(Trans)Gender divides in Athletics
The case for a fair playing field
Gender in athletics is complicated and controversial.
As we all probably know, testosterone is probably the biggest performance enhancing drug out there, and the corresponding gulf between men and women’s athletic performance is huge.
Athletic differences between men and women
In running (any distance), Olympic men are routinely around 11% faster than Olympic women - that gap sounds small, but it’s HUGE
The female 100m world record wouldn’t even qualify for the Olympics if run by a man. Talented high school boys routinely run faster than female Olympians - that’s how big an 11% gap is!
Male Olympic javelin throwers throw ~30% farther than women Olympians, with a heaver javelin (800g vs 600g)
The fastest female baseball pitch is 65mph - male pitchers routinely exceed 100mph, with the fastest recorded at 105.8mph
Women are 19% shorter on the long jump
In weightlifting, Olympic men outperform by 30% on average in each weight class, and in Powerlifting, 65%
In moderately trained individuals, men produce a 162% stronger punch than women on average, and even the weakest man’s punch was stronger than the strongest woman’s
If you compare elite female records in sprinting, long jump, or discus, the most talented schoolboys equal or surpass them at about age 14-15
The average 18 year old boy can throw 3x farther than the average 18 year old girl
If you picked a thousand men off the street, 997 of them would have a stronger upper body than the average woman
One fun fact you may not know - it’s not just testosterone.
Having a Y chromosome itself, even with androgen insensitivity, likely drives significant athletic advantages, which we see in cases of female-phenotype athletes with Y chromosomes and androgen insensitivity - XY women are hugely (50-100x) over-represented in elite sport.1
Being androgen insensitive, they aren’t affected by testosterone levels either way, but they are affected by Y chromosome advantages. It is unlikely they would be over-represented to such a huge degree (50-100x) unless those advantages were significant.
And what could those athletic advantages be? A lot of the advantages men have comes from more than just testosterone - they come from height,2 more muscle, more strength, lower body fat (which increases their power-to-weight ratio), limb proportions, bigger hearts, tendon force and stiffness, and narrow hips.3
Of course we can’t talk about gender gaps in athletics without talking about male / female division, transgender athletes, and IOC criteria.
The IOC requires total testosterone to be below 10nmol / L for a year before competition as a woman.
That’s 288 ng / dl, which is actually quite high. The normal male range for Total Testosterone is roughly 250 - 900 ng / dl. The normal female range is 15-70 ng/ dl, so a 288 being permissible is pretty generous, more than 4x the usual top of the female range.
On the one hand, great! It totally makes sense that female athletes would have higher testosterone than the average woman, and you don’t want to exclude them. 4x seems pretty generous - I’d sure be happy if I could have competed at 3600 ng / dl total testosterone as a man (a super-physiological level that’s impossible to reach without steroids), but you know, I’m sure they have their reasons.
But is this a fair criteria to define somebody as “female” for the purposes of elite competition?
As we’ve just been discussing, men enjoy multiple advantages in athletics besides testosterone. Actually, I’ll just put a complete list in a table here:
Those advantages don’t go away when you suppress your testosterone.
Most M2F individuals do lose some muscle mass after transition - we know that muscle mass and strength are both significantly affected by testosterone.4
How could you compare this to isolate the “male” but not the “testosterone” advantage? What if you look at trans men (started male but no testosterone, henceforth M2F) versus trans women (started female, added testosterone, henceforth F2M)?
Gooren et al (2004)5 looks at thigh muscles after 3 years of hormonal transition, and finds thigh muscle area is ~13% higher in M2F vs F2M.
The overall change in muscle mass after the 1 year period advocated by the IOC is generally around 5%. But men have ~30-40% more muscle mass than women - reducing that by 5-13% isn’t really fair to competitors who are born women.
Wiik et al (2020)6 looked at quadriceps cross sectional area in M2F, and found the usual 4-5% decline. But they also looked at “radiological attenuation of the quadriceps muscle, a valid proxy of contractile density,” and found zero change after 12 months (and a +6% change in F2M). Measuring knee extension and knee flexion strenth, Wiik found that M2F remained ~50% stronger than both F2M and a reference group of females.
