
Female athletes across the country continue to face situations in which they are forced to compete against males, due in large part to athletic association policies that allow this to happen.
In one recent story, San Jose State University volleyball player Brooke Slusser joined two lawsuits against the Mountain West Conference and the NCAA for threatening privacy, safety, and fairness for female athletes by allowing males to compete in their sports.
Other stories, such as that of former University of Pennsylvania swimmer Lia Thomas, have continued to fuel the debate about fair competition in women’s sports. In 2022, Thomas—a male identifying as a female—shattered records in multiple women’s swimming events, displacing female athletes from the winners’ podium.
While common sense is enough to show the harms caused by these policies, a detailed expert report from Dr. Gregory Brown, a professor of exercise science at the University of Nebraska, sheds more light on the physiology behind why allowing men to compete in women’s sports is unfair to women and girls.
Dr. Brown has authored more than 40 peer-reviewed publications, more than 50 peer-reviewed presentations, and multiple book chapters in the field of exercise science. He has also served as a peer reviewer for over 25 professional journals, including the American Journal of Physiology, the International Journal of Exercise Science, The Journal of Strength and Conditioning Research, and the Journal of Applied Physiology. Dr. Brown’s work has also included research into the effects of testosterone supplements in men and women and competitive differences between men and women in sports.
The expert report summarizes multiple studies from around the world that demonstrate the physical advantages males experience in athletic competition. Additionally, these studies challenge the misconceptions that male physical advantages exist only after puberty and can be eliminated by testosterone suppression.
We summarize Dr. Brown’s key arguments here, but you can read his full expert report below.
1. In nearly every sport, men outperform women
Similarly gifted and trained males have physical advantages over females—from greater height and weight and larger, longer, and stronger bones to larger muscles, lower body fat, higher rates of metabolizing and releasing energy, and greater levels of testosterone. These innate physiological traits translate to competitive advantages for men over women. By the numbers, men have:
- 60-100% greater arm strength
- 57% greater average grip strength
- 25-60% greater leg strength
- 162% greater punching power
- 10-13% faster speed in both short and long-distance running
- 15-24% greater jumping ability
Studies have also found that men:
- Throw a baseball 35% faster than women
- Serve a tennis ball 15% faster
- Hit a golf ball 15% faster
- Throw a javelin 30% farther
- Spike a volleyball 29-34% faster
- Kick a soccer ball with 20% greater velocity
- Have 4-16% faster reaction times
As one study noted, even when male and female Olympic weightlifters of the same body weight are compared, men lift between 30% and 40% more than the women. Without comparing similar body weights, the male record is 65% higher than the female record.
2. Male athletic advantages exist even before puberty
Most of us tend to attribute male physiological advantages to the developmental changes caused by male puberty. But while boys’ physiological and performance advantages accelerate rapidly from the onset of puberty, data show that male athletic performance advantages exist before puberty—even as early as the age of 3.
In his report, Dr. Brown points to a European study that examined the athletic performances of over 10,000 boys and girls of elementary school age. The study found that between ages 6 and 11, boys have significant advantages in “speed, lower- and upper-limb strength and cardiorespiratory fitness.” In the study, the boys outperformed girls at every age in measures of handgrip strength, standing long jump, 20-m shuttle run, and predicted VO2 max. VO2 max refers to maximal oxygen consumption, which correlates to 30-40% of success in endurance sports.
Multiple other studies cited by Dr. Brown show similar results in young boys and girls in athletic performances like running, bent arm hang time, vertical jump height, throwing velocity, etc. These advantages only increase once puberty begins.
3. Male athletic advantages exist even after testosterone suppression
Many athletic associations have relied on testosterone suppression in males identifying as female in an attempt to level the playing field.
But the available evidence shows that the suppression of testosterone in a male after puberty does not substantially eliminate the male athletic advantage. In fact, studies find that males retain a strong performance advantage even after lengthy testosterone suppression.
- One longitudinal study found that males who went through testosterone suppression “lost only 7% hand strength after 12 months of treatment, and only a cumulative 9% after two years.” (Recall that men have about 60% greater hand grip strength compared to women). Testosterone suppression did little to eliminate the male advantage.
- Another longitudinal study documented the testing of “isometric strength levels measured at the knee” after 12 months of testosterone suppression and found that strength levels “were maintained over the [study period].” The study also concluded that “muscle strength after 12 months of testosterone suppression was comparable to baseline strength.” As a result, those men still “remained about 50% stronger” compared to women.
- One study that measured running speed in a 1.5-mile-distance run found that before testosterone suppression, “the [male to female] study group ran 21% faster than the … female average,” but after 2 years of testosterone suppression, that same group still ran 12% faster.
- Anecdotal evidence from female-identifying male athletes like Cece Telfer and Lia Thomas also shows that even following the NCAA’s testosterone suppression protocols did little to decrease their performance (Telfer’s performance actually increased!) and stop them from dominating women’s events.
Thus, while testosterone suppression can modestly reduce the performance advantages that men typically have, it can’t eliminate all of them. Furthermore, suppressing testosterone doesn’t address important physiological advantages that males maintain. Even after testosterone suppression, males still retain advantages in skeletal configuration, cardiovascular performance, muscle mass, etc.
Dr. Brown concludes, “Available research enables us to sort out, in some detail, which specific physiological advantages are immutable once they occur, which can be reversed only in part, and which appear to be highly responsive to later hormonal manipulation. The bottom line is that very few of the male physiological advantages … are largely reversible by testosterone suppression once an individual has passed through male puberty.” And numerous international studies published in the last 5 years have only made this clearer.
In 2021, the government-commissioned Sports Councils of the United Kingdom conducted their own study and concluded, “[T]he latest research, evidence and studies made clear that there are retained differences in strength, stamina and physique between the average woman compared with the average transgender woman or non-binary person registered male at birth, with or without testosterone suppression.”
It’s also important to note that suppressing testosterone before puberty will likely not eliminate the advantages boys already have. As Dr. Brown notes, “[T]here is no published scientific evidence that the administration of puberty blockers to males before puberty eliminates the pre-existing athletic advantage that prepubertal males have over prepubertal females in almost all athletic events.”
Dr. Brown’s report makes scientifically clear what common sense tells us: when gender identity trumps biology, women’s athletic opportunities will cease to meaningfully exist. As Dr. Brown summarizes, whether at the elite, collegiate, scholastic, or recreational levels, males will retain a competitive advantage over “equally gifted, aged, and trained” females, with or without testosterone suppression. Scientific research continues to point to the necessity of creating policies that will protect women’s athletic opportunities and ensure women and girls are not forced to compete against men.