Cycling's governing body has become the first sport to update its eligibility rules for transgender athletes with stricter limits that will force riders to wait longer before they can compete after undergoing any transition treatment.
The Union Cycliste Internationale (UCI) announced it was halving the maximum permitted plasma testosterone for trans women to compete in the female category from 5 nmol/L to 2.5 nmol/L and doubling the period they must remain below that threshold before being allowed to compete from one to two years.
The UCI said recent scientific studies showed that "the awaited adaptations in muscle mass and muscle strength/power" among athletes who have made a transition from male to female takes at least two years.
"Given the important role played by muscle strength and power in cycling performance, the UCI has decided to increase the transition period on low testosterone from 12 to 24 months," the governing body said after a management board meeting.
"This value corresponds to the maximum testosterone level found in 99.99% of the female population," the governing body said.