Editing Biomechanics (section)

== Subfields ==
=== Biofluid mechanics ===
[[File:Redbloodcells.jpg|right|thumb|[[Red blood cell]]s]]

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. 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]]. At the microscopic scale, the effects of individual [[red blood cells]] become significant, and whole blood can no longer 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.<ref>{{cite journal | last1=Aboelkassem | first1=Yasser | year=2013 | title=Selective pumping in a network: insect-style microscale flow transport | journal=Bioinspiration & Biomimetics | volume=8 | issue=2 | pages=026004 | doi=10.1088/1748-3182/8/2/026004| pmid=23538838 |bibcode=2013BiBi....8b6004A | s2cid=34495501 }}</ref>

=== Biotribology ===
Biotribology is the study of [[friction]], [[wear]] and [[lubrication]] of biological systems, especially human joints such as hips and knees.<ref>{{cite book|title=Biotribology|last1=Davim|first1=J. Paulo|date=2013|publisher=John Wiley & Sons|isbn=978-1-118-61705-2}}</ref><ref>{{Cite journal|date=2021|editor-last=Ostermeyer|editor-first=Georg-Peter|editor2-last=Popov|editor2-first=Valentin L.|editor3-last=Shilko|editor3-first=Evgeny V.|editor4-last=Vasiljeva|editor4-first=Olga S.|title=Multiscale Biomechanics and Tribology of Inorganic and Organic Systems|journal=Springer Tracts in Mechanical Engineering|language=en-gb|doi=10.1007/978-3-030-60124-9|isbn=978-3-030-60123-2|issn=2195-9862|doi-access=free}}</ref> 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.<ref name="Whitney, G. A. 2014">{{cite journal | last1 = Whitney | first1 = G. A. | last2 = Jayaraman | first2 = K. | last3 = Dennis | first3 = J. E. | last4 = Mansour | first4 = J. M. | year = 2014 | title = Scaffold-free cartilage subjected to frictional shear stress demonstrates damage by cracking and surface peeling | journal = J Tissue Eng Regen Med | volume = 11 | issue = 2 | pages = 412–424 | doi = 10.1002/term.1925 | pmid = 24965503 | pmc = 4641823 }}</ref>

=== Comparative biomechanics ===
{{Unreferenced section|date=January 2025}}
[[File:penguinu.jpg|thumb|right|[[Chinstrap penguin]] leaping over water]]
Comparative biomechanics is the application of biomechanics to non-human organisms, whether used to gain greater insights into humans (as in [[Biological anthropology|physical anthropology]]) or into the functions, ecology and adaptations of the organisms themselves. Common areas of investigation are [[animal locomotion]] and [[List of feeding behaviours|feeding]], as these have strong connections to the organism's [[Fitness (biology)|fitness]] and impose high mechanical demands. Animal locomotion has many manifestations, including [[running]], [[jumping]] and [[Flying and gliding animals|flying]]. Locomotion requires [[energy]] to overcome [[friction]], [[drag (physics)|drag]], [[inertia]], and [[gravity]], though which factor predominates varies with environment.{{Citation needed|date=December 2010}}

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.{{citation needed|date=January 2018}}

=== 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 model]]s and [[Computer simulation|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.<ref name="Bidhendi2018" /> 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.<ref>{{Cite journal |last=Tsouknidas |first=Alexander |last2=Savvakis |first2=Savvas |last3=Asaniotis |first3=Yiannis |last4=Anagnostidis |first4=Kleovoulos |last5=Lontos |first5=Antonios |last6=Michailidis |first6=Nikolaos |date=November 2013 |title=The effect of kyphoplasty parameters on the dynamic load transfer within the lumbar spine considering the response of a bio-realistic spine segment |url=https://linkinghub.elsevier.com/retrieve/pii/S0268003313002192 |journal=Clinical Biomechanics |language=en |volume=28 |issue=9-10 |pages=949–955 |doi=10.1016/j.clinbiomech.2013.09.013}}</ref> This has led finite element modeling (or other discretization techniques) to the point of becoming ubiquitous in several fields of biomechanics while several projects have even adopted an open source philosophy (e.g., BioSpine).<ref>{{Cite web|url=https://blog.ucbmsh.org/department/computational-biomechanics|title=Computational Biomechanics – BLOGS|access-date=26 October 2021|archive-date=4 April 2022|archive-url=https://web.archive.org/web/20220404153131/https://blog.ucbmsh.org/department/computational-biomechanics|url-status=dead}}</ref> 

