Save female sports evidence thread

[Helleofabore]

I am conscious that the Break it Down for me thread is nearly full. I am therefore hoping that this thread can be an archive thread just for the sports evidence that we can all access and refer to. Now that MNHQ has given us the option for saving threads so we can find them easily, I figure it is a good time.

Please post studies, papers, media articles that pull together references, or informative articles, tweets, videos. Just on sport, the latest policies around sport.

I don't want to be the thread police, but ask that we keep this free of discussion. Can I ask that if you want to discuss something you see here, you start a thread to do so?

Because I would like this to be just information stashed so that people can find the links easily so they also know where to start. And getting into discussion on this thread will mean it will fill up.

Thanks.

A video reminder from ICONS

SEX DIFFERENCES IN DISC GOLF EVEN FROM AGE 10

Sex Differences in Disc Golf Performance: Implications for Eligibility Criteria for Women's Competitions

Tommy R. Lundberg & Justin Menickelli

25th July 2025

https://onlinelibrary.wiley.com/doi/10.1002/ejsc.70008

Summary

Marked sex differences in disc golf performance were observed, with males significantly outperforming females in player rating, throwing distance, and accuracy at both professional and amateur levels.

The differences in performance were evident from a young age, with boys performing better than girls in the junior divisions from the age of 10.

This study provides data that can inform policy decisions on eligibility criteria for women's disc golf competitions.

Conclusions
We report significant sex differences in disc golf performance, with males outperforming females in player rating and throwing distance at both professional and amateur levels. Differences in throwing accuracy and putting consistency (fairway hits and circle 1X putting) are smaller but still considerable, and large sex differences are observed in preadolescent juniors. These differences are likely explained by male advantages in muscle size, stature, arm span, and fiber type composition. Consequently, disc golf organizations are faced with the task of formulating eligibility criteria for women's competitions, considering the tension between inclusion of athletes in female sport based on gender identity and maintaining fairness in competition. This may ultimately require a conscious choice between these two objectives, as it seems that fair competition may not be reconciled with either self-identification or testosterone suppression. Thus, if fairness is the primary objective, the current results suggest that the women category should be for females only.

IS INCLUSIVE ALWAYS ‘INCLUSIVE’

A good explainer from Jon Pike.

https://x.com/sportseenuk/status/1978358073887502530?s=46

Jon points out that there is no pressure at all on Paralympic Events to make them inclusive to able bodied people and people would be rightly uncomfortable with pressure to include able bodied people who have limited their abilities in Paralympic events.

He poses the question why female events have been singled out to allow a group of male people who have limited their abilities to access the protected events for female athletes.

DIFFERENCE IN HANDGRIP STRENGTH NOTED EVEN BEFORE PUBERTY

Interesting research and important when discussing inclusion of male athletes who have not experienced male puberty / androgenisation in female sports.

https://onlinelibrary.wiley.com/doi/10.1002/ajhb.70155

When and Why Do Sex Differences in Handgrip Strength Emerge? Age-Varying Effects of Testosterone From Childhood to Older Adulthood

Jun Seob Song, Heontae Kim, Myungjin Jung

First published: 06 October 2025

ABSTRACT
Objectives : On average, males are stronger than females, with hormonal changes during puberty often cited as a contributing factor to this advantage. However, not all evidence consistently supports this explanation. The purpose of this study was to determine (1) when sex differences in handgrip strength and testosterone emerge, and (2) whether testosterone mediates the sex difference in handgrip strength and if this effect varies across age.

Methods : Time-varying effect modeling (TVEM) was used to examine age-specific trajectories of handgrip strength and testosterone, and to assess whether these trajectories differed by sex. A moderated mediation analysis was conducted to test whether the sex difference in handgrip strength was mediated by testosterone level, and whether this effect varied across age. Data were drawn from the 2011–2012 and 2013–2014 cycles (N = 11,035) of the National Health and Nutrition Examination Survey.

Results : TVEM indicated that the sex difference in handgrip strength emerged at age 8, whereas the sex difference in testosterone level became evident at age 10. A moderated mediation analysis revealed that testosterone mediated the association between sex and handgrip strength, and this effect decreased with age (IMM = −0.18, 95% CI: −0.20, −0.16).

Conclusion : Sex difference in handgrip strength appears to be driven, in part, by the testosterone levels. However, this difference can be observed even before the onset of puberty, which suggests that testosterone alone does not fully explain the sex difference in muscle strength. This finding may have important implications for decisions regarding inclusivity and fairness in sports that emphasize strength.

TRANSWOMEN ARE DISADVANTAGED BECAUSE AFTER TREATMENT THEY ARE UNDERPOWERED

A thread by Dr Emma Hilton. 1:25 PM · Nov 4, 2025

The claim that won't die: trans-identifying males are "underpowered" and therefore "disadvantaged" in sport.

"One can imagine a large car with a small engine competing against a small car with a small engine, and that summarizes the playing field." Joanna Harper, Huff Post, 2016.

"You have a bigger body, and you have a smaller engine to move that vehicle around." Yannis Pitsiladis, BBC, 2019.

"giving trans women the disadvantage of having to power larger skeletal frames with reduced strength and aerobic capacity." Jamie Agapoff, 2025.

What happens when a trans-identifying male suppresses testosterone? They lose a bit of muscle mass. Their haemoglobin drops to female-typical levels. The claim that won't die rests on the idea that trans-identifying males retain their skeletal frame and most of their muscle mass, but become unable to move it around a sports fields, rendering them "disadvantaged".

The words "underpowered" and therefore "disadvantaged" are carefully chosen, and typically leave the reader to infer that this means "underpowered" and therefore "disadvantaged" compared to females. So it's fair to have them in female sport, right?

Wrong.

When a given trans-identifying male loses some muscle mass and some oxygen-carrying capacity - and assuming he doesn't counter by increasing training load - he will indeed feel it more of a struggle to transport his male body around. His relative performance (whether that's relative strength or whatever) will decrease. So per kg of bodyweight, his deadlift gets worse.

But that doesn't make him "underpowered" and therefore "disadvantaged" compared to females. It makes him "lower powered" and therefore "disadvantaged" compared to his former performance.

What would have to happen to make a trans-identifying male genuinely "underpowered" compared to females. Let's take a female of the same skeletal size/shape and activity. She carries X amount of muscle mass to shift her body around.