Van Caenegem et al (2015)7 looked at grip strength. Grip strength has long been an anthropometric proxy for overall strength, and men are typically 20-50% stronger than women in grip strength. M2F retained a +23% grip strength advantage over F2M after 2 years of hormonal transition. A similar study by Scharff et al (2019)8 found a +17% advantage.
Lapau et al (2008)9 took the longest window look, and compared people who had transitioned at least 3 years ago, and with mean transition duration of 8 years, and showed that their M2F cohort had 17% less lean mass and 25% lower peak quadricep strength than control males. But they were all still in the 90th percentile of lean body mass for women, and their grip strength was still 25% higher than the female control average.
I think it should be noted, all of these studies were on laypeople, not athletes. We know a couple of things that would make this picture even more M2F athlete skewed:
Muscle mass and strength is retained more under load - an M2F athlete who trains regularly is likely not going to decline even the small amounts that the study populations did.
The greater mitochondria and motor control units that athletes create via training would likely continue being higher after transition.
Explosiveness and power are largely driven by fast twitch type 2 fibers, and men have more of these types of fibers, and more muscle area with these types of fibers, and fibers largely do not change.10
Why do these small differences matter?
First, they’re not small - if an 11% difference in running means talented high school boys can outrun female Olympians, a 20% difference in muscle mass or strength is a big deal. But ultimately it matters because when you’re at the limits of human performance, people specialize.
Back in the late 1800’s, it was thought that the ideal athlete was like the ideal beauty - if you average a bunch of faces, the averaged face is more beautiful than the great majority of the input pictures. Similarly, it was thought that the ideal athlete would be like the Vetruvian Man - perfectly proportioned, not too big, not too small, not too skinny or too bulky…a well rounded athlete.
This was laughably wrong.
Elite athletes specialize
In 1925, as a result of a couple of generations of athletes and coaches following that “well rounded” idea, the average Olympic volleyball player and discus thrower were the same size, as were high jumpers and shot putters.
As you can see in the image above, that is not where athletes are today, they are all in vastly different phenotypical spaces, because they’ve specialized.
In 1995, Olympic shot putters were 2.5 inches taller and 130 pounds heavier than high jumpers.
In the 1970’s, 250lbs was big for an NFL lineman - now the average lineman weighs 310 lbs.
In the 8 years after Dick Fosbury invented the Fosbury Flop (in 1968) for high jumping, the average height of elite high jumpers increased 4 inches.
In general, athletes have gotten heavier and taller across all sports (save marathon, 800m+ running, and gymnastics), and it’s not just mass and height.
Elite athletes have weird proportions
Basketball players, tall as they are, have much larger arm breadth than height. An average player is 6’ 7” tall, but has a 7’ 0” wingspan.
Top water polo players have longer lower arms, and elite weightlifters have increasingly shorter forearms relative to their height.
Athletes in jumping sports like basketball and volleyball have a short torso and long legs.
60 meter sprinters are nearly always shorter than 100, 200, and 400m sprinters.
Female swimmers have narrower hips than regular women, yes - but they are also narrower than average *men.*
Michael Phelps, famously, is 6’ 4” but has a 32 inch inseam, and long arms with oversized hands and feet.
What I’m saying here is that people SPECIALIZE. Elite sport is impossibly competitive, and any slight advantage will be exploited fully, to the extent that all of our elite athletes are weirdly proportioned, because it gives them an edge somewhere in the single percents or decimal places.
If M2F athletic competition is allowed, they are coming in with significant advantages that don’t go away upon hormonal transition.
They start off taller and with more mass, on average.
Height is an advantage in most sports, and most Olympians in both men and women are significantly taller than the male and female population averages.
They start off with Y chromosomes, and the attendant physiological advantages we saw in the table above.
Hormonal transitioning leaves even untrained M2F individuals significantly stronger and more muscular than both F2M and female populations.
As male athletes, they have built their muscle mass, muscle and tendon strength, mitochondria, motor units, and work capacity as men, to a level far higher than female athletes can achieve, and they retain most of those advantages after transition.
M2F athletes are a unique athletic phenotype, in other words, and much like 7 footers with oversized wingspans in basketball, it is a phenotype that is uniquely suited to dominating female athletic competitions due to all these differences and advantages.
As we’ve seen, it may take a few decades, but elite competitive vacuums that benefit from a unique phenotype will absolutely be filled by that phenotype.
