The short version
Claim we investigated
Transgender girls who went through male puberty keep an athletic advantage over other girls.
True. Male puberty's edge stays without hormones, and a year or two of hormones removes only part of it. School rules that admit transgender girls often make hormones optional, so the teenage boys' edge of 10-18% can stay whole. Where hormones are used, studies find most strength and speed remain for at least two years.
Quote or cite this fact-check
FactHub rates the claim “Transgender girls who went through male puberty keep an athletic advantage over other girls” True (high confidence): Male puberty's edge stays without hormones, and a year or two of hormones removes only part of it. Reviewed November 5, 2026. https://facthub.org/n/article/trans-girls-athletic-advantage/3
Key points
What the evidence establishes
- Established. Hormones are optional: in 12 of 15 states we checked that let transgender girls play, eligibility rests on gender identity; none requires hormones.
- Established. Boys and girls perform about alike until about 12; by 18, boys lead by roughly 10% to 18% in running and jumping.
- Established. After about a year of hormones, adult transgender women's testosterone fell a median 96%, but strength was nearly unchanged.
- Established. In Air Force fitness tests, transgender women still ran 1.5 miles about 12% faster than the average woman after two years of hormones.
- Established. Studies cited as showing no advantage found differences too uncertain to measure, or weaker results only per pound of body weight.
- Not shown. Evidence is strongest for girls untreated or on hormones a year or two; for girls blocked at puberty's start, data are thin and no sports results exist.
The evidence
The conclusion rests on the combined record. Expand each item to see its role and limitations.
| Method | Institution / country | Year(s) | What it shows | Key limitation | Primary links |
|---|---|---|---|---|---|
| Performance records by age: Norway's top 100 athletes at each age from 11 to 18, USA Swimming's top time standards by age, and every finish in Washington's 2022-2026 state 1600m finals | Norwegian Olympic Federation, USA Swimming, Washington Interscholastic Activities Association, FactHub Research Team Norway, United States | 2015, 2022, 2023, 2024, 2025, 2026 | Before about age 12, boys and girls perform nearly alike. Among Norway's best young athletes, the gap grows from under 5% at age 11 to 10-18% at 18 in sprints, middle distance and jumps. In USA Swimming's top standards it grows from under 2% at 10-11 to about 12% at 18. By high school the result is near-total separation: in Washington's 2022-2026 state 1600m finals, 273 of 276 boy finalists beat the fastest girl. A review of the research says the gap becomes significant at puberty and that it is bigger where muscle and explosive strength matter most. | These records compare boys and girls, not transgender girls. They show what male puberty adds; they do not show how much of it hormones or blockers take away. Record lists describe the best young athletes, not average students. | Tønnessen E, Svendsen IS, Olsen IC, Guttormsen A, Haugen T (PLOS ONE) Hilton EN, Lundberg TR (Sports Medicine) FactHub Research Team FactHub Research Team |
| Text of the high-school athletic association rules (or controlling state law) in the states that let transgender girls play on girls' teams, read in November 2026 | Washington Interscholastic Activities Association, Oregon School Activities Association, Maine Principals' Association, Endocrine Society United States | 2017, 2026 | About 18 states and the District of Columbia let transgender girls play on girls' high-school teams. We could read the governing rule for 15 of those states. In 12 of them, eligibility rests on gender identity: California, Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New York, Oregon, Vermont and, until Initiative 638, Washington. Colorado and Rhode Island leave it to schools, and Illinois reviews cases. None of the 15 requires hormone treatment or a testosterone test. Washington's rule let students compete by gender identity "or the gender most consistently expressed," with eligibility lasting their whole school career. Maine's says no medical records may be requested. So a transgender girl who went through all of male puberty with no treatment can join girls' teams in most of these states. The main U.S. medical guideline starts puberty blockers only after puberty begins. | Rules show what is allowed, not how many transgender girls take hormones or blockers. States also do not track how many transgender girls compete, so how often an advantage changes results is unmeasured. We could not open the rules for Michigan, Hawaii or the District of Columbia, and counted the states that limit girls' teams by law from a public tracker without re-reading each statute. Rules change: Washington's ended with Initiative 638 in November 2026, and Minnesota's is under review. | Washington Interscholastic Activities Association (WIAA) Hembree WC, et al. (Endocrine Society) Maine Principals' Association Oregon School Activities Association (OSAA) |
| Systematic review of before-and-after studies of adult transgender women on testosterone suppression and estrogen, with FactHub medians across every adult 12-month study group in its tables | Loughborough University, University of Manchester, Karolinska Institutet, Amsterdam UMC, Ghent University Hospital United Kingdom, Sweden, Netherlands, Belgium, Norway | 2019, 2020, 2021 | Across 12 adult study groups, a year of hormones cut testosterone by a median of 95.6%, into the female range. The body changed far less: hemoglobin fell a median 7.0%, muscle size 6.4% and lean mass 4.0%, while strength was about unchanged (median +0.5%; groups from -7.1% to +2.0%). In the largest study, 249 women lost 4.3% of grip strength, and their typical grip was still in the top 5% for women their age. A second review reached the same answer, about 5% lost, and the systematic review found strength, lean mass and muscle area still above women's after three years. | Participants were adults, and almost none trained for sport. Groups were small (11 to 249 women), and few studies run past a year. The medians weigh each study group equally. | FactHub Research Team Harper J, O'Donnell E, Sorouri Khorashad B, McDermott H, Witcomb GL (British Journal of Sports Medicine) Scharff M, Wiepjes CM, Klaver M, Schreiner T, T'Sjoen G, den Heijer M (Endocrine Connections) Hilton EN, Lundberg TR (Sports Medicine) |
| Before-and-after records of U.S. Air Force fitness tests (push-ups, sit-ups and a 1.5-mile run) of 46 transgender women, compared with the average Air Force woman under 30 | U.S. Air Force, Children's Mercy Kansas City United States | 2016, 2017, 2018, 2021 | This is the only study that tracked real physical performance through treatment. Before hormones, transgender women ran 1.5 miles 147 seconds (21%) faster than the average Air Force woman. The gap shrank but did not close: 97 seconds in the first year, 64 at 1-2 years and 90 seconds, still about 12% faster, at 2-2.5 years. After the one year of suppression that sports bodies then required, they were about 9% faster. Push-up and sit-up advantages did fade: by 2-2.5 years they were no longer statistically clear. | The participants were service members, not competitive athletes, and the comparison is an Air Force-wide average, not women with matched training. Few reached the 2-2.5 year band, so its estimate is wide (10 to 169 seconds). The authors note results could differ for people treated early in puberty. | FactHub Research Team FactHub Research Team Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine) |
