Anatomical and physiological differences between males and females give males athletic advantages when compared with similarly aged, talented, and trained females.

N o matter where you stand on the issue of gender ideology, it’s hard for anyone to watch a male athlete compete against females and think it’s fair competition between equally matched contestants. Sports underscores the inherent biological differences that exist between men and women and the importance of following common sense and science.

State officials have rightly been concerned by the increasing number of men allowed to enter women’s athletic competitions and the enormous detriment that poses to women. Half of the states have passed laws protecting women’s sports.

The federal government may now be following this trend. A bill is quickly making its way through Congress that affirms Title IX’s equal opportunity provisions for women and girls based on sex (and not gender identity). And, on National Girls and Women in Sports Day, President Donald Trump signed an executive order saying that Title IX requires keeping males out of women’s sports.

This order correctly recognizes that sex matters in sports, as an increasing amount of peer-reviewed research confirms. In fact, the more studies that are performed and the more research that’s conducted, the clearer it becomes that males have an inherent physical advantage over females in nearly all sports. The advantage emerges almost as early as it can be measured and is not eliminated by puberty blockers, testosterone suppression, or cross-sex hormones.

As an exercise physiologist, I’ve spent many years studying the biological factors that influence health and human performance. The sex-based anatomical and physiological differences between males and females give males athletic advantages when compared with similarly aged, talented, and trained females.

Males have inherent biological advantages, such as greater height, more lean body mass and muscle mass, greater muscle strength, larger hearts and lungs, higher maximal oxygen consumption, and stronger and denser bones than females. As a recent paper noted, teenage boys and adult men outperformed girls and women by 10 to 15 percent in running, 15 to 20 percent in jumping, and 30 to 60 percent in strength.

This is true even for males who haven’t gone through puberty yet.

Some activists claim that male athletic advantage doesn’t emerge until puberty, but recent research shows that’s just not the case. An analysis of eight years of top track-and-field performances showed that boys ages eight and younger outperformed girls of the same ages by 19.3 percent in shot put, 32.6 percent in javelin, and 4.7 percent in long jump. In running, the eight-and-under boys were 4.0 to 6.7 percent faster than girls, depending on the event distance. And in swimming, boys ages ten and younger were 1.2 to 2.6 percent faster than girls in most events.

So even if some of these young boys began taking puberty blockers at the onset of puberty, their athletic advantage over similarly aged girls would already be locked in. And keeping in mind that high-level swimming and athletic events are consistently decided by margins of less than 1 percent, these advantages matter.

Research on puberty blockers and cross-sex hormones confirms that male athletic advantages are not erased. A recent study shows that while puberty blockers impair male strength development, teenage males on puberty blockers still experience greater increases in strength than females. And several studies have shown that males who use puberty blockers and feminizing hormones still grow to normal adult male body height, which is typically 5 to 6 inches taller than females. Having more muscle mass and greater body height gives tremendous, biologically based advantages to males in sports.

The story is the same for testosterone-suppressing drugs, which are often prescribed alongside estrogen to “transitioning” males in mid-to-late adolescence. Even after males have undergone testosterone suppression, research shows that, while some biological advantages decrease, they still outperform similarly aged and trained women. Men have 30 to 60 percent higher muscle strength than women, and undergoing testosterone suppression decreases that strength by only 0 to 9 percent — a far cry from an even playing field for even the strongest female athletes.

There isn’t a way to equalize those substantial differences to make it fair for female athletes. As long as men are allowed to line up next to women at a track or swimming meet or to play volleyball or basketball against them, they will knock women off podium spots and prevent them from advancing to championship rounds, not to mention the threat they pose to women’s physical safety in contact sports.

To truly protect girls’ and women’s hard-fought advancements and equality in athletics, sports must be separated based on sex. Fair competition matters, even if the athletes are not competing for a championship or prize money. To the extent that this biological reality is reflected in laws and policies like President Trump’s executive orders, those efforts are grounded in scientific evidence.