Liam Smith contributed this story.

According to British newspaper The Times, the IOC is expected to issue new guidelines halving the permitted level of testosterone allowed in female athletes eligible for women’s sporting events.

The revised guidelines comes only a few months after two transgender athletes made headlines by dominating their respective sport disciplines. The first was Laurel Hubbard, a weightlifter from New Zealand. An accomplished domestic lifter as a male, she drew the ire of fellow female competitors after winning silver at the 2017 World Weightlifting Championships. Most recently, she qualified for the 2018 Commonwealth Games, but an elbow injury during the competition forced her withdrawal from the event while leading the field.

The second, and perhaps most notorious case due to volleyball’s status as a mainstream international sport, is Brazilian Tifanny Abreu. She made volleyball history when she became the first trans female to play in Brazil’s Superliga. Since then, she broke the competition’s single game scoring record, and has dominated the league’s offensive statistics. Such performances drew the ire of many teams, players, and fans, who asked the Brazilian Volleyball Federation (CBV) to find a “solution” to the situation. Her performance led many to believe that she would be called up to Brazil’s NT, but a request from the FIVB and CBV prevented coach José Roberto Guimarães to do so.

We haven’t seen that level of impact in swimming yet – the major development of 2015 was Schuyler Bailar becoming the first openly transgender NCAA swimmer in memory. But Bailar, recruited to Harvard’s women’s swim team before switching to the men’s program, wouldn’t be affected by the new rules, which govern testosterone levels in male-to-female athletes competing in women’s sports.

There has been a lot of debate in the specific scientific community as to how much advantage a transgender woman has against their cis-gender opponents, with no firm answers yet.

Trans athletes were first allowed to compete in the 2004 Winter Olympics as long as they had gone through gender confirmation surgery and had been on hormones for at least two years. The surgical requirement was dropped in 2015 and the hormones period were lowered to a year. However, as of 2018, no openly transgender athlete has competed in either the Winter or Summer Olympic Games.