| Clinic studies of transgender girls treated with puberty blockers and estrogen in Belgium and the Netherlands | Ghent University Hospital, Amsterdam UMC Belgium, Netherlands | 2022, 2025 | No study has measured race times or game results of transgender girls. In Ghent, 26 transgender girls who started blockers at the earliest stages of puberty (average age 13.3) had grip strength at about 16 closer to girls' than to boys'. But in Amsterdam, transgender girls treated with blockers and estrogen during puberty still grew to an average 180 cm, about 1.5 standard deviations above the average woman, taller than roughly 94% of women. Height helps in sports such as basketball and volleyball. | Both are small, single-clinic studies run by clinics that provide the treatment. Grip strength is one simple measure, not sports performance. Most Dutch patients started blockers later in puberty, after the boys-girls gap opens. | Ciancia S, et al. (International Journal of Transgender Health) Boogers LS, et al. (Journal of Clinical Endocrinology & Metabolism) |
| Two one-time comparisons of transgender women on hormones with women and men: 23 who trained regularly (2024, funded by the International Olympic Committee) and 15 non-athletes on hormones for about 14 years (2022) | University of Brighton, International Olympic Committee (funder), University of Sao Paulo United Kingdom, Brazil | 2022, 2024 | In this 2024 study, transgender women on hormones for about six years had stronger grips than the women (40.7 vs 34.2 kg) and similar total aerobic capacity. They scored lower on measures divided by body weight, such as jump height per kilogram, because they carried more body fat. The authors said the results should caution against bans not based on sport-specific research. A 2022 Brazilian study of non-athletes found the same pattern after about 14 years of hormones: transgender women's strength and aerobic capacity were below men's but above women's. | It measured each person once, so it cannot show what hormones changed. Participants were recreational, recruited online, and not matched on training; critics argue the transgender women were not comparable athletes. Measures divided by body weight can make a heavier, stronger person look weaker. | Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine) Alvares LAM, et al. (British Journal of Sports Medicine) |
| Meta-analysis of 52 studies comparing transgender women with women and men, mostly at one point in time, plus before-and-after studies of hormones | University of Sao Paulo Brazil | 2026 | This 2026 analysis is the study most often cited for "no advantage." It called transgender women's strength and aerobic capacity "similar" to women's. But its estimates were too uncertain to show equality. For upper-body strength, the best estimate favored transgender women, and the plausible range ran from a small deficit to a very large advantage. The authors graded that evidence very low certainty. Their own before-and-after results show hormones lowering transgender women's lean mass and upper-body strength over one to three years, so they started higher. Transgender women also kept more lean mass than women. | It pools small studies that measured different things in different people, mostly non-athletes about three years into hormones. It did not test speed or sport performance, and it says little about people who went through puberty without treatment. A result that is not statistically significant is not evidence of no difference. | Sieczkowska SM, et al. (British Journal of Sports Medicine) |
1. The boys-girls gap opens at puberty and is large by high school Performance records by age: Norway's top 100 athletes at each age from 11 to 18, USA Swimming's top time standards by age, and every finish in Washington's 2022-2026 state 1600m finals
Before about age 12, boys and girls perform nearly alike. Among Norway's best young athletes, the gap grows from under 5% at age 11 to 10-18% at 18 in sprints, middle distance and jumps. In USA Swimming's top standards it grows from under 2% at 10-11 to about 12% at 18. By high school the result is near-total separation: in Washington's 2022-2026 state 1600m finals, 273 of 276 boy finalists beat the fastest girl. A review of the research says the gap becomes significant at puberty and that it is bigger where muscle and explosive strength matter most.
Limit: These records compare boys and girls, not transgender girls. They show what male puberty adds; they do not show how much of it hormones or blockers take away. Record lists describe the best young athletes, not average students.
Verify: Performance development in adolescent track and field athletes according to age, sex and sport discipline (2015) Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage (2021) Boys' swimming edge over girls grows from age 12 (chart) Boys' and girls' state mile times barely overlap (chart)
- Boys and girls perform about equally in running and jumping until about age 12; after that, boys pull ahead. Tønnessen E, Svendsen IS, Olsen IC, Guttormsen A, Haugen T (PLOS ONE)
- The boys-girls gap grows from under 5% at age 11 to 10-18% at 18 in every event studied. Tønnessen E, Svendsen IS, Olsen IC, Guttormsen A, Haugen T (PLOS ONE)
- The male performance advantage appears at puberty. Hilton EN, Lundberg TR (Sports Medicine)
- Boys' and girls' top swimming standards differ by under 2% at ages 10-11; the boys' edge grows every year from 12 to about 12% at 18. FactHub Research Team
- In Washington's 2022-2026 state 1600m finals, 273 of 276 boy finalists ran faster than the fastest girl finalist. FactHub Research Team
- The male edge is largest in sports that rely on muscle mass and explosive strength, especially in the upper body. Hilton EN, Lundberg TR (Sports Medicine)
2. Under school rules that admit transgender girls, hormones are usually optional Text of the high-school athletic association rules (or controlling state law) in the states that let transgender girls play on girls' teams, read in November 2026
About 18 states and the District of Columbia let transgender girls play on girls' high-school teams. We could read the governing rule for 15 of those states. In 12 of them, eligibility rests on gender identity: California, Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New York, Oregon, Vermont and, until Initiative 638, Washington. Colorado and Rhode Island leave it to schools, and Illinois reviews cases. None of the 15 requires hormone treatment or a testosterone test. Washington's rule let students compete by gender identity "or the gender most consistently expressed," with eligibility lasting their whole school career. Maine's says no medical records may be requested. So a transgender girl who went through all of male puberty with no treatment can join girls' teams in most of these states. The main U.S. medical guideline starts puberty blockers only after puberty begins.
Limit: Rules show what is allowed, not how many transgender girls take hormones or blockers. States also do not track how many transgender girls compete, so how often an advantage changes results is unmeasured. We could not open the rules for Michigan, Hawaii or the District of Columbia, and counted the states that limit girls' teams by law from a public tracker without re-reading each statute. Rules change: Washington's ended with Initiative 638 in November 2026, and Minnesota's is under review.