To become "underpowered", T suppression would not simply have to reduce muscle mass in the trans-identifying male to female levels (and it doesn't anyway), it would have to 'overshoot' female levels. That is, he would need to end up with lower muscle mass than his female peer to become "underpowered" compared to her.

There is simply no reason to argue this is plausible. There is no particular biological mechanism that would support his final muscle mass being lower than a female comparator. And the estrogen he takes likely protects his existing muscle mass anyway.

The same argument applies to hemoglobin, although here, the trans-identifying male does meet female levels. Well, Hb isn't the only contributor to CV capacity (stroke volume, blood volume, lung surface etc). But even it was, it wouldn't make him "underpowered" compared to his female comparator.

Beware the tricksy words used in the claim that won't die. Trans-identifying males might have lesser relative power than they used to possess. But the disadvantage is against their former self, not compared to females.

https://x.com/FondOfBeetles/status/1985700002576957445

THE OLYMPIC TIMELINE ON THE INCLUSION OF MALE PEOPLE IN FEMALE SPORT (AWAITING IOC CONFIRMATION IN WINTER 2026)

Just to recap how we got here in my opinion

1992 - Dr. Arne Ljungqvist becomes a member of the IOC and continue to date an educational program to inform the IOC about scientific and
ethical issues related to laboratory-based gender verification.

1996 - Most major professional medical societies have passed resolutions against chromosome-based gender screening in sports.

1996-1997 - IOC World Congress on Woman and Sport passes a resolution to abandon gender verification at the Olympics. Women's Sports Foundation
publishes a policy statement against blanket chromosome screening in support of IAAF model. The Norwegian parliament outlaws gender verification in sport. The IOC Medical Commission is unconvinced and the Atlanta Committee for the Olympic Games is contractually committed to on-site, laboratory-based, gender veritication of all female althletes competing in women's events.

1997-1998 - Arguments for and against change are presented to the IOC Athlete Commission by Professor A. Liungqvist and Dr. B. Dingeon, respectively. Prince de Merode and Dr. Hay argue for their original policy of blanket gender verification at IOC-sponsored sporting events. Athletes Commission nonetheless calls for the discontinuation of the present system and rccommenda replacing it with a "reserve clause" system based on IOC Medical Commission intervention on an individualized basis, following scientific and ethical guidelines.

1999 - IOC Executive Board accepts unanimous recommendations of its Athletes Commission. Blanket gender verification screening of all female
athletes will not be conducted at the 2000 Millennia1 Games in Sydney, on a conditional basis for later review.

Importantly, for the 1996 Atlanta Olympics they surveyed the female athletes and found:

"At the time of testing, all female athletes at the Atlanta Games were offered a questionnaire written in both English and French asking whether in their view testing of females should be continued in future Olympics and whether or not
they were made anxious by the testing procedure. Of the 928 athletes who responded, 82% felt that testing should be continued and 94% indicated that they were not made anxious by the procedure. Forty-six athletes were made "anxious" by the testing requirements that preceded their competitive events.

No males were found to masquerade as females, and all females who were found to be SRY positive competed."

"Of the 928 athletes who responded, 82% felt that testing should be continued"

www.nature.com/articles/gim2000258.pdf?origin=ppub&utm_medium=affiliate&utm_source=commission_junction&utm_campaign=CONR_PF018_ECOM_GL_PHSS_ALWYS_DEEPLINK&utm_content=textlink&utm_term=PID100045542&CJEVENT=f4d4c8630a0411ed831b01a80a1c0e11

2003 - Stockholm Consensus proposal

"In 2003, the International Olympic Committee (IOC) Medical Commission, claiming guidance from “the best information available at the time,” decided to allow male transsexuals to compete in the women’s category. This decision was contingent upon several conditions to ensure fairness: a) the removal of their testes at least two years prior to competition; b) legal recognition as “female”; and c) hormone profiles aligned with those of natal females."

archive.today/F5HFc

2004 - May 2004 they announce that they will allowed male people who surgically removed their testes to compete in female competition. Because once you allow one group of male people in, you must equally allow the other in or you are discriminating against transgender people.

https://olympics.com/ioc/news/ioc-approves-consensus-with-regard-to-athletes-who-have-changed-sex-1

2015 -Then in 2015, a campaign group including Harper, using Harper’s flawed study (see nequals8.com web site) convinces the IOC that it is unfair discrimination to exclude any male with a transgender identity describing themselves as a woman. The IOC changes the policy to allow them.

https://nequals8.com

^https://cgscholar.com/bookstore/works/race-times-for-transgender-athletes^

https://stillmed.olympic.org/Documents/Commissions_PDFfiles/Medical_commission/2015-11_ioc_consensus_meeting_on_sex_reassignment_and_hyperandrogenism-en.pdf

2016 -Then came the Rio trio in the female 800m and we start to see the testosterone suppression of the male people with DSDs come in. Semenya takes this to court in 2019. Appealed 2020. The evidence presented confirmed 5ARD and testosterone of 21 nmol/L.

2021 - 2020 Tokyo games held in 2021 was the testosterone suppressed games. Hubbard, a late 40 something male in female event where next youngest was probably a decade and a half younger, shines light on the issue.

https://www.theguardian.com/sport/2021/jul/29/ioc-praises-weightlifter-laurel-hubbard-ahead-of-transgender-athletes-olympic-debut

The IOC reacts by announcing a review.

The new guidelines released Nov 2021 devolve responsibility for policy to each discipline’s international federation. ie. They force the sporting federations to make the hard decisions that the IOC refuse to make.

https://stillmed.olympics.com/media/Documents/Beyond-the-Games/Human-Rights/IOC-Framework-Fairness-Inclusion-Non-discrimination-2021.pdf#_ga=2.219716894.621299853.1686571450-594927581.1678187184

They also reaffirm that 'inclusivity' is their over all priority. They say that safety is as well, but this is clearly contradictory when you consider boxing as an example.

The IOC is clear that they RECOGNISE that the inclusion of male athletes will be UNFAIR but their priority is inclusion. Richard Budgett said this.

The federations then develop their own policies. that have done this are : FINA, WA, UCI, IBA and WR. FIFA for instance announced a review years ago and done nothing. IBA announced their new policy in 22/23.

