Scientists whose papers are cited by a Heritage Foundation report on women in sports say the conservative think tank, which has influenced several high-profile Trump administration policies, misrepresents their research and neglects the science.

Scott Yenor, chair of the Heritage Foundation’s American Citizenship Initiative, argues in the July 8 report that Title IX, a 1972 law that bans sex discrimination in education, including sports, “has evolved from a seemingly modest anti-discrimination statute into a powerful engine of feminist social engineering.”

Essentially, in the report, Yenor suggests that women are biologically programmed not to take part in certain high-impact sports and that proportional equality in school sports isn’t desirable or backed by science.

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This interpretation of the evidence is remiss at best, says Carlos Hernando Domingo, a professor at Spain’s University of Jaume I, whose research was cited by Yenor.

“All high-performance sport carries direct health risks,” Hernando Domingo says. “Regardless of sex, the possibility of injury, as well as physiological or psychological disorders, are elements that must be considered in all training processes aimed at achieving maximum athletic performance.”

In the report, Yenor argues that moderate physical activity can contribute to “health, good habits, vigor, bodily toughness, grace, confidence, social connection of teamwork, and beauty” for women. Yenor cites several scientific papers, including one co-authored by Hernando Domingo, that he claims show elite training can cause women to have irregular menstrual cycles and infertility issues.

“A woman who fills up her late teens and early twenties (until she is 25, say) with elite sports competition runs a not insubstantial risk of having compromised fertility for as much as a third of her fertility window,” Yenor writes in an e-mail to Scientific American. “Fertility for women really falls off in the early- to mid-thirties. Men have much longer windows.”

While engaging in high-performance sports may alter women’s menstrual cycles, “this does not indicate damage to the female reproductive system,” Hernando Domingo says. And as soon as women reduce their training or stop, their menstrual cycle stabilizes. “It is a situation high-performance female athletes accept,” he adds, “just as any elite athlete accepts the inherent risks of training at the highest competitive level.”

Pennsylvania State University professor Mary Jane de Souza, whose work on female athletes’ menstrual cycles was also cited by Yenor, says his argument is “selective” and discounts discrimination.

“It selectively emphasizes evidence supporting natural sex differences and the costs of proportionality while giving comparatively little attention to the extensive historical discrimination that motivated Title IX and the measurable gains women have achieved because of it,” de Souza says.

The Heritage Foundation has previously pushed for overhauling scientific funding in a way critics say will politicize research. And this is not the first time conservatives have taken aim at Title IX: the Trump administration has sought to roll back the law’s protections and to ban transgender girls and women from taking part in sports.

This new attack on Title IX is alarming, says Traci Carson, an epidemiologist and an amateur competitive cyclist, who has studied the effects of athletic training on women’s fertility.

“My gut reaction as a lifelong athlete myself—an adolescent college athlete, semi-professional adult athlete—I just thought of all the generations of young women that could potentially be affected by this and all the opportunities that sport brought me in my life,” she says.

Much of Carson’s work has focused on what was used to be called the female athlete triad—namely, how irregular menstrual cycles, low energy availability and lower bone mineral density can affect women in high-intensity sports. More recent research has shown that, aside from menstrual issues, male athletes can suffer from similar problems, resulting in a new name: Relative Energy Deficiency in Sport (RED-S).

The Heritage Foundation doesn’t mention RED-S. But the logic that high-intensity or elite-level training may influence fertility extends to men, too. A 2025 review, published in the Journal of Clinical Medicine, found intense training had negative effects on seminal volume and sperm concentration and movement and could cause sperm to become misshapen. Training could also lead to DNA fragmentation or damage to sperm cells, which might cause miscarriages, as well as to concerningly high levels of white blood cells in ejaculate.

“Men also have reproductive consequences,” Carson says. “They’re just harder to detect because it’s things like sperm quality.... And so they usually go undetected until maybe they’re trying to conceive.”

The Heritage Foundation’s Yenor dismisses the notion that elite sports pose any threat to male fertility, observing to SciAm that, since 1990, Super Bowl–winning quarterbacks have had a higher than average number of children.

“The compromises therefore matter less for men, and the risks appear to be smaller, too,” he adds. “Fertility rates of elite competitors among men exceed the national average by a lot.”

Regardless of whether an athlete is male or female, any fertility issues associated with training tend to abate after a few months of rest.

This has prompted some women’s professional sports associations to make changes to allow athletes to compete more safely. Last year the Women’s Tennis Association (WTA) began offering rankings protection if players decide to undergo an egg or embryo freezing procedure. In a paper in the British Journal of Sports Medicine, members of the WTA’s performance and health staff stressed the importance of providing support, rather than discouragement, to athletes seeking to preserve their fertility. And under the terms of a 2020 collective bargaining agreement, the Women’s National Basketball Association offers insurance of up to $60,000 over the span of a career for fertility treatments, including cryopreservation, to players with two years or more in the league.

These examples are illustrative of the fact that athletes already take their fertility and menstrual cycles into consideration, Carson says.

Jaime Schultz, a professor at Penn State, who focuses on the history of gender and sports, worries that any further attempts to change Title IX could have far-reaching ramifications for women’s sports—and education.

“If we roll back Title IX again, it’s not just about sports: What does this do for other educational programs?” she says. “If we don’t have some sort of legal mechanism to insist on some kind of gender parity, it’s just going to throw everything back 100 years.”