Meredith, a 19-year-old psychology student from New York, remembers that "weird tingly feeling" as a child, doing workouts for gymnastics.
She called it the "candlestick," the exercise where she would raise and lower her legs, tightening her lower abdominal muscles.
Now, a new study suggests some women don't need a lover or sexual fantasy to experience sexual pleasure or even orgasm. Exercise can do the trick.
For years, fitness and women's magazines have touted the apocryphal "coregasm," but now researchers say that hundreds of women are getting the unintended benefits of those tummy crunches.
Knowing the orgasm feeling was a bonus for Meredith, once she became sexually active, she said. And now, she openly talks about her coregasm.
"Being a part of so many clubs in college and get-to-know-you games, it's an ice breaker," she said.
An estimated 45 percent of the women who responded to the researchers' online request for women who had either exercise-induced orgasm (EIO) or exercise-induced sexual pleasure (EISP) said their first experience was during abdominal exercises, followed by weight lifting (26.5 percent), yoga (20 percent), bicycling (15.8 percent), running (13.2 percent) and walking/hiking (9.6 percent).
Any exercise that involves the core muscles seems to trigger that sense of pleasure -- chin-ups, climbing ropes and especially the "captain's chair," a rack with padded arm rests that allows the legs to hang free before lifting the knees to the chest.
A handful of women said they even had sexual feelings while mopping or walking.
From a physiological standpoint, "coregasm" makes sense, according to fitness experts. In both exercise and sex, the heart rate and breathing are faster and there is increased blood flow.
The study was published in a special issue of the peer-reviewed journal, Sexual and Relationship Therapy. Herbenick includes some of the experiences in her new book, "Sex Made Easy," due out in April.
"I was biking up a hill," she quotes one 41-year-old. "I had to really grind into the pedals. This must have caused me to rub on the seat in just the right away. I thought I was starting to cramp, but soon realized it felt great. [I] thought I should stop, but chose not to!
"I [had an orgasm] for the very first time shortly after that!" she said. "I never admitted to what had actually happened and I have tried to replicate it ever since -- with no luck!"
Another woman, 23, told Herbenick: "If I engage my lower stomach muscles -- the ones below my navel-- I get a sharp increase in pleasure, perhaps leading to orgasm. This is particularly true if I sit in a straddle position and reach forward. Also, if I lie on my back and stretch one of my legs up, pulling it towards me, I'll probably orgasm after a minute or two."
Herbenick, who is also an advice columnist, said this "exploratory" study is a first step to learning more about the "physical processes" of sexual pleasure.
"Exercise-induced orgasm is something we really know nothing about -- not scientifically," she said. "[Sexologist Alfred] Kinsey mentioned it in his ['Sexual Behavior in the Human Female'] book in 1953, and it sort of got left there."
Coregasms Dated Back to Childhood
Herbenick and her co-author Dr. J. Dennis Fortenberry, professor at the Indiana University School of Medicine, evaluated the responses of 370 women aged 18 to 63, who responded to their query online.
"We didn't know how many women we would find and it turns out, it wasn't that difficult," she said. "In five weeks, we found 100 women who had experienced orgasm and a couple of hundred others who didn't have orgasm but felt highly aroused and close to orgasm."
Researchers sent emails to various web sites geared to fitness and health. Of the respondents, 124 said they had experienced exercise-induced orgasm (EIO) and 246 reported exercise-induced sexual pleasure (EISP).
Most were in a relationship or married, and about 69 percent identified themselves as heterosexual.
Some older women told them that they had first experienced EIO or EISP in childhood during the President's Challenge, a fitness initiative that was launched in the 1960s. One woman said she had attained orgasm during exercise, but never when she had marital sex.
Other key findings of the study were that those who had experienced EIO and EISP had done so on more than 10 occasions. Most said they were self-conscious when it happened in public places, but about 10 percent could not control their experience.
Most said that when it occurred, they were not sexually fantasizing.
Of the EIO group, 51.4 percent reported experiencing an orgasm in connection with abdominal exercises within the previous 90 days.
Sheila Hageman, a mother and blogger from Stratford, Conn., said she has experienced "pleasure and even orgasmic like feelings" without fantasy or stimulation during yoga exercises.
"It usually happens after lots of sun salutations when I'm pretty drenched in sweat," said Hageman. "My whole is body buzzing from the movement and my mind enters this totally transcendental, but at the same time grounding, burst."
She's had the same experience with breathing exercises -- "the snapping in of your belly in a meditative state."
Terri Walsh, owner of ART Studio NYC, said of coregasm, "I believe it totally."
"I never had anybody have an orgasm in my presence -- as far as I know," said Walsh, 48. "But I definitely heard about it in my spinning classes. A lot of exercise, when it's done properly, can get you in tune with your body. Sometimes you get in tune with it quicker than your mind can."
Walsh said she has also heard of women having orgasms during yoga with deep abdominal contractions that can expand to the pelvic floor.
"Sometimes "it's a surprise to the woman who's getting it," she said.
Herbenick said that research will continue in order to help those who may never have experienced orgasm.
"These data are interesting because they suggest that orgasm is not necessarily a sexual event, and they may also teach us more about the bodily processes underlying women's experiences of orgasm," she said.
The study also might normalize the experience for women, or possibly enhance arousal during masturbation or sex with a partner, according to Herbenick.
"It may be that exercise -- which is already known to have significant benefits to health and well-being -- has the potential to enhance women's sexual lives as well," she said.