Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage.

Hilton and Lundberg, 2020. A lay summary.

Full text (open access):

1. INTRODUCTION | Sports performance is strongly influenced by muscle, skeleton and cardiovascular (CV) capacity, which differ significantly between males and females. Comparing like-for-like competition, the male advantage appears insurmountable. Further, male advantage may create safety and athlete welfare concerns. Thus, to ensure that both men and women can enjoy sport in terms of fairness, safety and inclusivity, most sports are divided into male and female categories.

Transgender women (TW) may wish to compete in the female category. Current IOC policy: “it is necessary to ensure insofar as possible that trans athletes are not excluded,” yet also: “the overriding sporting objective is and remains the guarantee of fair competition”. And the IOC concludes: “restrictions on participation are appropriate to the extent that they are necessary and proportionate to the achievement of that objective.”

IOC criteria by which TW may compete in the female category: solemn declaration of female gender identity and maintenance of testosterone (T) levels <10 nmol/L for at least 12 months prior to competing/during competition. We surmise the IOC believes these T criteria sufficient to remove the sporting advantages of males over females and deliver fair and safe competition within the female category. Are they?

2. BIOLOGICAL BASIS FOR MALE PERFORMANCE ADVANTAGE | Males and females develop differently, and sports differences are evident pre-puberty. Compared with girls, boys can run +10% faster, jump +10% further, have +10% higher grip strength, and have higher CV (VO2max) capacity. Early differences might be mediated by genetics (6500 genes expressed differently between males and females, 3000 muscle-related) and/or “mini-puberty” (male babies get a burst of T at 1-6 months old).

During puberty, testes-derived T levels increase 20-fold in males, but remain low in females. T in males induces changes in muscle, strength, skeleton and hemoglobin levels and thus, divergence of athletic performances.

As a result of androgenization, males have (briefly): larger and denser muscle mass, greater muscular force production, lower fat and different fat-muscle distribution, stiffer connective tissue, longer and larger skeletal structure, and superior CV function. These properties are advantageous in almost all sports.

3.1 SPORTS PERFORMANCE DIFFERENCES – ELITE | We compared elite athletes records/performances in a range of disciplines, and found (overview): +11-13% advantage in rowing, running and swimming; +18% advantage in jumping events (long, high, triple); +20% advantage in sports where upper body strength is dominant (e.g tennis, baseball, field hockey).

We examined performance metrics in elite athletes. Vertical jump performance is +30% greater in elite males. Throwing represents the widest sex difference from an early age and in Olympic javelin throwers, peak velocities of the shoulder, wrist, elbow and hand are +13-21% higher for male athletes.

The increasing performance gap as upper body strength becomes critical is likely explained by the observation that males have disproportionately greater strength on their upper compared to lower body. Males also have longer arms than females, which allows greater torque production from the arm when, for example, throwing a ball, punching or pushing.

We explored mass-strength relationships in Olympic weightlifting records. Males are ~30% stronger than females of the same mass and height (see 69kg [1998-2018 records] and 55kg [2019-] categories). In fact, males are stronger than higher weight category females. The performance gap increases to ~40% in open weight categories, where height and weight are no longer limited. In powerlifting the gap between open male and female records is +65%.

Translated to competition, in running events where the male-female gap is approximately 11%, approximately 10 000 males have personal best times that are faster than the current Olympic 100 m female champion. This example illustrates the “real life” effect of an 11% gap between males and females.

Furthermore, examination of selected junior male records, which surpass adult elite female performances by the age of 14-15 years, demonstrates superior male performance within a few years of the onset of puberty.

These data overwhelmingly confirm that testosterone-driven puberty, as the driving force of development of male secondary sex characteristics, underpins sporting advantages that are so large no female could reasonably hope to succeed without sex segregation in most sporting competition.

3.2. SPORTS PERFORMANCE DIFFERENCES – NON-ELITE |The male performance advantages described in athletes are similar in magnitude in untrained people. For example: VO2max is 12-15% higher in males than in females; lower-limb muscle strength is 50% higher in males and females; males have 57% greater bicep size and 89% stronger bicep curl than females; males produce 162% power than females in a punch motion.

