Trans women could be banned from women's rugby.
World Rugby has drafted a 38-page document which claims that trans women hold “significant” physical advantages over biological women.
The document claims that the International Olympic Committee (IOC)’s guidance on trans inclusion are not fit for purpose.
The Guardian claim the document says that there is "at least a 20-30% greater risk" of injury when a biological woman is tackled by someone who has gone through male puberty.
The document's guidelines are based on a study by Swedish lecturer Tommy Lundberg.
In a study of eleven trans women and twelve trans men - none of whom were athletes - Lundberg found that transgender men in his study increased muscle mass and strength significantly after 12 months of testosterone therapy.
He added that "transgender women did not lose strength at all despite inhibited testosterone production.
"In addition, the effect on muscle mass of the transgender women was less pronounced than many people previously thought, losing only 5% of the muscle volume over the thigh muscles."
In 2015, the IOC stated that transgender men are allowed to compete in the male category without restrictions, while transgender women must have testosterone levels below 10 nmol/L for at least 12 months prior to competition.
Last year, the IAAF introduced new rules regarding trans athletes competing. Famously, these changes in regulation were challenged by Caster Semenya.
World Rugby say the IOC's rules regarding the lowering of testosterone levels are not fit for purpose.
The draft proposals have been sent to individual unions for their feedback.
“Current policies regulating the inclusion of transgender women in sport are based on the premise that reducing testosterone to levels found in biological females is sufficient to remove many of the biologically-based performance advantages," the draft report says. "However, peer-reviewed evidence suggests this is not the case.
“Cis women players (who do not undergo androgenisation during development) who are participating with and against trans women (who do undergo androgenisation during development) are at a significantly increased risk of injury because of the contact nature of rugby," it adds.
"While there is overlap in variables such as mass, strength, speed and the resultant kinetic and kinematic forces we have modelled to explore the risk factors, the situation where a typical player with male characteristics tackles a typical player with female characteristics creates a minimum of 20% to 30% greater risk for those female players.
"In the event of smaller female players being exposed to that risk, or of larger male players acting as opponents, the risk increases significantly, and may reach levels twice as large, at the extremes."
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