Verify: WIAA Handbook 2026-27, Rule 18.16.0, Gender Identity Participation Endocrine Treatment of Gender-Dysphoric/Gender-Incongruent Persons: An Endocrine Society Clinical Practice Guideline (2017) MPA Handbook 2026-27, Gender Identity Participation Policy OSAA Handbook 2026-27, Section 37
- Washington students competed in the category matching their gender identity, with no hormone or medical test. Washington Interscholastic Activities Association (WIAA)
- Once granted, eligibility lasted for the student's whole time in school sports. Washington Interscholastic Activities Association (WIAA)
- The main U.S. guideline says puberty blockers start only once puberty has begun (Tanner stage 2), so some male puberty comes first. Hembree WC, et al. (Endocrine Society)
- Maine's rule forbids asking for medical records to establish a student's gender identity. Maine Principals' Association
- Oregon's rule sets eligibility by the gender identity a student tells the school, with no medical step. Oregon School Activities Association (OSAA)
3. A year of hormones removes testosterone but little muscle or strength Systematic review of before-and-after studies of adult transgender women on testosterone suppression and estrogen, with FactHub medians across every adult 12-month study group in its tables
Across 12 adult study groups, a year of hormones cut testosterone by a median of 95.6%, into the female range. The body changed far less: hemoglobin fell a median 7.0%, muscle size 6.4% and lean mass 4.0%, while strength was about unchanged (median +0.5%; groups from -7.1% to +2.0%). In the largest study, 249 women lost 4.3% of grip strength, and their typical grip was still in the top 5% for women their age. A second review reached the same answer, about 5% lost, and the systematic review found strength, lean mass and muscle area still above women's after three years.
Limit: Participants were adults, and almost none trained for sport. Groups were small (11 to 249 women), and few studies run past a year. The medians weigh each study group equally.
Verify: Median change after about 12 months of hormone treatment (saved analysis) How does hormone transition in transgender women change body composition, muscle strength and haemoglobin? Systematic review with a focus on the implications for sport participation (2021) Change in grip strength in trans people and its association with lean body mass and bone density (2019) Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage (2021)
- After about a year of hormones, testosterone fell a median 95.6% across 12 adult study groups, hemoglobin 7.0%, muscle size 6.4% and lean mass 4.0%, while strength changed +0.5% (groups ranged from -7.1% to +2.0%). FactHub Research Team
- Strength, lean mass and muscle area stay above women's even after three years of hormones. Harper J, O'Donnell E, Sorouri Khorashad B, McDermott H, Witcomb GL (British Journal of Sports Medicine)
- The reviewers conclude strength may be largely kept for the first three years. Harper J, O'Donnell E, Sorouri Khorashad B, McDermott H, Witcomb GL (British Journal of Sports Medicine)
- After a year of hormones, the typical transgender woman's grip was still stronger than that of most women her age. Scharff M, Wiepjes CM, Klaver M, Schreiner T, T'Sjoen G, den Heijer M (Endocrine Connections)
- Across before-and-after studies, a year of testosterone suppression reduced lean mass, muscle area and strength by only about 5%. Hilton EN, Lundberg TR (Sports Medicine)
- The reviewers conclude that suppressing testosterone only slightly reduces transgender women's muscular advantage. Hilton EN, Lundberg TR (Sports Medicine)
4. Air Force fitness tests: still faster after two years Before-and-after records of U.S. Air Force fitness tests (push-ups, sit-ups and a 1.5-mile run) of 46 transgender women, compared with the average Air Force woman under 30
This is the only study that tracked real physical performance through treatment. Before hormones, transgender women ran 1.5 miles 147 seconds (21%) faster than the average Air Force woman. The gap shrank but did not close: 97 seconds in the first year, 64 at 1-2 years and 90 seconds, still about 12% faster, at 2-2.5 years. After the one year of suppression that sports bodies then required, they were about 9% faster. Push-up and sit-up advantages did fade: by 2-2.5 years they were no longer statistically clear.
Limit: The participants were service members, not competitive athletes, and the comparison is an Air Force-wide average, not women with matched training. Few reached the 2-2.5 year band, so its estimate is wide (10 to 169 seconds). The authors note results could differ for people treated early in puberty.
Verify: Air Force 1.5-mile run gap by time on hormones (saved analysis) Air Force push-ups, sit-ups and run by time on hormones (saved analysis) Effect of gender affirming hormones on athletic performance in transwomen and transmen: implications for sporting organisations and legislators (2021)
- Transgender women ran 1.5 miles 147 seconds faster than the average Air Force woman before hormones and 90 seconds faster (95% CI 10 to 169) after 2 to 2.5 years. FactHub Research Team
- At 2 to 2.5 years, push-up and sit-up differences from the average woman were no longer statistically significant; the run difference was. FactHub Research Team · Qualifies
- After two years of hormones, push-up and sit-up advantages were gone, but trans women still ran 1.5 miles about 12% faster than the average woman. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine)
- After the one year of suppression that sports bodies then required, trans women still ran 9% faster. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine)
- The authors say results could differ for people who start treatment soon after puberty begins. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine) · Qualifies
5. The little research on transgender teens is mixed Clinic studies of transgender girls treated with puberty blockers and estrogen in Belgium and the Netherlands
No study has measured race times or game results of transgender girls. In Ghent, 26 transgender girls who started blockers at the earliest stages of puberty (average age 13.3) had grip strength at about 16 closer to girls' than to boys'. But in Amsterdam, transgender girls treated with blockers and estrogen during puberty still grew to an average 180 cm, about 1.5 standard deviations above the average woman, taller than roughly 94% of women. Height helps in sports such as basketball and volleyball.
Limit: Both are small, single-clinic studies run by clinics that provide the treatment. Grip strength is one simple measure, not sports performance. Most Dutch patients started blockers later in puberty, after the boys-girls gap opens.
Verify: Effects of puberty suppression on bone, body composition, handgrip strength and glucolipid profile in early-pubertal transgender adolescents (2025) Transgender Girls Grow Tall: Adult Height Is Unaffected by GnRH Analogue and Estradiol Treatment (2022)
- Trans girls who started blockers early in puberty had grip strength at 16 closer to girls' than to boys'. Ciancia S, et al. (International Journal of Transgender Health) · Qualifies
- Trans girls treated with blockers and estrogen during puberty reached about 180 cm, roughly 1.5 standard deviations above the average woman. Boogers LS, et al. (Journal of Clinical Endocrinology & Metabolism)
6. One-time comparisons cited for "no advantage" still found transgender women ahead in raw strength Two one-time comparisons of transgender women on hormones with women and men: 23 who trained regularly (2024, funded by the International Olympic Committee) and 15 non-athletes on hormones for about 14 years (2022)
In this 2024 study, transgender women on hormones for about six years had stronger grips than the women (40.7 vs 34.2 kg) and similar total aerobic capacity. They scored lower on measures divided by body weight, such as jump height per kilogram, because they carried more body fat. The authors said the results should caution against bans not based on sport-specific research. A 2022 Brazilian study of non-athletes found the same pattern after about 14 years of hormones: transgender women's strength and aerobic capacity were below men's but above women's.
Limit: It measured each person once, so it cannot show what hormones changed. Participants were recreational, recruited online, and not matched on training; critics argue the transgender women were not comparable athletes. Measures divided by body weight can make a heavier, stronger person look weaker.
