New study shows that testosterone treatment boosts athletic performance in young women

October 20, 2019 • 9:00 am

People have argued for years about whether high testosterone can influence performance via either a supplement or as a natural condition in women athletes. Apparently until now there have been no properly-controlled studies of this issue. Now, however, a group of seven researchers from Sweden’s Karolinksa University Hospital, the Monaco Institute of Sports Medicine, the University Cote d’Azur and the Swedish School of Sports and Health Sciences have conducted a double-blind, randomized, and placebo-using controlled study on 48 young women showing that higher testosterone improves some (but not all) measurements of performance, but does increase the authors’ main index of performance: running time to exhaustion. Higher testosterone achieved by body creams also significantly increase body mass.

You can access the study, published in British Journal of Sports Medicine, by clicking on the link below, or going to the pdf here.  The reference is at the bottom.

As the authors note, “This study is the first randomised, placebo controlled trial investigating the effect of testosterone on physical performance in young, physically active women.” They used 48 women in their study, divided into control and treatment groups. This isn’t a large sample size, but it’s hard to do this kind of work because it causes body changes in some of the subjects.

Individuals were randomized and then half of them smeared a testosterone cream on their thigh daily for ten weeks, and the other half a placebo cream (side effects of the testosterone cream included acne and increased hair growth). Then the authors administered both groups several athletic tests as well as measuring circulating testosterone levels and body mass.

The summary at the paper’s outset pretty much tells the tale:

Apparently the authors’ main test of athletic performance was “time to exhaustion” when running on a treadmill, and that increased on average by about 16 seconds, a highly significant difference (over 8%) above the placebo group (p > 0.001). The Wingate test, a 30-second test of anaerobic power on a cycle, also showed slightly higher performance in the testosterone-treated group (p. < 0.05), but there was no difference between the groups in force generated during jump tests (a surrogate for jump height) or in knee extensor torque.

The difference in serum hormone levels was significantly higher in the treatment group (p. < 0.001), and lean mass and lower lean mass were significantly higher as well (p = 0.04), while there was no significant difference in body fat percentage or in total and spinal bone mineral density.

Note that the level of serum testosterone levels in the treatment group (4.3 nmol/liter) was still below the Olympic committee’s upper limit (5 nmol/liter), but much higher than the 0.9 nm/liter in the control group. This means that significant athletic ability was gained without exceeding the threshhold that would bar one from competing in female Olympic events. According to the authors, the levels of testosterone are radically different—in fact, nonoverlapping—in ‘normal’ males vs. ‘normal’ females:

“As determined by tandem mass spectrometry, the normal female range of circulating testosterone is 0.1–1.8 nmol/L and does not overlap with the normal male range (7.7–29.4 nmol/L). The dose we used resulted in an increase in mean serum testosterone of 4.3 nmol/L, which is clearly below the male range, and yet increased some indices of aerobic and anaerobic performances.”

But they add that some rare developmental conditions in women that affect sex development also cause increased testosterone levels as well as inducing increased lean body mass and higher physical performance. I found these data interesting:

The prevalence of 46XY, DSD [difference in sex development, with women having a Y chromosome] among elite female athletes is estimated to be about 140 times greater than in the general population. There is controversy internationally on whether it is fair to allow these hyperandrogenic individuals with high testosterone levels to compete against women with normal female androgen levels.Indeed, some scientists and human rights advocates consider that an individual who has been assigned female gender at birth, raised as a girl and who is socially accepted as a woman, should be allowed to compete in the women’s category, irrespective of her levels of testosterone and androgen receptor sensitivity.

Overall, the authors conclude this:

Our study supports a causal effect of testosterone on physical performance, as measured by running time to exhaustion, in young healthy women. Thus the ergogenic effect of short term moderately increased testosterone concentration seemed to apply for aerobic performance only. Testosterone also promoted a leaner body composition with an increase in muscle mass although body weight was unchanged.

There are, then, implications from this study about how to regulate participation in elite sports, though it’s above my pay grade to suggest rules, because (as I’ve said before), this is a difficult biological and ethical issue.

