A major analysis published in the British Journal of Sports Medicine found that, after one to three years of hormone therapy, trans and cis women have comparable levels of athletic fitness.

The new systematic review from a team of researchers, entitled “Body composition and physical fitness in transgender versus cisgender individuals: a systematic review with meta-analysis,” looked at 52 different studies that examined the possible athletic advantage trans women may have in sports over cis women. Those studies involve 6,485 people total: 2,943 trans women, 2,309 trans men, 568 cis women, and 665 cis men. Most of the studies involved adults, but seven involved teens.

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The researchers found that trans women likely have somewhat different body composition than cis women and cis men, which included body fat comparable to cis women (so, much greater than cis men’s) and some more lean mass compared to cis women. Lean mass is often used as a proxy for muscle mass.

However, that extra lean mass didn’t translate into differences in upper- or lower-body strength, the researchers found. Trans and cis women had comparable physical strength, which was lower than that of the cis men in the data sets.

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Cardiovascular strength was also the same between cis and trans women, and it was lower than that of cis men.

The researchers also found that several years of hormone therapy resulted in increased lean mass, decreased fat, and greater strength for trans men.

“The convergence of transgender women’s functional performance with cisgender women, particularly in strength and aerobic capacity, challenges assumptions about inherent athletic advantages derived solely from [gender affirming hormone therapy] or residual lean mass differences,” the researchers concluded.

The researchers noted limitations in the data they used. The studies they examined didn’t include any elite athletes, who may have different reactions to hormone therapy. Moreover, there was a lack of studies that included participants of diverse ages, sports, or competitive levels.

“Ideally, to resolve speculation, future long-term, longitudinal studies should prioritise performance-specific metrics in transgender athletes,” the researchers wrote. “However, one should be aware of the scarce number of transgender athletes, particularly in the elite sport, which complicates the feasibility of conducting powered studies involving high-performance transgender athletes within specific sport disciplines.”

Supporters of bans on trans women in women’s sports usually argue that trans women have a major, insurmountable advantage that, if they were allowed to compete, would exclude cis women from achievement in sports entirely. Often, conservatives will point to competitions where cis men outperform cis women as evidence of this, even though no one is advocating for cis men to compete in women’s sports.

That domination hasn’t happened. Trans women remain a small minority even in sports where they are allowed to compete, partly due to trans women’s small numbers but also because a big part of the advantage that male-bodied people have over female-bodied people in sports is due to hormones.

Conservatives still argue, though, that having gone through testosterone puberty can give trans women an advantage that they will never lose, but research is showing that that permanent advantage doesn’t seem to exist, at least not for all measures of fitness. A study published in the British Journal of Sports Medicine in 2024 found that trans women may have a disadvantage in sports compared to cis women when it comes to bone density and lung function. That study was much smaller than the 2026 study discussed above.

The exclusion of trans women from women’s competitions, including in events like chess, darts, and cheerleading, has led many to believe that discussions of fairness in women’s sports are actually fig leaves to cover for antipathy towards trans people. Many supporters of trans women in sports also say that the idea that cis men have an unassailable advantage is itself rooted in misogyny.

“I think society seems to forget just how amazingly good and talented female professional athletes are in all sports,” trans golfer Hailey Davidson wrote in 2024. “I mean those women are just insanely good and I can only dream of working towards playing alongside of them one day but in reality that is always a longshot and will require all I have even for the tiniest of chances.”

“You know what really bugs me is that people think I win just by showing up,” she continued. “This is such a slap in the face to ALL female athletes being told that any male can transition and beat them regardless of the life of hard work those women put in.”

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