The WA have even stated that their new guidelines for the Olympics immediately excluded 13 males with DSDs with testosterone advantage from the competitions until those 13 male athletes chose to reduce their testosterone to 2.5 nmol/L for 2 years. 13 just in athletics competitions alone! (By the way, this reduction has already been shown to not eliminate unfair male advantage, but this is where we are at the moment.)

By the IOC removing the IBA from organising the boxing, the IOC left boxing only with the IOC inclusive guidelines.

So, we know from the announcement by Budgett from IOC in November 2021 that fairness was a lower priority to inclusion. It was along the lines of ‘we know it is unfair to include male people with pubertal advantage, but inclusion is our aim.’

And the IOC and other organisations still claim that Semenya is a 'female with naturally high testosterone' to this day. Despite the world being easily able to find the evidence presented to the CAS that Semenya is MALE with 5-ARD and had tested with a testosterone level of 21nmol/L. NO female has that level and is healthy. They are likely to be gravely ill.

2025 - Kirsty Coventry announces that she will 'protect' women's sport and that a committee will review the evidence.

10th November news has started to filter out that the IOC will exclude all male people

'The International Olympic Committee is set to announce a ban on transgender women in female competition early next year after a science-based review of evidence about permanent physical advantages of being born male.

The IOC’s guidance to Olympic sports has until now been that transgender women can compete with reduced testosterone levels but leaves it up to individual sports to decide. That is now set to change under its new president, Kirsty Coventry, who has promised to protect the female category.

The committee’s medical and scientific director, Dr Jane Thornton, last week presented to IOC members at a meeting in Lausanne the initial findings of a science-based review into the issues of transgender athletes and athletes with differences of sexual development (DSD) competing in female sport."

and

"It is understood the IOC is likely to announce its new policy early in the new year, possibly around the IOC session at the Milan-Cortina winter Olympics in early February.

Some work remains to be done to ensure the new policy is legally watertight. Until now the IOC’s policy has been based on recommendations and guidance to sports rather than actually being part of its eligibility rules."

and

“The new policy is also likely to cover DSD (differences of sex development) athletes — those who were raised as girls from birth but have male chromosomes and male levels of testosterone.”

https://archive.ph/kGpyI for the Times article above.

http://archive.today/TNLMM for the Telegraph article

https://x.com/mara_yamauchi/status/1988217357043724386?s=20

Some very clear points mentioned:

Mara says, "I'm here with a lot of my fellow sex realists. We are quietly protesting against parkrun's gender self ID categories. Any male if he says he's a woman or even if he doesn't say he's a woman, any male is welcome in the female category."

"Official results are published every week in descending order of speed. The rankings mean in reality it is a race and that is unfair for women and girls."

And then

"You can call it anything you like, but the facts of Parkrun are, measured courses, start and finish line."

Other brave women also keep raising the valid points such as:

"it's a race if you run it like a race"

and

"That opportunity to treat it like a race should be there for everybody because it is there for men"

We have had this discussion on MN numerous times now where people remind us that Parkrun have stated that they are 'not a race' and are not competitive events. However, if there is any ranking at all, and any records kept and/or published, this makes the events a competitive regardless of the denial by Parkrun.

This is a protest to highlight the clear discrepancy between what Parkrun say and what they do.

CHILDREN’s MUSCLE STRENGTH DIFFERENCES DUE TO SEX

Sex Differences in Upper- and Lower-Limb Muscle Strength in Children and Adolescents: A Meta-Analysis

James L. Nuzzo, April 2025

ABSTRACT

On average, adult men are physically stronger than adult women. The magnitude of this difference depends on the muscle tested, with larger sex differences observed in upper- than lower-limb muscles. Whether body region-specific sex differences in strength exist in children is unclear. The purpose of the current meta-analysis was to determine whether sex differences in muscle strength in children and adolescents differ between upper- and lower-limb muscles. Data were extracted from studies of participants aged ≤ 17 years who completed tests of maximal isometric or isokinetic strength of upper-limb muscles (e.g., elbow flexors and elbow extensors) or lower-limb muscles (e.g., knee extensors and ankle dorsiflexors). Participants were partitioned into three age groups: 5–10 years old, 11–13 years old, and 14–17 years old. The analysis included 299 effects from 34 studies. The total sample was 6634 (3497 boys and 3137 girls). Effect sizes of sex differences in upper- and lower-limb strength were g = 0.65 (95% confidence intervals (CI) [0.46, 0.84]) and 0.34 (95% CI [0.19, 0.50]) in 5–10-year-olds; g = 0.73 (95% CI [0.56, 0.91]) and 0.43 (95% CI [0.27, 0.59]) in 11–13-year olds; and g = 1.84 (95% CI [1.64, 2.03]) and 1.18 (95% CI [1.00, 1.37]) in 14–17-year-olds. Upper- and lower-limb strength were 17% and 8% greater in boys than girls when 5–10 years old, 18% and 10% greater when 11–13 years old, and 50% and 30% greater when 14–17 years old. Thus, boys are stronger than girls on average. This sex difference exists before puberty, increases markedly with male puberty, and is more pronounced in upper- than lower-limb muscles throughout development.

Summary

-Before, during, and after puberty, boys are stronger than girls on average.

-The sex difference in muscle strength increases markedly with male puberty, averaging ∼10% in 5–10-year-olds and then ∼40% in 14–17-year-olds.

-Throughout development, sex differences in strength are more pronounced in upper- than lower-limb muscles.

Conclusion

Muscle strength is greater in boys than girls before, during, and after puberty, though the presence of this sex difference is more certain after puberty. At all stages of development, the difference is greater in upper- than lower-limb muscles. Between 5 and 13 years old, boys have, on average, 17%–18% greater upper-limb strength than girls and 8%–10% greater lower-limb strength. Male puberty causes the sex difference in muscle strength to increase dramatically, such that, between the ages of 14–17 years, boys have, on average, 50% greater upper-limb strength than girls and 30% greater lower-limb strength. Sex differences in body height, body mass, and body composition are the likely causes of greater muscle strength in boys than girls throughout development.

Trans table tennis players to be banned from competing against biological females after landmark Supreme Court ruling | Daily Mail Online

ANOTHER EXAMPLE OF HOW A FEW CAN NEGATIVELY IMPACT MANY

Tweet from Mara Yamauchi on 13th December 2025

x.com/mara_yamauchi/status/1999910910782222623?s=46

“At least 11 males ran in the Female category in UK parkrun today.