Verify: Strength, power and aerobic capacity of transgender athletes: a cross-sectional study (2024) Cardiopulmonary capacity and muscle strength in transgender women on long-term gender-affirming hormone therapy: a cross-sectional study (2022)
- The transgender women, on hormones for about six years, had stronger grips than the women. Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine)
- They jumped lower per kilogram of body weight than the women. Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine) · Qualifies
- The authors caution against bans not based on sport-specific research. Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine) · Contradicts
- The transgender women had taken hormones for about 14 years. Alvares LAM, et al. (British Journal of Sports Medicine)
- Even so, their strength and aerobic capacity were higher than the women's and lower than the men's. Alvares LAM, et al. (British Journal of Sports Medicine)
7. The 2026 analysis cited for "no advantage" could not tell either way Meta-analysis of 52 studies comparing transgender women with women and men, mostly at one point in time, plus before-and-after studies of hormones
This 2026 analysis is the study most often cited for "no advantage." It called transgender women's strength and aerobic capacity "similar" to women's. But its estimates were too uncertain to show equality. For upper-body strength, the best estimate favored transgender women, and the plausible range ran from a small deficit to a very large advantage. The authors graded that evidence very low certainty. Their own before-and-after results show hormones lowering transgender women's lean mass and upper-body strength over one to three years, so they started higher. Transgender women also kept more lean mass than women.
Limit: It pools small studies that measured different things in different people, mostly non-athletes about three years into hormones. It did not test speed or sport performance, and it says little about people who went through puberty without treatment. A result that is not statistically significant is not evidence of no difference.
- The meta-analysis called transgender women's upper-body strength "similar" to women's, but its estimate favored transgender women and its confidence interval ran from a deficit to a very large advantage, graded very low certainty. Sieczkowska SM, et al. (British Journal of Sports Medicine) · Qualifies
- In the same analysis, hormones reduced transgender women's lean mass and upper-body strength over 1-3 years, meaning they started higher. Sieczkowska SM, et al. (British Journal of Sports Medicine)
- Transgender women kept more lean mass than women. Sieczkowska SM, et al. (British Journal of Sports Medicine)
- The authors conclude the evidence, mostly low certainty, does not support an inherent advantage for transgender women. Sieczkowska SM, et al. (British Journal of Sports Medicine) · Contradicts
Common questions 11
“Transgender girls have no athletic advantage over other girls.”
Where rules make hormones optional, a girl who went through male puberty keeps the boys' edge of roughly 10-18% by age 18. Even with hormones, studies find most strength and speed remain for years.
- The boys-girls gap grows from under 5% at age 11 to 10-18% at 18 in every event studied. Tønnessen E, Svendsen IS, Olsen IC, Guttormsen A, Haugen T (PLOS ONE)
- Washington students competed in the category matching their gender identity, with no hormone or medical test. Washington Interscholastic Activities Association (WIAA)
- Strength, lean mass and muscle area stay above women's even after three years of hormones. Harper J, O'Donnell E, Sorouri Khorashad B, McDermott H, Witcomb GL (British Journal of Sports Medicine)
- After two years of hormones, push-up and sit-up advantages were gone, but trans women still ran 1.5 miles about 12% faster than the average woman. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine)
See the evidence: The boys-girls gap opens at puberty and is large by high school
“A 2026 analysis of 52 studies shows transgender women have no strength or fitness advantage after hormones.”
"No significant difference" meant too uncertain to tell: the authors rated the evidence very low certainty, and their best estimate still had transgender women stronger in the upper body.
- The meta-analysis called transgender women's upper-body strength "similar" to women's, but its estimate favored transgender women and its confidence interval ran from a deficit to a very large advantage, graded very low certainty. Sieczkowska SM, et al. (British Journal of Sports Medicine) · Qualifies
- In the same analysis, hormones reduced transgender women's lean mass and upper-body strength over 1-3 years, meaning they started higher. Sieczkowska SM, et al. (British Journal of Sports Medicine)
- The authors conclude the evidence, mostly low certainty, does not support an inherent advantage for transgender women. Sieczkowska SM, et al. (British Journal of Sports Medicine) · Contradicts
See the evidence: The 2026 analysis cited for "no advantage" could not tell either way
“An Olympic committee-funded study shows transgender women have physical disadvantages compared with women.”
Transgender women scored lower only when results were divided by body weight, because they carried more fat; in raw strength they gripped harder than the women. The study measured each person once.
- The transgender women, on hormones for about six years, had stronger grips than the women. Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine)
- They jumped lower per kilogram of body weight than the women. Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine) · Qualifies
- The authors caution against bans not based on sport-specific research. Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine) · Contradicts
“The Air Force study found transgender women lost their advantage after two years of hormones.”
Short answer: Not in running
The push-up and sit-up gaps faded after two years, but the running gap did not: transgender women still ran 1.5 miles about 12% faster than the average woman. The authors also note that weight gain on hormones can lower push-up scores, which may hide some upper-body strength.
- After two years of hormones, push-up and sit-up advantages were gone, but trans women still ran 1.5 miles about 12% faster than the average woman. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine)
- At 2 to 2.5 years, push-up and sit-up differences from the average woman were no longer statistically significant; the run difference was. FactHub Research Team · Qualifies
- Transgender women ran 1.5 miles 147 seconds faster than the average Air Force woman before hormones and 90 seconds faster (95% CI 10 to 169) after 2 to 2.5 years. FactHub Research Team
See the evidence: Air Force fitness tests: still faster after two years
“A Brazilian study found transgender women on long-term hormones end up "intermediate" between men and women.”
Short answer: Still ahead of women
Even after about 14 years of hormones, the transgender women in that study had more strength and aerobic capacity than the women; "intermediate" means between men and women, not equal to women. All 15 were non-athletes measured once.
- The transgender women had taken hormones for about 14 years. Alvares LAM, et al. (British Journal of Sports Medicine)
- Even so, their strength and aerobic capacity were higher than the women's and lower than the men's. Alvares LAM, et al. (British Journal of Sports Medicine)
“A study of transgender runners found their performance fell to women's level after hormones.”
Short answer: Eight adults, self-reported
That 2015 study used self-reported race times from eight adult hobby runners, and its own author now says it lacked rigour: only about half the times were checked, and training and hormone levels were not recorded. It says nothing about strength sports or about teenagers who went through male puberty.
- The author of the 2015 study of eight runners now says it lacked rigour: about half the self-reported times were checked, and training and hormone levels were not recorded. Harper J, et al. (European Journal of Sport Science)
“Scientific reviews found no evidence that transgender women have an advantage.”
Short answer: Too early, or misread
Those reviews found no proof of an advantage, not proof of none. The 2017 review said research was too limited to decide. Most strength studies came later. A 2022 Canadian review said Air Force runners lost all advantage within a year, but that study found them still 9% faster.
