Could your post-gym spa habit affect your ability to have a baby? It’s a belief that gets repeated regularly online. But Prof Colin Duncan, a fertility expert at the University of Edinburgh, says things aren’t as clearcut as people make out. Cisgender men produce sperm in the testicles. It’s from here that these male reproductive cells are released to inseminate the eggs women produce.

Duncan says that repeated exposure to higher temperatures, such as those found in saunas, do inevitably have some effect on how much sperm is made by them. “Testicles are located outside the body because they work better when they’re cooler. If you’re incubating them in a sauna then they don’t work quite as well.”

Most of the time this is nothing to worry about, says Duncan. “The testicles are designed to produce way more sperm than is actually required for fertility. If you go for the odd sauna, it’s going to make absolutely no difference.” What about if you’re a daily visitor? “If you’re having extreme saunas for a long time every day, it will reduce your sperm count.”

Most people will still have plenty of sperm, he says, so this decreased sperm count shouldn’t have a noticeable effect on fertility. He points to the Finns, who he says use saunas much more than British people do. “They don’t seem to have a bigger problem with infertility.”

The men this does matter to are those with borderline low sperm counts anyway. Perhaps those who have already seen their GP after experiencing fertility issues. Duncan says that the “crucial” advice he gives men who come to his clinic is: “If you’re doing anything in excess – whatever it is – it’s probably worth moderating that.”