Why transwomen shouldn't play top-level women's rugby

Exercise physiologist and high-performance sports consultant DR ROSS TUCKER explains how World Rugby determined its new transgender guidelines.

Most people will agree that women need sport for women, because the physiological differences between men and women are so large that if you didn’t have a category that protects women’s space, they would basically disappear from sport.

That might sound dramatic, but consider that in the 100m sprint – which is the simplest sporting task we know – the best woman athlete in history is beaten every year by thousands of men and boys. So there are 16-year-old boys who are better than the best adult woman ever. It’s the same in the marathon. It doesn’t matter where you look – biological males outperform biological females.

Why? Mostly, but not exclusively, because of testosterone. Testosterone results in more muscle, more powerful muscle, a lower body fat percentage, a different shape of the skeleton, thicker and denser bones, and a larger heart and larger lungs. All those things added up make better athletes.

So, in the Olympic Games, we have a 100m men’s champion in Usain Bolt and a women’s champion in Shelly-Ann Fraser-Pryce. They are equal in the sense that they are the best sprinters in the human race within their categories, but Bolt is 15% faster than she is.

So we protect women’s sport for fairness, and then for rugby, of course, there’s a safety issue, because of all those things I mentioned – muscle, power, size, strength. The sport has an obligation to ensure that women are protected from excessive injury risk.

World Rugby’s previous transgender policy was basically the International Olympic Committee’s policy.

This goes back to 2003 when rugby said it wanted to be inclusive, which I think is good. Sport wants to be reflective of society and in society, people have every right to identify however they wish.

But because of these biological differences between men and women, sport realised that it couldn’t just allow males into women’s sport, so it tried to ‘fix’ this problem by forcing or asking athletes to lower their testosterone levels.

The IOC policy said athletes could take testosterone-lowering medication for 12 months – or have surgery – to get their testosterone levels below the concentration of 10 nmol/L and then they are clear to play women’s sports.

So that was the World Rugby policy, although we had recently lowered it to 5 nmol/L for reasons not worth going into here.

Now, there are about a dozen studies that look at what happens to people when you lower their testosterone levels. When World Rugby had its meeting in London earlier this year we had people present that data to us.

It is very striking that the difference between biological male and female is much larger than the reduction when you lower testosterone levels.

Take strength, for instance. The difference between biological male and female is about 50%. The studies show that after lowering testosterone, the male loses 5-10% of that strength. So you start at 50% and end at 40%, which is still a big advantage for the athlete. The difference between lean mass in biological male and female is in the range of 40-50%. When you lower testosterone, the athlete loses 0-10% of lean mass.

So transwomen, after lowering their testosterone levels, still have advantages over cisgender women.

This research isn’t on rugby players – no one has ever taken a team of rugby players, lowered their testosterone levels for 12 months and seen what happened. And that's not going to happen. But they have looked at healthy males who have done it and the result is that the biological advantage is largely retained.

Based on the published evidence, we simply could not see a way to guarantee that a transgender woman loses enough of her strength, mass, speed and power advantage to ensure the safety of biological females.

As a sport, we want rugby to be inclusive, fair and safe. Based on the evidence that is available right now, we cannot balance all three things. And if you can’t balance them, you have to prioritise them.

The decision therefore, which I don’t think is difficult, is that safety is No 1 – you cannot expose people to a risk that is unduly high and ask them to accept that. No 2 is fairness and then, unfortunately, inclusion comes third.

And that’s what led to World Rugby’s updated policy.

– Tucker was speaking to Cato Louw in a Instagram Live. Watch the full chat below.

Summary of transgender biology and performance research