- The review itself says there was too little research to conclude either way. Jones BA, Arcelus J, Bouman WP, Haycraft E (Sports Medicine)
- The review said there was no firm evidence of an overall performance benefit after 12 months of suppression. Canadian Centre for Ethics in Sport (CCES) · Contradicts
- It described the Air Force study as showing transgender women lost all performance advantage within 12 months, which the study itself does not say. Canadian Centre for Ethics in Sport (CCES)
- After the one year of suppression that sports bodies then required, trans women still ran 9% faster. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine)
See the evidence: Air Force fitness tests: still faster after two years
“Transgender girls who start puberty blockers early end up with girls' strength.”
Short answer: Grip roughly; height no
In one Belgian study of 26 transgender girls blocked at the start of puberty, grip strength at about 16 was closer to the average girl's than to a boy's. But Dutch transgender girls treated during puberty still grew to about 180 cm, taller than roughly 94% of women. No study has measured these girls' sports results, and most state rules that admit transgender girls do not require blockers at all.
- Trans girls who started blockers early in puberty had grip strength at 16 closer to girls' than to boys'. Ciancia S, et al. (International Journal of Transgender Health) · Qualifies
- Trans girls treated with blockers and estrogen during puberty reached about 180 cm, roughly 1.5 standard deviations above the average woman. Boogers LS, et al. (Journal of Clinical Endocrinology & Metabolism)
- Washington students competed in the category matching their gender identity, with no hormone or medical test. Washington Interscholastic Activities Association (WIAA)
See the evidence: The little research on transgender teens is mixed
“Hormones bring transgender women's oxygen-carrying blood down to women's levels.”
Short answer: Yes, within about 4 months
Yes: hemoglobin, which carries oxygen to the muscles, falls to women's typical levels within about four months of hormones. It is one of the few measures that fully changes, and it may matter most in endurance events. Muscle size and strength change much less, and in the Air Force study running speed stayed well above women's for at least two years.
- Hemoglobin, which carries oxygen to muscles, falls to women's levels within about four months of hormones. Harper J, O'Donnell E, Sorouri Khorashad B, McDermott H, Witcomb GL (British Journal of Sports Medicine) · Qualifies
- After two years of hormones, push-up and sit-up advantages were gone, but trans women still ran 1.5 miles about 12% faster than the average woman. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine)
See the evidence: Air Force fitness tests: still faster after two years
“Michael Phelps has genetic advantages too, and nobody bans him.”
Short answer: A different kind of gap
Sports separate by sex because of one advantage big enough to sort nearly everyone: after puberty, males outperform females by roughly 10% to 30% in running, jumping and swimming. Individual gifts, like Phelps's, vary within each category. Whether that gap should decide eligibility is a values question; that the gap exists, and mostly survives a year or two of hormones, is what the research measures.
- The male performance advantage appears at puberty. Hilton EN, Lundberg TR (Sports Medicine)
- Boys and girls perform about equally in running and jumping until about age 12; after that, boys pull ahead. Tønnessen E, Svendsen IS, Olsen IC, Guttormsen A, Haugen T (PLOS ONE)
See the evidence: The boys-girls gap opens at puberty and is large by high school
“Sports bodies let transgender women compete after a year of lowered testosterone, so a year must be enough.”
Short answer: Most have dropped that rule
The International Olympic Committee once allowed it after 12 months of testosterone below 10 nmol/L. Reviews of the evidence since then found strength and muscle largely kept after a year, and World Athletics excluded transgender women who went through male puberty in 2023. The IOC limited its female category to biological females in 2026.
- The IOC's earlier rule let transgender women compete after 12 months of testosterone below 10 nmol/L. Hilton EN, Lundberg TR (Sports Medicine) · Qualifies
- After the one year of suppression that sports bodies then required, trans women still ran 9% faster. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine)
See the evidence: Air Force fitness tests: still faster after two years
Conclusion
The claim holds for the girls it names. Male puberty, which begins around 11 or 12, gives boys roughly a 10% to 18% edge in running and jumping by 18, and more in strength. Where school rules let transgender girls play on girls' teams, eligibility usually rests on gender identity, and hormones are optional. A girl who went through male puberty without treatment carries that edge in full.
Hormones shrink the edge but do not erase it quickly. Testosterone drops into the female range within months, and hemoglobin follows within about four. Muscle and strength move far less: a median 4% to 6% loss in lean mass and muscle size and essentially no change in strength after a year. Transgender women in the Air Force still ran about 12% faster than the average woman after two years, though their push-up and sit-up edge had faded.
How much this matters varies by sport. The male edge is largest where muscle and explosive strength count, and height carries over into sports such as basketball and volleyball. Endurance is mixed: hemoglobin normalizes, yet the Air Force running gap persisted. Most competitions score absolute performance, which is why per-pound comparisons can understate the gap.
The studies most cited for "no advantage" do not show equality. The 2026 meta-analysis found differences too uncertain to measure and still leaned toward a strength edge. The best evidence shows incomplete loss of advantage at one to three years, but sport-specific, multi-year data on trained athletes remain scarce. Confidence is high for girls who went through puberty untreated or with a year or two of hormones. For girls blocked at the first signs of puberty, evidence is thin, and we do not rate them.
How we checked
- Defined the claim from viral posts saying transgender girls have no athletic advantage, narrowed to the group most school rules admit without treatment: transgender girls who went through some or all of male puberty, with or without hormones. Rated the affirmative claim, and rated the viral wording separately as a common question.
- Read WIAA Rule 18.16.0 in the 2026-27 handbook to confirm what eligibility required.
- Read the primary papers: the Harper et al. (2021) systematic review, Hilton and Lundberg (2021), Scharff et al. (2019), Roberts et al. (2021), Hamilton et al. (2024), Tønnessen et al. (2015), Ciancia et al. (2025), Boogers et al. (2022) and the Endocrine Society guideline.
- Built a FactHub dataset: every adult 12-month study group in the Harper review tables, with medians and ranges, and the Air Force Table 4 results with confidence intervals; cross-checked the largest study groups against the original papers. Inclusion rule: adults measured at about 12 months; adolescent cohorts and other follow-up lengths were listed but left out.
- Weighed evidence that cuts against the claim's rating, including the IOC-funded study and the early-blocker study, and recorded each line's limits.
- Reused FactHub's published charts on the boys-girls gap by age and Washington state 1600m finals rather than rebuilding them.
- Read the studies most often cited for "no advantage" (the 2026 meta-analysis by Sieczkowska and colleagues, Hamilton et al. 2024, Alvares et al. 2022 and others) and checked what each measured, its sample and its certainty.
