and Sports Management Group.

The Rock 'n' Roll Marathon and Half Marathon is the oldest of the series races. Started in 1998 in San Diego, it has events in 19 U.S. cities this year, and will expand to Madrid next year. True to the series name, these runs are as much a party as a competition. Bands play every few blocks, though I largely ignore them, listening instead to the voice in my head telling me to run through the pain.

A new series, the women-only Diva's Half Marathon, was launched last October on New York's Long Island. That first race attracted participants from all 50 states, said Pozo, the organizer. This year, races have been added in Honolulu, Vail, Colo., and Puerto Rico.

Disney hosts a variety of events at both Disney World and Disneyland, and Royal Caribbean hosted a 5K race for cruise ship passengers on the island of St. Maarten last December.

There's even a Seven Continents Club, boasting more than 300 members who have run marathons in North America, South America, Europe, Asia, Africa, Oceania and Antarctica, according to Marathon Tours & Travel of Boston.

So why do runners travel so much?

Some go to the fast courses hoping to qualify for the Boston Marathon or a personal best. I travel for the variety, and came to New Orleans to run the half-marathon and sightsee with my family for four days. It gets boring running hundreds of miles in the same area.

Then there's the demographic of runners. At the Diva's run, nearly 40 percent of the participants were ages 30 to 39 — working years when people are more likely to have disposable income.

"Running has not been affected by the recession," Pozo said, noting all a runner needs is a pair of shoes. While people may feel that going to a spa or a fancy resort is extravagant these days, going somewhere to run doesn't have that same connotation.

"It's taking that vacation and not calling it a vacation," Pozo said. "And ya, I'm going to lay by the pool and I'm going to be there for four or five days."

To add to the good feelings, many of the events double as charity fundraisers. The Mardi Gras run, for instance, raised money for the American Cancer Society.

The race organizers lure us to different cities by offering special medals to those participating in multiple events. Elizabeth Williams, 28, visiting from Scranton, Pa., to run her second half-marathon, is planning three others this year in Kentucky, Missouri and California.

She said the fact that the Rock 'n' Roll Series gives out fancy medals "for running more than one of their races just amps the experience up for me."

"I won't ever win a race. I don't expect to even place well in my age group — but it's nice to feel like you won something after all the hard work, sacrifice and grit that it took to get here."

About 15,000 people ran at least two Rock 'n' Roll marathons or half-marathons last year in order to receive the "Rock Encore" medal, while more than 250 received "Rock Legend" medals for competing in seven or more races in 2010, said Dan Cruz, a spokesman for organizer Competitor Group.

As I shuffled through New Orleans, all I wanted was to finish that one race. I was moved by the cheering crowd, and felt I would let them — and me — down if I failed. One group served king cake, but I was too focused to stop.

My last race was different. At the Royal Victoria Half Marathon in Victoria, British Columbia, my running was easy. I sampled the beer and biscotti and enjoyed the scenery.

But not in New Orleans. The only sight I wanted to see was the finish line. Finally, there it was. My 10-year-old daughter, alarmed by my limping, dashed out from among the spectators to help me across the finish line. My 13.1 miles were complete.

Knowing I'd be tired after the run, we spent the afternoon on a van tour through the Garden District, a cemetery and the areas affected by Hurricane Katrina.

Heading to breakfast Monday at Cafe du Monde, walking through the French Quarter, it was easy to spot the many runners. We moved tentatively, nursing sore muscles or blisters.

Sitting outdoors sipping coffee and eating a beignet, I noticed the people at the adjacent table were wearing marathon shirts. With that common bond, we started to chat, and I learned that Cliff Phillips, 44, of Marietta, Ga., has run five full marathons from San Diego to New York City.

"At the end of the day my marathons have become an education for my kids and an adventure for my family — all while I keep myself in shape," he explained.

Phillips is a travel agent specializing in helping runners book their trips. Race organizers offer "official hotels" with discounted pricing, but Phillips offers alternatives.

With the pain in my knee reduced to a dull ache, I thought to myself that I'd need to keep him in mind when I run my next race.

But with so many destinations to choose from, where should I run?

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If You Go...

ROCK 'N' ROLL MARATHON: http://runrocknroll.competitor.com/. Races and events in 19 cities in 2011.

DIVAS HALF MARATHON SERIES: http://www.runlikeadiva.com. Races and events in four cities in 2011.

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