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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