Computational biomechanics is an essential ingredient in surgical simulation, which is used for surgical planning, assistance, and training. In this case, numerical (discretization) 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 [[biomaterial]]s and biofluids is usually carried forth with the concepts of [[continuum mechanics]]. This assumption breaks down when the [[length scale]]s of interest approach the order of the microstructural details of the material. One of the most remarkable characteristics of biomaterials is their [[hierarchy|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 (biology)|tissue]] and [[organ (anatomy)|organ]] levels.{{citation needed|date=January 2018}}

Biomaterials are classified into two groups: hard and [[soft tissues]]. Mechanical deformation of hard tissues (like [[wood]], [[Seashell|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 relies on the [[finite strain theory]] and [[computer simulation]]s. The interest in continuum biomechanics is spurred by the need for realism in the development of medical simulation.<ref name="Fung">{{harvnb|Fung|1993|}}</ref>{{rp|568}}

=== Neuromechanics ===
[[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.<ref name="Niklas">{{cite book | last=Niklas | first=Karl J. | title=Plant Biomechanics: An Engineering Approach to Plant Form and Function | url=https://archive.org/details/plantbiomechanic0000nikl/page/622 | url-access=registration | publisher=University of Chicago Press | edition=1 | year=1992 | location=New York, NY | page=[https://archive.org/details/plantbiomechanic0000nikl/page/622 622] | isbn=978-0-226-58631-1 }}</ref> Application of biomechanics for plants ranges from studying the resilience of crops to environmental stress<ref>{{cite journal | last1 = Forell | first1 = G. V. | last2 = Robertson | first2 = D. | last3 = Lee | first3 = S. Y. | last4 = Cook | first4 = D. D. | year = 2015 | title = Preventing lodging in bioenergy crops: a biomechanical analysis of maize stalks suggests a new approach | journal = J Exp Bot | volume =  66| issue = 14 | pages =  4367–4371| doi = 10.1093/jxb/erv108 | pmid = 25873674 | doi-access = free }}</ref> to development and morphogenesis at cell and tissue scale, overlapping with [[mechanobiology]].<ref name="Bidhendi2018">{{cite journal|last1=Bidhendi|first1=Amir J|last2=Geitmann|first2=Anja|title=Finite element modeling of shape changes in plant cells|journal=Plant Physiology|date=January 2018|volume=176|issue=1|pages=41–56|doi=10.1104/pp.17.01684|pmid=29229695|pmc=5761827}}</ref>

=== Sports biomechanics ===
{{Main|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 [[sports injury|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]] (e.g., [[strain gauge]]s), [[electrical engineering]] (e.g., [[digital filter]]ing), [[computer science]] (e.g., [[numerical methods]]), [[gait analysis]] (e.g., [[force platform]]s), and [[clinical neurophysiology]] (e.g., [[Electromyography|surface EMG]]) are common methods used in sports biomechanics.<ref name="Bartlett">{{cite book|title=Introduction to sports biomechanics|last=Bartlett|first=Roger|publisher=Routledge|year=1997|isbn=978-0-419-20840-2|edition=1|location=New York, NY|page=304}}</ref>

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.<ref>{{cite book|title=Secrets of Russian Sports Fitness & Training|author=Michael Yessis|year=2008|isbn=978-0-9817180-2-6}}</ref>

=== 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.<ref>{{cite web |title=The top 10 causes of death |url=https://www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death |website=World Health Organization |publisher=WHO}}</ref> 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 (e.g. temperature).<ref>{{cite journal |last1=Evers |first1=Tom M.J. |last2=van Weverwijk |first2=Antoinette |last3=de Visser |first3=Karin E. |last4=Mashaghi |first4=Alireza |title=Single-cell analysis of innate immune cell mechanics: an application to cancer immunology |journal=Materials Advances |date=2024 |volume=5 |issue=12 |pages=5025–5035 |doi=10.1039/D3MA01107K|doi-access=free |hdl=1887/4038368 |hdl-access=free }}</ref> 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
*[[Ergonomy]]
*[[Forensic biomechanics|Forensic Biomechanics]]
* Human factors engineering and occupational biomechanics
*[[Forensic biomechanics|Injury biomechanics]]
*[[Implant (medicine)]], [[Orthotics]] and [[Prosthesis]]
*[[Kinaesthetics]]
*[[Kinesiology]] (kinetics + physiology)
*[[human musculoskeletal system|Musculoskeletal]] and orthopedic biomechanics
*[[Rehabilitation (neuropsychology)|Rehabilitation]]
*[[Soft body dynamics]]
*[[Sports biomechanics]]