Editorial note: Scope: this article rates whether transgender girls who went through male puberty keep an athletic advantage. It does not rate girls who started puberty blockers at the first signs of puberty, for whom evidence is thin, and it does not judge whether any eligibility policy is fair. In our own voice we say transgender girls and women; quotes keep the authors' terms. No athlete is named. FactHub takes no position on any ballot measure. No external specialist review has been recorded.
Expert-review status
No external specialist review has been recorded.
Funding and conflicts
Funding: No external funding for this piece.
Ownership: Published by the FactHub Research Team.
Conflicts: None known.
Sources 22
Sources are labeled by kind, with what this fact check takes from each, so readers can check the evidence independently.
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Peer-reviewed study
Tønnessen E, Svendsen IS, Olsen IC, Guttormsen A, Haugen T (PLOS ONE).
Performance development in adolescent track and field athletes according to age, sex and sport discipline (2015)
Free copy
DOI: 10.1371/journal.pone.0129014
Analysis of the 100 best Norwegian boys and girls at each age from 11 to 18 in the 60 m, 800 m, long jump and high jump.
Reliability: Peer-reviewed study by Norwegian sports scientists of national performance records; it predates and does not address transgender eligibility.
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Boys and girls perform about equally in running and jumping until about age 12; after that, boys pull ahead.
What the source says
Male and female athletes perform almost equally in running and jumping events up to the age of 12. Beyond this age, males outperform females.
Abstract, Results -
The boys-girls gap grows from under 5% at age 11 to 10-18% at 18 in every event studied.
What the source says
The performance sex difference evolves from < 5% to 10-18% in all the analyzed disciplines from age 11 to 18 yr.
Abstract, Results
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Peer-reviewed study
Hilton EN, Lundberg TR (Sports Medicine).
Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage (2021)
Free copy
DOI: 10.1007/s40279-020-01389-3
Narrative review of sex differences in performance and of before-and-after studies of testosterone suppression in transgender women.
Reliability: Peer-reviewed review from the University of Manchester and Karolinska Institutet; no funding or conflicts declared. A 2023 critique in the same journal (doi 10.1007/s40279-023-01928-8) disputes its use of absolute rather than size-adjusted figures.
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The male performance advantage appears at puberty.
What the source says
the performance gap between males and females becomes significant at puberty
Abstract -
Across before-and-after studies, a year of testosterone suppression reduced lean mass, muscle area and strength by only about 5%.
What the source says
the loss of lean body mass, muscle area and strength typically amounts to approximately 5% after 12 months of treatment
Abstract -
The reviewers conclude that suppressing testosterone only slightly reduces transgender women's muscular advantage.
What the source says
the muscular advantage enjoyed by transgender women is only minimally reduced when testosterone is suppressed
Abstract -
Qualifies: The IOC's earlier rule let transgender women compete after 12 months of testosterone below 10 nmol/L.
What the source says
requiring total serum testosterone levels to be suppressed below 10 nmol/L for at least 12 months prior to and during competition
Abstract -
The male edge is largest in sports that rely on muscle mass and explosive strength, especially in the upper body.
What the source says
The performance gap is more pronounced in sporting activities relying on muscle mass and explosive strength, particularly in the upper body.
Abstract
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Peer-reviewed study
Harper J, O'Donnell E, Sorouri Khorashad B, McDermott H, Witcomb GL (British Journal of Sports Medicine).
How does hormone transition in transgender women change body composition, muscle strength and haemoglobin? Systematic review with a focus on the implications for sport participation (2021)
Free copy
DOI: 10.1136/bjsports-2020-103106
Systematic review of 24 studies of non-athletic transgender women on hormones, with tables of each study's before-and-after values.
Reliability: Peer-reviewed systematic review led by Loughborough University researchers; no specific funding and no competing interests declared. Its tables are the source of FactHub's 12-month medians.
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Qualifies: Hemoglobin, which carries oxygen to muscles, falls to women's levels within about four months of hormones.
What the source says
After 4 months of hormone therapy, transwomen have Hgb/HCT levels equivalent to those of cisgender women.
Abstract, Results -
Strength, lean mass and muscle area stay above women's even after three years of hormones.
What the source says
values for strength, LBM and muscle area in transwomen remain above those of cisgender women, even after 36 months of hormone therapy.
Abstract, Results -
The reviewers conclude strength may be largely kept for the first three years.
What the source says
These findings suggest that strength may be well preserved in transwomen during the first 3 years of hormone therapy.
Abstract, Conclusion
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Peer-reviewed study
Scharff M, Wiepjes CM, Klaver M, Schreiner T, T'Sjoen G, den Heijer M (Endocrine Connections).
Change in grip strength in trans people and its association with lean body mass and bone density (2019)
Free copy
DOI: 10.1530/EC-19-0196
The largest before-and-after study: 249 transgender women in the European ENIGI clinic cohort, grip strength measured before and after a year of hormones.
Reliability: Multicenter clinical cohort in Amsterdam, Ghent and Oslo; authors declare no conflict of interest.
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After a year of hormones, the typical transgender woman's grip was still stronger than that of most women her age.
What the source says
After 12 months, the median grip strength of transwomen still falls into the 95th percentile for age-matched females.
Discussion
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Peer-reviewed study
Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine).
Effect of gender affirming hormones on athletic performance in transwomen and transmen: implications for sporting organisations and legislators (2021)
DOI: 10.1136/bjsports-2020-102329
Study of U.S. Air Force fitness-test records of 46 transgender women and 29 transgender men before and during hormone treatment.
Reliability: Peer-reviewed study by military and academic pediatricians using Air Force records; no specific grant. The participants were service members, not competitive athletes.
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After two years of hormones, push-up and sit-up advantages were gone, but trans women still ran 1.5 miles about 12% faster than the average woman.
What the source says
After 2 years of taking feminising hormones, the push-up and sit-up differences disappeared but transwomen were still 12% faster.
Abstract, Results -
After the one year of suppression that sports bodies then required, trans women still ran 9% faster.
What the source says
However, transwomen still had a 9% faster mean run speed after the 1 year period of testosterone suppression that is recommended by World Athletics for inclusion in women's events.
Abstract, Summary -
Qualifies: The authors say results could differ for people who start treatment soon after puberty begins.
What the source says
It is possible that these results could be different among transwomen who begin gender affirming hormone therapy shortly after the onset of puberty and never experienced the ergogenic benefits of testosterone exposure.
Discussion
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Peer-reviewed study
Hamilton B, Brown A, Montagner-Moraes S, et al. (British Journal of Sports Medicine).
Strength, power and aerobic capacity of transgender athletes: a cross-sectional study (2024)
Free copy
DOI: 10.1136/bjsports-2023-108029
One-time comparison of 23 transgender women, 21 women, 19 men and 12 transgender men who trained regularly, recruited through social media; funded by the International Olympic Committee.
