Biomechanics

Biomechanics
J. Paulo Vilas-Boas, Ph.D
Leandro Machado, Ph.D
jpvb@fade.up.pt; lmachado@fade.up.pt; filipas@fade.up.pt
4- Cinemetria (FS)
- APAS
- Radar
- Acelerómetro
Filipa Sousa, Ph.D
5- Dinâmica (LM)
- Força/ Equilíbrio de forças
- Momento
- Trabalho e Energia
- Pressão
6- Dinamometria (FS)
- Célula de carga
- Plataforma de forças
- Pressão Plantar
Aulas
Programa
1- Apresentação
- Introdução à Biomecânica (JPVB)
2- Fundamentos de trigonometria e geometria (LM)
3- Cinemática (FS)
- Posição, Deslocamento
- Planos e eixos
- Movimentos anatómicos
- Escalas
- Tipos de movimento
- Velocidade (LM)
- Aceleração
7- Dinâmica de Fluídos (LM, JPVB)
- CFD
8 - Mecânica Músculo-tendinosa (FS)
9 - EMG (LM)
10- Biomecânica das habilidades fundamentais (FS)
- Marcha
- Corrida
- Saltos
- Lançamentos
11- Projectos (LM) (FS)

Bibliografia
Biomechanics
Introductory concepts
Introductory concepts

Força / Peso
Força / Peso
15
10
5
Nelson Évora - componente vertical 4 passagens
0
0 20 40 60 80 100
t
norm
12
10
8
6
4
2
Naide Gomes - componente vertical 3 passagens
0
0 20 40 60 80 100
t
norm

BIO MECHANICS
Physics
Thermodynamics (energetics)
Electricity
Optics
Biophysics
Biology
Bioenergetics
Bioelectricity
Bio-optics
Mechanics Biomechanics
MECHANICS
Physics:
“The quest for the TOTAL theory”
The movement (and balance) study
How is the movement (or balance) like?
What causes the movement (or balance)?

BIO
Complexity:
Organization:
Heterogeneity
Articulated
Redundant
Behavior:
Self propelled
Arbitrary
Biodiversity
BIO MECHANICS
SUBJECT:
Non
deterministic
The forces produced and
acting over the biological
systems, and the
movements and balances
that they produce
BIO MECHANICS
The study of the
biological systems,
based on criterions,
principles, laws, and
methods of mechanics
Historical highlights
From Nigg & Herzog (1994)

Historical highlights Historical highlights
Historical highlights
Antiquity – Greeks – Natural Philosophy
Thales (624-545 B.C.)
Pythagoras
(582 B.C.) &
Hippocrates
(470-360 B.C.)
From Nigg & Herzog (1994)
Natural science detached from religion
“…all things have form, all things are form, and all forms can be defined by
numbers”
Pythagoras believed that mathematical relations held the secrets of the
universe, including music.
Hippocrates’ emphasis on observation and experience of the senses
pioneered the use of rational scientific thought in the practice of
medicine.
Antiquity
Maya
Egyptians
Mesopotamians
Phoenicians
Greeks
Developed knowledge:
Astronomy, Mathematics, …
Leisure & Sport
Natural Philosophy
Golden age
Hellenistic age
Conquest by the Roman Empire
Historical highlights
Antiquity – Greeks – Golden age
Plato (427-347 B.C.) believed the world of senses to be an illusory shadow of
reality. Ideas were the only reality, and true knowledge could not be obtained
through the study of nature. The pursuit of truth required contemplation, not
action.
Politics and Ethics prevail.
Knowledge & Myth
Kinematics
and Art;
Surface
Anatomy
(Plato and Aristotle)
Aristotle (384-322 B.C.) believed that mathematics provided a good model for a well-organized
science, and that science is aimed to explain nature.
Aristotle believed life was capable of mechanical expression. According to him, every motion
presupposed a mover.
All that is moved, should be moved by something else. The MOTOR must either be present within
the mobile, or be in direct contact with it. Action at a distance was inconceivable.
Aristotle's’ text About the Movement of Animals, described movement and locomotion (gait,
muscular action,…) for the first time, based on observation.
“… for just as the pusher pushes, so the pusher is pushed”