Two ran at the same parkrun. One got 7th Female so nearly the entire female field got bumped down, of whom 13 women got bumped down 2 places.

Of these 11 men, at least 7 have broken UKA rules by racing in the Female category in licensed events (one has broken the rules at least 8 times & uses the slogan “F* UK Athletics”). One of them is this man - “F* JK Rowling”. 👇

Between them, these 11 men bumped down >1000 females.”

MALE CHILDREN HAVE GREATER GRIP STRENGTH FROM BIRTH

https://onlinelibrary.wiley.com/doi/full/10.1002/ejsc.12268

Sex Differences in Grip Strength From Birth to Age 16: A Meta-Analysis
James Nuzzo, published 15 February 2025

ABSTRACT

In 1985, Thomas and French published results of a meta-analysis that examined sex differences in grip strength in children 5 years of age and older. Their analysis included results from only four studies, and no update has been published. The purpose of the current study was to use meta-analysis to examine sex differences in grip strength from birth to age 16. The analysis included 808 effects from 169 studies conducted in 45 countries between 1961 and 2023. The total sample was 353,676 (178,588 boys, 175,088 girls). From birth to 16 years of age, grip strength was consistently greater in boys than girls. Between 3 and 10 years old, the effect size was small-to-moderate, with female grip strength equaling 90% of male grip strength (Hedges g = 0.33–0.46). At age 11, the effect size decreased slightly, likely due to girls reaching puberty before boys (g = 0.29, 95% confidence intervals (CI) [0.22, 0.35]). At age 13, the effect size increased markedly likely due to male puberty (g = 0.63, 95% CIs [0.55, 0.70]). By age 16, the sex difference in grip strength was substantial, with female grip strength equaling 65% of male grip strength (g = 2.07, 95% CIs [1.86, 2.27]). Secondary analyses revealed that the sex difference in grip strength is broadly similar between countries and has been mostly stable since the 1960s, except for a narrowing of the difference among 5–10-year-olds after 2010. Various biological factors explain why, on average, boys are stronger than girls from birth onward.

Summary

On average, boys have greater grip strength than girls from birth onward.

Girls' grip strength is ∼90% of boys' grip strength up to about age 12 and ∼65% by age 16.

Sex differences in childhood and adolescent grip strength are broadly similar between countries and have been mostly stable since the 1960s.

Conclusion

Boys have greater grip strength than girls from birth onward. Prior to age 11, the sex difference in grip strength is small-to-moderate in size, with female grip strength about 90% of male grip strength. At age 11, the sex difference in grip strength decreases because girls reach puberty earlier than boys. Nevertheless, boys still retain a strength advantage at age 11. After male puberty, the size of the sex difference in grip strength increases markedly. At age 16, female grip strength is 65% of male grip strength. With a few exceptions, the observed effect sizes have been largely consistent across time and place. Together, with other findings from the biological and medical literature, the current results suggest a largely biological origin of the sex difference in grip strength in children and adolescents.

Here is a video with Dr Mike Joyner going through male sex advantages in sports.

Thanks for the video, which will be my evening viewing today!

SUMMARY OF MALE ADVANTAGE MIKE JOYNER ET AL

https://journals.physiology.org/doi/full/10.1152/japplphysiol.00615.2024

published January 2025

Authors: Michael J. Joyner, Sandra K. Hunter and Jonathon W. Senefeld

Evidence on sex differences in sports performance

Abstract
Sex differences in sports performances continue to attract considerable scientific and public attention, driven in part by high profile cases of: 1) biological male (XY) athletes who seek to compete in the female category after gender transition, and 2) XY athletes with medical syndromes collectively known as disorders or differences of sex development (DSDs). In this perspective, we highlight scientific evidence that informs eligibility criteria and applicable regulations for sex categories in sports. There are profound sex differences in human performance in athletic events determined by strength, speed, power, endurance, and body size such that males outperform females. These sex differences in athletic performance exist before puberty and increase dramatically as puberty progresses. The profound sex differences in sports performance are primarily attributable to the direct and indirect effects of sex-steroid hormones and provide a compelling framework to consider for policy decisions to safeguard fairness and inclusion in sports.

Statement 1: Biological Males as a Group Outperform Biological Females in Athletic Events Dependent on Strength, Speed, Power, and Endurance

Statement 2: The Male-Female Performance Gap Is Evident before Puberty

Statement 3: The Male-Female Performance Gap Increases after the Onset of Puberty and Is Associated with Changes in Body Structure, Physiology, and Function

Statement 4: The Principal Driver of the Increased Male-Female Performance Gap in Adults Is the Surge in Endogenous Testosterone among Biological Males Starting during Puberty

Statement 5: Changes in the Female Body during Puberty and Female Physiology throughout an Athletic Career Can Contribute to the Male-Female Performance Gap by Limiting Training, Performance, and Muscle Regeneration after Injury or Detraining among Females

Statement 6: Endogenous Testosterone Suppression among XY Athletes Who Have Experienced Masculinizing Puberty, Modestly Reduces Athletic Performance, but a Large Male-Female Performance Gap Remains

Statement 7: When Biological Females (XX) Use Exogenous Testosterone after Puberty (e.g., “Doping”) and Train for Sports, Their Performance Is Enhanced but the Male-Female Performance Gap Does Not Close

SUMMARY
There are profound sex differences in human performance in athletic events determined by strength, speed, power, endurance, and body size such that males outperform females. These sex differences in athletic performance exist before puberty and increase dramatically as puberty progresses. The sex differences are markedly greater in magnitude (10%–40%) than the advantages that policy-making bodies seek to eliminate when they regulate equipment or drugs that could enhance performance. As one example, World Athletics amended regulations on shoe manufacturing after advanced footwear technology was linked to a 1%–2% performance advantage relative to other racing footwear. Regulation of sports technology and potential performance-enhancing drugs is typically based on an evidence base that is general in nature and based on plausibility, mechanism of action, and real-world data as opposed to RCTs. In this context, exogenous androgens administered to female (XX biology) athletes improve performance but do not close the male-female performance gap and do not eliminate the male advantage. Testosterone suppression among male (XY biology) athletes who have undergone male puberty reduces performance but much of the male advantage is retained, including: 1) muscle strength, power, and size, 2) maximal aerobic capacity, and 3) other potentially performance-enhancing attributes such as height and limb length. This evidence summary may provide a useful framework to understand claims about the nature and extent of the evidence that supports existing eligibility guidelines and to consider the merits of reforms that would govern the classification of transgender athletes and athletes with certain DSDs in competitive sports. Both the magnitude and duration of the influence of testosterone and puberty on sports performance should be recognized with appropriate consideration.

