Elastic Mechanisms in the Locomotion of Vertebrates

Elastic mechanisms serve many functions in the locomotion of vertebrate animals. The ligamentum nuchae in the necks of ungulates gives some support to the head while allowing it to be lowered to the ground for feeding. Tendons in the distal parts of the legs of mammals save energy by stretching and recoiling in each step, enabling the animal to bounce along like a child on a pogo-stick. The same tendons aid jumping by recoiling rapidly like a catapult. An aponeurosis in the back serves as a spring in galloping, halting and reversing the swing of the legs. The elastic compliance of paw pads cushions impacts with the ground. The compliance of the tendons that move our fingers makes it easier for us to control the forces exerted by our fingers but harder to control their positions. The elastic properties of the diaphragm and abdominal wall may give resonant properties to the respiratory system, enabling running movements to drive breathing in some mammals. These and other possible functions of elastic mechanisms are reviewed.