biomechanics and biomechanical analysis 0x50volume · biomechanics and biomechanical analysis...
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Biomechanics and Biomechanical Analysis
Introduction
Historical overview
Biomechanical– Description– Analysis– Assessment
• http://www.motionanalysis.com/about_mac/50x50volume.html
Biomechanics
What is biomechanics?
The application of mechanical principles in the study of living organisms
The science concerned with the internal and external forces acting on the human body and the effects produced by those forces
BiomechanicsThe “bio” part should be obvious, but what is mechanics?
Physics
Mechanics Other areas of physics
Statics Dynamics
Kinematics Kinetics
Biomechanics
How does biomechanics relate to other areas of movement science?
Movement Science
Biomechanics Exercise Physiology
Motor Behavior
Exercise/Sport Psychology
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The Interdisciplinary Nature of Biomechanics
Reflected by ASB membership categories
– Engineering & Applied Physics (50%)– Exercise & Sport Science (18%)– Health Science (15%)– Biological Science (<10%)– Ergonomics & Human Factors (<10%)
Biomechanics
Who studies biomechanics?– Exercise Scientists – Athletic Trainers– Physical Therapists – Biomedical Engineers– Biologists– Orthopaedic/Sports Physicians– Physical Educators / Coaches– Ergonomists
Major Areas of Study
Sports Performance Sports Injuries
Major Areas of Study
Gait Analysis Fracture Mechanics
Major Areas of Study
Equipment DesignErgonomics
Historical Roots
Aristotle (~ 400-300 BC)
Rebelled against Platonic philosophy
Studied motion and hypothesized about the effects of forces (“just as the pusher pushes, so is the pusher pushed”)
Wrote On the Movement of Animals - first written account of locomotion
Plato (~ 450-350 BC)
Did not value experimentation and observation, but did establish mathematics as the basis for science
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Galen (~ 100-200 AD)
Was trained in both medicine and mathematics
Established medicine as a comprehensive science: wrote a medical text (On The Use Of Parts) that dominated medicine for 1400 years
Made extensive study of muscles and movement
World’s first sports medicine doctor – primary physician to the Roman gladiators
Archimedes (~ 300-200 BC)
Developed many important proofs and theorems in mechanics and mathematics, many based on Aristotle’s theories
Established areas of statics and hydrostatics
Fast-forward 1200 years……
da Vinci (1452-1519)
Best known as an artist, but primarily worked as an engineer
Made many contributions to mechanics
Applied mechanical principles to human anatomy
Vesalius (1514-1564)
Established modern science of anatomy
Challenged many of Galen’s theories, and proved many to be wrong
Championed need for physicians to learn anatomy by dissection of human cadavers
Galileo Galilei (1564-1642)
Made numerous contributions to mechanics and established the scientific method
Studied human jumping, equine and insect locomotion, and floatation of the human body
Wrote an unpublished work, The Movement of Animals, well before Borelli
Studied scale effect on biological materials
William Harvey (1578-1657)
Applied first systematic experimental approach to study of human physiology
Discovered circulation of the blood by action of the pumping heart
Giovanni Borelli (1608-1679)
Generally considered to be the “father” of biomechanics: ASB’s highest award is named after Borelli
Trained in both physiology and mathematics (by a student of Galileo’s), he rigorously applied mechanical principles to biology
Wrote the 2nd book titled On the Movement of Animals (~ 2000 years after Aristotle)
Studied numerous aspects of human movement and muscle function
Many of his ideas on muscle were flawed, but still revolutionary at the time
Isaac Newton (1642-1727)
Revolutionized mechanics by postulating four basic laws:
Law of gravityLaw of inertia (1st law)Law of acceleration (2nd law)Law of action-reaction (3rd law)
Newton’s 2nd law forms the basis for all kinetic analyses of human motion
Made numerous other contributions in mathematics, optics, astronomy, etc
Helped establish the formal theoretical approach to scientific inquiry
The Weber brothers:
Eduard (1795-1881)Wilhelm (1804-1891)
Formulated over 100 hypothesis regarding human locomotion in On the Mechanics of the Human Gait Tools, but lacked the ability to verify many of them
Following Newton, there were further advances in mechanics by:
Leonhard Euler (1707-1783)Jean le Rond D’Alembert (1717-1783)Joseph Lagrange (1736-1815)
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Etienne Marey(1838-1904)
Revolutionized motion analysis by the use of sequential, multiple exposure, and motion photography
Etienne Marey(1838-1904)
Edweard Muybridge(1830-1904)
Muybridge produced an astounding collection of photographs of humans and animals in motion, but Marey was the true scientist of human movement
Edweard Muybridge(1830-1904)
Edweard Muybridge(1830-1904)
Braune & Fischer:Wilhelm Braune (1831-1892)Otto Fischer (1861-1917)
Conducted first 3D analysis of human locomotionResults published in The Human GaitData collected in one night, analysis took years!
