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American Heritage Dictionary:
bi·o·me·chan·ics |
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McGraw-Hill Science & Technology Encyclopedia:
Biomechanics |
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.
Most tissues are too soft for the available sensors, so direct attachment not only will distort what is being measured but also will damage the tissue. Devices are needed that use optical, Doppler ultrasound, electromagnetic, and electrostatic principles to measure deformations and forces without having to touch the tissue.
All living tissues have numerous constituents, each of which may have distinctive mechanical properties. For example, elastin fibers give some tissues (such as blood vessel walls) their spring-like quality at lower loads; inextensible collagen fibers that are initially wavy and unable to bear much load become straightened to bear almost all of the higher loads; and muscle fibers contract and relax to dramatically change their properties from moment to moment. Interconnecting all these fibers are fluids, proteins, and other materials that contribute mechanical properties to the tissue.
The mechanical property of the tissue depends not only upon the inherent properties of its constituents but also upon how the constituents are arranged relative to each other. Thus, different mechanical properties occur in living tissues than in inert materials. For most living tissues, there is a nonlinear relationship between the deformations and the applied forces, obviating a simple index like the elastic modulus to describe the material. In addition, the complex arrangement of the constituents leads to material properties that possess directionality; that is, unlike most inert materials that have the same properties regardless of which direction is examined, living tissues have distinct properties dependent upon the direction examined. Finally, while most inert materials undergo small (a few percent) deformations, many living tissues and cells can deform by several hundred percent. Thus, the mathematics necessary to describe the deformations is much more complicated than with small deformations.
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. See also Cardiovascular system.
Blood is a suspension of blood cells in plasma. The mammalian red blood cell consists of a membrane enveloping a homogeneous cytoplasm rich in hemoglobin, but it has no nucleus or organelles. While the plasma and the cytoplasm behave as fluids, the red blood cell membrane has viscoelastic properties; its elastic modulus in uniaxial deformation at a constant area is four orders of magnitude lower than that for areal deformation. This type of biomechanical property, which is unusual in nonbiological materials, is attributable to the molecular structure of the membrane: the lipid membrane has spanning proteins that are linked to the underlying spectrin network. The other blood cells (leukocytes and platelets) and the endothelial cells lining the vessel wall are more complex in composition and biomechanics; they have nuclei, organelles, and a cytoskeletal network of proteins. Furthermore, they have some capacity for active motility. See also Blood; Cytoskeleton.
Cardiac muscle and vascular smooth muscle cells have organized contractile proteins that can generate active tension in addition to passive elasticity. Muscle cells, like other cells, are surrounded by extracellular matrix, and cell-matrix interaction plays an important role in governing the biomechanical properties and functions of cardiovascular tissues and organs. The study of the overall performance of the cardiovascular system involves measurements of pressure and flow. The pressure-flow relationship results from the interaction of the biomechanical functions of the heart, blood, and vasculature. To analyze the biomechanical behavior of cells, tissues, organs, and systems, a combination of experimental measurements and theoretical modeling is necessary. See also Muscle.
Other organ systems present many quantitative and qualitative differences in biomechanical properties. For example, because the cardiovascular system is composed of soft tissues whereas bone is a hard tissue, the viscoelastic coefficients and mechanical behaviors are quite different. Cartilage is intermediate in stiffness and requires a poro- elastic theory to explain its behavior in lubrication of joints. In general, living systems differ from most physical systems in their nonhomogeneity, nonlinear behavior, capacity to generate active tension and motion, and ability to undergo adaptive changes and to effect repair. The biomechanical properties of the living systems are closely coupled with biochemical and metabolic activities, and they are controlled and regulated by neural and humoral mechanisms to optimize performance. While the biomechanical behaviors of cells, tissues, and organs are determined by their biochemical and molecular composition, mechanical forces can, in turn, modulate the gene expression and biochemical composition of the living system at the molecular level. Thus, a close coupling exists between biomechanics and biochemistry, and the understanding of biomechanics requires an interdisciplinary approach involving biology, medicine, and engineering.
TechEncyclopedia:
biomechanics |
The study of the anatomical principles of movement. Biomechanical applications on the computer employ stick modeling to analyze the movement of athletes as well as racing horses.
