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Existing gender categories in sport should perhaps be abandoned in favour of a more ''nuanced'' approach in the new transgender era, the University of Otago researchers say.
''The IOC [International Olympic Committee] guidelines are trying to push people into one group or the other, male or female,'' Otago bioethicist Associate Prof Lynley Anderson said yesterday.
''We've got a problem here.
''It's a problem too for transmen, who will struggle to compete because of their previous female physiology.
''To be simultaneously inclusive and fair at the elite level some innovative thinking is required.
''We conclude that the gender binary in sports has perhaps had its day,'' Prof Anderson said.
In an extended essay published in the latest issue of the Journal of Medical Ethics, the researchers said the current IOC guidelines were ''poorly drawn''.
Dr Taryn Knox, also of the Dunedin Bioethics Centre, and Otago physiologist Prof Alison Heather were the other authors.
The researchers disputed the higher testosterone levels allowed for transwomen under the IOC guidelines amounted to ''a tolerable unfairness''.
Prof Heather said higher testosterone levels conferred an all-purpose benefit for most sports, and hormone therapy did not mitigate all the benefits of a previous male physiology in competition.
Under current guidelines, a transwoman must show her total testosterone level in serum has been below 10nmol/L (nanomoles per litre) for at least 12 months before her first competition.
Prof Anderson said it was important to both extend and celebrate diversity while maintaining fairness in sport for cis-women - women who were born female and identify as women.
The guidelines allowing male-to-female transgender athletes to compete in the women's category at the elite level have raised significant debate since they were introduced in 2015.
The recent case of New Zealand weightlifter Laurel Hubbard, a transwoman competing in the 2018 Commonwealth Games, had polarised opinions about the inclusion of transwomen in women's sport.
Prof Anderson said more could be learned from the Paralympic movement, which had ''some interesting ways'' of structuring competition to take into account diversity and fairness.
Various solutions were possible, and the development of algorithms could account for a range of physical and social parameters to help achieve fairness.