Biomechanics


Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to organs, cells and cell organelles, and even proteins using the methods of mechanics. Biomechanics is a branch of biophysics.
File:Giovanni Borelli - lim joints.jpg|thumb|right|Page of one of the first works of Biomechanics in the 17th century

Etymology

The word "biomechanics" and the related "biomechanical" comes from the Ancient Greek βίος bios "life" and μηχανική, mēchanikē "mechanics", referring to the mechanical principles of living organisms, particularly their movement and structure.

Subfields

Biofluid mechanics

Biological fluid mechanics, or biofluid mechanics, is the study of both gas and liquid fluid flows in or around biological organisms. An often studied liquid biofluid problem is that of blood flow in the human cardiovascular system. Blood flow can be modeled by the Navier–Stokes equations. In vivo whole blood is assumed to be an incompressible Newtonian fluid. This assumption fails when considering forward flow within arterioles. At microscopic scales, effects of individual red blood cells become significant, and whole blood cannot be modeled as a continuum. When the diameter of the blood vessel is just 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 a single file. In this case, the inverse Fahraeus–Lindquist effect occurs and the wall shear stress increases.
An example of a gaseous biofluids problem is that of human respiration. Respiratory systems in insects have been studied for bioinspiration for designing improved microfluidic devices.

Biotribology

Biotribology is the study of friction, wear and lubrication of biological systems, especially human joints such as hips and knees. In general, these processes are studied in the context of contact mechanics and tribology.
Additional aspects of biotribology include analysis of subsurface damage resulting from two surfaces coming in contact during motion, i.e. rubbing against each other, such as in the evaluation of tissue-engineered cartilage.

Comparative biomechanics

Comparative biomechanics is the application of biomechanics to non-human organisms, whether used to gain greater insights into humans 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.
Comparative biomechanics overlaps with many other fields, including ecology, neurobiology, developmental biology, ethology, and paleontology. Comparative biomechanics is often applied in medicine as well as in biomimetics, which looks to nature for solutions to engineering problems.

Computational biomechanics

Computational biomechanics is the application of engineering computational tools, such as the finite element method to study the mechanics of biological systems. Computational models and simulations are used to predict the relationship between parameters that are otherwise challenging to test experimentally, or used to design more relevant experiments reducing the time and costs of experiments. Mechanical modeling using finite element analysis has been used to interpret the experimental observation of plant cell growth to understand how they differentiate, for instance. In medicine, over the past decade, the finite element method has become an established alternative to in vivo surgical assessment. One of the main advantages of computational biomechanics lies in its ability to determine the endo-anatomical response of an anatomy, without being subject to ethical restrictions. This has led finite element modeling to the point of becoming ubiquitous in several fields of biomechanics while several projects have even adopted an open source philosophy.
Computational biomechanics is an essential ingredient in surgical simulation, which is used for surgical planning, assistance, and training. In this case, numerical methods are used to compute, as fast as possible, a system's response to boundary conditions such as forces, heat and mass transfer, and electrical and magnetic stimuli.

Continuum biomechanics

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 microstructural details of the material. One of the most remarkable characteristics 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 into two groups: hard and soft tissues. Mechanical deformation of hard tissues may be analysed with the theory of linear elasticity. On the other hand, soft tissues usually undergo large deformations, and thus, their analysis relies 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.

Neuromechanics

uses a biomechanical approach to better understand how the brain and nervous system interact to control the body. During motor tasks, motor units activate a set of muscles to perform a specific movement, which can be modified via motor adaptation and learning. In recent years, neuromechanical experiments have been enabled by combining motion capture tools with neural recordings.

Plant biomechanics

The application of biomechanical principles to plants, plant organs and cells has developed into the subfield of plant biomechanics. Application of biomechanics for plants ranges from studying the resilience of crops to environmental stress to development and morphogenesis at cell and tissue scale, overlapping with mechanobiology.

Sports biomechanics

In sports biomechanics, the laws of mechanics are applied to human movement in order to gain a greater understanding of athletic performance and to reduce sport injuries as well. It focuses on the application of the scientific principles of mechanical physics to understand movements of action of human bodies and sports implements such as cricket bat, hockey stick and javelin etc. Elements of mechanical engineering, electrical engineering, computer science, gait analysis, and clinical neurophysiology are common methods used in sports biomechanics.
Biomechanics in sports can be stated as the body's muscular, joint, and skeletal actions while executing a given task, skill, or technique. Understanding biomechanics relating to sports skills has the greatest implications on sports performance, rehabilitation and injury prevention, and sports mastery. As noted by Doctor Michael Yessis, one could say that best athlete is the one that executes his or her skill the best.

Vascular biomechanics

The main topics of the vascular biomechanics is the description of the mechanical behaviour of vascular tissues.
It is well known that cardiovascular disease is the leading cause of death worldwide. Vascular system in the human body is the main component that is supposed to maintain pressure and allow for blood flow and chemical exchanges. Studying the mechanical properties of these complex tissues improves the possibility of better understanding cardiovascular diseases and drastically improves personalized medicine.
Vascular tissues are inhomogeneous with a strongly non linear behaviour. Generally this study involves complex geometry with intricate load conditions and material properties. The correct description of these mechanisms is based on the study of physiology and biological interaction. Therefore, is necessary to study wall mechanics and hemodynamics with their interaction.
It is also necessary to premise that the vascular wall is a dynamic structure in continuous evolution. This evolution directly follows the chemical and mechanical environment in which the tissues are immersed like Wall Shear Stress or biochemical signaling.

Immunomechanics

The emerging field of immunomechanics focuses on characterising mechanical properties of the immune cells and their functional relevance. Mechanics of immune cells can be characterised using various force spectroscopy approaches such as acoustic force spectroscopy and optical tweezers, and these measurements can be performed at physiological conditions. Furthermore, one can study the link between immune cell mechanics and immunometabolism and immune signalling. The term "immunomechanics" is some times interchangeably used with immune cell mechanobiology or cell mechanoimmunology.

Other applied subfields of biomechanics include

  • Allometry
  • Animal locomotion and Gait analysis
  • Biotribology
  • Biofluid mechanics
  • Cardiovascular biomechanics
  • Comparative biomechanics
  • Computational biomechanics
  • Ergonomics
  • Forensic Biomechanics
  • Human factors engineering and occupational biomechanics
  • Injury biomechanics
  • Implant, Orthotics and Prosthesis
  • Kinaesthetics
  • Kinesiology
  • Musculoskeletal and orthopedic biomechanics
  • Rehabilitation
  • Soft body dynamics
  • Sports biomechanics

    History

Antiquity

can be considered the first bio-mechanic because of his work with animal anatomy, writing the first book on the motion of animals, De Motu Animalium, or On the Movement of Animals. He saw animal's bodies as mechanical systems, pursued questions such as the physiological difference between imagining performing an action and actual performance. In another work, On the Parts of Animals, he provided an accurate description of how the ureter uses peristalsis to carry urine from the kidneys to the bladder.
With the rise of the Roman Empire, technology became more popular than philosophy and the next bio-mechanic arose. Galen, physician to Marcus Aurelius, wrote his famous work, On the Function of the Parts. This would be the world's standard medical book for the next 1,400 years.