HANDELSMAN STUDY ON PRE-PUBERTAL DIFFERENCES

A study pointing out that it could be effects from the mini puberty as an infant and/or muscle memory differences between male and female children.

The ontogeny of sex differences in exercise performance

https://academic.oup.com/jes/article/10/4/bvag042/8500320?login=false#google_vignette

David Handelsman and Grant Tomkinson

April 2026

Abstract
Sex differences in adult athletic performance are driven by the 20-to 30-fold increase in testosterone production of male puberty creating larger and stronger muscle, bone and cardiorespiratory functions, and higher hemoglobin creating male physical advantages in power sports, where strength, speed, or endurance determine success. Before puberty, boys also surpass girls in age-group records despite no difference in circulating testosterone over the decade from minipuberty to puberty. However, the relative magnitude of the prepubertal, relative to pubertal, sex differences in exercise performance remain uncertain. To investigate the magnitude of these differences in a unitary dataset, this was a secondary analysis of a exercise performance of 85 347 healthy 9- to 17-year-old Australian schoolchildren between 1985 to 2009. Boys surpassed girls in 8 of 9 exercises excepting 1, a stretching exercise, in which girls surpassed boys. For each exercise the magnitude of the pubertal changes were much larger than those of prepubertal differences. These findings in normative tests extend previous studies of competitive age records of prepubertal children and compare the same tests over the pubertal transition. These findings confirm that the quantitatively dominant sex differences in exercise performance are those of puberty. That at least 1 prepubertal exercise test is dominated by girls indicates that the prepubertal differences are more likely to be biological rather than sociological, related to boy's greater habitual play or exercise. It is postulated that these prepubertal sex differences may arise from the combination of androgen imprinting during minipuberty propagated by muscle memory.

Discussion

The present findings are consistent with the evidence of sex-related differences in prepubertal children as assessed from age group records in athletics and swimming competitions [6, 7, 16-22]. These sex differences are likely due to the combination of androgen imprinting during male minipuberty plus the effects of muscle memory.
Male minipuberty involves sustained exposure to elevated circulating testosterone concentrations for the first 6 months of neonatal life in boys, but not girls [12]. These reach transiently for a few months adult male concentrations [29-31] sufficient to invoke androgenic effects. This is manifest in androgen-dependent sex differences in testis [32-35], penile [36] and somatic [37] growth as well as muscle mass and strength [38, 39]. Furthermore, neonatal testosterone exposure dictates the sexual dimorphism in patterns of pulsatile GH secretion, which in turn determines highly specific sex-specific expression of hepatic cytochrome P450 metabolizing enzymes and other enzymes including steroid 5α reductase type 2 [40-45]. In addition to the androgen imprinting of male minipuberty, the present findings may also be due to muscle memory. That is a mechanism proven experimentally in rodents whereby initial muscle stimuli (exercise, androgens) primes the muscle cells so that subsequent stimuli trigger a greater muscular force response starting from a higher baseline [46]. This mechanism reflects stimulus-induced fusion of muscle stem (satellite) cells with multinucleate myofibers, thereby increasing the numbers of myonuclei which then remain after the initial stimulus ceases. This creates a higher latent starting point for response to a renewed stimulus [25]. Although this mechanism remains difficult to prove in humans and further research is needed, if it prevails in humans then the androgen imprinting in male minipuberty may prime muscles to a stronger response to the future stimuli such as the dramatic rise in circulating testosterone of male puberty [47]. In concert, these 2 features may explain the finding that boys exercise performance generally surpasses that of age-matched prepubertal girls [16-22, 48].

Although late gestational effects of high testosterone exposure in girls with congenital adrenal hyperplasia have lasting neurobehavioral effects into postnatal life such as increased male-typical preferences for play and sexuality [49], it is not known if those late gestational effects influence the same androgen-sensitive features of male minipuberty.

The Y chromosome has the evolutionarily specialized role for male sex determination, achieved by its expressing the SRY gene, the single master gene necessary and sufficient to induce testis development [50]. SRY gene expression dictates male genetic and phenotypic sex signifying that a testis is, or likely will be, present, which is then capable of synthesizing and secreting testosterone to achieve adult male testosterone concentrations and, subject to normal androgen sensitivity, will achieve the physical advantages of male puberty for exercise. The other Y chromosome genes, fewer than 40, are involved in cellular housekeeping and not reproductive roles [51], and none has any role in exercise performance [1, 4].

The differences observed in this study are based on calendar age group data as objectively determined from the date of birth recorded in birth certificates. However, the substantial variability among individuals and ethnicities in the age and tempo of puberty may create anomalies when findings are based on the extremes of individual record performance. The performances of those with earlier onset and faster progression of puberty and growth toward adult body dimensions may have a physical performance advantage during childhood and adolescence. To partially overcome this potential extremity bias of the individual record holders, sex- and age-specific records of the top 10 and top 100 performances have been examined with concordant findings [6, 18-22]. Such findings are consistent with the findings of the present study, which bring more of a community focus and show that for most, but not all exercises, prepubertal boys typically outperform age-matched girls in study cohorts that are broadly population-representative.

The present findings are also consistent with other reports of prepubertal sex differences in exercise performance with boys outperforming girls on most, but not all, exercises [6, 7, 16-22]. A notable finding in the present study is that at least for 1 exercise test—the sit-and-reach test of flexibility—girls outperformed boys at every age with the gap larger after puberty. Similar findings of girls' superiority in flexibility have been reported elsewhere [52, 53]. These findings cast doubt on the hypothesis that the sex-related differences before puberty are due to boys having greater habitual physical activity levels (eg, recreational sports participation) [54, 55]. Instead, these collective findings argue for a biological basis for the sex-related differences in exercise performance during childhood and adolescence rather than behavioral or psychosocial causes.