This highlights the difference in upper body capacity between males and females, and shows that sex differences in parameters such as mass, strength and speed may combine – synergise – to produce even larger sex differences in sport-specific actions.

For example, the average 17 yr old male throws a ball further than 99% of 17 yr old females, despite no single variable (arm length, muscle mass etc.) reaching this numerical advantage. Similarly, no single parameter that produces punching actions achieves +162% magnitude of difference between males and females.

4. IS MALE PERFORMANCE ADVANTAGE LOST IN TW? | We performed a systematic search of the scientific literature addressing skeletal and muscle characteristics of TW.

4.1 SKELETON | There are multiple studies of bone health in TW. TW often have low baseline bone mineral density (BMD), attributed to low levels of physical activity, especially weight-bearing exercise, and low Vitamin D levels. However, TW generally maintain bone mass over the course of at least 24 months of T suppression. There may even be small but significant increases in BMD at the lumbar spine.

Given the maintenance of BMD and the lack of a plausible mechanism by which T suppression might affect bone length and hip width, we conclude that sporting advantage conferred by skeletal size and bone density would be retained despite T reductions compliant with the IOC’s current guidelines.

4.2 MUSCLE AND STRENGTH | We found 12 longitudinal (“before-after”) studies examining the effects of T suppression on lean body mass or muscle size in TW. The collective evidence suggests that 12 months, the most commonly examined intervention period, of T suppression to female-typical reference levels results in a modest (approximately -5%) loss of lean body mass or muscle size.

Comparison with baseline measurements from females shows that TW retain 13-39% more muscle mass than females. The reduction achieved by 12 months of T suppression is small relative to the initial superior mass.

Three of the above studies included strength measurements: first, hand-grip strength was reduced by -9% after 24 months of T suppression (+23% advantage retained over female controls); a second study of hand-grip strength showed -4% in grip strength after 12 months of T-suppression (+17% advantage retained over female controls); a study of quad strength after 12 months of T suppression showed negligible loss (+41% advantage retained over female controls).

These longitudinal data comprise a clear pattern of very modest to negligible changes in muscle mass and strength in TW suppressing T for at least 12 months.  Muscle mass and strength are key physical parameters that constitute a significant, if not majority, portion of the male performance advantage. Thus, our analysis strongly suggests that the reduction in T levels required by many sports federation policies is insufficient to remove or reduce the male advantage, in terms of muscle mass and strength, by any meaningful degree.

We found one major cross-sectional (“after only”) study that measured muscle mass and strength in TW, recruited after orchiectomy and approximately 8 years of T suppression. TW had 17% less lean mass and 25% lower quad strength than control males.

This comparison suggests that prolonged T suppression substantially reduces muscle mass and strength in TW. However, the typical gap in lean mass and strength between males and females at baseline exceeds the reductions reported in this study. For example, the final grip-strength was still +25% higher than matched female reference values.

Furthermore, given that TW often have slightly lower baseline measurements of muscle and strength, and baseline measurements were unavailable for these TW, the above calculations using control males reference values may be an overestimate of actual loss of muscle mass and strength in these TW.

4.3 ENDURANCE PARAMETERS | No controlled longitudinal study has explored the effects of T suppression on endurance-based performance.

An analysis of self-selected and self-reported race times for eight TW runners of various age categories who had, over an average 7 year period, competed in sub-elite middle-long distance races within both the male and female categories has suggested that T suppression reduces running performance by approximately the size of the typical male advantage.

However, factors affecting performances, including training, injury, race course and weather conditions, were uncontrolled for, and there were uncertainties regarding which race times were self-reported vs. which race times were actually reported and verified.

Furthermore, one runner improved substantially post-transition, which was attributed to improved training. This demonstrates that performance decrease after transition is not inevitable if training practices are improved.

