The following is excerpted from This is Your Brain on Sports.

In this book, L. Jon Wertheim and Sam Sommers challenge conventional wisdom, uncover the hidden influences in sports and uses reams of data to investigate questions that tug at every fan. Why are rivalries so important? Why are quarterbacks so damn good looking? (Or are they?) What’s the appeal of the t-shirt cannon? Why do hockey goons win more fights at home? Through the prism of behavioral economics, neuroscience, and psychology, they reveal the hidden influences and surprising cues that inspire and derail us—on the field and in the stands—and by extension, in corporate board rooms, office settings, and our daily lives. Here, the authors— one a writer at Sports Illustrated, the other a Tufts psychology professor—consider the wisdom of abstaining from sex before competition.

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Asked what he would have been if not a soccer player, the British striker Peter Crouch paused for a moment. Then he replied memorably, “A virgin.” Jason Giambi, the baseball slugger, had a slightly less decorous take on the considerable overlap between sex and sports. While playing for the Oakland A’s, he wore a T-shirt underneath his No. 16 jersey that bore this bit of doggerel: Party Like a Rock Star. Hammer Like a Porn Star. Rake Like an All-Star. When Wilt Chamberlain famously boasted of having slept with 20,000 women, it triggered a round of guffaws—as well as a memorable Saturday Night Live sketch starring M.C. Hammer. (“I remember Cheryl. Number 13,906. But in my heart she was number 2,078. Cheryl was so full of life, love and laughter.”)

Entire forests have been felled—and innumerable pixels have been consumed—in discussions of athletes and their virility. Capaciously muscled, physically fit players in their athletic prime are often also in their sexual primes as well.

But the more we’ve learned about athletes and their heroic carnal appetites—from Tiger Woods to NBA player Gary Payton (who sired two sons, Gary Jr. and Gary II, within four months of each other) to the litany of athletes who have circulated images of their proverbial junk on social media—the more Chamberlain’s numerical claim sounds not like laughable hyperbole but like an indiscreet boast. It recalls the old joke about the hardest part of playing in the NBA: trying to keep a straight face while you tell your significant other how much you’ll miss her on a road trip. Or, as a colleague of Jon’s once put it, “Joe DiMaggio had a hearty appetite for chorus girls but, lucky for his legacy, Thedirty.com was not around to chronicle his bedroom exploits.”

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Yet there is a time when some athletes have been uncharacteristically celibate: before competition. This dates to the ancient Olympics, when Plato warned competitors to refrain from sexual intimacy, lest they tire themselves out. More than a few years later, Burgess Meredith, in his role as Mickey the trainer, warned Rocky Balboa: “Women weaken legs.” Muhammad Ali and Mike Tyson seem to have agreed, each having taken vows of chastity in the weeks preceding fights. (Ali’s theory was that ejaculation sapped a man of valuable testosterone.) While coaching the Buffalo Bills, Marv Levy reportedly decreed before the team’s four Super Bowls that his players were to avoid their wives and girlfriends. (Lot of good that did the Bills.)

This belief persists, at least in some corners. During the 2014 World Cup, several teams barred their players from having sex on grounds that it might undercut performance. “There will be no sex in Brazil,” asserted Safet Susic, the coach of Bosnia-Herzegovina’s national team. “This is not a holiday trip. We are there to play football.” Miguel Herrera, Mexico’s coach, was even harsher, telling the newspaper Reforma, “If a player cannot endure a month or 20 days without having intercourse, then [he is] not prepared to be a professional.” (That Herrera’s team had been rocked by a prostitution scandal may have had something to do with this stance.)

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But is this myth or science? Is there any evidence that intercourse saps an athlete of strength and stamina? Does sex before competition affect performance?

One of the first efforts to document the effects of sex on athletic performance was conducted by exercise physiologists Tommy Boone and Stephanie Gilmore. For a study that was published in 1995, they recruited 11 male volunteers to complete two sessions of a “maximal treadmill test,” in which the speed and grade of the machine were increased every three minutes until a participant was unable to continue. The sessions were scheduled one week apart. For one session, participants were instructed to have sexual intercourse 12 hours before arriving at the lab; for the other, they were under strict no-sex orders the night before. (The research team did not know which session was which, so as not to bias its interpretation of the data.)

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Across a wide range of physiological measures, the researchers found no difference between the post-sex and post-abstinence treadmill sessions. Aerobic power, heart rate, blood pressure, respiration ... none of these varied significantly. In the no-sex baseline sessions, the men were able to stay on the treadmill an average of 13 minutes. The average for sessions 12 hours after sex? Also 13 minutes.