There is a well-established basis for the binary sex classification for fairness and safety in adult elite sports based on physical advantages arising from male puberty [1, 4]. Nevertheless, the need for a binary sex classification is not evident or necessary in sports or events where physicality is not crucial to success (eg, board sports, target shooting). Nor is sex classification required in recreational, community, and junior (<12 years old) sports like in soccer, where mixed sex competitions already exist. However, future elite athletes often start competing at an early age so that competitive underage events, where times or distances are recorded, or where girls are at greater risk of injury competing against boys may require adult sex categories for fairness and/or safety.

The present findings reinforce other recent findings [6, 7, 16-22], indicating that there is a physical performance advantage for boys in most, but not all, exercise disciplines before puberty. Hence, whether this requires sex-selective sporting events in childhood depends on the importance of the outcome to the competitors. If children are seriously competing for medals, podium places, or team inclusion, then sex-specific events are required depending on the sports discipline involved. Where the outcomes are not critical, such as in recreational or communal sports events or where the noncompetitive social and physical activity rationales predominate, then sex-specific events may not be useful or warranted.

This study has strengths in that it used large, general, and broadly representative samples of apparently healthy children of known age and sex who were tested using widely known, feasible, scalable, standardized exercise performance tests. It is limited in that performance testing was not overtly competitive between individuals so that it may not be directly comparable with formal competitive athletic performances in childhood analyses of world or national age-group records are probably biased toward the early maturing children when based on world or national age-group records. Additionally, the physical impact of male puberty is not finalized by the age of 17 years so the magnitude of the pubertal effect on exercises may be underestimated.

@Helleofabore I so appreciate this thread - so good to have all this evidence neatly in one place. Thank you.

SEX DIFFERENCES IN MUSCLE STRENGTH RELATIVE TO BODY MASS: A META-ANALYSIS

James Nuzzo & Matheus Pinto in pre-print March 2026

https://sportrxiv.org/index.php/server/preprint/view/777/version/970

pdf version: https://sportrxiv.org/index.php/server/preprint/view/777/1674

ABSTRACT

On average, human males have greater body masses and generate more muscle force than human females, and body mass and muscle strength correlate. Normalizing muscle strength to body mass (strength-to-body mass ratio) might mathematically eliminate the sex difference in strength, but this has not been examined on a large scale. Here, we conducted a meta-analysis to determine if a sex difference exists in the strength-to-body mass ratio. We identified 78 studies that reported a total 352 effects comparing mean strength-to-body mass ratios in males and females. The total sample was 122,434 (61,042 males, 61,392 females). Grip strength was the most common test (21.9% of effects). The strength-to-body mass ratio was 25% greater in males than females (response ratio = 1.25 (95% prediction intervals (PI) [0.93, 1.67]). The strength-to-body mass ratio was 17% greater in males than females for lower-limb muscles (response ratio = 1.17 (95% PI [0.87, 1.59]) and 35% greater for upper-limb muscles (response ratio = 1.35 (95% PI [0.87, 1.60]). The strength-to-body mass ratio was 3% greater in males than females when 3-10 years old (95% PI [0.84, 1.27]), 9% greater when 11-13 years old (95% PI [0.89, 1.34]), 25% greater when 14-17 years old (95% PI [1.02, 1.54]), 35% greaterwhen 18-64 years old (95% PI [1.10, 1.66]), and 33% greater when ≥65 years old (95% PI [1.08, 1.65]). Thus, males generally have greater muscle strength than females even when strength is normalized to body mass. Factors other than body mass contribute to sex differences in strength.

Conclusion

The current meta-analysis has revealed that the strength-to-body mass ratio is generally greater in males than females. This result was more apparent in mean relative strength than in variability. The size of the sex difference in the strength-to-body mass differs with age and muscle group tested. It is greater in adults than children, and it is greater in upper-than lower-limb muscles. The results also suggest that body mass is not the only factor that contributes to the sex differences in muscle strength, and that normalizing absolute strength to total body mass does not fully account for the male strength advantage.

STUDY INTO DIFFERENCE IN PERFORMANCE & BODY AFTER 6 MONTHS GAHT

https://www.preprints.org/manuscript/202602.1137

Giuseppe Seminara, Francesca Greco et al
February 2026

Abstract
Background/Objectives: Gender-affirming hormone therapy (GAHT) is a cornerstone of medical transition, yet its early effects on physical performance and body composition remain partially explored, particularly in non-athletic individuals. This pilot study aimed to evaluate the short-term, within-individual changes in strength, anthropometry, and body composition in not-athletic transgenders during the first six months of GAHT.

Methods: This prospective longitudinal study enrolled 19 participants (8 assigned female at birth [AFAB]; 11 assigned male at birth [AMAB]). Participants were assessed at baseline (T0) and after six months of GAHT (T6). Assessments included bioelectrical impedance analysis (BIA) for body composition, isometric leg extension (maximal force [Fmax] and endurance), 1-repetition maximum (1RM) bench press, handgrip strength (HG), and submaximal cycle ergometry for VO2max estimation.

Results: In the AFAB group, GAHT led to a significant increase in total testosterone (TT), fat-free mass (+3.5 kg; p = 0.020), Fmax (p = 0.015), and 1RM bench press (+13.0 kg; p = 0.009). A strong correlation was found between TT increases and 1RM improvements (r = 0.718). Conversely, the AMAB group achieved significant suppression of TT and gonadotropins but exhibited remarkable stability in all anthropometric parameters and functional performance metrics, with no significant declines in strength or cardiorespiratory fitness (p > 0.05).

Conclusions: These findings reveal a distinct sexual dimorphism in the early response to GAHT. While AFAB individuals experience rapid functional and anabolic gains, AMAB individuals maintain physical stability during the first six months of therapy. Our findings suggest the recommendation to lifestyle shifts from sedentary to active physical training session in transgender individuals to preserve them from potential metabolic adverse effects of GAHT in the long-term.

SEX DIFFERENCES IN PHYSICAL FITNESS AMONG 10,000 ADOLESCENTS 13-15

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0345291

Ali Gorzi ,Hamid Rajabi, Mina Khantan, Tommy R. Lundberg
March 20, 2026

Abstract

Physical fitness during adolescence is critical for health and sports participation, with sex-specific developmental trajectories influencing performance. The aim of this cross-sectional study was to examine sex differences in physical fitness among non-athletic adolescents aged 13–15 years and to provide reference values for fitness parameters across age and sex. We assessed 9,669 non-athletic adolescents (64% females) aged 13–15 years. Fitness tests included Sargent jump, standing long jump, 30m sprint, medicine ball chest throw, and 6-minute shuttle run. Interactions between sex and age were analyzed using two-way ANOVA, with effect sizes (Cohen’s d) and mean differences calculated between 13–15 years of age. Pearson correlation coefficients were used to examine relevant relationships, and were compared between sexes using Fisher’s r-to-z transformation.