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Oxford Food & Fitness Dictionary:
biomechanics |
The application of physics and mechanics to the study of movement. In sport, biomechanics is especially concerned with how the human body applies forces to itself and objects with which it comes into contact, and how the human body is affected by external forces. A sound knowledge of biomechanics equips a coach, athlete, or other performer to choose appropriate training techniques, and to detect and understand faults that may arise in their use.
Oxford Dictionary of Sports Science & Medicine:
biomechanics |
The study of forces and their effects on living organisms. See also exercise and sport biomechanics.
Saunders Veterinary Dictionary:
biomechanics |
The application of mechanical laws to living structures.
Wikipedia on Answers.com:
Biomechanics |
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This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2009) |
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Biomechanics (from Ancient Greek: βίος "life" and μηχανική "mechanics", In Modern Greek, εμβιομηχανική[1]) is the study of the structure and function of biological systems such as humans, animals, plants, organs, and cells[2] by means of the methods of mechanics.[3]
The word biomechanics developed during the early 1970s, describing the application of engineering mechanics to biological and medical systems.[4][not in citation given]
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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 system 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 modeling, computer simulation and experimental measurements.
Applied subfields of biomechanics include:
In sports biomechanics, the laws of mechanics are applied in order to gain a greater understanding of athletic performance and to reduce sport injuries as well. Elements of mechanical engineering (e.g., strain gauges), electrical engineering (e.g., digital filtering), computer science (e.g., numerical methods), gait analysis (e.g., force platforms), and clinical neurophysiology (e.g., surface EMG) are common methods used in sports biomechanics.[5]
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The mechanical analysis of biomaterials and biofluids is usually carried forth with the concepts of continuum mechanics. This assumption breaks down when the length scales of interest approach the order of the micro structural details of the material. One of the most remarkable characteristic of biomaterials is their hierarchical structure. In other words, the mechanical characteristics of these materials rely on physical phenomena occurring in multiple levels, from the molecular all the way up to the tissue and organ levels.
Biomaterials are classified in two groups, hard and soft tissues. Mechanical deformation of hard tissues (like wood, shell and bone) may be analysed with the theory of linear elasticity. On the other hand, soft tissues (like skin, tendon, muscle and cartilage) usually undergo large deformations and thus their analysis rely on the finite strain theory and computer simulations. The interest in continuum biomechanics is spurred by the need for realism in the development of medical simulation. [6]
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Under certain mathematical circumstances, blood flow can be modeled by the Navier–Stokes equations. In vivo whole blood is assumed to be an incompressible Newtonian fluid, however, this assumption fails when considering forward flow within arterioles. In microscopic scale, the effects of individual red blood cells becomes significant, and whole blood can no longer be modeled as a continuum. When the diameter of the blood vessel is slightly larger than the diameter of the red blood cell the Fahraeus–Lindquist effect occurs and there is a decrease in wall shear stress. However, as the diameter of the blood vessel decreases further, the red blood cells have to squeeze through the vessel and often can only pass in single file. In this case, the inverse Fahraeus–Lindquist effect occurs and the wall shear stress increases.
The main aspects of Contact mechanics & tribology are related with friction, wear and lubrication. When the two surfaces come in contact during motion i.e. rub against each other, friction, wear and lubrication effects are very important to analyze in order to determine the performance of the material. Biotribology is a study of friction, wear and lubrication of biological systems especially human joints such as hips and knees. For example, femoral component and tibial component of knee implant rub against each other during daily activity such as walking or stair climbing. If the performance of tibial component needs to be analyzed, the principles of biotribology are used to determine the wear performance of the implant and lubrication effects of synovial fluid. In addition, the theory of contact mechanics also becomes very important for wear analysis.
Comparative biomechanics is the application of biomechanics to non-human organisms, whether used to gain greater insights into humans (as in physical anthropology) or into the functions, ecology and adaptations of the organisms themselves. Common areas of investigation are Animal locomotion and feeding, as these have strong connections to the organism's fitness and impose high mechanical demands. Animal locomotion, has many manifestations, including running, jumping and flying. Locomotion requires energy to overcome friction, drag, inertia, and gravity, though which factor predominates varies with environment.[citation needed]
Comparative biomechanics overlaps strongly with many other fields, including ecology, neurobiology, developmental biology, ethology, and paleontology, to the extent of commonly publishing papers in the journals of these other fields. Comparative biomechanics is often applied in medicine (with regards to common model organisms such as mice and rats) as well as in biomimetics, which looks to nature for solutions to engineering problems.
