Exploring Biomechanics, Animals in Motion

Scientific American Library Series #40

by R. McNeill Alexander

Examines the entire range of animal movements. Beginning with humans and other complex animals and ending with single-celled organisms, the book describes and illustrates how animals move. It explains the relation between energy costs and the ability to do work and exert force.

Genres: Science, Nonfiction, Biology

Paperback

First published May 1, 1992

About the author

Professor of Zoology

Reviews

[Rossdavidh · Rating 3 out of 5]

There are people who study animals (other than humans). There are people who study mechanics (the science of machines, not the people who work on them, although I suppose somebody must study them also). And then, there are those people who study the mechanics of animals. How do muscles work (at the molecular, fiber, and macro level)? How do fish move, and what does that have in common with how birds move when they fly? How do both compare to how much smaller organisms like insects or bacteria move through the same substance (which, to them, seems much more viscous)?

How do you measure all that you need to know for this?

This book was written in 1991, and I'm sure a lot has been added to it since then, but even then it was amazing how much had been done. Imagine making the water equivalent of a wind tunnel, training fish to swim in it, making it a sealed system, and then measuring precisely the oxygen content of the water so that you can tell how hard the fish is working to keep up. Imagine doing something similar with a duck swimming, or any bird flying.

The book does not skimp on illustrations, and thank goodness. We see illustrations of a plane wing in cross section, a graph of the tradeoff between power and airspeed for planes, a graph of the tradeoff between airspeed and sinking speed for gliders, and then a diagram titled "A wind tunnel used for testing the gliding ability of birds", which shows what looks like a pigeon about to fly into an enormous cannon. Vultures soaring in thermals. Albatrosses slope-soaring along a wave (which is that thing they do where they fly parallel to the beach with almost no effort).

There are chapters on walking and running, jumping, climbing and crawling, gliding and soaring, floating, swimming, and whatever it is you call what an amoeba does. There are a lot of stories about researchers doing ingenious things to coax animals into doing their thing (whichever of the above it is) in a controlled fashion for them to measure, or else just finding a way to measure them as they go naturally about it. An example:

"As dusk approached each evening, Scholey settled down on a chair on the sun deck, waiting for the flying squirrels to emerge from their holes. With him he had a panoramic photograph of the forest edge and a stopwatch. When the squirrels came out and began to glide, he would mark, on the photograph, the positions on the trees at which each glide started and ended, and he would time the glides with the stopwatch. He watched the squirrels until they disappeared into the forest or it became too dark to see them. On the following day, using surveying instruments, he measured the length of each glide, and the height lost."

Researchers must, I suppose, be meticulous people, and in many of these cases also willing and able to cobble together from existing techniques a new way of measuring something which had not been measured before. By the way, flying squirrels lose about a meter of height for every 5 meters traveled.

I admit that, in addition to enjoying learning about how the animals moved, I enjoyed reading tales like this of the behavior of researchers in their native habitat. Picturing Scholey out there on his sun deck, with a stopwatch and panoramic photograph and (I like to imagine) broad-brimmed hat, was just fun. All of science relies, more I think than on the theorizers who are more likely to get the accolades and fame, on an army of creative and industrious observers like this. It is somewhat interesting to learn that the ratio of the cost of force to distance, is equal to the force times the fascicle length divided by the step length, but the reality is I'm never going to need that particular equation in my life. It is good to know that there are people out there looking into many such nooks and crannies of the natural world, however, and bringing back knowledge of what they have seen there.

[Katelyn Jenkins · Rating 5 out of 5]

Truly am grateful for this read.
It is just astonishing, from the concepts and theories to the impossible photographs and insightful diagrams. It teaches its reader the fundamentals of physics for biological life and the mechanics (movements) of animals (including humans) to a stunning degree a person, really, cannot get anywhere else.
There is a reason for every action, and a purpose to every evolved form. Animators should definitely read this, along with any person with an interest in how birds fly, athletes achieve impossible speeds, centipedes walk, geckos hang anywhere and anywhere they wish, and how energy gives way to incredible miracles.
Give this a go, please.

[Roland W. · Rating 4 out of 5]

Very interesting study of how members of the animal kingdom move. The great variety of motions used are detailed in an interesting and understandable way. It was of particular interest to find out how little is understood with regard to many of these processes and the competing theories being brought forward.

[Al · Rating 4 out of 5]

This was a very well written and interesting book on how animals move. Prof. Alexander writes for the non-specialist, and does a great job explaining the physics of animal movement. His writing style held my interest throughout the book. The first chapter on muscles does a very good job in explaining how muscles work through lengthening and shortening, how force is exerted, and how they control movement. This chapter lays an excellent foundation for the chapters that follow. The other chapters explain walking, running, jumping, all types of flight, swimming and "Small-Scale Locomotion". Alexander readily admits that there is still much to be learned about animal locomotion, starting with energy consumption of muscles and how they effectively exert force. An additional attraction of this book is the fact that insects are included, especially in the chapter on flapping flight. After reading this, I am much more observant of the animals and insects I see around me.

[Forn · Rating 4 out of 5]

Although this book is a real scientific book, most of it is easy to understand, if the reader has a minimal understanding of physical processes. You'll get interesting insights in how animals (and human beings) really move (including bumble bees, who can fly). Most interesting for me was the way, how the author explains by easy formulae, how things should work, and then shows, how experiments proved the results, and that physics absolutely rule the whole world in motion.

[Craven Lovelace · Rating 5 out of 5]

An outstanding introduction to the subject of biomechanics that may prove to be particularly useful for non-specialists. (I came to it as an animator wanting to know more about how organic bodies work.) Alexander's "Principles of Animal Locomotion" is more in-depth, but this book is both copiously illustrated and quickly immersive, and can often be found quite cheap.