Since ancient times, bathing in cold water has been known as a means of hardening the body. However, winter swimming (ice bathing) has only developed into an organized sport since the 1970s, primarily in the new federal states of Germany. This book now provides a comprehensive overview of this extreme sport. Two distinguished medical professionals, after years of scientific research, discuss the practice (behavior during ice bathing, duration of stay in ice water) and physiology (effects on heat balance and circulation, influence on the nervous and immune systems) of winter swimming and present the documented health benefits of regular participation. Additionally, alternative hardening methods such as sauna and Kneipp therapy are also covered.