Canadian cyclist Rachel McKinnon (L) prepares to race against Australian Amber Walsh (2nd R) in their F35-39 sprint semi-final during the 2019 UCI Track Cycling World Masters Championship, in Manchester. Photo by OLI SCARFF/AFP via Getty Images
Artillery Row

The flawed science of trans inclusion in women’s sport

Advocates are embracing unreliable studies to justify unfair competition

Following an embarrassing climbdown over the proposed inclusion of transgender cyclist Emily Bridges in a women’s elite race, British Cycling is calling for “a coalition to share, learn and understand more about how we can achieve fairness in a way that maintains the dignity and respect of all athletes.” There’s really no need. The UK Sports Council Equality Group did this work last year, and concluded it was not possible to “balance” trans inclusion in the female category with fairness and safety for females. 

Multiple studies have shown that testosterone suppression does not change male physiological and anatomical characteristics by much. As described in peer-reviewed journals here and here, the measured effects are insufficient to eliminate male performance advantage and guarantee fairness for female sport.

Study participants have a vested interest in getting the right answer

Nonetheless some argue for more or better scientific studies. One such is transwoman Joanna Harper, whose previous work led to the adoption of testosterone suppression by several international sports federations and the International Olympic Committee, though the IOC has now dropped the requirement and says there should be “no presumed advantage” for transwomen, i.e. males, over women. Harper says previous studies are inadequate because they were not among athletes, and is now investigating via a PhD study at Loughborough University, allegedly sponsored by the IOC. 

The study measures performances of male athletes from a range of sports who are suppressing their testosterone as part of a transition to become transwomen. Harper has spoken of testing the athletes on indoor bikes, rowing machines and timed sprinting on running tracks. Harper is hoping to show a decline in performance roughly equal to the typical male advantage. This is a flawed starting point, since comparing male with male performance is not the point — it’s male with female that matters. But there’s a bigger problem. The study design cannot reliably test the hypothesis. Here’s why. A robust scientific study looks like this:

  1. There is a hypothesis which can be disproven, and study participants don’t know what it is, so they can’t consciously or subconsciously behave in ways that influence the study.
  2. There is a test group and a control group. 
  3. Participants are “blind”. Those being studied don’t know who’s in the test group and who’s in the control group. Ideally, they don’t know what a “good” result looks like. They may not even know what is being measured. This is so that participants can’t deliberately or inadvertently bias the results. Sometimes they simply want to please the researcher. If they don’t know, they can’t.
  4. Researchers are also “blind”. This makes the gold standard, a “double blind” study. The researchers don’t know who’s in which group so they can’t deliberately or accidentally bias the results or read them knowing what they’re looking for.


This study has a hypothesis: that testosterone suppression reduces male performance advantage by an amount comparable to the typical difference between male and female elite athletes. But it has none of the other elements. Everyone is in the test group. There is no control group. Everyone knows what the desired results are. Data to support the Harper hypothesis are easier to obtain than data which would disprove it, because the latter require maximal effort at all times. Perhaps worst of all, and rarely seen in academic research, the study participants also have a vested interest in getting the right answer. So there is no incentive for them to try hard. 

Since the methodology has not been published, we can’t say how these design issues are to be addressed. Monitoring objective measures such as heart rate might help prove how hard they are trying. But it’s hard to see how this study can yield good data. 

All the participants will benefit from a study proving that testosterone suppression slows you down. So will Harper, backing up their earlier poor-quality study, built on anecdotal evidence, on which the IOC previously relied. What’s more, it’s easy to achieve. If these athletes had to try their hardest to qualify for an Open event, the data might have value. But elite young males start with a 10-20% advantage over elite females. 

As we saw with the UPenn swimmer Lia Thomas, and now with British cyclist Emily Bridges, the problem can be that they remain embarrassingly advantaged. Anyone who’s done an active ECG test knows it gets hard at the end. Rowers push for personal bests on the standard 2000m ergo test. Cyclists and track athletes push against their own past performances and each other. But here is a group of competitive young males with much to gain and nothing to lose by easing off. This is a study in which slowing down makes you a winner. We can predict the results.

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