Reliability: Funded by an International Olympic Committee research grant; one author sits on the IOC Medical and Scientific Commission. A published letter argues the transgender women, with the most body fat of any group, were not representative of athletes; the authors replied disputing that.
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The transgender women, on hormones for about six years, had stronger grips than the women.
What the source says
higher absolute handgrip strength (TW 40.7±6.8 kg, CW 34.2±3.7 kg, p=0.01)
Abstract, Results -
Qualifies: They jumped lower per kilogram of body weight than the women.
What the source says
lower relative jump height (TW 0.7±0.2 cm/kg; CW 1.0±0.2 cm/kg
Abstract, Results -
Contradicts: The authors caution against bans not based on sport-specific research.
What the source says
these results should caution against precautionary bans and sport eligibility exclusions that are not based on sport-specific (or sport-relevant) research
Abstract, Conclusion
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Peer-reviewed study
Ciancia S, et al. (International Journal of Transgender Health).
Effects of puberty suppression on bone, body composition, handgrip strength and glucolipid profile in early-pubertal transgender adolescents (2025)
Free copy
DOI: 10.1080/26895269.2024.2353224
Ghent, Belgium clinic study of 26 transgender girls who started puberty blockers at the earliest stages of puberty (mean age 13.3), measured again around 16.
Reliability: Retrospective clinic study from Ghent University Hospital, a gender clinic that provides the treatment it studied.
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Qualifies: Trans girls who started blockers early in puberty had grip strength at 16 closer to girls' than to boys'.
What the source says
In both trans boys and trans girls, grip strength at t2 was more similar to cisgender girls than to cisgender boys.
Results
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Peer-reviewed study
Boogers LS, et al. (Journal of Clinical Endocrinology & Metabolism).
Transgender Girls Grow Tall: Adult Height Is Unaffected by GnRH Analogue and Estradiol Treatment (2022)
Free copy
DOI: 10.1210/clinem/dgac349
Amsterdam clinic study of adult height in 161 transgender girls treated with puberty blockers and estrogen.
Reliability: Retrospective cohort from Amsterdam UMC, a gender clinic that provides the treatment it studied.
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Trans girls treated with blockers and estrogen during puberty reached about 180 cm, roughly 1.5 standard deviations above the average woman.
What the source says
to an adult height of 180.4 ± 5.6 cm (male height SDS –0.48 ± 0.78; female height SDS + 1.55 ± 0.89)
Results, Growth and adult height
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Academic
Hembree WC, et al. (Endocrine Society).
Endocrine Treatment of Gender-Dysphoric/Gender-Incongruent Persons: An Endocrine Society Clinical Practice Guideline (2017)
DOI: 10.1210/jc.2017-01658
The Endocrine Society's clinical guideline for hormone treatment of transgender adolescents and adults.
Reliability: Professional-society guideline written by an appointed task force; it recommends the treatment it describes.
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The main U.S. guideline says puberty blockers start only once puberty has begun (Tanner stage 2), so some male puberty comes first.
What the source says
We recommend treating gender-dysphoric/gender-incongruent adolescents who have entered puberty at Tanner Stage G2/B2 by suppression with gonadotropin-releasing hormone agonists.
Abstract
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Government
Washington Interscholastic Activities Association (WIAA).
WIAA Handbook 2026-27, Rule 18.16.0, Gender Identity Participation
The rulebook of Washington's high-school athletic association, which set eligibility before Initiative 638.
Reliability: The governing rule itself. The handbook names no hormone, testosterone or medical requirement for gender-identity eligibility.
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Washington students competed in the category matching their gender identity, with no hormone or medical test.
What the source says
Athletes will participate in programs consistent with their gender identity or the gender most consistently expressed.
Rule 18.16.0, p. 42 -
Once granted, eligibility lasted for the student's whole time in school sports.
What the source says
the eligibility is granted for the duration of the student's participation and does not need to be renewed every sports season or school year.
Rule 18.16.0, p. 42
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FactHub record
FactHub Research Team.
Median change after about 12 months of hormone treatment (saved analysis)
FactHub's medians across every adult 12-month study group in the Harper et al. review tables.
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After about a year of hormones, testosterone fell a median 95.6% across 12 adult study groups, hemoglobin 7.0%, muscle size 6.4% and lean mass 4.0%, while strength changed +0.5% (groups ranged from -7.1% to +2.0%).
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FactHub record
FactHub Research Team.
Air Force 1.5-mile run gap by time on hormones (saved analysis)
Roberts et al. Table 4 differences from the average Air Force woman, with 95% confidence intervals.
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Transgender women ran 1.5 miles 147 seconds faster than the average Air Force woman before hormones and 90 seconds faster (95% CI 10 to 169) after 2 to 2.5 years.
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FactHub record
FactHub Research Team.
Air Force push-ups, sit-ups and run by time on hormones (saved analysis)
All three Air Force fitness measures compared with the average woman, with significance.
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Qualifies: At 2 to 2.5 years, push-up and sit-up differences from the average woman were no longer statistically significant; the run difference was.
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FactHub record
FactHub Research Team.
Boys' swimming edge over girls grows from age 12 (chart)
FactHub chart of USA Swimming's top time standards for boys and girls by age.
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Boys' and girls' top swimming standards differ by under 2% at ages 10-11; the boys' edge grows every year from 12 to about 12% at 18.
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FactHub record
FactHub Research Team.
Boys' and girls' state mile times barely overlap (chart)
FactHub chart of every finish in Washington's 2A-4A state 1600m finals, 2022-2026.
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In Washington's 2022-2026 state 1600m finals, 273 of 276 boy finalists ran faster than the fastest girl finalist.
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Peer-reviewed study
Sieczkowska SM, et al. (British Journal of Sports Medicine).
Body composition and physical fitness in transgender versus cisgender individuals: a systematic review with meta-analysis (2026)
Free copy
DOI: 10.1136/bjsports-2025-110239
Meta-analysis of 52 studies (6,485 people) comparing body composition and fitness of transgender and non-transgender people, and changes on hormones.
Reliability: Peer-reviewed meta-analysis from the University of Sao Paulo group of Bruno Gualano; registered in PROSPERO (CRD42024562210). The authors graded nearly all transgender-women comparisons as very low certainty. A preprint version appeared on medRxiv in May 2025.
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Qualifies: The meta-analysis called transgender women's upper-body strength "similar" to women's, but its estimate favored transgender women and its confidence interval ran from a deficit to a very large advantage, graded very low certainty.
What the source says
upper-body strength (SMD 0.54, 95% CI -0.95 to 2.02, GRADE: very low)
Abstract, Results -
In the same analysis, hormones reduced transgender women's lean mass and upper-body strength over 1-3 years, meaning they started higher.
