Transgender athlete Rachel McKinnon successfully defended her track World Championship title in Manchester.

McKinnon became the first transgender racer to win a rainbow jersey last season, competing in the 35-39 age category sprint during the UCI Masters Track World Championships in Los Angeles.

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The Canadian returned to defend the title in the 2019 Masters Worlds in Manchester last weekend, where she set a new world best time in qualifying and went on to take gold in the sprint for a second consecutive year.

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McKinnon, an assistant professor of philosophy, went into the gold medal ride-off against Dawn Orwick (USA) on Saturday (October 19), where she claimed victory.

Orwick beat McKinnon in the 500m time trial at the Worlds to take the gold medal, while McKinnon took silver.

Both of McKinnon’s victories have been met with celebration from some while others have raised questions about the fairness of transgender women competing in women’s categories.

Speaking before the event, McKinnon told Sky News: “By preventing trans women from competing or requiring them to take medication, you’re denying their human rights.”

Dr Rachel McKinnon, who was born a biological male, says all her medical records say female, her doctor treats her as a female, and her racing licence says female, but that “people who oppose her existence still want to think of her as male.”

Transgender athletes have been allowed to compete in the Olympics since 2004 but under the requirement they had undergone gender confirmation surgery and been on hormone therapy for two years.

In 2015, these rules were relaxed to remove the need for surgery and the athletes must have a testosterone level below 10nmol/L for at least 12 months prior to their first competition. The average range for adult females is 0.52 to 2.8 nmol/L, with levels above 2.7 described as the “upper limit of normal.”

Athletes who transition from female to male are allowed to enter in male competition without restriction.

Transgender athletes were due to face tighter restrictions by the 2020 Olympics in Tokyo, as the maximum level of testosterone allowed was due to be halved, but the guidelines have been delayed because the International Olympic Committee can’t reach an agreement.

Emerging research from the Karolinksa Institute in Sweden suggests that testosterone suppression for transgender women has little effect on reducing muscle strength.

A study by Loughborough University academics was carried out after the Rio 2016 Olympics after concerns about transgender athletes having an advantage.

After reviewing 31 national and international transgender sporting policies, including those of the International Olympic Committee (IOC), the Football Association and the Lawn Tennis Association, the study concluded that a majority unfairly discriminated against transgender people, especially trans women.

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The researchers said that there is no evidence that transgender women have a sporting advantage over athletes born female.

PhD student Beth Jones, who was involved in the study, said: “Our research has also shown that these stringent and unfair policies have a negative impact on transgender people’s experiences of sport and physical activity, even when the activity is engaged in at a recreational level, such as considering joining a local football team or going to the gym.”

The researchers suggested that if size or strength of competitors is a concern, different sporting categories not based on gender should be considered.