The World Cup's "No Sex" Rule Is Older Than FIFA. And It Still Doesn't Work.

The 2026 World Cup is over, and one of the sport’s oddest traditions came through it untouched. So we went looking for the evidence behind the pre-match sex ban. There is very little of it.

On Sunday night at the stadium in East Rutherford, Spain beat Argentina 1 to 0 to win the World Cup. It went to extra time, and for 120 minutes Emiliano Martinez threw himself at everything Spain sent his way. Ferran Torres, on as a substitute, scored the only goal in the 106th minute. Lionel Messi, in what appears to have been his last World Cup match, ended the night in tears. “They were better, to be honest,” he said afterward.

A Long, Strange Tradition

For the month that led up to that game, players across the tournament had been told to stay away from their own partners while the football was on.

The tradition is old and strange, and hardly modern at all. Ahead of the 2014 tournament, Bosnia and Herzegovina’s coach, Safet Sušić told reporters, flatly, that there would be “no sex in Brazil.”

That same summer, Mexico’s manager Miguel Herrera imposed a full month-long ban. His message to the squad was blunt: If a player can not endure a month or 20 days without having sex, then you are not prepared to be a professional.

And back in 2009, England’s manager, Fabio Capello quietly rationed how much time England’s squad got with their partners. England lost to Germany 4 to 1 anyway.

Football is not the worst of it. Boxing has kept the same rule going for a century. Muhammad Ali was said to abstain for six weeks before a fight, and the British super middleweight Carl Froch once went three months.

Earlier this year, audio leaked of an NBA owner asking his team to give up sex for ten weeks during a playoff run, citing the discipline of the Spartans. Those same Spartans, for what it’s worth, lost at Thermopylae.

The Theory, and Where It Comes From

The claim is a familiar one. Sex is said to drain a man’s testosterone, testosterone is supposed to supply his strength and aggression, and so the player who gives in the night before is expected to turn up on Saturday already weakened.

It is not a modern idea. The Greeks and Romans held that a male athlete had to conserve his seed to preserve his “masculine vitality” before competition. A coach banning sex for a month is not being modern about it. He is repeating something close to two thousand years old.

What the Research Keeps Finding

The trouble is that the penalty keeps failing to appear. Researchers have looked for it for decades and come back with nothing.

A 2025 paper in Physiology & Behavior tested 21 male athletes on strength and endurance twice: half an hour after they had masturbated, and again after a week without sex. Sex shortly before exercise made no measurable difference to their results. This is not a new finding. In 2000, a McGill researcher named Ian Shrier reviewed 31 separate studies for the Clinical Journal of Sports Medicine and reached the same conclusion.

It also helps that sex burns very little energy. The figure usually put on it is around 25 calories, which is not the sort of exertion that shows up in a professional athlete’s legs the following day.

The testosterone claim does not hold up well either. Levels can rise and fall around sex, but the change is brief and the hormone returns to normal soon afterward, so there is no lasting drop to affect a player the next day.

The One Grain of Truth

There is a version of the rule that does hold up, and it is about timing rather than abstinence.

When researchers tested high-level male athletes on a cycle ergometer, sex the night before did no harm. The only effect they recorded was a higher heart rate when sex took place less than two hours before exercise. That is the whole evidence base for a tradition that has cost professional athletes a great deal of collective celibacy. Leaving a couple of hours before kickoff covers it.

If anything, the effect can run the other way. Sex lowers stress and helps with sleep, which matters for a player lying awake the night before a major match. In that situation it is less a distraction than a form of free sports psychology.

So What Are Coaches Actually Afraid Of?​

Most likely not the sex.

Casey Stengel, who managed the Yankees to seven titles, is often credited with settling the question decades ago. Asked whether he let his players sleep with their wives before a game, he said the sex was never the problem; it was staying out all night looking for it. The exact wording has never been nailed down, and slightly different versions turn up in print from the 1960s onward.

He had a point. When experts are pressed on it, they tend to say the same thing: coaches are not worried about what happens in the bedroom, but about what it takes to get there. The late nights out, the drinking, the relationship that falls apart in the group stage and follows a squad from city to city for a month. A blanket ban is a crude way of telling grown men to stay in and sleep.

It is also, from start to finish, a male story. Every ban mentioned here was imposed on a men’s team, and every study cited was run on male athletes. The rule was never really about physiology. It rests on a very old idea about what a man is supposed to hold in reserve.

What Actually Loses a World Cup Final

The final that just finished is a fair illustration of what really decides these games.

Spain did not win because they were more abstinent than Argentina. They won because a fresh substitute still had his legs in the 106th minute, because Martinez kept them in the game with a final-record 11 saves, and because their defense was tight enough that they conceded a single goal across the whole tournament. Argentina did not lose over a broken curfew. They lost because they ran out of ideas and then out of composure, with Enzo Fernandez sent off in stoppage time for a second booking in a final that turned into 24 fouls and a run of yellow cards.

That is what coaches are actually afraid of: lost focus, lost composure, a team that stops thinking. None of it has anything to do with who did or did not have sex the night before.