Even the Guardian, woke as it is, reports the results of this study pretty much straight (click on screenshot below), quoting several people who say that testosterone supplements clearly increase athletic performance (by 8%, a “huge effect in sports”), and that testosterone level is “the best indicator of sex difference.”

The Guardian also reports that the International Association of Athletic Federations has announced it will “impose an upper limit for testosterone levels on trans female athletes competing in middle-distance events.”  This may force Caster Semenya, a gold-medalist Olympic runner, to take testosterone reducing medication to compete in events between 400 m and a mile, and must keep her testosterone levels continually below 5 nmol/liter. (Semenya has challenged the past rules about that limit.)

This new study is also relevant to an editorial published in the British Medical Journal last March, before the new data came out (click on screenshot below), saying that new rules were premature because there weren’t any good scientific studies of the effects of serum testosterone levels on athletic performance, and that the IAAF’s already-existing regulations (an upper limit of of 5nmol/liter) risked “setting an unscientific precedent for other cases of genetic advantage”. The editorial ends like this:

History compels us to ensure that decisions about genetic superiority are supported by objective, rigorous, and reproducible data. Although this is purely conjecture, we venture that the Olympian gods smile down on winners like Mokgadi Caster Semenya when they perform extraordinary feats of human endeavour.

That last pronouncement, in the absence of data last March, seems premature—almost a bit virtue flaunting—as it uses “the Olympian gods” as a surrogate for “we editors.”

At any rate, this new study, while based on a small sample (24 women in each group), clearly mandates further work, but also puts the lie to the claim that testosterone has no relationship to athletic ability. The data now show that it seems to.  Whatever rules will follow findings like this (and, as I said, I’m not in a position to make them), I still maintain that “self identification” as a women, as is the rule in Connecticut, the UK, and soon in California, is not sufficient to allow a biological male to compete in women’s athletic events. There must be some kind of standard based on biology rather than psychology or mere assertion.


Hirschberg, A. L., J. Elings Knutsson, T. Helge, M. Godhe, M. Ekblom, S. Bermon, and B. Ekblom. 2019. Effects of moderately increased testosterone concentration on physical performance in young women: a double blind, randomised, placebo controlled study. British Journal of Sports Medicine: bjsports-2018-100525.

56 thoughts on “New study shows that testosterone treatment boosts athletic performance in young women

  1. Take a steroid consistently over two and a half months and you grow muscle mass. Who knew?


    I’m glad they did the study, because I think the social decisions around this need near-irrefutable empirical data to inform them. However, the result is not surprising in the least. At least, not to me.

    1. Yeah, it’s like doing a study on HGH. There’s a reason athletes have been trying to get away with it for years.

      I’m a huge MMA fan. Back before there was widespread testing, certain fighters were absolute monsters. Once TRT was banned, they became flabby shells of themselves. Not only does high testosterone provide more muscle mass, better long-term performance, strength, etc., but it also provides confidence.

      Look up what people call “TRT Vitor.” Vitor Belfort was a monstrous, nigh-unbeatable slab of muscle who knocked everyone out when he was on TRT back in the day, but once they stopped him from using it, he became flabby and stopped winning fights. He lost his muscle, his confidence, his power…

      Difference between TRT and non-TRT Vior

      This has been seen with many MMA fighters from back in the day, and some still get caught for trying to use TRT or other testosterone-enhancing drugs.

      1. I don’t think anyone ever disputed testosterone’s muscle mass building capabilities. Everyone is familiar with the over-roided muscle builders, men & women.

        But apart from muscle mass, the question- does testosterone make biological women better at other measures of athleticism like time to exhaustion- needs to be answered. Many sports, like running, do not put a premium on large muscle mass, so does testosterone contribute to performance enhancement in those sports in women? A good question. This experiment suggests that at least some performance parameters other than muscle mass are affected.

        More scientific work needs to be done, but how to use what comes out of that work is a wholly other problem.