Hemoglobin level appears to decrease by ~10% with T suppression in TW, with a predicted performance penalty associated with reduced oxygen-carrying capacity. However, factors such as total blood volume, heart size and contractility, and blood vessel supply also play a role for the final oxygen uptake. Thus, while a reduction in hemoglobin is strongly predicted to reduce endurance performance in TW, it is unlikely to completely close the baseline gap in aerobic capacity between males and females.

The typical increase in body fat noted in TW may also be a disadvantage for sporting activities (e.g. running) where body weight is a disadvantage. It is unclear to what extent the expected increase in body fat could be offset by nutritional and exercise countermeasures, and individual variation is likely to be present. In longitudinal studies, some TW appear resistant to increased body fat.

5. DISCUSSION | The data presented here demonstrates that superior skeletal and muscle metrics achieved by males at puberty, and underpinning a considerable portion of the male performance advantage over females, are not removed by the current regimen of T suppression permitting participation of transgender women in female sports categories. Rather, it appears that the male performance advantage remains substantial.

Currently, there is no consensus on an acceptable degree of residual advantage held by TW that would be tolerable in the female category of sport. Given the IOC position that fair competition is the overriding sporting objective, any residual advantage carried by TW raises obvious concerns about fair and safe competition in the numerous sports where muscle mass, strength and power are key performance determinants.

5.1 ATHLETIC STATUS | Despite the current absence of data from athletic TW, it is possible to evaluate potential outcomes in athletic TW compared with the untrained cohorts presented above. 

The first possibility is that athletic TW will experience similar reductions (approximately -5%) in muscle mass and strength as untrained TW, and will thus retain significant advantages over a comparison group of females.

A second possibility is that by virtue of greater muscle mass at baseline, pre-trained athletic TW will experience larger relative decreases in muscle mass and strength if they converge with untrained TW, particularly if training is halted during transition, although there is no rationale to expect a weaker endpoint state than untrained TW (and thus, advantage will be retained).

Finally, training before and during the period of T suppression may attenuate the expected reductions, such that decreases in muscle mass and strength will be smaller or non-existent in TW who undergo training. Multiple, well-controlled studies of males suppressing T for research purposes or during prostate cancer treatment show that even moderate resistance training can mitigate muscle and strength loss, and even permit large gains, during T suppression. Considering TW athletes who train during T suppression, it is plausible to conclude that any losses will be similar to or even smaller in magnitude than documented in the longitudinal studies described in this review.

Thus, we argue that it is implausible that athletic TW would achieve final muscle mass and strength metrics that are at par with reference females at comparable athletic level.

5.2 BEYOND MUSCLE MASS AND STRENGTH | Muscle mass is not the only contributor to strength. The importance of the nervous system for muscle activation and strength must be acknowledged. In addition, factors such as fiber types, biomechanical levers, pennation angle (how nerves and muscles join) and tendon composition may all influence muscular force. While there is currently limited information on how these factors are influenced by testosterone suppression, impact seems to be minute.

There is no research evaluating the effects of T suppression on other performance markers known to be affected by T and some of them measurably different between males and females, include visuospatial abilities, aggressiveness, coordination and flexibility.

5.3 TESTOSTERONE-BASED CRITERIA | Sports federations such as World Athletics have recently lowered the eligibility criterion of T to <5nmol/L. From the studies summarised here, it is apparent that most interventions result in almost complete suppression of T levels, certainly well below 5 nmol/L. Thus, we question whether current circulating T level can be a meaningful decisive factor, when in fact not even suppression down to around 1 nmol/L removes the skeletal and muscle mass/strength advantage in any significant way.

In terms of duration of T suppression, it may be argued that although 12 months of treatment is not sufficient to remove the male advantage, perhaps extending the time frame of suppression would generate greater parity with female metrics. However, based on the studies reviewed in here, evidence is lacking that this would diminish the male advantage to a tolerable degree. On the contrary, it appears that the loss of lean mass and grip strength is not substantially decreased at year 2 or 3 of T suppression, nor evident in cohorts after an average 8 years after transition.

From a medical-ethical point of view, we question whether a requirement to lower T to ensure sporting participation can be justified at all. If the advantage persists to a large degree, as evidence suggests, then targeting a certain T level will not achieve its objective and may drive medical practice that an individual may not want or require, without achieving its intended benefit.

