The book is organised into chapters detailing different animals and their ability to use their natural advantages for greatest endurance and explains how Heinrich used this knowledge to become an ultra-runner.
Why We Run focuses on how antelope, deer, wolves, bees, frogs, camels and other animals exhibit endurance techniques that humans later adopted.
Birds have a majority of slow twitch fibrous muscles that are adapted for long travel times as well as the ability to simultaneously inhale and exhale.
The book concludes as Heinrich completes an ultra-marathon and reflects on the biology, anthropology, psychology and philosophy that affected his life along with the animals and their metabolic functions.
The title was changed due to a complaint from Sean Gibbon, author of Run Like the Antelope, a book about the rock band Phish.