        1. Almost all sports do put a premium on longer ability to train, speed of recovery time, speed of injury healing, bone density, etc., all of which are contributed to by testosterone. Testosterone has had many known effects for as long as people have been taking steroids and HGH. TRT is a significantly newer wrinkle, but still produces similar results.

          I do think athletes should be able to take something like anabolic steroids for a predetermined period after suffering a serious injury like certain bone fractures, and then be forced to be off that medication for a time determined to be sufficient to remove any beneficial side effects.

          1. I’d disagree with the latter point. Not because of concern over possible advantage, but because I fear any outside interference with the work of the endocrine system. Better give the athletes time to recover naturally (there should be insurance to soften the financial losses).

            1. Yeah, all top pros have insurance on them. I can see arguments both ways. We know anabolic steroids speed up recovery (and some study has shown they make the recovery better, e.g. making the bone heal harder than it would have on its own), but there should be studies on the long-term effects of continually using this kind of treatment before we let it through. I guess I had to rethink that one. Thanks.

  2. The testosterone cream had noticeable side effects, so many of those receiving the testosterone cream would presumably know what cream they were getting. Not that I doubt the results, but would that not have potentially invalidated the experiment?

    1. a. the effects weren’t common

      b. you’d have to posit that the noticing of those effects had something to do with changing body mass and improving athletic ability.

      So no, I don’t think this invalidated the experiment, not unless you think that noticing the effects improved endurance and changed body mass. I suspect that if you eliminate the people who reported effects, given the significance level, things wouldn’t change.

      The only way to obviate this problem, which has been done in some studies of psychotropic drugs, but would be nearly impossible here, is to give an “active placebo”: a placebo that has physiological effects, but not on the character of interest.

      1. Just to be safe: I do not doubt the results. But, yes, I think that knowing you are in the testosterone group may well improve your performance and maybe even influence your weight gain. It would be interesting to know what happened when, as you say, you eliminated people with obvious side effects.

    2. In addition to Jerry’s comments, my (admittedly layperson) understanding of such medical trials is that sometimes even people in the control group report side effects. The mind is a strange thing. So another reason results stay valid.

  3. It would seem to me that, until they do additional testing that proves somehow that testosterone does not affect these athletic abilities there needs to be regulation. It is simple not fare to let women compete with high levels. The question always is, who is not getting a fare deal?

  4. This means that significant athletic ability was gained without exceeding the threshhold that would bar one from competing in female Olympic events.

    I deduce that a large slew of trainers are carefully dosing their next generation of athletes to be within the Olympic specialist’s guidelines, so as to not trigger a ban, but still get maximal effect.
    Because, as you know, in sport, it’s not the taking part that counts, but the winning.

    1. Nonsense. Winning is the principal goal of competitive athletes but the vast majority of all sport is done by non-competitive athletes. Taking part IS what counts. Just last season, my son’s soccer team worked extraordinarily hard to make a tournament they had no hope of winning. They made it and, as expected, were knocked out in the first round. He and 18 other teens (and coaches, parents, fans and friends) were absolutely thrilled about it.

      1. “the vast majority of all sport is done by non-competitive athletes.”

        The vast majority of *everything* is done by non-competitive people. (Substitute ‘non-professional’ or ‘non-elite’ as necessary).

        That doesn’t alter the fact that, at the top level, pressures and competition are intense. Anybody who isn’t extremely competitive and intent on winning isn’t going to be at the top level. As you just said.

        Nobody expects your son’s soccer team to be snacking on steroids.


      2. Actually, EdwardM, I should be more nuanced about it. Aidan’s slightly facetious comment ‘it’s all about the winning’ applies to most sport we see on TV (because usually the top level gets televised).

        Lower down, it is about taking part, BUT people like to know they’re competing against others of roughly similar ability. That’s why ‘classes’ exist, to give the middle-achievers a chance. Absent that chance, what’s the point?

        So ‘winning’ still comes into it, just on a more circumscribed level. I’ll bet your son’s soccer team counted making the tournament as a ‘win’.


