Sandra Bullock's husband's mistress revealed she often gets approached by men who are into "pedal pumping." Anneli Rufus on a strange sex fad in conservative America.

The foot is slender, sleek, unmistakably female, and about a size 8, partially enclosed in a six-inch, sequinned white-satin stiletto sandal. In the video, it repeatedly and fruitlessly depresses the car's gas pedal as the woman revs the ignition and coaxes, "Come on. Start." Cherry-red polish glints on her nails, and a gold ring encircles her middle toe.

Aroused yet?

If so, congratulations: You're into pedal pumping, a sexual fetish that vaulted into public view when it was revealed that Michelle "Bombshell" McGee, the tattooed stripper who had a squirm-worthy affair with Sandra Bullock's husband Jesse James, wrote in her profile at SoCalGlamourGirls.com: "My feet are perfect and I still get a lot of foot fetish requests like pedal pumping."

“Conservative guys, working-class guys, like the idea of a very ladylike foot with a perfect pedicure in a big old truck.”

It's may not have the cachet of S&M or the infamy of golden showers (which earned entries in one of the alleged Tiger Woods "sexts" posted online this week). But in some parts of the country, pedal pumping—a fetish in which men watch women trying to start stubborn cars—is an American classic.

"It's a combination of the foot fetish with the all-American car fetish," says sexologist Dr. Susan Block, who has been featured on HBO's Real Sex and Cathouse and has pumped her fair share of pedals. "The basic kinetic movement is a masturbatory motion: the muscles releasing and contracting as the foot rubs repetitively against a phallic symbol, which is the gas pedal. Men think of themselves as cars. The 'vroom' of the engine reminds them of their own libidos being revved up by this hot woman."

Thousands of videos—some staged, some candid, some featuring celebrities—are posted on YouTube under "pedal pumping," "revving," and "cranking." Thousands more are sold via Web sites such as PumpThatPedal.com, PedalFloored.com, PedalSupreme.com, and StuckChicks.com. At the "Pedal Mall" at PedalPumping.org, visitors can buy short streaming video scenes with titles like "Brake Failure in White Miniskirt," whose synopsis reads: "Lots of engine revving and brake pedal slamming! Check out my big puddle of brake fluid!" (Five minutes, $4.99.)

Block says most of the pedal-pumping enthusiasts she's worked with hail from red-state America, because "they're more car- and truck-oriented, and they like to see their women as being more different from men." Indeed, the damsel-in-distress paradigm is key in many pedal-pumping vids. They're "helpless, stuck females overwhelmed by the power of this big, old vehicle." But not all of the women struggle—some of the ladies of pedal-pumping videos rev happily, representing the strong woman bonding with her powerful machine. Each type attracts its own audience.

In the end, though, it usually comes down to an irresistible urge to combine a love of feet with a love of horsepower, says Block. "Conservative guys, working-class guys, like the idea of a very ladylike foot with a perfect pedicure in a big old truck."

Alexandar Bahunjek operates DriveBabes.com, along with the bike-themed MopedBabes.com and StuckChicks.com.

"The most important thing is the foot," Bahunjek says, but beyond that it's a matter of taste. The subculture subdivides into various selective niches seeking sandals, sneakers, pointy-toed pumps, stockinged feet, clean bare feet, and even dirty bare feet.

"You also have people who like girls wearing sandals, thigh-high boots, platform shoes. But most of my fans and members like open high heels, where you can see the heels along with the rest of the feet. Also, people like the girls to floor the gas pedals, so it's a combination of women in sexy outfits and the sound of the engine. Then you have people who love the combination of pedal pumping and engine sounds," and others who like it best "when the women have to pump the pedal fast."

"For a very sexy video," he says, the most popular choice by far "is an elegantly dressed lady in open high heels. Personally, I like the combination of a sexy girl pushing the pedal—seen as a whole person, not just the feet. I also like high heels, so the combination of sexy girls in high heels sitting in cars I like very much. Pedal pumping is not just for feet lovers or shoe lovers."

The pedal-pumping fan who operates PumpThatPedal.com under the username "ShisHKbob" describes two more surefire turn-ons: "The act of the toes scrunching, spreading, and wiggling," and the woman "interacting with the car by talking to it, bouncing in the seat ... or by various other body or facial expressions."

For some fans, in fact, he says, it's simply all about the car.

"Some people could care less about who is in the driver's seat as they just want to see the car do certain things. Smoke coming from the exhaust pipes and a wheel spinning in mud are two examples. These guys make up their own storylines in their heads. ... For them, the key element is the specific part of the vehicle, and it implies a lot more than what someone not into that would or could gather."

"Take the spinning wheel in mud," he continues. "They see the wheel spin forward, backward, faster, and slower as a meter of the level of desperation the girl has reached. I guess it's more suspenseful and erotic for them to not see everything and those parts that leave stuff to the imagination is what sets them off."

Agreeing that this is a fetish largely confined to Republican-leaning states—he says the highest concentration of pedal-pumping content providers are located in the Southeast—ShisHKbob also confirms that it's a fetish almost exclusively for men.

"There are a few 'women' that are into this, but I say that very cautiously as this community has been plagued with poseurs over the years. For these guys, acting as females on forums and in emails, they just want to try and lure stories from other people. For them, the thrill is reading about this stuff."

Although Block has met at least one man who warmly "remembers watching Mommy struggling with the old family car" back home in Louisiana, most pedal-pumping enthusiasts started out as run-of-the-mill foot fetishists. They ultimately settled upon a feet-in-cars fixation because it's not as explicit, and thus safer to watch at work or with family nearby. And it's easier to find online, often for free, than hardcore foot-fetish material, which typically features nudity.

Pedal-pumping videos "aren't as good as 'foot jobs,' but they're easier to get," Block says. "You can't show a foot job on YouTube, but you can show this."

Robert Lawrence, president of the Center for Sex and Culture in San Francisco, sees pedal pumping as a confluence of two classic fetishes, podophilia and voyeurism, plus "interest in a specific car part—the gas pedal—or object: the car." He says he knows of no statistics charting pedal-pumping's numbers or demographics, but if Michelle McGee's revelation suddenly spikes its popularity, he won't be surprised.

"The sudden interest in any specific fetish will lead to a popular upswing for a while before it dies down," Lawrence says, citing clown sex and balloon sex as prime examples of fetishes that boomed after the release of sexual anthropologist Katharine Gates' 2000 book Deviant Desires.

But for many pedal-pumping enthusiasts, there's nothing fleeting about the fetish at all. Dr. Block says some approach her wanting to understand why they have this fetish and how to cope with it.

"If they can't get off without looking at this one very specific thing, it can be awkward," Block says. "They don't want to have to keep asking their wives to get up in the middle of the night and get into the truck."

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Anneli Rufus is the author of many books, including Party of One: The Loners' Manifesto and the Nautilus Award-winning Stuck: Why We Don't (or Won't) Move On, and the coauthor of still more, including Weird Europe and The Scavengers' Manifesto. In 2006, she won a Society of Professional Journalists award for criticism.