Historical highlights
Antiquity – Greeks – The Hellenistic age
Founded by the conquests of Alexander the Grate
and the foundation of Alexandria (The Museum of Alexandria)
Herophilos (300 B.C.) – Created the modern Anatomy and Physiology, with the systematic dissection.
Erasistratis (280 B.C) – Applied physical concepts to the understanding of anatomy. Was the first to
describe the muscles as organs of contraction.
Archimedes (287-212 B.C.) – With a lever he will move the Earth if he have a place
to stand to do so.
Equilibrium of Planes – How to find the CG of parallelogram, triangle, trapezium
Floating Bodies – Principles of water displacement
“How to move a given weight by given force?”
He dominated Statics and Hydrostatics until the time of Stevin (1548-1620) and
Galileo Galilei (1564-1642)
Historical highlights
Antiquity
- Knowledge and myth were separated
- Mechanical and mathematical paradigms were developed
- Anatomical paradigms were developed
- First biomechanical analysis of the human body was performed
Historical highlights
Antiquity – Greeks – The conquest by Rome
Hero of Alexandria 62 ( A.D.) – Teaches Physics at Alexandria (Mechanics, Optics, Pneumatics) He used
gases to invent mechanisms.
The Aristotelic causes of movement
Galen 131-201 ( A.D.) – Physician of the College of Gladiators, became probably the first Sport
Physician in History.
De Usu Partium (the Use of the Parts) is considered to be the first text on Physiology
De Motu Musculorum (On the movement of muscles) established Myology. “…enervation that makes
muscle substance into muscle proper” (the transmitters of the spiritus animalius from the brain into
the muscle.
He described tonus, and distinguished between agonistic and antagonistic muscles, and motor and
sensory nerves.
Historical highlights
The Middle Ages (200 B.C.-1450 A.D.)
Scientific Development decreased
Religious and spiritual
development increased
Those were the ages of the ARAB scholars, saving knowledge by translating the texts from
Greek to Arabic
St. Augustine (354-430 A.D.) incorporated Neoplatonic doctrines into
Christian beliefs.
“… the only type of knowledge to be desired was the knowledge of God
and the Soul, and no profit was to be had from investigating the realm of
nature”
St. Thomas Aquinas (1277) integrated Aristotelian philosophy into
Christian beliefs, from the Arabic translations.
Contributions of the MA to the development of Biomechanics are minimal.

Historical highlights
The Italian Renaissance (1450-1527)
The revival of ancient Greek Philosophy, Literature, Art and freedom of thought and
ethics. Nevertheless a scientific community didn’t exist.
The authority of the church was replaced by the authority of the
ancients
Michelangelo, Leonardo da Vinci (1452-1519) and Machiavelli
emerged as the Renaissance men.
The parallelogram of forces, simple and compound forces, studied friction, and questioned
Aristotle’s relationships between force, weight, and velocity.
“… an object offers as much resistance to the air as the air does to the object”
Da Vinci’s mechanical analysis of human movement included joints, muscles, bones, ligaments,
tendons and cartilage. He discarded the Aristotelian theory of Pneuma. “Spiritual force” replaced
it.
Historical highlights
The Italian Renaissance (1450-1527)
- Scientific work was revived
- The foundations of modern anatomy and physiology were laid
- Movement and muscle action were studied as connected
entities.
Historical highlights
The Italian Renaissance (1450-1527)
Vasselius (1514-1564) – Was authorised to make dissections of
cadavers of executed criminals and noticed that Galen’s anatomy
mixed human and animal characteristics.
De Humani Corporis Fabrica Libri Septem was published in 1543,
in the same year as Copernico’s Revolutionibus Orbium
Coelestium.
Vesalius demonstrated that muscle shortens and become thicker
during contraction.
He consider muscle to be compose of the substance of the
ligament and tendon, being divided into a great number of fibres
Fallopius (1523-1562) – Was mainly devoted to fibrous tissues:
“… motion requires a fibrous nature sin the actual body that is
moved.”. He adopted the Galen’s theory that the Spiritus
Animalis was the cause of muscular contraction, and carrier of
the motor/spiritual function of the brain.
Historical highlights
The Scientific Revolution of the XVII th century
Kings, Counts, wealthy families, Universities, and the Vatican supported men of science -
Galileu Galilei (1564-1642), Kepler (1571-1630), Descartes (1596-1650), Newton (1642-1727)
Intellectual freedom, as well as new ideas and finings were highly respected
Experimentation becomes the cornerstone
Galileu Galilei (1564-1642) – Showed that the rate of a fall is not a function of the falling object’s
weight (Aristotelian approach).
He was about to publish De Animaliam Motibus (The movement of animals), previously than
Borelli’s De Motu Animalum (1680-81) by 40 years!
He studied the biomechanics of human jump, the gait oh horses and insects, and human
floatability conditions (Discourses on Two New Sciences, 1638).
Scaling foundations were introduced (the three times sized animal femur).