        1. Hell, even before high school, it was about winning. We wanted to win. If I was on my middle school hockey or tennis team and the other team was winning due to unfair advantages, I would have been seriously pissed off.

          As average adults, we often take part in sports just to play, but that’s because we’re too old to be on a team that wins things. We just want to stay in shape. Even then, competitive sports is often part of a drive to win. I still get angry at myself when I drop a service game in tennis and/or lose a match I should have won. Competition is a part of us; it’s an instinct.

          But, in high school (well, I made varsity hockey in middle school), we were going to the state championships every season. That was a big deal. To get cheated there would have been heartbreaking.

          1. I entirely agree.

            (The only competitive thing I do is occasional car club autocrosses and ‘motorkhanas’, mostly on grass. This is one-car-at-a-time, against the clock.

            I compete mostly because it’s fun thrashing round a paddock flat-out and sideways, but the competitive instinct kicks in. There are always four or five cars and drivers much more competitive than mine, but I try to win my ‘class’. If there are no defined classes I mentally select the group of cars/drivers of roughly equivalent performance and try to beat them. If there are ‘classes’ and one of the super-competitive cars got put in ‘my’ class for some odd reason, I would be disconcerted.)


            1. Hey, we’re human. Competition is built into us through evolution. Is there any higher species out there that doesn’t compete in some way?

              That’s actually an interesting question…

    2. It’s actually quite easy to obtain medications that contain steroids. And I suspect that many amateur athletes, and those seeking to make it to the next level, are using doctor-prescribed steroids, such as Albuterol, to assist performance. Yes, the goal of competition is to win, but many athletes do participate because of the community, identity, and pride it provides. We often don’t discuss (or know about) the athletes who are benefiting from naturally or artificially high testosterone levels when they aren’t winning.

      1. I can’t imagine something like albuterol being used except through a hidden device during competition to get more oxygen in the blood by further expanding the lungs’ capacity to take in air, and, even then, the risk wouldn’t be worth it.

        There are many medications with steroids, but anabolic steroids are the important ones that build muscle mass and provide other performance-enhancing effects (increased ability to train for longer periods, etc.)

    3. Of course they will.

      And if trans women can have levels approaching 5, which is an enourmous increase over bio women, then all women ought to be able to.
      But I think that is unfair as bio women may not want such extra high levels.

      To say nothing of other advantages.

  5. I suspect the rules will shift and become more stringent if there is a rise in male to female athletes competing at the elite level.

    Biological males who identify as women deserve the same compassion as all humans, however, the right to compete in a specific group should only be granted if the rights of that group are preserved. Depending on the time of transition and the sport involved, humans with a Y chromosome not only benefit from inherent advantages, but risk harm to the female athletes against which they’re playing.

    Regulation could require hormone therapy begin prior to puberty. But I fear this may compel parents of children with early talent in sports, who are also experiencing gender dysphoria, to condone unnecessary and potentially damaging therapies. Lowering testosterone as an adolescent or adult does not reverse growth in muscles, bones, hands and feet, nor can it manipulate a skeleton so that alignment and function match that of a woman.

    Women with an intersex condition, or a man who transitions to a woman, have had the benefit of many years of marinating in testosterone, increasing mitochondrial density and assisting development of VO2max. How does that compare to a woman who increases her testosterone over the course of 10 weeks?

    1. “Biological males who identify as women deserve the same compassion as all humans, however, the right to compete in a specific group should only be granted if the rights of that group are preserved. Depending on the time of transition and the sport involved, humans with a Y chromosome not only benefit from inherent advantages, but risk harm to the female athletes against which they’re playing.”

      Well said. Fallon Fox, an MMA fighter who transitioned from male to female, was only able to fight from 2012 to 2014. One of her opponents said the follow after Fox broke the opponent’s orbital bone and gave her a severe concussion during the first round of their bout:

      “I’ve fought a lot of women and have never felt the strength that I felt in a fight as I did that night. I can’t answer whether it’s because she was born a man or not because I’m not a doctor. I can only say, I’ve never felt so overpowered ever in my life and I am an abnormally strong female in my own right. Her grip was different, I could usually move around in the clinch against other females but couldn’t move at all in Fox’s clinch…”

      At that point, Brents already had 13 pro bouts on her record (and, I’m sure, several more amateur bouts), so she knew what she was talking about.

