Biomechanics and
Biomechanical Analysis
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Introduction
Historical overview
Biomechanical
– Description
– Analysis
– Assessment
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
Biomechanics
Biomechanics
The “bio” part should be obvious, but what
is mechanics?
How does biomechanics relate to other areas
of movement science?
Physics
Mechanics
Statics
Dynamics
Kinematics
Movement
Science
Other areas
of physics
Biomechanics
Exercise
Physiology
Exercise/Sport
Psychology
Motor
Behavior
Kinetics
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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%)
Major Areas of Study
Sports Performance
Sports Injuries
Major Areas of Study
Biomechanics
Who studies biomechanics?
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Exercise Scientists
Athletic Trainers
Physical Therapists
Biomedical Engineers
Biologists
Orthopaedic/Sports Physicians
Physical Educators / Coaches
Ergonomists
Major Areas of Study
Gait Analysis
Fracture Mechanics
Historical Roots
Plato (~ 450-350 BC)
Equipment Design
Ergonomics
Did not value experimentation and
observation, but did establish
mathematics as the basis for science
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
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Archimedes (~ 300-200 BC)
Fast-forward 1200 years……
Developed many important proofs and
theorems in mechanics and mathematics,
many based on Aristotle’s theories
da Vinci (1452-1519)
Established areas of statics and hydrostatics
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
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
Made extensive study of muscles and movement
Challenged many of Galen’s theories, and
proved many to be wrong
World’s first sports medicine doctor – primary
physician to the Roman gladiators
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
Isaac Newton (1642-1727)
Revolutionized mechanics by postulating
four basic laws:
Law of gravity
Law of inertia (1 st law)
Law of acceleration (2 nd law)
Law of action-reaction (3 rd law)
Newton’s 2 nd 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
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 2 nd 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
Following Newton, there were further
advances in mechanics by:
Leonhard Euler (1707-1783)
Jean le Rond D’Alembert (1717-1783)
Joseph Lagrange (1736-1815)
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
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Etienne Marey
(1838-1904)
Edweard Muybridge
(1830-1904)
Edweard Muybridge
(1830-1904)
Revolutionized motion analysis by
the use of sequential, multiple
exposure, and motion photography
Muybridge produced an astounding
collection of photographs of humans
and animals in motion, but Marey was
the true scientist of human movement
Etienne Marey
(1838-1904)
Edweard Muybridge
(1830-1904)
Braune & Fischer:
Wilhelm Braune (1831-1892)
Otto Fischer (1861-1917)
Conducted first 3D analysis of human locomotion
Results published in The Human Gait
Data collected in one night, analysis took years!
DuBois Reymond (1818-1922)
Guillaume Duchenne (1806-1875)
Developed modern EMG techniques
Duchenne 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
Biomechanical Analysis
What qualifies as a “biomechanical analysis”?
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
Measurement, Description, &
Monitoring
Many studies that were purely descriptive in
nature have been passed off as assessments
or analyses of human movement
• Measurement – the process of ascertaining
the dimensions, quantity, or capacity of
something
What is the difference between:
measurement
description
monitoring
analysis
assessment
• Description – the process of representing or
depicting a measurement quantitatively or
pictorially
• Monitoring – tracking changes in a measured
quantity over time
Analysis
Analysis 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
from: Winter (1990)
Note that a given measure can lead to different
descriptions, and a single description can arise
from various measurement instruments
• The analysis may also combine different data,
yielding a quantity that can not be measured
– Inverse dynamics
– Mechanical power analysis
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EMG Processing
Joint Power Analysis
ground
reaction
forces
segment
kinematics
dynamic
equations
joint
moments
joint
power
from: Winter (1990), fig 8.10
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?
Where is Biomechanics
Going Tomorrow?
• Emphasis on purely descriptive studies is
being left behind (perhaps not fast enough)
New advances in measurement techniques and
experimental designs
• Mechanistic, scientific approaches are being
used to:
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– imaging / MRI / DEXA
– in vivo measurement of forces
and motion
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?
Up Next…
Theoretical investigations using computer
models of the musculoskeletal system
– movement simulation
– joint load estimation
Topics
– Sampling theory
– Analog to Digital Conversion (ADC)
Readings
FMUS
– Robertson (2004) Introduction pp. 1 – 5
– Robertson (2004) Chapter 11, pp. 227-238
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