When you’re competing in the world’s most-watched sporting event, you don’t take any chances with your body. So while experts may disagree about whether having sex before a game can affect a player’s performance, many teams at this year’s World Cup have implemented sex bans.

“There will be no sex in Brazil. They can find another solution, they can even masturbate if they want. I am not interested what the other coaches do, this is not a holiday trip, we are there to play football at the World Cup,” Safet Susic, the coach of Bosnia-Herzegovina’s national soccer team told reporters of his team’s ban in April.

On Tuesday, Quartz broke down the sex rules for the World Cup teams. To sum up:

Sex is permitted on these teams: Germany, Spain, the United States, Australia, Italy, Netherlands, Switzerland, Uruguay and England

Sex is banned on these teams: Russia, Bosnia and Herzegovina, Chile and Mexico

And the rules are complicated on these teams: France (you can have sex but not all night), Brazil (you can have sex, but not “acrobatic” sex), Costa Rica (can’t have sex until the second round) and Nigeria (can sleep with wives but not girlfriends)

The rules for the remaining teams are unknown.

Are some sex rules excessive? Probably. The two most common concerns about pre-game sex are that intercourse might make a player tired and weak or it could affect him psychologically. Studies have shown that the former is a myth.

Many coaches and athletes believe that abstaining from sex builds up aggression, a belief that probably stems from ancient civilizations like the Greeks, who thought that men derived strength from their semen. This theory is so pervasive that even Muhammed Ali refused to have sex six weeks before a fight, fearing that ejaculation would release the testosterone (and therefore aggression) he needed for a boxing match.

But in fact, the opposite has been proven to be true. Studies show testosterone increases after sex. “After three months without sex, which is not so uncommon for some athletes, testosterone dramatically drops to levels close to children’s levels,” Emmanuele A. Jannini of the University of L’Aquila in Italy who has studied the affect of sex on athletic performance told National Geographic. “Do you think this may be useful for a boxer?”

Which means that sex may actually increase performance by releasing testosterone into the body.

And sex doesn’t exhaust athletes. Most bedroom sessions burn only 25 to 50 calories, the equivalent of walking up two flights of stairs. For an all-star athlete, that’s nothing. Studies show that having sex the night before a competition has no affect on strength or endurance.

Whether coitus would affect the soccer players psychologically is harder to test, but experts maintain that it can have a positive mental effect. “If athletes are too anxious and restless the night before an event, then sex may be a relaxing distraction,” Ian Shrier, a sports medicine specialist at McGill University, wrote in a 2000 review of 31 studies on sex and sports titled “Does Sex the Night Before Competition Decrease Performance?” published in the Clinical Journal of Sports Medicine.

Some experts even argue that previous World Cups wins prove sex can be beneficial.

“The Netherlands national soccer team, at the 1978 World Cup in Argentina, is an example of this,” Juan Carlos Medina, general coordinator of the sports department at Tecnologico de Monterrey in Mexico told CNN. “Some of those players were accompanied by their wives, and they won the second place. I don’t say this is a determinant factor, but it brings support.”

“Even Pele confessed that he never suspended sexual encounters with his wife before a game, I mean, that thing about sex helping to relax is a verified truth,” he added.

Ultimately whether sex will negatively impact a person’s emotions before a game depends on each individual. Some find it’s a relief, others a distraction (especially if it keeps them up all night). “In general, an athlete should never try something before an important competition that they have not already tried in lesser competitions or practice,” Shrier concludes.

Write to Eliana Dockterman at eliana.dockterman@time.com.