Sport saves females: Fatima Whitbread

At 11 years old, Fatima Whitbread picked up a javelin. 14 years on, at the 1986 European Championship, she broke the female world record (77.44m) and won gold. A year later, she was the World Champion.

During her javelin career, Whitbread accrued 2 World Championship medals, 2 Olympic medals, 2 Commonwealth Games medals and a European Championship, one of the greatest female javelin throwers of her time and an iconic figure in female athletics.

Throughout her life, both on and off the field, Whitbread has been the personification of triumph over adversity, a female of quite extraordinary character.

As a competitor, Whitbread was no stranger to the abuse many powerful female athletes are subjected to, where misogyny, racism, and doping accusations are aimed at women who defy “white western ideals”.

“Ideal” can be, of course, somewhat subjective. As Whitbread has rather sharply and rather wonderfully pointed out: “I’m not Bo Derek and if I were, I wouldn’t have been able to throw a javelin”.

But it is her courage during her youth that is most remarkable. Her horrific early years included abandonment as a baby, a succession of children’s homes, and an abusive and violent mother who facilitated rape against her.

Bereft of love, trouble at school, child psychiatry. She is candid about her childhood and her story is not mine to tell on the limited medium of Twitter. It is, however, a childhood, nobody should ever experience.

However, during her early teenage years, she was trained (later adopted) by Mary Whitbread, and a promise to her new mother “to behave” shifted Whitbread’s path in life from lost girl to world beater.

Whitbread is not the only athlete to credit sporting ambition and success as a life-changer. Sport can save young people from child abuse, from drugs, from gangs, from eating disorders, from bullying.

Sport is a step towards the social mobility denied to so many, offering a route out of poverty and acquired societal status. For females, sport boosts self-esteem, builds confidence, hones ambition, creates leaders. In a white man’s world, sport is a pathway to equality.

Imagine if Whitbread, or any of our young girls, missed her chance because a teenage male took her coaching slot, her equipment bursary, her track time, her scholarship, her qualifying spot, her podium place.

Imagine being high schooler Chelsea Mitchell, and seeing two unadulterated males beat you easily to the finish line, the leader setting a new female state record in the process. Imagine being relegated to third place and race reports neglecting to use your name.

High school junior Selina Soule complained in the media: “We all know the outcome of the race before it even starts; it’s demoralizing.” How many girls will give up when they know they can never win?

Mitchell and Soule represent many young girls who are going to lose races, games and accolades to male athletes. I cannot consider what else may be lost for these girls.

At 11 years old, Fatima Whitbread picked up a javelin, and it changed her life immeasurably. It was, in her own words, her “saviour”. Let’s not deny other young girls that same chance.

From humans to asparagus, females are females

Many people attempt to undermine the material reality of sex by highlighting weird and wonderful examples of variation in the natural world.

“But clownfish change sex [therefore sex is not objectively defined]”

“But some animals don’t have X/Y chromosomes [therefore the human system is unreliable]”

“But some people have reproductive disorders [therefore sex doesn’t exist]”

Here is my response.


Clownfish. These fish, like many others, are sequential hermaphrodites. In the case of clownfish, a group contains one dominant female and if she is removed from the group, a male changes into a female to replace her. Sex change in clownfish occurs when the testicular tissue of the bipotential gonad is regressed and ovarian tissue promoted.  

How to recognise a female clownfish: She’s usually big. Oh, and she makes large gametes.

