Up To Speed: A New Book Illuminates the Understudied Physiology of Female Athletes

Updated May 9, 2025 07:17AM

What is holding women back from reaching their full potential in sports? Is it the burden of waxing and waning hormones that move the goal posts in every stage of life? Lack of access to gear designed for the female body? Or the notion that women are playing catch up after being discouraged from living an active lifestyle for generations?

It’s all that and more. That’s what science writer and Women’s Running contributor Christine Yu argues in her new book Up to Speed: The Groundbreaking Science of Women Athletes. The book takes a 360-degree look at women in sports, examining what athletes have been told in the past, what researchers and innovators are doing today to make sports better for girls and women, and what questions still need to be answered in the future about female physiology to maximize the population’s potential. Yu examines female physiology as neither a problem nor a prize, but as a puzzle yet to be solved.

Yes, it is a book about science, but you don’t have to be scientifically inclined to appreciate the arguments in Up to Speed. And maybe you’ll learn something about the female body (as I did, even after inhabiting one for all these years). “To understand our experience with exercise and sports, we need to become body literate,” writes Yu in the second chapter titled ‘More Than Just Hormonal.’ To lay that foundation she draws on an impressive collection of experts like exercise physiologists Stacy Sims and Anthony Hackney, sports physician and medical director of Boston Children’s Hospital’s Female Athlete Program Kathryn Ackerman, and sports dietitian Louise Burke, to name a few.

Though Up to Speed is not a self-help book offering prescribed guidance, Yu does take a positive solutions-based approach when writing about truly challenging issues. For example, in the chapter titled ‘The Dreaded Female Body,’ she details the complexity behind why women have a high prevalence of certain sports injuries (concussions, ACL tears, and stress fractures). Those injuries have traditionally been blamed on things inherent to the female body like hormones, lax joints, or a wider pelvis.

“Focusing on biologically based sex differences perpetuates the idea that there is something inherently defective and risky about women’s bodies and their participation in sports. It can be a particularly disempowering narrative, leaving girls and women in a seemingly helpless situation,” she writes. While she notes injuries will never be eliminated, the chapter goes on to cite encouraging female-specific prevention strategies experts are trying including targeted mobility work, multidisciplinary centers, and even some fancy tech that includes augmented reality.

Beyond injury, Yu leaves no stone unturned, expertly tackling issues especially pertinent to the running community like RED-S and the prevalence of under-eating. She examines hormones, menstruation, nutrition, psychology, puberty, pregnancy, and menopause, and how they all relate to one another in an athlete’s life. She gives example after example of women who are excelling in spite of the institutions not built for them. The lingering message: imagine the heights women could reach one day if only they had the same research and support that male athletes do.

But it’s not all positive. I found myself scribbling ‘WTF’ in the margins on multiple occasions. Like learning about female cyclists who have to undergo labiaplasty to deal with saddles not built for female anatomy. “It’s the gear that should be fixed, not the vulvas,” Yu writes. (If you don’t know what a vulva or labia is, that might be a sign that you should read this book.)

Another hot button topic she does not sidestep: the argument around biological sex. It’s a topic that several sports, including running, have been grappling with in terms of defining fairness. World Athletics has recently updated its eligibility regulations for transgender and DSD competitors. The new considerations include barring transgender women from competition and tightening testosterone restrictions for DSD athletes. While many people in and outside of sport have opinions, decisions can’t be made without untangling the complicated web of sex and gender. Yu tries to dispel the myth that gender is binary by explaining the wide reaching technical makeup of biological sex and how those variables can present differently in people. “Recognizing that sex (and gender) exist on a spectrum is crucial,” she writes. “We can’t improve our understanding of exercise physiology and sports science if we don’t study the full diversity of human beings.”

Up to Speed ultimately sheds light on issues women in sports face with the stark understanding that it is not up to women alone to fix them. “The onus is placed on women to overcome the obstacles inherent in a system that was rigged against them from the get-go. When they don’t succeed they are blamed for their short-comings,” she writes. Ultimately, researchers, doctors, coaches, product designers, and many more actors will have to step in and step up on behalf of all women and girls.