Introduction for Biomechanics Part I

Biomechanics is the application of mechanical principles to biological systems, such as humans, animals, plants, organs, and cells. Perhaps one of the best definitions was provided by Herbert Hatze in 1974: "Biomechanics is the study of the structure and function of biological systems by means of the methods of mechanics". The word biomechanics developed during the early 1970s, describing the application of engineering mechanics to biological and medical systems.

Biomechanics is closely related to engineering, because it often uses traditional engineering sciences to analyse biological systems. Some simple applications of Newtonian mechanics and/or materials sciences can supply correct approximations to the mechanics of many biological systems. Applied mechanics, most notably mechanical engineering disciplines such as continuum mechanics, mechanism analysis, structural analysis, kinematics and dynamics play prominent roles in the study of biomechanics.
Usually biological systems are more complex than man-built systems. Numerical methods are hence applied in almost every biomechanical study. Research is done in a iterative process of hypothesis and verification, including several steps of modelling, computer simulation and experimental measurements.

A field that combines the disciplines of biology and engineering mechanics and utilizes the tools of physics, mathematics, and engineering to quantitatively describe the properties of biological materials. One of its basic properties is embodied in so-called constitutive laws, which fundamentally describe the properties of constituents, independent of size or geometry, and specifically how a material deforms in response to applied forces. For most inert materials, measurement of the forces and deformations is straightforward by means of commercially available devices or sensors that can be attached to a test specimen. Many materials, ranging from steel to rubber, have linear constitutive laws, with the proportionality constant (elastic modulus) between the deformation and applied forces providing a simple index to distinguish the soft rubber from the stiff steel. While the same basic principles apply to living tissues, the complex composition of tissues makes obtaining constitutive laws difficult.

The biomechanical properties and behaviors of organs and organ systems stem from the ensemble characteristics of their component cells and extracellular materials, which vary widely in structure and composition and hence in biomechanical properties. An example of this complexity is provided by the cardiovascular system, which is composed of the heart, blood vessels, and blood.