If we allow M2F competition in elite female competitive fields, there’s a good chance we would drive out most or all of the born-female athletes within a couple of decades.
Just like you no longer see average sized shot putters or volleyballers, or 250 lb linebackers. I for one, would not like for female-born women to be unable to compete and earn medals on a level playing field, and think that many others might share that view.
The reason M2F individuals might want to compete as women is likely some combination of identity and the fact that they’re no longer competitive as men - but they are “unfairly” competitive against born-female women to the same extent they’re no longer competitive against men.
The whole reason we have female divisions in sport is because we want to encourage a fair playing field, in which women can compete and win.
Given the large suite of physical advantages M2F individuals enjoy, I don’t believe that competing against M2F athletes is a fair playing field for born-female women.
The way the rules are written now, and given the gap in male / female performance, any male athlete could hop on hormones for a year, come in and dominate their event as a woman.
I know that sounds pretty silly and unlikely on it’s face, but let me paint a few plausible scenarios for you:
Today, many Kenyans ($1.8k GDP per capita) and Ethiopians ($1k GDP per capita) compete as runners overseas, because the prize purse for winning even a tiny American or European race is significant to them. They can come back with several years worth of GDP per capita by going and racing, and they do this often.
Any runner that keeps placing out of the money on a male race can totally dominate any female event, and the prize purses would actually matter to them and help feed their family.
Olympic medals are awarded with significant cash prizes by most countries. In the US, we’re so rich in medals we’re stingy and only award $38k for a Gold - but most European countries award between $100-200k. Poorer countries tend to award even higher prizes, like Philippines ($200k), Malaysia ($236k), Thailand ($365k), or Indonesia ($346k). Singapore and Hong Kong both award more than $700k!
That’s a significant financial incentive, and given the gap in male / female performance, essentially any talented high school and above male athlete could hop on hormones for a year, compete, win a gold and the prize (maybe even in multiple events), and then de-transition.
China, Russia, or Iran decides it’s a matter of national face, and “encourages” a good chunk of their elite male athletes to go on hormones for a year to do this across multiple events, dominating the entire female Olympics across multiple sports.
Am I saying that transgender athletes shouldn’t be allowed to compete in sports at all?
Not at all! I think anyone who wants to compete in athletics should be encouraged to the utmost. I simply don’t want to lose all born-female athletes at the elite level, and think that female-born women should be able to compete on a fair playing field.
Let’s have a “Nonbinary” division, to go with our men’s and women’s divisions today, and let’s choose our divisions by a combination of testosterone limit and gender at birth.
An index of the fitness and athletics posts here.
At the 1996 Olympics, 7 / 3387, or about 1 in 480 women, were XY with androgen insensitivity, but in the general population, it’s between 1 in 20-64k.
Notable examples of XY female athletes include Maria Jose Martinez-Patino., Erika Coimbra, Wonkam, Ambroise, Karen Fieggen, and Raj Ramesar.
Average female height in the US: 5’ 4.” Average female height for Olympians:
Volleyball: 6"‘ 2”
High Jump: 5’ 10”
Basketball: 6’ 0”
Shot Put: 5’ 10”
Gymnastics: 5’ 3”
Narrow hips are so much of an advantage, women reach their maximum sprint speed at age 14.
Doping scandals are ubiquitous, so I’ll just pick one example: 75 of the top 80 female shot put throws of all time happened between 1975 and 1990, the time of rampant female Eastern bloc doping.
Another fun factoid - do you know there’s a gene variant that makes you immune to doping tests? It makes you metabolize testosterone so fast your T/E ratio never shows doping. Carriers of two copies of a particular version of the UGT2B17 gene pass T/E tests even if doping. 80%(!) of Asians have it, and about 7% of Europeans.
doi: 10.1530/eje.0.1510425
doi: 10.1210/clinem/dgz247
doi: 10.1530/EJE-14-0586
doi: 10.1530/EC-19-0196.
doi: 10.1016/j.bone.2008.09.001.
James Nuzzo (2023) did a meta analysis looking at athletes specifically, finding that “men exhibit greater cross-sectional areas for all muscle fiber types and greater area percentages for Type II muscle fibers.” https://doi.org/10.1002/ca.24091