If you’ve ever wondered just how much cold a human being can tolerate, or how much heat, water pressure, air pressure, or physical exertion the human frame can safely function in,  take a look at “Life at the Extremes: The Science of Survival” by Frances Ashcroft.  Ashcroft is a professor of physiology at Oxford who also offers first-hand accounts of the subject material, whether that be from climbing Kilimanjaro or soaking in Japanese hot springs. She succeeds in making a scientific topic highly accesible, educational and entertaining.

The book is essentially a survey of what our environmental limits are and how it is that we know them, as well as live within them. The science behind these topics is extremely clear and well presented. Each chapter offers tutorials in the interaction of various human body systems and environmental conditions, ranging from extreme heat and cold to the effects of altitude sickness and the ocean depths at which oxygen becomes toxic. The chapter on human speed and endurance is especially interesting in that it provides an excellent synopsis of muscular function and the related physiological and chemical processes, as well as the narrowing search for hard limits to human athletic performance. While we may never experience some of these situations for ourselves, a knowledge of how, when and why the body fails is invaluable for karate students and teachers alike.

Ashcroft’s explanations are jammed full of related facts from history and the animal world that shed some light on our own limits and adaptations. For example, the relationship between a muscle’s size and the speed at which it can contract tends to limit larger animals from being sprinters. Horses and kangaroos sidestep this issue by utilizing more numerous short muscles to load specialized tendons, providing an elastic rebound on each step, thus reducing energy expenditure and allowing them to move at high speeds. Human beings have a less specialized version of this adaptive mechanism: the calf muscle and Achilles tendon.

If karate is ultimately a process of learning what we can survive, “Life at the Extremes” should be interesting reading indeed.