The application of biomechanical principles to plants and plant organs has developed into the subfield of plant biomechanics.[7]
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Aristotle wrote the first book on biomechanics, De Motu Animalium, or On the Movement of Animals. He not only saw animals' bodies as mechanical systems, but pursued questions such as the physiological difference between imagining performing an action and actually doing it. Some simple examples of biomechanics research include the investigation of the forces that act on limbs, the aerodynamics of bird and insect flight, the hydrodynamics of swimming in fish, and locomotion in general across all forms of life, from individual cells to whole organisms. The biomechanics of human beings is a core part of kinesiology.
Probably Leonardo da Vinci could be recognized as the first true biomechanician, because he was the first to study anatomy in the context of mechanics. He analyzed muscle forces as acting along lines connecting origins and insertions and studied joint function. He also intended to mimic some animal features in his machines. For example, he studied the flight of birds to find means by which humans could fly. Because horses were the principal source of mechanical power in that time, he studied their muscular systems to design machines that would better benefit from the forces applied by this animal.[8]
Galileo Galilei was interested in the strength of bones and suggested that bones are hollow for this affords maximum strength with minimum weight. He noted that animals' masses increase disproportionately to their size, and their bones must consequently also disproportionately increase in girth, adapting to loadbearing rather than mere size the bending strength of a tubular structure such as a bone is increased relative to its weight. This surely was one of the first grasps of principles of biological optimization.[8]
In the 16th century, Descartes suggested a philosophic system whereby all living systems, including the human body (but not the soul), are simply machines ruled by the same mechanical laws, an idea that did much to promote and sustain biomechanical study. Giovanni Alfonso Borelli embraced this idea and studied walking, running, jumping, the flight of birds, the swimming of fish, and even the piston action of the heart within a mechanical framework. He could determine the position of the human center of gravity, calculate and measured inspired and expired air volumes, and showed that inspiration is muscle-driven and expiration is due to tissue elasticity. Borelli was the first to understand that the levers of the musculoskeletal system magnify motion rather than force, so that muscles must produce much larger forces than those resisting the motion. Influenced by the work of Galileo, whom he personally knew, he had an intuitive understanding of static equilibrium in various joints of the human body well before Newton published the laws of motion.[9]
In the 19th century Étienne-Jules Marey used cinematography to scientifically investigate locomotion. He opened the field of modern 'motion analysis' by being the first to correlate ground reaction forces with movement. In Germany, the brothers Ernst Heinrich Weber and Wilhelm Eduard Weber hypothesized a great deal about human gait, but it was Christian Wilhelm Braune who significantly advanced the science using recent advances in engineering mechanics. During the same period, the engineering mechanics of materials began to flourish in France and Germany under the demands of the industrial revolution. This led to the rebirth of bone biomechanics when the railroad engineer Karl Culmann and the anatomist Hermann von Meyer compared the stress patterns in a human femur with those in a similarly shaped crane. Inspired by this finding Julius Wolff proposed the famous Wolff's law of bone remodeling.[10]
The study of biomechanics ranges from the inner workings of a cell to the movement and development of limbs, to the mechanical properties of soft tissue, and bones. As we develop a greater understanding of the physiological behavior of living tissues, researchers are able to advance the field of tissue engineering, as well as develop improved treatments for a wide array of pathologies.
Biomechanics is also applied to studying human musculoskeletal systems. Such research utilizes force platforms to study human ground reaction forces and infrared videography to capture the trajectories of markers attached to the human body to study human 3D motion. Research also applies electromyography[11] (EMG) system to study the muscle activation. By this, it is feasible to investigate the muscle responses to the external forces as well as perturbations.
Biomechanics is widely used in orthopedic industry to design orthopedic implants for human joints, dental parts, external fixations and other medical purposes. Biotribology is a very important part of it. It is a study of the performance and function of biomaterials used for orthopedic implants. It plays a vital role to improve the design and produce successful biomaterials for medical and clinical purposes.
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 | American Heritage Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| McGraw-Hill Science & Technology Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| TechEncyclopedia. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher. © 1981-2012 The Computer Language Company Inc. All rights reserved. Read more |
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| Oxford Food & Fitness Dictionary. Food and Fitness: A Dictionary of Diet and Exercise. Copyright © 1997, 2003 by Oxford University Press. All rights reserved. Read more |
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| Oxford Dictionary of Sports Science & Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved. Read more |
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| Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
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| Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Biomechanics. Read more |