DuBois Reymond (1818-1922)Guillaume Duchenne (1806-1875)
Developed modern EMG techniquesDuchenne published Physiology of Movements
Julius Wolff (1834-1910)
Formulated Wolff’s Law, stating that mechanical loading dictates bone growth and remodeling
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A.V. Hill (1886-1977)Major contributions were in muscle mechanics and thermodynamics but also studied human sprinting
Nicholas Bernstein (1896-1966)Conducted extensive biomechanical studies of human movement in Russia - work was virtually unknown in the West until 1967
Wallace Fenn (1893-1971)First calculations of different components of mechanical work in human running
Herbert Elftman (deceased – unknown date)Estimated mechanical work done by muscles in walking and running
More recent developments• 1967 - First International Seminar on Biomechanics
held in Zürich
• 1973 - International Society of Biomechanics* founded during a conference at Penn State
• 1977 - American Society of Biomechanics* founded
• Universities begin to offer advanced courses and degrees in biomechanics
• Scientific journals with “biomechanics” in the title begin to appear
*Prof. Robert Shapiro - founding member
Biomechanical AnalysisWhat qualifies as a “biomechanical analysis”?
Many studies that were purely descriptive in nature have been passed off as assessmentsor analyses of human movement
What is the difference between:measurementdescriptionmonitoringanalysisassessment
• Measurement – the process of ascertaining the dimensions, quantity, or capacity of something
• Description – the process of representing or depicting a measurement quantitatively or pictorially
• Monitoring – tracking changes in a measured quantity over time
Measurement, Description, & Monitoring
Note that a given measure can lead to different descriptions, and a single description can arise from various measurement instruments
from: Winter (1990)
AnalysisAnalysis is any mathematical operation performed on the measured data to aid in assessment
• The analysis may simply change the form of the data– Smoothing– Rectifying
• The analysis may also combine different data, yielding a quantity that can not be measured– Inverse dynamics– Mechanical power analysis
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dynamic equations
joint moments
segment kinematics
ground reaction forces
joint power
from: Winter (1990), fig 8.10
EMG ProcessingJoint Power Analysis Assessment
The purpose of assessment is to arrive at an answer to a question about some physical movement
The analysis of the data should lead to the answer of the question that was initially posed– If not, then improper or incomplete
measurements were made
Examples:– Did surgery lead to appropriate gait changes?– Did training lead to positive changes in running
performance?
Where is Biomechanics Today?
• Emphasis on purely descriptive studies is being left behind (perhaps not fast enough)
• Mechanistic, scientific approaches are being used to:– uncover basic aspects about how the body works– determine the efficacy of treatment programs– determine the efficacy of training programs– improve human performance– minimize the risk of human injury
Where is Biomechanics Going Tomorrow?New advances in measurement techniques and experimental designs
– imaging / MRI / DEXA– in vivo measurement of forces
and motion
Where is Biomechanics Going Tomorrow?Theoretical investigations using computer models of the musculoskeletal system
– movement simulation– joint load estimation
FMUS
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Up Next…
Topics– Sampling theory– Analog to Digital Conversion (ADC)
Readings– Robertson (2004) Introduction pp. 1 – 5– Robertson (2004) Chapter 11, pp. 227-238