Historical highlights
The Scientific Revolution of the XVIIth century
Galileu Galilei (1564-1642) The father of Biomechanics
Theory of uniform movement
Theory of projectiles
Theory of the inclined plane
The definition of Momentum
Foundations for the three laws of Newton
“If I was able to see further was because I stood
on the shoulders of giants”
Santorio (1561-1636) – Weighted himself and his solid and liquid inputs and
output, experiments were laying the foundations of metabolism.
William Harvey (1578-1657) – Discovered circulation, the capillaries
connecting the arterial and venous circulation (without a microscope!), and
the systole as the active action of the heart (against Gelen’s concept).
Described the heart as a pump. He was the first “Cardiac Biomechanicist”.
He died of a stroke.
Renée Descartes (1596-1650) – Discovered the Cartesian Coordinate System observing a fly in
the corner of the bedroom. One of the fathers of Mechanical Philosophy: “Changes observed in
the natural world should be explained only in terms of motion and rearrangements of parts of
matter” (L’homme, 1664, distinguish man from animals by the soul).
Historical highlights
The Scientific Revolution of the XVIIth century
Isaac Newton (1642-1727), the “orchestra conductor”
(Koestler, 1959)
Kepler´s lows of motion of heavenly bodies
Galileo’s law of falling bodies and projectiles
Descartes law of inertia which require straight motion if no external force acted
Philosophiae Naturalis Principia Methematica (1686)
The law of inertia
The law of acceleration due to an acting force
The law of action and reaction
The law of gravity
The fundamental tool for kinematic and
kinetic analysis of movement
All motions in the universe can be described and / or predicted. As long as the movement was
with relative speeds, which were small compared to the speed of light.
Historical highlights
The Scientific Revolution of the XVIIth century
Giovanni Borelli (1608-1679), was granted by Queen Christina for the
investigation of the mechanics of the human body
The father of Biomechanics?
The Motu Animalum, 1680
Historical highlights
The Scientific Revolution of the XVIIth century
Jan Swammerdam (1643-1680) – Constancy of frog’s muscle volume during contraction
William Croone (1633-1684) – The brain must send a signal to the muscles to cause contraction
Niels Stensen (1638-1686) – Precise descriptions of muscular structure
Francis Glisson (1597-1677) – The theory of irritability of muscles
Clopton Havers (1655-1702) – Systematic study of bone with a microscope. Bone is organic and
inorganic in nature, with tubular cavities.

Historical highlights
The Scientific Revolution of the XVIIth century
- Experiment and theory were introduced as complementary parts
of scientific investigation
- The Newtonian mechanics was established
- The Mechanical Philosophy and Newtonian mechanics provide
impetus to study human movement
Historical highlights
The Enlightenment: XVIIIth Century
Science was not organized as today: the current subdivision into disciplines started at that time!
Von Haller (1708-1777) – Recognised the role of electricity (a new discover) in muscle contraction,
but refrain to associate it to the “spiritus animalius” that controlled movements
Keill (1674-1719) – Calculated the number of fibres in a certain muscle and the tension per fibre to
lift a given weight
Daniel Bernoulli (11700-1728) – Developed a mechanical theory of muscle contraction. Breathing
and the mechanical work of the heart were also studied.
Nicholas Andre (1658-1742) – Coined the term “orthopaedics” (1741) and postulated that muscle
unbalances can produce skeleton deformities. Exercise in childhood is recommended to prevent
deformities
Jean Jallabert (1746) – Was the first to rehabilitate paralysed muscles through electricity
Luigi Galvani (1737-1798) – Muscles and nervous cells are able to produce electricity
- Galvanic Electricity. He is considered the father of Bioelectricity.
Robert Whytt (1714-1766) – Demonstrate the reflex action in the spinal chord in 1751,
and localized the sites of single reflexes
Historical highlights
The Enlightenment: XVIII th Century
Science was not organized as today: the current subdivision into disciplines started at that time!
Euler (1707-1783), D’Alembert, Lagrange
Euler (1707-1783) – Expanded Newton’s laws to be applied to rigid and
fluid bodies on Earth, and not only to material points and celestial
bodies. He start to develop the concept of conservation of energy
D’Alembert (1717-1783) – Expanded Newton’s action / reaction law to
moving objects
Lagrange (1736-1815) – Treated mechanical problems with differential
calculus. Newton’s 2nd law was expressed in terms of kinetic and
potential energy.
Historical highlights
The Enlightenment: XVIIIth Century
- The concept of force become more clearly understood
- The concepts of conservation of momentum and energy started
to develop
- Mathematical consolidation of mechanical laws took place
- Muscle contraction and action was recognised as influenced by
mechanical, bio-chemical, and electrical forces