Significant sex-by-age interactions were observed for all fitness parameters (p < 0.001). Boys showed greater differences than girls from 13 to 15 years, with mean differences for Sargent jump (7.0 vs. 1.6 cm), standing long jump (28 vs. 7 cm), 30m sprint (−0.54 vs. −0.01 s), medicine ball throw (1.6 m vs. 0.4 m), and 6-minute shuttle run (2.0 vs. −0.3 laps). Height correlated moderately with the power-based tests in both sexes (p < 0.001), particularly in boys (R = 0.21 to 0.56 depending on age and test), but not with endurance. Correlations between tests were stronger (p < 0.01) in boys for all comparisons except medicine ball throw vs. shuttle run.

We conclude that boys show larger fitness differences from 13 to 15 years of age than girls, likely due to pubertal changes that increase stature and improve muscle mass and body composition. These reference values serve as a basis for sex-specific interventions to improve adolescent health, performance, and sports participation.

Summary

Boys showed significantly greater fitness differences than girls across the age spectrum. Significant plateau effects were inferred from girls’ physical fitness data.

The positive correlations between height and strength/power-based fitness metrics were considerably stronger in boys than in girls.

By understanding these sex-specific patterns, educators, coaches, and health professionals can design more effective and targeted interventions to support adolescent physical development, prevent injury, improve performance, and promote lifelong engagement in physical activity and sport.

INJURY RATES BETWEEN MALE AND FEMALE ELITE TENNIS PLAYERS

There are studies on injuries at Grand Slam level that might be useful in considering how female bodies are different to male bodies. Of course, female players play on the same court size so have to travel just as far with shorter legs and reach with shorter arms.

The injury rates are also obviously based on 3 sets per match for female players vs 5 for male players.

WIMBLEDON

Here is a study for Wimbledon over 10 years

https://bjsm.bmj.com/content/51/7/607

Women are noted to be more prone to injury (both sexes noted to be more prone to carrying chronic injury) and the injury areas more prone are feet and wrist. This data is obviously based on the women doing three sets.

It found :
”Injury rate was lower for male players (17.7 injuries per 1000 sets played) than female players (23.4 injuries per 1000 sets played). There was variability in the numbers of injuries reported by men and women players over the 10-year period”

FRENCH GRAND SLAM

https://pmc.ncbi.nlm.nih.gov/articles/PMC11015763/

here is a review from the French grand slam. While they have said there is little difference, the raw data does show female people had higher injuries over male people. I don’t believe it is a stretch to surmise that if women were in the court longer for 5 sets this would increase. I cannot remember but I don’t believe the data was reduced to per 1000 sets as the Wimbledon data was. Perhaps they would have concluded differently if it was. Perhaps not.

The numbers recorded were:
”The number of injuries in female and male players was similar (392 vs 358, respectively)”

AUSTRALIAN OPEN

Here is a review of the injuries at the Australian Open

https://pubmed.ncbi.nlm.nih.gov/28687543/

Results: Female players experienced more injuries than male players (201.7 vs 148.6). The shoulder (5.1±1.1 injuries per year), foot (3.2±1.1), wrist (3.1±1.5) and knee (3.1±1.1) were the most commonly injured regions among females. Knee (3.5±1.6), ankle (2.3±1.3) and thigh (2.3±1.5) were the most prevalent male injuries. Upper arm injuries and in-event treatment frequency increased by ≥2.4 times in both sexes over the 5-year period. Muscle injuries were most frequent. There was a greater than twofold increase in men and women with stress fractures over the 5-year period. The torso region, including the neck, thoracic spine, trunk and abdominal, lumbar spine, hip and groin, pelvis/buttock, attracted high in-event treatment frequencies in both sexes.

Other reviews

In the pdf “INJURY TRENDS IN PROFESSIONAL TENNIS ACROSS DIFFERENT”, it also noted that female professional players have a higher rate of injury. And that the zones of injury of feet and wrists, particularly tendons, was common across different studies. Just copy and search for the title. I cannot link it as it is a downloadable.

This link below is from Tennis Australia and it notes that the Australian Open has higher injury rate for female players too (this could be exacerbated by heat too)

https://www.tennis.com.au/wp-content/uploads/2019/02/InjuriesthroughelitepathwayHPEDMFINAL.pdf

for the Australian figures it noted the rates of 68.9 female and 41.2 male (per 10,000 game exposures). This is also with the female players only playing 3 sets.

Again the above is based on a three set match.

KINGS COLLEGE REVIEW

This link below is a review from Kings College

https://lbsm.co.uk/wp-content/uploads/2022/05/tennis-risk-factors.pdf?srsltid=AfmBOope4np57NdXHwHSmgWZe9FUqNhwEP6YMzSzJiX0VOS8Y-beQkpZ

THE INTRINSIC AND EXTRINSIC RISK FACTORS FOR INJURY IN PROFESSIONAL TENNIS PLAYERS ON CLAY AND GRASS COURT: A SYSTEMATIC
REVIEW

This paper has reviewed the studies I linked and others too.
It says this about sex

”Wimbledon competition which is played on grass court reported that injury rate was higher in female players (23.4 injuries per 1000 sets played) than in male players (17.7 injuries per 1000 sets played) [5]. There was no direct comparison of injury rate between clay courts and grass courts in the data of this study, but Hartwell et al. reported the difference between hard courts and clay courts [13]. They suggested that female players were more injured on clay courts (3.4 injuries per 1000 MEs) than male players (3.29 injuries per 1000 MEs), despite the higher injury rate in male players. Female players were four times more injured on clay courts than hard courts*.
Thus, it can be concluded that female tennis players are observed more injuries than male players on clay courts and grass courts, and female players are more injured on clay courts compared to grass courts.”

Totally agree.

2026 UPDATE TO THE IOC FEMALE SPORTS CATEGORY ELIGIBILITY POLICY

Here is the statement:

https://www.olympics.com/ioc/news/international-olympic-committee-announces-new-policy-on-the-protection-of-the-female-women-s-category-in-olympic-sport

here is the policy

https://stillmed.olympics.com/media/Documents/International-Olympic-Committee/EB/policy/policy-on-the-protection-of-the-female-category-english.pdf

THE POLICY

For the purpose of this Policy, the IOC has adopted the consensus definitions of the Working Group, which are set out in Schedule 1.

