Do Transgender Athletes Have a Biological Advantage in Sport?

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How an NCAA swimming champion sparked controversy

Transgender swimmer, Lia Thomas, hit the headlines in March when she was crowned NCAA Champion having won the 2022 collegiate title in the Women’s 500-yard freestyle in March this year.

Lia, now a member of the University of Pennsylvania’s women’s varsity team, previously competed on the Men’s team before her transition. Her victory sparked a number of controversial comments, bringing to the fore the sensitive topic of trans-athletes.

Former athletes spoke up. Olympic Female medalists, in Swimming and Athletics, made their feelings known — They believe that transgender women should not be allowed to compete against biological women.

Are they right or wrong?

  1. Sonia O’Sullivan (Ireland) — Athletics
  2. Sharon Davies (UK) — Swimmer

This poses an interesting question:

Should a man, who transitions to a woman, be allowed to compete against biological women?

As you can imagine this is a hot-topic in the world of sport. It’s certainly something that people are talking about, questioning the logic with women’s sport in mind.

There are also those who feel they can’t speak out, at least not publicly. They fear become a target, labelled as un-woke, anti-trans, or even sued.

This article will explore the data that swimming can offer us. 


Before I dive into the rationale, I must point out false information that’s floating around in the media. As an ex-swimmer I know that I’m qualified to critique and evaluate the facts for non-swimmers.

So allow me to make you aware of the following facts:

  1. 2022 — Lia Thomas won the Women’s NCAA title in the 500 yard freestyle in a time of 4:33.24
  2. 2022 — Media reports inferred that Lia Thomas lifetime best was outside the top 400 in the male category. This is true based on her 2022 time, but false with respect to her best time ever
  3. 2019 — According to USA Swimming, Lia Thomas was ranked 65th in the Men’s 500 yard freestyle with a time of 4:18.72, a massive 15 seconds faster than her winning time in the Women’s event this year
  4. 2019 — Also according to USA Swimming, Lia Thomas recorded a time of 9:55.75 in the Men’s 1,000 yard freestyle in 2019, ranking 7th in the nation

Now that we have a starting point, data-led reference points, I feel obliged to highlight a couple of other noteworthy facts:

500-yard Freestyle

  • Women’s — Lia Thomas’ best ever time (4:18.72, recorded as a Male swimmer in 2019) is 6 seconds faster the than the US record held by Katie Ledecky at 4:24.06
  • All time top 25 performers — Katie Ledecky holds 21 of the top 25 times ever record in this event, Lia Thomas ranks 25th

1,000-yard Freestyle

  • Women’s— Lia Thomas’ best ever time (9:55.75, recorded as a Male swimmer in 2019) is 4 seconds faster the than the US Women’s record, held by Katie Ledecky at 9:59.65
  • All time top 25 performers— Katie Ledecky owns 16 of the top 25 times ever record in this event and her national record is 11 seconds faster than the number 2 in this discipline

So please ignore the false-media spun by click-bait-junkie tabloids.

The Athletes

Above all it’s important to respect the athletes. 

When sporting bodies allow a new variable to be introduced, with nebulous boundaries, naturally the balance of fairness is questioned and open to critique, compromising the integrity and credibility of sport.

So this piece is dedicated every athlete the world over.

Boiling Point

Now back to the point of this piece — a potential boiling point.

Some argue that it boils down to the science, biological-science, given that Men have a natural unfair advantage.

A fair point that’s worth exploring.

Taking hormones to reduce testosterone during transitioning is just one dimension of a complex spectrum, but there are other factors. For example, one obvious factor is the difference in form — the contrasts in body composition between female and male adults.

Let’s deduce what we know:

  • Men are naturally stronger
  • And, Men are naturally taller


Historically Male and Female sports have been separated for such reasons. Let me refer to the US population data (available online) for reference:

  • Roughly 1% of US Women are over 6 feet tall
  • Compared to 15% of Men over 6 feet tall

For the US population alone, with 332 million people, the numbers are:

  • Women over 6 feet tall = 1% of 332 million = 3.3 million
  • Men over 6 feet tall = 15% of 332 million = 49.8 million

So what the data tells us is this:

For every 100 Men over 6-foot tall there are 6 Women.

A ratio of 100:6 equates to 17–1 … good odds in the betting side of sports, but not for female competitors.

Talk on Water

My satirical subheading is by no means Biblical disrespect, far from it. 

Swimming is the only valid watermark that we can use right now. 

The data available online can allow us to make sense of an unknown social dynamic that most of us do not understand, which has already been applied in Sport.

My aim is to educate the non-swimming world by using data as a benchmark. With respect to Lia Thomas, her times shed a light on this dilemma in the sporting world.

Lia was not slouch as a male freestyler. In my time, the 1990s, a 4:18 in the 500 yard freestyle was quick. 

Data Source —

In fact, if you swam a 4:18 in the 500 yard free you made the final at NCAAs.

Today its different.

Miles apart

Swimming, being unnatural to humans, has the biggest time improvements at elite level compared to any other sport, by a mile.

On that note, let’s compare miles.

Take the mile in Athletics. Long before Roger Bannister broke the magical four-minute mile, the first World Record stood at 4:14.4.

Today the record is 3:43.13, which is a 14% improvement.

No let’s compare to swimming. The World Record for the 1500m freestyle (just under a mile, but an Olympic event), set at the 1908 Olympics was 22:48.4 — a time that modern competitive swimmers cruise in warmup.

Today the record is 14:31.02 — a whopping 57% improvement.

This leads on to my next point.

Leaps and splashes

Evolution differed from sport to sport, as demonstrated above.

So with Transgender athletes in mind, allow me to grab the data available online for Lia (William) during her career in Men’s swimming in the 500-yard freestyle. 

Data by USA Swimming

As you can see Lia was 65th in the Men’s national rankings in 2019. 

While her time as a male swimmer would have qualified for the Top-8 at the Men’s NCAA finals in 1996, the 65th ranked athlete in the female event this year was 10 seconds slower that Lia’s winning time.

Beg to Differ

I tend to shy away from topics that I’m not qualified to comment on.

Then again, I don’t think many people are qualified to discuss the topic of the advantages or disadvantage of ‘Transgender Athletes in Sport’ other than the athletes competing right now.

What I do know is this:

  1. Data, and
  2. Swimming

I admit that the sample audience above is tiny, but as an ex-swimmer I find it hard to look beyond times and rankings — it’s in our DNA.

One swim enthusiast said to me:

You can’t argue with data — Numbers just don’t lie — So times are the most honest reference point we have in Sport! — Phil Winston 

Is he right? 

According to Swimming data, he is.

What the Swimming data is showing us is that there is an advantage for athletes who transition from Male to Female.

Like their male counterparts, Female athletes have trained and competed in their chosen sport for years, decades even. So being suddenly pitted against a competitor with natural physical advantages must be disheartening.

So is there an advantage for athletes who transition from Male to Female in other Sports?


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