Historical highlights
The XIX th Century: the gait century
Development of science and its applications to human movement during the XIX th century was
influenced by the XVIII th Century, namely: Rousseau, the Watt’s Steam Machine, and the French
Revolution
Development of
sport and leisure
J. J. Rousseau (1712-1778) – Emile (1762) – Revived the
complementarities between body and mind, encouraging the return to
NATURE and PHYSICAL ACTIVITY
J. Watt (1736-1819) – Invented the Steam Machine (1777) – Potentiated
the industrial revolution, the LEISURE time, recreation, and SPORTS
French Revolution (1789) – The end of the monopoly of leisure and
sports by the dominant social classes.
Renewed scientific interest in human locomotion
Historical highlights
The XIX th Century: the gait century
Marey (1838-1904)
Historical highlights
The XIX th Century: the gait century
Renewed scientific interest in human locomotion
Observation
Photography Quantification of human and animal locomotion
Eduard Weber (1795-1881) and Wilhelm Weber (1804-1891) – Published in
1836 the “Die Mechanik der menchlichen Gewerkzeuge” (On the mechanics of
the human gait tools)
Etienne Jules Marey (1838-1904) – Transformed the science
of locomotion from observational to one based on
quantification
Edward Muybridge (1830-1904) – Was introduced to animal
movement analysis by Mr. Stanford (Stanford University),
to explain high speed trot in horses. He produced about
20.000 images of human and animal locomotion.
Historical highlights
The XIX th Century: the gait century
Marey (1838-1904)
Etienne Jules Marey (1838-1904) – Was the first to combine and synchronize kinematic and
kinetic measurements.
Storage and reutilization of elastic energy
He also provide insight into:
Ground reaction forces and CG movement
EMG patterns
Dependency of energy cost on movement characteristics

Historical highlights
The XIX th Century: the gait century
Chronophotography
Historical highlights
The XIX th Century: the gait century
Muybridge (1830-1904)
Historical highlights
The XIX th Century: the gait century
Historical highlights
The XIX th Century: the gait century
Animal Locomotion
Animals in Locomotion
The Human Figure in Motion
Muybridge (1830-1904)
Wilhelm Braune & Otto Fischer (1891) – Conducted the first 3D analysis of human gate, making precise
mathematical analysis possible. They used night photographs of light tubes over a black suit.
They used night photographs of light tubes over a
black suit. The preparation of each subject took
8h.
The CG and moments of inertia of the body and all segments were calculated experimentally, with the use
of two frozen cadavers
Braune died after data collection and Fischer took
several years to complete data processing, which
is now performed in REAL TIME
Der Gang des Menschen (1895-1904)

Historical highlights
The XIX th Century: the gait century
Du Bois Reymond (1818-1922) and Duchene (1806-1875) – Laid the foundations of electromyography
Refined the methods for measuring currents in 1841, and traced electricity in
contracting muscle to its independent fibres
Volkmann (1862) – Described the effects of pressure on bone growth
In 1866 published Physiologie des Movements,
which describe the function of every important
superficial muscle
Van Mayer (1867) – Described the relationship between the bone architecture and its function
Historical highlights
The XX th Century
Characteristics of the XXth century that influenced the development of Biomechanics:
Mechanical, industrial and technological development associated to two world wars
Popular, social and financial recognition of Sport and human performance
Explosion of financial support for medical and health care research
Cochran & Stobbs (1968), from Bartlett (1997) Silveira et al. (2005), Radiol. Bras.
Historical highlights
The XIX th Century: the gait century
- Measuring methods were developed to quantify kinematics and
kinetics, and were extensively applied to human gait analysis
- Measuring methods were developed to quantify electrical current
during muscular activity
- Engineering principles were applied to biological and
biomechanical analysis
Historical highlights
The XIX th Century: the gait century
Light-trace Photography
Vilas-Boas (1994)