Anglerfish. These fish display extreme dimorphism between the sexes. The tiny males permanently fuse themselves to a female, adopting a parasitic lifestyle for the privilege of being first to contribute sperm to laid eggs.
How to recognise a female anglerfish: She is big and can be decorated with several parasitic males. Oh, and she makes large gametes.
Seahorses. Female seahorses deposit their eggs into the male brood pouch where he fertilises them. She then lounges around while the male carries and births the baby seahorses. Sounds great.
How to recognise the female: She’s big and she’s winning at life. Oh, and she makes large gametes.
Birds. Birds genetically determine sex, but using ZW, not XY, chromosomes. Males, with ZZ, are the homogametic sex and females, with ZW, determine the sex of babies. It’s not clear how ZZ triggers male development.
How to recognise the female: Like most female birds, she prefers discreet clothing. Oh, and she makes large gametes.
Crocodiles. Sex is determined by environmental temperature during the middle third of development. Male development requires intermediate temperatures, while females develop at lower or higher extremes.
How to recognise the female: Hard as nails, unlike her male counterpart, she can handle anything outside “tepid”. Oh, and she makes large gametes.
Platypuses. Platypuses have five pairs of sex chromosomes. Females have five pairs of XX and males five pairs of XY, but pairs 3 and 5 look a bit more like ZW chromosomes (see birds above) than mammalian XY chromosomes. And the way they segregate these chromosomes when they make gametes is just wild. I guess you could say they’re complicated creatures.
How to recognise the female: She’s the only furry mammal that lays eggs – this is one unique female. So obviously, she makes large gametes.
Hyena. Female spotted hyenas have a pseudo-penis which is internalised during mating and through which she gives birth. Because retraction of this pseudo-penis is controlled by the female, she is the sole arbiter of when intercourse will occur, suggesting that female spotted hyenas cannot be raped.   
How to recognise the female: She’s giving birth through a massively overgrown clitoris, what more do you want as an identifying feature? Oh, and she makes large gametes.
Lily. Like many flowering plants, lilies are simultaneous hermaphrodites. This means they contain both male and female reproductive systems in the same individual.
How to recognise the female part: it doesn’t give you hayfever and it makes large gametes.
Flatworms. More simultaneous hermaphrodites. When it comes to reproducing, individuals penis fence to determine which will take the male role. Most of the time, no-one wins and they each, perhaps dejectedly, spaff over the other.
How to recognise the female part: I can’t think of a funny comment here. It makes large gametes.
Bees. Sex in bees is determined by number of chromosome sets. Females have two pairs of 16 chromosomes (32 total) while males have a single set of 16 chromosomes. Males develop from unfertilised eggs and their only genetic material is derived from their mother. Male sperm is used to create eggs with two pairs of 16 chromosomes. This means male bees have neither a father nor sons. But he must have a grandfather and may have grandsons. 
How to recognise the female: she makes large gametes.
Asparagus. No sense of sexed self and no plausible mechanism for social construction of gender. How to recognise the female: she makes large gametes.
Tuatara. Sex determination so extremely temperature sensitive that climate change is causing them to be largely male. How to recognise the male: he makes small gametes. He can also be seen looking annoyed at enforced incel status.
Peafowl. Sexual selection gone mental. How to recognise the female: she makes large gametes. And she’s not a massive freaking showoff, like this fella…
Mushrooms. Delicious. How to recognise the female: there are no females (‘there is only Zuul’). ‘Female’ and ‘male’ are predicated on two and only two differential gametes, and fungi don’t have them thingies, settling instead for equivalent gametes labelled +/-, or A/B, or yawn.
Straw-not technically a berry-berries. Delicious hermaphrodites. Genetic sex determination is polygenic and may reasonably be described as a (limited) spectrum. How to recognise the female part: it makes large gametes.
Head lice. Annoying buggers. The female transmits chromosomes she inherited from either her mum or dad; the male *only* transmits chromosomes he inherited from his mum. How to recognise the female: she makes large gametes.

Harder, better, faster, stronger: why we must protect female sports

In 1988, at the US Olympic trials in Indianapolis, Florence Griffith Joyner romped home in the female 100m quarterfinals to set a new world record of 10.49 seconds (1). This was an astonishing moment in female sports, and not just because of her (in)famous six inch long fingernails. In an event where records usually progress by mere 100ths of a second, she smashed the existing female world record time by nearly three 10ths (the previous holder was Evelyn Ashford, running 10.76s). The world went ‘Flo Jo’ crazy as they celebrated the ‘Fastest Woman Ever’, an accolade she still holds today, some 30 years on from the event and 20 years after her death.