  6. I was on stanazanol(sp?)for six months in my mid thirties to stop menstruation in an attempt to clean up the endometriosis that was preventing me from conceiving. That steroid was what allowed Ben Johnson to win the Gold medal in the 100 metres at the Olympics. (the medal was revoked when the doping was discovered) I can attest to my fat outer thighs and breasts disappearing, my waist widening, huge arm muscles forming and my inner thighs increased in muscle size. I built a rock garden I was SO strong. I could exercise much longer without tiring, and my recovery time was practically non existent. There is NO doubt in my mind that testosterone has a HUGE affect on a female body, and if I’d been racing or lifting weights my performance I’m sure would’ve increased. So there you have it from someone who was there. (Note: I never did conceive AND I now have fat outer AND inner thighs.)

    1. That is very interesting although I would have bet my house on that being the outcome.

      I have had personal experience with low T and supplements and there is no question about the physiological boost.

  7. Given the reasonable case that testosterone impacts performance, trans females should not be allowed to compete with natural-born females, but I don’t see how it’s fair that a girl with a higher than a regulated testosterone level should be disqualified from competing with other girls. I also question the validity of using a single metric like testosterone to determine overall performance and hence, eligibility at the edge cases.

    1. Are there any cases of natural born females exceeding any given limit?

      The reason there is a male female category divide is because the difference in testosterone is so huge and completely unambiguous that it is self-evident. It is THE thing that makes the difference.

      Men have on average 10 times (roughly) the female level.

      There is no overlap.
      The highest in the female outliers is way below the lowest level in normal men.

      1. That’s comforting to hear. I posted my comment without any knowledge of the natural distribution of the male and female testosterone levels.

        However, I understand that the car of Semenya is where she has an rate hormonal developmental condition that causes her body to create more testosterone levels as a girl. You could argue that that makes her not quite a girl and justly subject to special conditions. If this is the case, I would side with Semenya. It’s a more obvious and advantages phenotype then others that gives performance boosts, but a valid phenotype for inclusion as a girl in every other way.

        1. The problem is that, inside her body, Semnya has testes (which produce testosterone) and no womb or ovaries (and thus does not produce female hormones at the rate of a normal female). For the purposes of sport, she is essentially biologically male. You can even see it when you look at her build — she looks like someone who grew up with male levels (or close to them) of testosterone. This would give her all the biological advantages we’ve been discussing.

        2. In other words, it’s not about the chromosomes, but about how her body developed due to them. I could see a person with her condition who developed like a female being allowed to compete with other females, but Semenya doesn’t seem to be such a person.

          1. OK, that changes my opinion on the matter a bit, especially because of the visual that info gives me. But the testosterone has to come from somewhere right? Based on reasons given in my reply to infinite, I would still let them compete with other women.

        3. Caster Semenya is a male pseudohermaphrodite, which means only some testosterone receptors are not working. That caused him (her) to have female external genitals (a vulva and a dead end vagina), but for most other areas he (she)’s clearly a male. The first time I heard him (her) on radio I thought it was his (her) trainer talking.
          (S)he sounds like male, looks like a male (if you don’t look into his(her) panties), moves like a male and is married to a female.
          Hermaphroditism is a condition that has dramatic consequences for those suffering from it, however, I think it makes no sense to let them compete in female competitions.
          If you do, we might just as well abandon female competitions.
          Really the easiest way is to look at the genes: if a Y chromosome is present, no competing in female events. Period. (I said the simplest, not necessarily the best, although I tend to think so)
          Of course, there are ‘mosaics’. How common are XX/XY mosaics?

