Like all runners, Whitney Lasseter had often experienced butterflies before races. But the first time she entered the Caliente Bare Dare 5K, she hid behind her car until just moments before the start.

That's because the runners in this Florida event compete nude, except for their shoes and the occasional GPS watch.

"I didn't want everyone to see me naked,” says Lasseter (pictured) who ended up winning among the women and who won again the next year. "There were people there I see at regular races -- actual people who I knew. But I just kind of got the nerve up and went out and did it."

More runners are getting up the nerve to run naked, in a growing number of clothing-optional runs -- nearly 30 of them, nationwide -- that are beginning to emerge from beneath the radar.

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There's even a National Championship of Nude Running and a 5K Nude Racing Series, consisting of five runs in Texas and Oklahoma, organized by the American Association for Nude Recreation, with another circuit proposed for Florida. And what is apparently the first-in-the-nation naked obstacle race debuted in Burlington, Wisconsin, in June.

"Of course, there's no razor wire or anything like that to catch on dangly bits,” says Rich Gilbreath, director of the new race called Mud, Sweat, and Boobs.

Most of these runs are held at nudist resorts or on other private property, but they’re increasingly attracting runners with no experience of nudism who want to try something different.

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"There's no question there's a bucket-list mentality to this," says Pete Williams, director of the Caliente Bare Dare 5K, at the upscale Caliente Resort in Land O’Lakes, Florida. This year's race, held in May, attracted a record 312 runners from 25 states. Williams also directs the Streak the Cove 5K in Kissimmee, Florida, in September.

“We get a lot of top runners from around Florida” for the run, Williams says. The course records are a respectable 15:49 and 19:29 for men and women, respectively.

There are some things about these races that differ from conventional events. Participants are allowed to remain anonymous, with results often posted only by first name and last initial, for example. Many are not timed.

But other features are surprisingly similar. Tourist agencies in places like Pasco County, Florida, encourage the nude runs there because of the business they bring in. And, yes, you often get a T-shirt.

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What is purportedly the oldest of these clothing-optional events celebrates its 30th anniversary July 27: The USATF-sanctioned Bare Buns Fun Run in Deer Lake, Washington.

So many more have started up since then that some have added new traditions to distinguish themselves. The Color Me Bare run, for instance, in Los Gatos, California, features "paint throwers" who cover the naked runners with a mix of corn starch and powdered tempera along the course.

“More and more people are discovering the pleasure of being outdoors without clothes on,” says Cindy Gregory, special events coordinator for the Lupin Lodge resort, where the race debuted in May with about 60 runners. “They’d always wanted to participate in a nude run and thought this was a great way to do it.”

Many runners with no experience of nudism find they like the idea, and stick around for clothing-optional ice-cream socials, barbecues, live music, and other events that follow, organizers of these competitions say.

“It was interesting to talk to the people who had never done it before. They had a blast. They never put their clothes back on,” says Gilbreath, of Mud, Sweat, and Boobs, which was followed by a roasted turkey cookout.

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That was different from their attitudes before the event, he says. "They’re just so nervous. They ask us things like, 'Should I wear shoes?'" (The answer, at most of the races, is yes.)

"It's a great introduction to nudism," says Ashley Beahan, spokeswoman for the American Association for Nude Recreation. "You don't have to worry about clothes bunching. It's a free feeling. It’s more relaxing, exciting."

There’s at least one conventional event, run in public, in which naked participants compete: San Francisco’s annual Bay to Breakers 12K. They use what they call the “Bare to Breakers” event to advocate for nudism.

After years of trying to keep them out, Bay to Breakers officials now tolerate the demonstrators, and the city lifts its ban on public nakedness for them, as long as the naked runners wear an official bib around their necks, a spokeswoman says.

Although they all say they’ve heard the jokes and puns, clothing-optional run organizers say they stand for something serious: Body acceptance.

"Until you get out there, you don't really understand it," says John Waldron, who organizes the Hidden River 5K in St. George, Georgia, and is trying to start a nude running series in the Southeast like the one in the Southwest.

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Lasseter, who no longer hides behind her car before the start of naked races, will likely sign up.

"Everybody always asks me, 'How do you even do that? Isn't everything flopping around? Is it uncomfortable?’ For me, it’s not. It's really free,” she says.

In fact, Lasseter says, she ran her 5K PR of 20:06 at the Caliente Bare Dare.

"I always make the joke, I have less drag. I'm way more aerodynamic with no clothes on," she says. "Once I did it once, it was so much fun, and every fear I had just went away."

After all, she says, “We were born naked. Our bodies were designed to be naked. So when we’re doing an activity like that, it’s not about our bodies. It’s our minds we have to tell to shut up."

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