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Every New Year’s Day at 6 a.m., my high-school team had swimming practice. Driving to the pool in the frozen Indiana darkness, I assumed the rationale was simply that the coach was a nonviolent psychopath. Someone had ruined his youth and now he wanted to ruin ours. We weren’t explicitly forbidden from going out and having fun on New Year’s Eve. But once you see one hungover person vomit in the pool, the team gets behind the idea of taking it easy.

Many athletes are explicitly told to avoid things that could truly detract from their performance. Often lumped into that is sex—specifically before a competition. The admonition is “passed down a lot by coaches, when things are intense and they want to get as much as possible out of players,” says Todd Astorino, a professor of kinesiology at California State University. He is part of a small number of scientists who have found that abstinence before competition seems to be, if anything, bad advice.

Astorino studies high-intensity interval training—intense workouts that involve a lot of grunting and cringing and last just a few minutes—so studying the physiology of sex wasn’t a total departure for him. Two years ago, one of his graduate students, a former football player, told him about receiving the old advice not to “fool around” the night before games. Astorino was indignant. “This doesn’t seem to make physiologic sense,” he recalls thinking.

So his research team designed a study. They had 12 athletes do exercises (leg curls and extensions) in a gym. The researchers measured the kinetic energy and torque generated on days when the men reported they’d had sex the evening prior, and days they said they hadn’t. Their study, “Effect of Sexual Intercourse on Lower Extremity Muscle Force in Strength-Trained Men” found, contrary to what the title implies, no effect.

At the risk of turning this into another “What is sex?” story, I had to ask how the terms were defined. “This was just college-aged men who were in a relationship with a woman,” Astorino told me, apologetically. Most research on this question has been done on (and by and from the perspective of) men. Astorino says he is trying to do better.

This limited definition of sex—as an act defined as completed whenever a male has an orgasm—was one of the problems that came up during the peer-review process. So was the question of sex positions. “One reviewer made the point that if the male was doing a lot of work, that might lead to more fatigue or muscle soreness than if he was playing a passive role,” Astorino said. And then there’s the question of duration. Sex can last anywhere from a few minutes to, I’ve heard, “all night long.” Most cases in Astorino’s study lasted less than 10 minutes. Only three fell in the 10–30 minute range. (Again, these were men in relationships, not living out the lyrics of a Boyz II Men song.)

Historians have traced the origin to archaic ideas about semen carrying testosterone out of the body. The first actual study of the idea, though, wasn’t until 1968. Warren Johnson set out “to test the traditional view of coaches and athletes that sexual release adversely affects motor performance.” He used a grip meter to assess the strength and endurance of the hand muscles in 10 married men on mornings after sex and mornings after no sex. There was no difference.

No further research was done on the topic for decades, even as coaches kept echoing the myth. A smattering of small studies in the 1990s found no effect of sex on subsequent performance. In a 2016 meta-analysis, researchers deemed the past studies universally weak and concluded “randomized controlled studies are urgently needed.” This has yet to happen. But at least in a relative way, the past two years have been a heyday for the field. Studies in 2018 included Astorino’s as well as another in which researchers measured strength, balance, agility, reaction time, and anaerobic power in 10 young men. Yet again, the studies found no difference based on night-prior sex.

Just this month, another study built in an even broader range of tests. Participants were evaluated on three separate occasions after having met one of three conditions on the previous night: sex, abstinence without other physical activity, and abstinence with physical activity. The third category involved “a 15-minute yoga exercise session intended to mimic the energetic cost of sexual activity.” The men then did tests of vertical jump, hand grip, and reaction time, among others. Nothing was affected.

“The hard data doesn’t suggest a reason to avoid sex before athletics,” the study’s lead author, Gerald Zavorsky, told me. He oversees the pulmonary-services lab at the University of California at Davis. He explained that most people expend few calories during sex. They’re also not putting enough energy into it that they deplete the muscle’s fuel stores (glycogen). Zavorsky’s passion for this subject runs deep. In 1996, he made it to the Canadian Olympic trials in the 800 meters by two-tenths of a second. This made him realize the importance of the tiniest variables in preparation. Like many others, he recalls his college track-and-field coach instructing “no hanky-panky the night before you compete. It’s going to drain you.”

A common explanation behind the old advice, Zavorsky explained, is the frustration-aggression hypothesis. That is, if you’re sexually frustrated, you might be able to direct that frustration toward defeating your opponent. If you’re really satisfied, you lose some edge. “If you don’t have that go-to tiger-lion attitude,” Zavorsky said, “then you don’t have as much of a desire to win.” Maybe you can’t be a good athlete if you’re too at peace? As the Olympic runner Marty Liquori once said: “Sex makes you happy. Happy people don’t run a 3:47 mile.”

Clearly, the research hasn’t borne out this sentiment. Nor have cases like Wilt Chamberlain, who claimed to have 20,000 sexual partners and was one of the greatest basketball players of all time. As Zavorsky says, there are lots of caveats to what is known.

For one, these studies involve self-reporting. “We couldn’t actually watch people have sex. For ethical reasons,” he noted. He mentioned the possibility of people coming to his lab to have sex and described trying to get research funding to get people to have sex in a chamber. I understood how that might raise questions.

For another, the data mostly comes from the night before competition. “We don’t know what happens if you decide to have a little fun 30 minutes before,” Zavorsky said. Testosterone levels fluctuate based on certain activities, including sex. The difference might not be huge, but athletes looking for extreme performance optimization on the range of a tenth of a second might go to lengths to time their peaks. If there were benefits in the very short term, coaches might change their tune. Locker rooms would have to be redesigned.

Looking back, my high-school coach probably wasn’t teaching history at a public school and coaching swimming because he hated kids and wanted to ruin their lives. The idea was to minimize variables in our routines. We always practiced early (usually at 5 a.m.). At the height of our training, we shouldn’t be deviating for even one night. This concept is better proved than anything about sex specifically: Before any sort of important event that requires physical and mental performance, breaking routine introduces risk, whether the action is sex or something else—your usual glass of wine at dinner, or going to bed at your usual bedtime.

If you typically have sex every night, it might throw you off not to. It might throw you off to have sex with a new person or in a new way.

In his own experience, however, Zavorsky found that even breaking routine isn’t always bad. He recounted to me in some detail a race where he “decided to take an opportunity with an extremely beautiful woman” the evening prior. The next day, he said, he ran “like the wind.” He chalks it up to putting him into that uniquely euphoric state of mind that dwindles over time when you repeatedly do anything.

“I think it was novel,” he said. “If you’ve been married for 10 years, because of the lack of novelty, I don’t think you’d see the same effect.”

So I suppose if you get an opportunity for exhilarating-but-not-exhausting sex, science is basically insisting you take it.

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