          1. So Semenya is effectively a male with vagina. If high testosterone, among other things, is a biomarker of maleness then I see the reason for barring them in competitive sports. If this biological fact is diametrically opposed to his/her personal history and self-identification, and if I still held my permissive stance, I would be essentially privileging her vagina over all else. That gets me closer to being a hypocrite since I defend trans people the same way. Alright, I think y’all are right.

            1. Yeah, I didn’t want to debate with you further because I wanted to respect your opinion, but I did want to say that, to me, privileging her outside vaginal-shaped (since it’s not really a vagina) genital area and self-identity as a woman to allow her to compete among women seems the same thing as allowing trans women who have had transition surgery to do the same. I couldn’t really see any difference between allowing Semenya to compete with women just because that’s how she’s identified her whole life and allowing a fully transitioned male-to-female trans person to do the same.

              Regardless, I so rarely see people change their minds after taking in all the facts (I, of course, am also guilty of this! Human nature, I guess). Big kudos to you for taking the most objective view of things you could, regardless of whether you came to my conclusion or someone else’s.

              1. I should’ve said “… since I don’t defend trans people the same way…”. Anyway, I’m as hard headed as the next man but I consciously try harder these days not to be and y’all make sense. Thanks for engaging.

              2. Same here. It’s part of why I comment here. People are good at articulating their reasons and sometimes change my mind. And thanks to you too.

  8. The whole point of women’s sport is to give women a fair chance. Allowing trans females to compete when they have a huge inbuilt advantage, just makes a nonsense of that.

    To any trans female, you just have to say, “Hard luck. Your ‘right’ to compete does not override the rights of thousands of other competitors. You run in the men’s class.”

    Any such ‘right’ is based on the assumption of competing on level terms, not with a huge advantage. One can have sympathy with such a person but not at the expense of others.

    As for ‘self identified trans female’ a la Connecticut, there’s a much more succinct word for that: cheat.


      1. XY female? Would that be Caster Semenya? (I’m a bit shaky on these technical terms).

        That is of course one of those borderline cases that make drawing a line so difficult – but a line obviously has to be drawn, it’s impossible to avoid.

        One slight mitigating factor is that there are apparently a very tiny number of such people (whereas there is a potentially unlimited number of physical-males-identifying-as-females), so even if Semenya is allowed to compete as a woman her influence is comparatively limited.

        I have much sympathy for her**, but I still think her interests have to take second place to the interests of sportswomen in general. I think the regulation requiring her to reduce her testosterone is probably the best compromise.

        **My sympathy is based, not least, on the fact that Semenya apparently always thought she was a woman. M-to-F transgenders can’t claim the same innocence.


        1. Looked it up and it’s not confirmed but she likely has that XY condition. I will still sacrifice the interests of the group to the individual here because: XY doesn’t make one automatically a male in context (both biological and environmental), and Semenya and others like her are living proofs of that; there’s no risk of typical females being overrun with atypical females, especial ones with competitive advantages; intersex females need a place to compete and as long as they have a vagina and identify as female, they qualify in the female leagues. I understand that my arguments can be used to say it discriminates against trans people and I accept that. What if Semenya really wanted to transition but didn’t to gain competitive advantage? Unless that can be proven I give the benefit of the doubt. This is where I would draw the lines.

          1. I would draw the line not at outside genitalia, but what’s biologically inside. While she may have a vagina on the outside, that’s only because her testes stayed inside her body; had they not, it seems we might be having a different conversation. Besides the vagina, she has no womb or ovaries, and she has male reproductive parts inside her body, not female. She is, IMHO for the purposes of sports, a biological male.

            1. I completely see your side but it’s not even what’s biological that counts, but also environmental and personal, which is to say how those testes being inside her have impacted on her view of herself and others’ treatment of her.

        2. I did not want to get personal and discuss Ms. Semenya’s anatomy. But, yes, it appears that she is an XY female. The compromise that she constrain her testosterone sounds good, but it ignores that she grew up with male hormones.

