In the world's premier winter sports country, Norway, the University of Tromsö has been awarded the equivalent of SEK 35 million for a research project on how the menstrual cycle and ovulation affect female athletes. The issue is not new in Sweden either, where Angelica Lindén Hirschberg has been an adviser to SOK before several Olympics, while Sweden has never earmarked research millions on the subject.

- There is a hypothesis that it is possible to optimize exercise based on the hormone cycles of the menstrual cycle, but today we have no scientific evidence that it would work. Much more and larger studies are needed, says Angelica Lindén Hirschberg to SVT Sport.

USA mapped people

The United States made a success of World Cup gold in football this summer, and some of the preparations were about mapping the players' menstruation to optimize recovery, sleep, diet and performance. Previous research shows that around 75 percent of all female athletes experience negative effects of their menstruation, and that about half of all female athletes use some form of hormonal contraceptive that affects their menstruation. However, the subject is slightly sensitive.

- Most people are probably interested in participating in research, because they think it is important. But it is clear that it may not be something you talk about with anyone, and especially not journalists, says Angelica Lindén Hirschberg with a smile.