Flo Jo

10.49s. That 10.49 seconds stands as one of the oldest world records in athletics (2). The closest a female has ever got to it is Carmelita Jeter, with 10.64s in 2009. Marion Jones is recorded as the third fastest 100m female sprinter, with 10.65s in 1998. However, her subsequent admission to steroid use before the 2000 Sydney Olympics means this result might be taken with a pinch of performance enhancing drugs. 10.49s is a time that today’s current crop of 100m female sprinters acknowledge is beyond their reach (3). The current ‘Fastest Women in the World’, 2016 Olympic champion Elaine Thompson and 2017 World champion Tori Bowie, have personal bests of 10.70s and 10.78s respectively. Shelly-Ann Fraser-Pryce, acknowledged as the greatest female sprinter of all time – her medal haul is astonishing – ran a 10.70s personal best in 2012.

There is controversy surrounding Flo Jo’s breathtaking sprint. Firstly, the trackside anemometer measured a wind rating of zero while the equivalent instrument on the adjacent triple jump runway recorded wind speeds that would render the time null (4). Interestingly, Flo Jo had never and would never run as fast as 10.49s, even with strong tailwinds. Nonetheless, the IAAF upheld the record. Even if the run were discounted, Flo Jo would still hold the world record for her 10.61s sprint in wind-legal conditions in the final of the same Olympic trial event. Secondly, that she ran so quickly in the absence of a tailwind is a subject of debate. Although never testing positive for performance enhancing drugs, Flo Jo’s sudden peak of speed, her visible increase in muscle mass and her unexpected retirement after the International Association of Athletics Federations (IAAF) announcement that drug testing would become mandatory has, and still does, arouse(d) suspicion (5).

A note: Neither of those points is disadvantageous to this article – indeed, if this female 100m world record was achieved in wind-assisted and drug-fuelled conditions, it makes the following far bleaker a picture than is presented.

Fast women and the 10% gap. Flo Jo was fast – her average speed over the 100m world record run was 34.3kmph, faster than any female human had run before and has run since – but fast is relative. She wasn’t as fast as a female cheetah – Sarah, from Cincinnati zoo, who could run 100m in 5.95s – or as an ostrich, who might average 70kmph, but with admittedly far inferior talons (6). However, short of an extraordinary exhibition meet for which I’d hope all participants are being paid handsomely, a match against an awkward land bird is unlikely for a female 100m runner. There is a more enlightening comparison amongst our own species.

The current male 100m record holder is Usain Bolt, who ran 9.58s in 2009. The time difference between Flo Jo and Bolt is 0.91s, and the time ratio is 0.91 (9.58/10.49). This equates to a 10% performance gap between male and female world records, and is remarkably similar across track races (2; Figure 1).

Figure 1. The 10% performance gap between male and female world records in track running. Time – hours:minutes:seconds.100ths.


Faster than Flo Jo. What’s 10% between males and females? Flo Jo is around 10m behind Bolt as he crosses the finish line, but there’s always some bloke who limps home last to great cheers and many congratulations for trying – would she beat that guy? The short answer is ‘no’. The general public may have a reasonable guess at what 10m of physical distance between Usain Bolt and Flo Jo looks like, but the general public is almost certainly going to underestimate the number of males who can occupy that 10m gap.

No female has broken the 100m ’10 second barrier’, or even been close. Males, however, have a list of sub-10 seconders.  There are 136 men who have run sub-10 second 100m sprints (2, 7). One naturally wonders how populous a list of males running faster than 10.49s would be. Well, it’s a long list, too extensive to plot from 1988 onwards. But in 2017 alone, the last full season of races, 744 senior males ran 100m faster than 10.49s for a combined total of 2825 runs (2; Figure 2).

Figure 2. In 2017, 744 senior males ran 2825 100m races faster than 10.49s. 

2017 races

The qualifying time for the male 100m event at the Rio 2016 Summer Olympics was 10.16s (8). The three males who competed for the US qualified with times of 9.80s (Justin Gatlin), 9.84s (Trayvon Bromell) and 9.98s (Marvin Bracy). In the event itself, 58 males ran faster than Flo Jo. Barely making it out of the preliminary rounds, Flo Jo would have finished in the bottom three of all of the eight heats (9). Obviously, she would have required an invitational place for this event, having not qualified in the first place.