Mexico made it to the Round of 16 in 2014, perhaps despite their coach. Photo via Getty


Five years later, a team of Spanish and Swiss researchers conducted a follow-up study, this one with a sample of higher-level athletes. The group included cyclists, long-distance runners, weightlifters, hockey players, and soccer players, all with experience in international competition. Again, the athletes completed a series of stress tests on several days, both after having had sex and after having abstained. The tests were run several times each day: either two and 10 hours after sex or in the morning and afternoon after a sexless night. The tests themselves were ergometric bicycle training until exhaustion—the difficulty level gradually increased until the athlete could not continue—and an arithmetic-based mental concentration task.

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As in the previous study, recent sex had no discernible impact on performance. Both when the athletes tried to achieve maximal physical exertion and when they tried to master the concentration task, their recent intimacies (or lack thereof) had no apparent effect. There was a slight (though not statistically significant) tendency for a somewhat slower post-workout recovery period two hours after sex, leading researchers to conclude that “the recovery capacity of an athlete could be affected if he had sexual intercourse two hours before a competition.” Other than that, there was no evidence that sex undermines later performance.

Total candor: This reservoir of research literature isn’t the deepest. There are only a handful of studies, each with a relatively small number of participants. And all the papers we uncovered focused on male athletes; we know even less about how recent sex affects women’s performance. But the published research paints a consistent story: The presumption that sex will undermine athletic performance is more urban legend—an old coaches’ tale, so to speak—than scientific fact.

Some science even suggests that if sex has any influence, it probably benefits performance. In one study involving women (but not athletes), researchers at Rutgers looked at the physical aftereffects of vaginal stimulation. They found that women who had just had an orgasm demonstrated huge jumps in both pain detection and pain tolerance (75% and 107% increases, respectively).

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As for Ali’s notion that sex saps a boxer’s testosterone? Well ... not so much. Emmanuele Jannini, an Italian endocrinologist who specializes in research related to sex, proposes precisely the opposite: Testosterone increases post-coitus. “After three months without sex, which is not so uncommon for some athletes, testosterone dramatically drops to levels close to children’s levels,” Jannini explained. In a one-two combination to the midsection of Ali’s abstinence theory, the endocrinologist added sarcastically, “Do you think this may be useful for a boxer?”

But it’s not just physical concerns that lead some athletes and coaches to embrace the doctrine of pre-competition abstinence. What about the underlying psychology of sex? Here’s Marty Liquori, once the world’s top-ranked 5,000-meter runner: “Sex makes you happy, and happy people don’t run a 3:47 mile.”

Well, one could just as easily argue the opposite. Consider the suggestion of Samantha McGlone—future Olympic triathlete—and her co-author Ian Shrier, a sports medicine researcher, in a paper published in 2000 in the Clinical Journal of Sport Medicine. “If athletes are too anxious and restless the night before an event,” they write, “then sex may be a relaxing distraction.” Here’s Pliny the Elder making essentially the same point in 77 CE: “Athletes when sluggish are revitalized by lovemaking.”

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The role of expectation is not to be dismissed, either. If you buy the idea that abstinence adds some juice to your fastball or shaves a few seconds off your pace, it may just do that. Believe that sex will boost athletic performance? Indulging may provide that extra bit of confidence or needed jolt. Athletes are creatures of routine, notoriously superstitious, so perhaps the best advice in preparing for a big competition is just to keep dancing with whoever brung you to the ball.

Most athletes don’t seem to believe that sex is a performance un-enhancer. In a recent survey, researchers in Slovakia and Serbia polled long-distance runners and race-walkers about their post-coital athletic capabilities. Close to 90% said that they experienced no deficits in athletic performance after having sex the night before. In fact almost half saw no problem with sexual activity just 30 minutes before a race.

At the Vancouver Winter Olympics, 2,000 virile athletes from around the world were lodged together in a self-contained village for two weeks. Before the Games were over, members of the Vancouver organizing committee had to make an emergency call for additional condoms, as the original inventory was already depleted.

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We’re confident that most coaches who endorse abstinence before competition aren’t basing their stance on strict scrutiny of the scientific literature. After all, according to McGlone and Shrier, your average romp between married partners burns fewer than 50 calories, equivalent to a leisurely walk around the block or up two flights of stairs. A literal roll in the hay seems more likely to lead to exhaustion (and injury) than a figurative one.

On the contrary, it doesn’t take a conspiracy theorist to suggest that a ban on sex is less about the sex than about the pursuit. “No sex allowed” might amount to coachspeak for “Get some sleep, don’t hurt yourself, and don’t do anything stupid.”

It was Casey Stengel, the hidebound Yankees manager, who had it right. “Being with a woman all night never hurt no professional baseball player,” he said. “It’s staying up all night looking for a woman that does him in.”


L. Jon Wertheim is the executive editor of Sports Illustrated. A sports journalist with a passion for psychology and economics, he is the author of such New York Times bestsellers as Scorecasting (written with Toby Moskowitz) and You Can’t Make This Up (written with Al Michaels). A huge sports fan, Sam Sommers is an experimental psychologist at Tufts University who studies the psychology of everyday life. He is the author of the critically acclaimed book Situations Matter.

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Top photo via Getty