When it comes to the toughest races in the world that push competitors to their absolute limits, a trend has captured public attention: female athletes have been beating the strongest male contenders, in events traditionally designed for men.

In Ultra Women, two endurance athletes delve into the surprising science of sporting performance to explore the physiological and psychological differences between the sexes. They ask: could fat stores and muscle type (and capacity for not sleeping) really give women an edge over men in ultra long distances? And what roles are played by pace, preparation, and motherhood?

Speaking to elite athletes, historians and scientists, the book unearths the largely unknown past of female endurance, from hunter- gathering to the early 20th Century discipline of pedestrianism. We meet poverty-stricken mother Stamata Revithi, who snuck into the 1896 Athens Olympics marathon, 1980s swimming pioneer Lynne Cox – who crossed the world’s coldest oceans in just a swimsuit – and Jasmin Paris, a British vet who ran almost non-stop to win a 268-mile mountain race, while breastfeeding.

Brimming with inspiring stories, Ultra Women blazes the trail laid by Caroline Criado Perez’s Invisible Women: Exposing Data Bias in a World Designed for Men. Upbeat and fast-paced, it sets out a blueprint for increasing female participation in sport.