For all disciplines on the Sports Programme of an IOC Event, including individual and team sports, eligibility for any Female Category is limited to Biological Females.

Eligibility for the Female Category is to be determined in the first instance by SRY Gene screening to detect the absence or presence of the SRY Gene. On the basis of the scientific evidence, the IOC considers that the SRY Gene is fixed throughout life and represents highly accurate evidence that an athlete has experienced or will experience Male sex development. Furthermore, the IOC considers that SRY Gene screening via saliva, cheek swab or blood sample is unintrusive compared to other possible methods.

Athletes who screen negative for the SRY gene permanently satisfy this Policy’s eligibility criteria for competition in the Female Category. Unless there is reason to believe a negative reading is in error, this will be a once-in-a-lifetime test.
With the exception of athletes with a diagnosis of CAIS or other rare DSDs that do not benefit from the anabolic and/or performance-enhancing effects of testosterone, no athlete with an SRY-positive screen is eligible for competition in the Female Category.

Athletes with an SRY-positive screen, including XY transgender and androgen-sensitive XY-DSD athletes, continue to be included in all other classifications for which they qualify, for example, they are eligible for (i) any Male Category, including in a designated Male slot within any mixed category, and (ii) any open category or in sports and events that do not classify athletes by Sex.

The IOC recognises that XY athletes who identify as women and who want the opportunity to compete at IOC Events according to their legal sex or gender identity may disagree with this Policy. However, after a thorough scientific review and consultations with constituents of the Olympic Movement, the IOC
determined that a Sex-based eligibility rule is necessary and adequate to the attainment of the IOC’s goals for competition at IOC Events.

This is under the definitions section:

Sex: Either of the two categories, Male or Female, into which humans are divided according to their reproductive biology.

Biological Female (Female): An individual who, regardless of their legal sex or gender identity, experienced female sex development usually based on their XX-chromosomes, ovaries, and estrogenic hormones.

Biological Male (Male): An individual who, regardless of their legal sex or gender identity, experienced male sex development usually based on their XY-chromosomes, testes/testicles and androgenic hormones.

SUMMARY OF THE FINDINGS OF THE SCIENCE THAT THE IOC FOUND COMPELLING EVIDENCE

Performance Advantage:

o Consistent with the functional effects of higher circulating testosterone levels, Males have larger and stronger skeletal muscle and bone, larger and stronger hearts, larger lung size, more red blood cells, and lower body fat than Females trained to the equivalent level.
Together these attributes afford Males individual sex-based performance advantages in sports and events that rely on strength, power and/or endurance.

o Female athletes experience performance disadvantages relative to Males, associated with Female anatomy and physiology, that contribute to overall Male performance advantage in sports and events that rely on strength, power and/or endurance. These disadvantages may include, for example, the menstrual cycle, gestation and anatomical differences such as periodic ligament laxity (looseness), wider hips and more breast tissue.

o XY Transgender athletes and athletes with certain XY differences/disorders in sex development (DSD) (as defined in Schedule 1) have anatomical and physiological advantages in line with being Male even as their legal sex, the manner in which they were raised, and/or their gender identity may vary. XY transgender athletes and athletes with XY-DSD typically have testes/testicles and testosterone levels in the Male range. The clear majority are androgen-sensitive, meaning that their bodies are receptive to and make use of that testosterone during growth and development and throughout their athletic career.

o Androgen-sensitive XY-DSD and XY Transgender athletes retain Male performance advantage due in part to training effects and fixed traits. There is no current evidence that testosterone suppression or gender-affirming hormone treatment eliminates this advantage.

o XY-DSD athletes with Complete Androgen Insensitivity Syndrome (CAIS) (defined in Schedule 1) and other rare XY DSDs that do not benefit from the anabolic and/or performance-enhancing effects of testosterone should, on that basis, be included in the Female Category.

Magnitude of Advantage:

At the elite level, the magnitude of the Male performance advantage is different depending on the sport or event:

o There is a 10-12 per cent Male performance advantage in most running and swimming events.

o There is a 20+ per cent Male performance advantage in most throwing and jumping events.

o The Male performance advantage can be greater than 100 per cent in events that involve explosive power, e.g. in collision, lifting and punching sports.

Variation in Advantage:

The extent of the performance advantage (and its implications) varies across sports and events and from occasion to occasion, depending on the athletes involved.

Safety risks:

In contact sports (e.g., individual and team combat, collision, projectile sports), the strength and power differential between Males and Females increases safety risks to Female athletes.

from

https://stillmed.olympics.com/media/Documents/International-Olympic-Committee/EB/policy/policy-on-the-protection-of-the-female-category-english.pdf

Thanks to everyone who has contributed to this thread. Had a discussion with a work colleague about the IOC's decision to ban males from women's sport and it was really useful to be able to point to so much research.

ROSS TUCKER’S DISCUSSION ON ACTIVIST’S POINTS ABOUT HUMAN RIGHTS AND CAIS TESTING

In this YouTube Short, Ross explains why the Human Rights objections to the IOC's Policy for Protection of Women's sport are so misguided. They seem not to appreciate that they're representing the rights of a group of males ahead of the rights of females to equality, safety, and fairness in sport. They also completely miss that the harms they are warning against are far worse without a universal screen-for-SRY and then test-for-advantage approach, and are hysterically and dishonesty portraying what women will experience and how women will benefit from the policy.

It goes with this tweet

https://x.com/scienceofsport/status/2038606531386634714?s=46

’The sky is falling as women are harmed - so say various Human Rights groups & people in response to the IOC's Policy to protect women's sport. Their views are misguided, uninformed & false. In this 15 min video, I explain what they get wrong & ignore:’

Then there is this video about testing for CAIS.

The IOC Policy, like those of other sports, says "No males in women's sport". But they make an exception - a condition called CAIS. This creates potential confusion, and even the possibility of a loophole that sports must be aware of to defend the integrity of women's sport. In this video, Ross explains how the SRY-screen would work, and how the test for advantage has to be held to a very high, rigorous and transparent standard, with a transparent technical document. He implores sports leaders to get this right, for the sake of the overall concept.