          Trans women, as far as sports is concerned, are not women but men who take female hormones; they should not be allowed to compete as women. Ms. Semenya is a harder case, and (oddly for me!) I am not entirely sure what I think.

        3. The number of such people may be tiny, but if they are deliberately tracked, recruited and trained, they may turn out numerous enough to occupy all leading positions in female sport.

  9. I thought the effects of testosterone on female athletic performance was made evident when the West German women’s Olympic teams suddenly won an enormous amount of gold medals back in the 70’s. Seems the unsuspecting athletes had been receiving large amounts of testosterone and steroids from their trainers. They suffered a lot of health problems later.

    Trans women who compete on women’s teams don’t just have higher amounts of testosterone than the women ( even with the “lowered” levels,) they have a male body which developed in male puberty. The polite fiction that identifying-as-a-woman is the real true scientific way to define womanhood doesn’t stand up in the real world. They should either compete on the men’s team, form trans teams, or graciously bow out. Women have had to fight quite a bit to gain equal rights in sports. It is not for them to do the gracious bowing.

  10. I am a bit puzzled and also surprised after reading the paper. Maybe I have misunderstood some aspects, especially the statistics. How can the testosterone group have more muscle compared to the placebo group without an increase in weight or a decrease in fat? And then there is no effect on the strength and power tests, or VO2 max but there is an affect on running to exhaustion. There is also something else I thought a bit weird – runners started out at different speeds on the treadmill. Is that to somehow get everyone to exhaustion in a similar time? I do wonder, as another commenter said, whether the increase running time is a psychological effect from subjects suspecting they were on testosterone.

    Having said all that, I’d be surprised if testosterone didn’t improve performance.

    1. That’s a great and interesting comment!
      It looks like you read this way more carefully than I did. My thought was initially exactly what Eric said in comment 1, so I wanted to see what you meant. It’s definitely not as clear cut as I thought.

      Body fat: The subjects on testosterone showed a decrease in body fat % in table 2. My guess is that what they mean is that there was no significant different between the two groups, but that the change in the testosterone group was significant. I think if you don’t lose or gain any participants, then it’s probably ok. But it’s a pretty interesting thought and I don’t think they worded whatever they do mean very clearly.

      Different speeds: apparently that was depending on “pretest results”. So I think your interpretation is probably good: I suspect there’s no point in starting a reasonably fit person at 1 kmph, so they follow some standard recipe from the literature.

      My view is that it’s a short study (10 weeks) with a small dose. I think that some of the results look like they indicate a stronger effect, but that it’s not statistically significant yet. Definitely merits some follow on work.

  11. All this study says is that a temporary increase in testosterone causes a temporary improvement performance. It says nothing about long term use or higher natural levels.

    It is possible that over years the body will adjust to a high level (natural or via treatment) of testosterone with decreased sensitivity and the short term effect will fade.

  12. “[…]the International Association of Athletic Federations has announced it will “impose an upper limit for testosterone levels on trans female athletes competing in middle-distance events.” This may force Caster Semenya, a gold-medalist Olympic runner, to take testosterone reducing medication”

    Uh? She’s not a trans female, so this sounds a lot like a non sequitur.

    1. Daniele: The IAAF decision re trans athletes is more recent than the one regarding DSD athletes such as Semenya.
      As quoted elsewhere, in athletics “biology must trump gender identity” or we may as well bid farewell to elite female athletics.
      The presence of DSD women at the elite level in athletics is many times their occurrence in the general population. For top runners such as US 800m record holder Ajee Wilson, the IAAF decision is of huge importance, as there was no way she’d ever win a race against Semenya. Our fastest women will never run as fast as even second tier men, and that’s why we have separate races, period.
      I feel very badly for Semenya, who has been treated abominably over the years. The present thread, in which many people made invasive comments about her genitals, makes me wince. It’s unfortunate that there’s no win-win possibility here. A key aspect of the IAAF’s DSD decision is the acknowledgement that, while discriminatory (i.e. against Semenya), “such discrimination is a necessary, reasonable and proportionate means” of “preserving the integrity of female athletics.”

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