Why do you shift from walking to running at a particular speed? How can we predict transition speeds for animals of different sizes? Why must the flexible elastic of arterial walls behave differently than a rubber tube or balloon? How do leaves manage to expose a broad expanse of surface while suffering only a small fraction of the drag of flags in high winds? The field of biomechanics - how living things move and work - hasn't seen a new general textbook in more than two decades. Here a leading investigator and teacher lays out the key concepts of biomechanics using examples drawn from throughout the plant and animal kingdoms. Up-to-date and comprehensive, this is also the only book to give thorough coverage to both major subfields of biomechanics: fluid and solid mechanics. Steven Vogel explains how biomechanics makes use of models and methods drawn from physics and mechanical engineering to investigate a wide range of general questions - from how animals swim and fly and the modes of terrestrial locomotion to the way organisms respond to wind and water currents and the operation of circulatory and suspension-feeding systems. He looks also at the relationships between the properties of biological materials - spider silk, jellyfish jelly, muscle, and more - and their various structural and functional roles. While written primarily for biology majors and graduate students in biology, this text will be useful for physical scientists and engineers seeking a sense of the state of the art of biomechanics and a guide to its rather scattered literature. For a still wider audience, it establishes the basic biological context for such applied areas as ergonomics, orthopedics, mechanical prosthetics, kinesiology, sports medicine, and biomimetics.