Historical highlights
The XX th Century
Jules Amar (1920) – Published The Human Motor analysing physical and physiologic components
of work, focusing into efficiency of human movements
Nicholas Bernstein (1896-1966) – Conducted “biodynamic” studies of human gait based on
mathematical approaches. Approached to ergonomics and studied coordination and regulation of
movement in both children and adults, creating theories of motor control and coordination
A. V. Hill (1886-1977) – Nobel Prize for Physiology and Medicine in 1923, experiencing on the
explanation of mechanical and structural function of human muscle
Elfman (1939) – Quantified internal forces in muscles and joints. Concluded that muscles act
regulating energy exchange, by using the strategies of transmission, absorption, release, and
dissipation
A. F. Huxley (1924- ) – Explained muscle shortening in 1953 through the sliding filament theory,
lately expanded to his Cross-bridge Theory
Historical highlights
The XX th Century
- Biomechanics developed as a discipline at the Universities
- Biomechanical research results were increasingly used in
practical applications (sports, medicine, industry)
- Biomechanics become a player in a multidisciplinary attempt to
understand human and animal movement and the effects of
movement on the muscle-skeletal system
Historical highlights
The XX th Century
The first breakthrough of biomechanics into the curricula of Universities was in sport related
disciplines in the early XXth century. Some Faculties of Physical Education start teaching
Biomechanics
Biomechanics vs. Kinesiology
21-23 August 1967 – First International Seminar on Biomechanics – Zürich – Switzerland.
Chairman : Wartenweiler
International Council of Sport and Physical Education of UNESCO
Topics:
- Technique of motion studies
- Telemetry
- Principles of human motion studies: general aspects of coordination
- Applied Biomechanics in work
- Applied Biomechanics in sports
- Clinical aspects
1973 – ISB was founded during the Penn State conference – Wartenweiler (1st President)
(International Congress of Biomechanics, since 1975 in Jyväskylä, Finland)
(World Congress of Biomechanics, 1989, San Diego, USA)
BIO MECHANICS
Ergonomical biomechanics
Work biomechanics
Occupational biomechanics
Clinical biomechanics
(...)
Orthopaedical biomechanics
Traumatological biomechanics
Sports biomechanics

Sports biomechanics
Aims:
to describe
to interpret
to explain
to model
to simulate
to transform
to optimize
Sport
movements
Sport
technique
to optimize
Sport
equipments
and materials
to prevent
injuries
BIO MECHANICS
Non-deterministic science
Mathematically
based
Complex
procedures
BIO MECHANICS
Biomechanics is somewhat more than
strict mechanics of rigid bodies
Some of the biomechanical systems
(bodies) are much more complex...
Articulated
Generators
of forces
Independent Redundant
... specially in sports biomechanics
BIO MECHANICS
Biomechanically, the HUMAN BODY can
be defined as:
A complex system of articulated
segments where movement is
produced by external forces, and by
internal forces, acting out of the
articular axes, that induces angular
displacements of the segments
Based in Amadio (1996)

BIO MECHANICS
V
External
biomechanics
Internal
biomechanics
MECHANICS
Statics
Dynamics
Kinematics
Kinetics
Fm
Homunculi control of human movement
MECHANICS
Statics
Dynamics
from Voughan et al. (1999)
Kinematics
Kinetics

MECHANICS
F = m . a
Dynamics
Unbalanced
forces
SF = 0
m
Kinematics
Kinetics
R
SF = R
SF = R = m * a
a = 0
a = const.
a = variable
MECHANICS
Statics
m
SF = 0
a = 0 (SF = m * a)
Balance
Static balance:
no movement (v = 0)
Dynamic balance:
uniform movement (a = 0; v = const.)
F = m . a
M F = I . a
M F = F . r
I = m . r 2

l 1
F
F * l 1 > < R * l 2
F * l 1 = R * l 2
l2
R
Areas of complex BIOMECHANICAL evaluation:
KINEMETRY ANTHROPOMETRY DYNAMOMETRY EMG
Position
Orientation
(time)
Movement
(Displacement)
Velocity
Acceleration
Dimensions
linear
surfaces
volumes
Inertial
characteristics
mass
moment of inertia
Inverse dynamometry
F = m * a
Forces
internal
external
Moments
(torques)
Pressures
Muscular
activity
Thermography
(adapted from Baumann, 1995)
Anthropometry

