NOBODY WOULD ever suggest that having a penis renders men less competitive with women in athletics, yet there is no sport in which having one’s genitalia on the outside is an advantage.

Perhaps this sounds absurd, but is it really any more ridiculous than suggesting women’s anatomy makes them incapable of competing alongside men in sports? Playing With the Boys explodes a host of myths about men’s and women’s biology and exposes the cultural biases that have shaped athletics and our bodies to argue for ending the imposition of sex-segregation in sports.

McDonagh and Pappano provide a useful history of the social construction of organized sports in the United States that is used to win over immigrants to an American national identity, improve the flagging health of working-class men, and physically strengthen the scions of the elite, masters of the universe whom a rising empire feared were going soft.

But one of the more fascinating aspects of their work is the physiological science and history they wield to make a case for how sports does not simply reflect the gender and sex biases of our culture, but actually help shape them. They argue, “coercive sex segregation does not reflect actual sex differences in athletic ability, but instead constructs and enforces a flawed premise that females are inherently athletically inferior to males.”

From childhood, gender biases determine whose athleticism is honed and whose is ignored. Researchers watching children’s T-ball—where a child hits the ball off a fixed tee—observe parents and coaches who step in to correct and coax the boys into holding the bat correctly and hitting the target; while girls, who are expected to flub up, go untrained and ignored. Even in our gym-body-obsessed culture, girls are still guided by trainers, coaches, and social norms away from developing large muscles or packing on more weight to compete in sports like football.

The dominant arguments common sense dictates are that women on average are smaller, weaker, and slower than men. Setting aside the fact that different talents and attributes are needed for different sports—NBA powerhouse Shaquille O’Neal, for example, would make an awful jockey—these arguments are not as ironclad on closer inspection.

Let’s cut to the chase. Men tend to weigh more and have greater muscle mass than women: men have 40–60 percent greater upper-body strength and 25–30 percent more lower-body strength. However, with training and nutritional guidance on par with men’s, female power lifters, for example, have narrowed the gap in actual strength to between 0 and 8 percent. There have even been studies where women’s lower-body strength used in performing leg-presses has exceeded that of men. While there is a connection between muscle size and strength, there is not a direct correlation, as other factors can influence an athlete’s strength such as age, limb and muscle length, and genetics.

When it comes to endurance sports, women can often leave men in the dust. Women’s greater amounts of estrogen seem to play a role in enabling some women to outperform men in endurance sports, especially in what are known as ultra-endurance sports. At marathon distances, twenty-six miles, women can perform identically to men—and in Boston’s 2003 Marathon the mean running time for the top 207 runners showed women’s times to be nearly five minutes faster, a mean time of 2:36:55 versus men’s men mean time of 2:41:33. But men on average have a harder time keeping up with women in ultra-endurance races of fifty-five miles or more.

Alaska’s Iditarod, the ultimate ultra-endurance sport, an annual 1,200-mile dogsled race from Anchorage to Nome, is frequently won by women. In addition to women’s capacity for greater stamina, it is one of several sports where women’s higher percentage of body fat also plays a role in providing a biological advantage.

Greater body fat yields greater insulation and buoyancy in swimming, which also reduces drag in the water. One female swimmer, Alison Streeter, has successfully finished the perilous twenty-one-mile British Channel crossing a record forty-three times. Women also hold the record for the twenty-two-mile open water swim from Catalina Island to California’s mainland.

The authors rightly lampoon the absurd sex-based rule differences, which are really about perpetuating the myth of women’s comparative frailty. Is it at all credible to argue the continuance of the 1902-based rule mandating women tennis players win the best two out of three matches, as opposed to men’s three out of five? C’mon, tennis pros like Serena and Venus Williams can’t hold out for longer? And are female badminton players honestly so fragile they cannot compete to fifteen points and must stop at eleven?

Playing With the Boys doesn’t sniff at the enormous advances in female athleticism as a result of Title IX, nor do the writers diminish the social gains of many girls and women who compete in women-only sports. Sports participation since the 1973 ruling skyrocketed at least 800 percent among all high school girls. Among Black high school girls, it rose 955 percent! The social impact on young women is undeniable as study after study proves women’s confidence, earnings potential, and even their tendency to leave a violent domestic situation goes up along with participation is sports.

Comparing photos of female college athletes over just the last thirty years reveals a remarkable alteration in women’s physiques. Women athletes today are demonstrably bigger, stronger, and faster than at any previous period as a result of the shifting cultural and political winds that opened vistas to them that were previously unimagined. It is an example of how the women’s liberation movement, along with advances in training and nutrition, didn’t just change laws, but actually altered women’s bodies.

McDonagh and Pappano challenge the notion that sex segregation should be mandated and enforced by the state or any other authority, which Title IX has served to codify. The institutional barriers help create and reinforce gender stereotypes and often exclude qualified athletes from competition. They detail cases in which women have succeeded and even excelled in sex-integrated sports from wrestling, baseball, swimming, and yes, even football.

Some of the most damning evidence against sex-segregation is presented where they show women who’ve been excluded from sex-integrated competition after besting men. Virne Mitchell lost her professional baseball contract at the age of seventeen after striking out both Babe Ruth and Lou Gehrig in 1931. Mills College fencer Helene Mayer had her men’s championship title revoked in 1938 after holding it for a day. As is common in these cases, the women’s victories were belittled, and the men they beat were excused for having gone lightly on them due to their looks or supposed frailty.

It’s impossible to speculate on the physical achievements and competitiveness women are ultimately capable of so long as we live in a society where women’s strength, speed, and endurance are not valued on par with men’s. Playing With the Boys makes the case for nixing the idea of male athleticism as the gold standard in sports and raises fascinating questions about the role of organized sports in shaping gender and sex norms.