The longer the distance run, the more women have an edge over their male competitors. Yet, the longer the distance, the less likely women are to start the race.

In this engrossing personal account, writer and sport scientist Jen Benson looks at the science and hidden history of ultramarathon running, and details her own attempts to finish a 100-mile race.

Jen lays bare the intensity, unexpected humour, and profound personal sacrifices that define the world of ultra-running, and delves into the fascinating science of ultra-endurance performance. Interweaved with this are the untold stories of trailblazing women from the last four decades, including Jasmin Paris, the first female finisher of the Barkley Marathons; Eleanor Robinson, the first woman to complete the 153-mile Spartathlon race; and Courtney Dauwalter, widely regarded as the greatest female ultra-runner of all time.

A testament to the feats of women that challenge the very limits of human capability, this is the remarkable sporting history of extreme performance hitherto untold.

Jen & Sim Benson are endurance athletes and award-winning outdoor adventure writers and photographers. Between them they've competed in over 100 marathons and ultra marathons, including some of the UK's toughest ultras - the Arc of Attrition 100-mile, Ultra Trail Snowdonia 100km and the North Coast 110-mile - as well as in the Alps and further afield. They are the authors of a number of books including Smart Running, Wild Running, Short Runs in Beautiful Places, The Adventurer's Guide to Britain and The Path She Runs - Jen's story of women in ultra running. They write for a wide range of publications including Runner's World, Women's Running and Trail magazines, and are weekly columnists for The Times.