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 in