What the source says
In transgender women, GAHT was associated with increased fat mass and reduced lean mass and upper-body strength over 1-3 years.
Abstract, Results -
Contradicts: The authors conclude the evidence, mostly low certainty, does not support an inherent advantage for transgender women.
What the source says
Current evidence is mostly low certainty and has heterogenous quality but does not support theories of inherent athletic advantages for transgender women over cisgender.
Abstract, Conclusion -
Transgender women kept more lean mass than women.
What the source says
While transgender women exhibited higher lean mass than cisgender women, their physical fitness was comparable.
Abstract, Conclusion
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Peer-reviewed study
Alvares LAM, et al. (British Journal of Sports Medicine).
Cardiopulmonary capacity and muscle strength in transgender women on long-term gender-affirming hormone therapy: a cross-sectional study (2022)
Free copy
DOI: 10.1136/bjsports-2021-105400
One-time comparison in Sao Paulo of 15 transgender women on hormones for about 14 years with 14 women and 13 men, none of them athletes.
Reliability: Peer-reviewed cross-sectional study from the University of Sao Paulo; a 2023 correction fixed group sizes and units and stressed that participants were non-athletes.
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The transgender women had taken hormones for about 14 years.
What the source says
The TW received hormone therapy for 14.4±3.5 years.
Abstract, Methods -
Even so, their strength and aerobic capacity were higher than the women's and lower than the men's.
What the source says
The mean strength and VO2 peak in non-athlete TW while performing physical exertion were higher than those in non-athlete CW and lower than those in CM.
Abstract, Conclusion
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Peer-reviewed study
Harper J, et al. (European Journal of Sport Science).
Changes in athletic performance in transgender athletes after gender-affirming hormone therapy (2025 follow-up of Harper 2015)
Free copy
DOI: 10.1002/ejsc.70036
Follow-up study by the author of the 2015 study of eight transgender runners, which describes that earlier study's weaknesses.
Reliability: Speaks against its own interest. Written by the 2015 study's own author, so its criticism of that study runs against the author's interest. Funded by Loughborough University.
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The author of the 2015 study of eight runners now says it lacked rigour: about half the self-reported times were checked, and training and hormone levels were not recorded.
What the source says
lacked rigour due to several methodological weaknesses: only ∼50% of the self‐reported times were verified, training differences pre‐GAHT and post‐GAHT were not reported and testosterone, oestrogen and haemoglobin concentrations were not measured.
Introduction
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Peer-reviewed study
Jones BA, Arcelus J, Bouman WP, Haycraft E (Sports Medicine).
Sport and transgender people: a systematic review of the literature relating to sport participation and competitive sport policies (2017)
Free copy
DOI: 10.1007/s40279-016-0621-y
Review of eight mostly qualitative studies and 31 sport policies; its only physiological data were one 2004 clinical study and the 2015 study of eight runners.
Reliability: Peer-reviewed review from Loughborough University and Nottingham; funded through a PhD studentship; no conflicts declared. Published before most before-and-after strength studies.
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The review itself says there was too little research to conclude either way.
What the source says
there is limited research from which to draw any conclusion about whether transgender people have an athletic advantage in competitive sport or not.
Section 4, Discussion
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Other
Canadian Centre for Ethics in Sport (CCES).
Transgender Women Athletes and Elite Sport: A Scientific Review (2022), archived copy
Non-peer-reviewed literature review commissioned by the Canadian Centre for Ethics in Sport; the original link now returns an error, so the archived copy is cited.
Reliability: Commissioned by CCES, a nonprofit funded in part by the Government of Canada; not peer reviewed; the report names no authors and says its scoping review could not be fully completed.
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Contradicts: The review said there was no firm evidence of an overall performance benefit after 12 months of suppression.
What the source says
There is no firm basis available in evidence to indicate that trans women have a consistent and measurable overall performance benefit after 12 months of testosterone suppression.
Executive Summary, p. 9 -
It described the Air Force study as showing transgender women lost all performance advantage within 12 months, which the study itself does not say.
What the source says
they saw that trans women lost all performance advantage during 12 months on HRT
pp. 25-26
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Other
Maine Principals' Association.
MPA Handbook 2026-27, Gender Identity Participation Policy
The rulebook of Maine's high-school athletic association.
Reliability: The governing rule itself, written by the association that runs Maine high-school sports.
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Maine's rule forbids asking for medical records to establish a student's gender identity.
What the source says
No medical records or official documents shall be requested or required to establish a student's gender identity.
Gender Identity Participation Policy
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Other
Oregon School Activities Association (OSAA).
OSAA Handbook 2026-27, Section 37
The rulebook of Oregon's high-school athletic association.
Reliability: The governing rule itself, written by the association that runs Oregon high-school sports.
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Oregon's rule sets eligibility by the gender identity a student tells the school, with no medical step.
What the source says
once a transgender student has notified the student's school of their gender identity (boy or girl), the student shall consistently participate as that gender for purposes of eligibility
Section 37
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FactHub dataset
Transgender women on hormones: what changes in a year, and Air Force fitness tests over 2.5 years
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Tables: harper-groups
Saved analysis twelve-month-change
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Tables: air-force-fitness
Saved analysis air-force-run-gap
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Tables: air-force-fitness
Saved analysis air-force-all-measures
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- FactHub chart hormones-year-testosterone-vs-strength
- FactHub chart air-force-run-gap-on-hormones
- FactHub chart sex-gap-swimming-by-age
- FactHub chart wa-state-mile-boys-vs-girls-finishes
Update history 3 changes, last
- First version.
- Asked the claim as a plain question and rated it in the affirmative (True); the viral "no advantage" wording is now a rated common question (False). Widened from Washington to school rules generally, led with hormones being optional, and added answers to studies cited for "no advantage", including the 2026 meta-analysis.
- After reader feedback: stated where confidence is high and where evidence is thin, added how the advantage varies by sport and the limits of long-term data, noted that states do not track participation, and added what each chart does not show.
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{"@context":"https://schema.org","@type":"ClaimReview","url":"https://facthub.org/n/article/trans-girls-athletic-advantage","datePublished":"2026-11-05","dateModified":"2026-11-05","author":{"@type":"Organization","name":"FactHub","url":"https://facthub.org/"},"claimReviewed":"Transgender girls who went through male puberty keep an athletic advantage over other girls.","reviewRating":{"@type":"Rating","alternateName":"True"},"image":"https://facthub.org/node-assets-v2/article/trans-girls-athletic-advantage/3/xc-start/social-1200x630.jpg"}This metadata helps machines discover the fact-check. It does not prove the conclusion or guarantee special treatment by a search engine.
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