But forget 58 senior males running at Olympic level. She’s not beating 64 junior UK males who have ever run under 10.49s (10). The most well-tuned, explosive woman who ever trained her eye down a 100m track is beaten by 64 bumfluffed British juniors.

She’s also not faster than lots of males who don’t run track professionally. Marvin Bracy, the US male qualifying for Rio 2016, is an NFL wide receiver, as is Tyreek Hill (10.19s; 11). South African rugby winger Tonderai Chavhanga is faster than Flo Jo (10.27s; 12). Her top speed of 34.32kmph is slower than that of Novak Djokovic as he moves across the tennis court (36.02kmph; 13). She’s even slower than Wayne Rooney at full pelt down the footie pitch (34.47kmph; 14), and he’s made of potato.

A note: Of course, I doubt either Djokovic or Rooney could sustain that speed for 100m.

Speed demons. This 10% performance gap between males and females is not just evident in runners but in other speed events such as swimming (15), cycling (16) and rowing (17; Figure 3). It’s so reliable a gap that when I considered double checking my scribbled multiplications, perhaps with a calculator, that there were definitely 420 seconds in 7 minutes, I knew my mental arithmetic was correct when my calculations delivered a ratio around 0.9.

Figure 3. The 10% performance gap between male and female world records is evident over many speed events. Time – hours:minutes:seconds.100ths. km – kilometres.


The 10% performance gap starts to widen as we stretch our search beyond speed (although it would reasonably be argued that the events in Figure 2 have a large strength component to performance). In jumping events, the gap is around 15% (2) and in throwing events, it is 20-30+% (18-20; Figure 4).

A note: It’s difficult to compare male and female distances in throwing events in field athletics as the weights of projectiles are different between categories. This serves to minimise the gap in distance thrown and, indeed, throws (pun intended) up anomalies such as a longer female record for discus (76.80m for a female throwing a 1kg discus, compared to 74.08m for a male throwing a 2kg discus; 2).

Figure 4. A widening performance gap between males and female world records in jumping and throwing events. m – metres. kmph – kilometres per hour.


Raw strength. Thus far, a comparison of male and female athletes in speed, jumping and throwing events has demonstrated a consistent performance gap. The final event type I will consider, one relying on sheer muscular strength, provides the most clear cut difference in male and female ability.

Olympic weightlifting (this is a discipline name, rather than an event occurring at the Olympics only) comprises two lifts – the snatch (a weighted barbell is lifted from the floor to overhead in one movement) and the clean & jerk (a weighted barbell is lifted from floor to upper chest, then upper chest to overhead, in two movements).  Records are held for individual lifts and competition results are delivered as a combined total of the athlete’s best lifts in each category in a single event (21).

The weight categories in weightlifting are different for males and females but both contain a 69kg (10st12lb) category. World records within this weight category are given in Figure 5. The performance gap of 20+% should no longer be surprising to us. However, there is something slightly more nuanced to be uncovered from this weightlifting data, namely how males and females perform compared to their relative sizes.

Figure 5. Females lag 20-25% behind males in Olympic weightlifting. kg – kilograms.


A problem of scale? There is no height or weight banding in sprinting. The typical male 100m sprinter is Justin Gatlin (100m in 9.74s), at 1.85m (6’1’’) and 83kg (13st1lb). Flo Jo, at 1.7m tall (5’6’’) and 58kg (9st2lb), represents the typical female counterpart. It is tempting to consider that the performance gap between male and female sprinters (and perhaps in other sports) is one of scale i.e. if Flo Jo had been 6 inches taller, the gap between male and female sprint records would narrow or even disappear.

A note: The most successful male and female sprinters of all time, Usain Bolt (1.95m [6’5’’], 94kg [14st11lb]) and Shelley-Ann Fraser-Pryce (1.52m [5’0’’], 52kg [8st2lb)], fall far outside these typical measurements.

