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 engaging 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.