A comparison of our 69kg Olympic weightlifting record holders suggests differently (Figure 6). Liao Hui (male; 166/198/359kg) and Oksana Slivenko (female; 123/156/276kg) were, at the time of their record breaking lifts, two people of the same weight and about an inch different in height. Hui outlifts Slivenko by 43kg in the snatch and 42kg in the clean & jerk, for a total of 85kg greater combined. 85kg is 13st5lb, about the weight of a typical male 100m sprinter, and over 30% of the female combined lift weight. Even when body size is approximately equivalent, females are not close to male strength.

The strongest female in the world. So, the 69kg male weightlifter hammers the 69kg female weightlifter on strength. Where are the females who are stronger than Hui? How tall and heavy are they? The answer is, in Olympic weightlifting, they don’t exist. Holding the records in the heaviest female weight category (+90kg) is Tatiana Kashirina, with 155/193/348kg (Figure 6). You’ve read that correctly. The male record holder for the 69kg category can outlift the female record holder in the top category, a female who has a 4 inch height advantage and over 6 stone of weight on him, a female who might reasonably be described as the strongest woman in the world. Clearly, the strength performance gap between males and females is not one of scale.

Kashirina would beat the male records in the 56kg (139/171/307kg) and 62kg (154/183/333kg) categories (21). Chen Lijun holds the clean & jerk and combined records at 62kg; he’s 1.62cm (5’4’’). So the strongest woman in the world has a shot against males who are 46kg (7st3lb) lighter and at least six inches shorter than her. She’s only lifting 13% more than the male record holder in a weight category almost half her bodyweight.

Figure 6. The male 69kg Olympic weightlifting world record holder is 30% stronger than his female counterpart and lifts heavier than the female world record holder in the top weight category. kg – kilograms. *All lifts are world records except Slivenko’s clean & jerk, where the record is Zarema Kasayeva’s 157kg.

lifting figures

Male puberty and testosterone. Testosterone, the androgen driving male physical development, is a wonderful hormone. It is responsible for advantageous skeletal features that develop during male puberty, such as increased height, increased bone size and density, longer limbs, wider hand spans and a narrower pelvis, all of which make a 100m sprint or a slam dunk far easier. It also directs hugely increased muscle building capacity, allowing higher absolute masses to be achieved in shorter training times, mass which, by the way, contains a higher proportion of fast twitch fibres (responsible for explosive power) than observed in female muscles. To support this superior physicality, males have greater lung capacity, a higher VO2 max (the amount of oxygen consumed during high intensity exercise), a bigger heart with faster stroke rate and higher levels of haemoglobin, and thus can oxygenate their muscles more efficiently.

Analysis of adult/senior female sporting performances demonstrate parity with males around the age of 15 years old for individual events, and perhaps younger in team sports. It’s no surprise that adult female athletes are outrun, outjumped, out thrown and outlifted when males get that all-important surge of testosterone that will propel their development into superior athletes. Testosterone-driven puberty has delivered us athletes like Usain Bolt, Sébastien Chabal and Anthony Joshua. As the original anabolic steroid (prior to steroids, performance enhancing drugs were stimulant or analgesic in nature), and used widely in the 1980s in state-led doping programmes, it has almost certainly delivered us a fair few elite females too.

Sex-segregation is necessary for female achievement. Female athletes are awesome creatures, pushing their bodies to ever further extremes in pursuit of sporting glory. Female sport is still largely overlooked in favour of its male equivalent, but the drive is there to increase participation in early years, to improve media coverage, to reward outstanding females with the fame, victory medals and, depending on the sport, prize money they deserve for being the best at what they do.

But males are harder. Males are better (at sports, at least). Males are faster. Males are stronger. The performance gap between male and female athletes is utterly astounding; it’s not a “gap”, it’s the Grand Canyon. Without sex-segregated sporting categories, the most wonderful 10.49s that female athletics has ever seen would be a footnote in history. We owe it to the female sports stars of today and to the girls who aspire to be tomorrow’s sporting heroes to fight for their right to take home gold.

  21. records