Biomechanical anthropometry
Zatsiorski adapted by de Leva (1996):
Segment
Mass
(%)
Longitudinal spot
of the CM (%)
r
sagital
(%)
r
transverse
(%)
r
frontal
(%)
F M F M F M F M F M
Head 6.68 6.94 58.94 59.76 33.0 36.2 35.9 37.6 31.8 31.2
Trunk 42.57 43.46 41.51 44.86 35.7 37.2 33.9 34.7 17.1 19.1
Trunk S 15.45 15.96 20.77 29.99 74.6 71.6 50.2 45.4 71.8 65.9
Trunk M 14.65 16.33 45.12 45.02 43.3 48.2 35.4 38.3 41.5 46.8
Trunk I 12.47 11.17 49.20 61.15 43.3 61.5 40.2 55.1 44.4 58.7
Arm 2.55 2.71 57.54 57.72 27.8 28.5 26.0 26.9 14.8 15.8
Lower Arm 1.38 1.62 45.59 45.74 26.1 27.6 25.7 26.5 9.4 12.1
Hand 0.56 0.61 74.74 79.00 53.1 62.8 45.4 51.3 33.5 40.1
Tight 14.78 14.16 36.12 40.95 36.9 32.9 36.4 32.9 16.2 14.9
leg 4.81 4.33 44.16 44.59 27.1 25.5 26.7 24.9 9.3 10.3
foot 1.29 1.37 40.14 44.15 29.9 25.7 27.9 24.5 13.9 12.4
Filme
Muybridge
(1830 - 1904)
Kinemetry
Quantitative
Detailed numeric
description of
movement
Videogrametria
SIMI
Number of
cameras
Synchronization Calibration
Electromagnetic video
Low frequency (

Digitizing the coordinates
of each joint centre in
each image…
Referencing anatomical
landmarks to a
anthropometric
biomechanical model
We obtain the position of
each model part (segment)
and of the total CM
It is possible to differentiate velocities and
accelerations, and to estimate forces
Kinematics
Video
Recording and
processing images
Kinematics
Axes
Planes
Coordinates
Planar (2D)
Spatial (3D)
Position
Position vector
Orthogonal
components of
the position
vector
Displacement
(displacement vector)
P 1
ISB
convention
P 2
yy
Calibrating the space for
real metric coordinates
acquisition
P 2
zz
P 1
xx
Kinematics
Video
Recording and
processing images

Kinematics
Video
Recording and
processing images
Dual-media video images for videogrametry
Vilas-Boas et al. (1997)
Dual-media video images for videogrametry
Vilas-Boas et al. (1997)
Dual-media video images for videogrametry
Vilas-Boas et al. (1997)

Dual-media video images for videogrametry
Kinematics
Velocimetry
Lima et al. (2006)
Kinematics
Velocimetry
Kinematics
Cable velocimeters: Velocimetry
Cable velocimeters:
Cable velocimeters:

Kinematics
Velocimetry
Kinematics
Velocimetry
Kinematics
Cable velocimeters: Velocimetry
Kinematics
Cable velocimeters: Velocimetry
Cable velocimeters:
Cable velocimeters:

Dynamometry
Direct dynamics
F S F = m . a a
Dynamics
Force transducers
Force plates
- Force plates
- Dynamic pressure transduction
- Load cells
:inverse dynamics
- Other methods and transducers
Force plates
Força / Peso
15
10
5
Different types 3D sensors
Dynamics
Nelson Évora - componente vertical 4 passagens
0
0 20 40 60 80 100
t
norm
(Bartlett, 1997)
Components of force and
torques that act upon the
subject
Força / Peso
Força / Peso
4
2
0
-2
-4
-6
Nelson Évora - componente antero-posterior 4 passagens
-8
0 20 40 60 80 100
t
norm
3
2
1
0
-1
Force plates
Nelson Évora - componente médio-lateral 4 passagens
-2
0 20 40 60 80 100
t
norm

Força / Peso
força normalizada
Dynamics
12
10
8
6
4
2
Naide Gomes - componente vertical 3 passagens
0
0 20 40 60 80 100
t
norm
Dynamics
-1
0 20 40 60 80 100
tempo normalizado
Vertical:
Máx: 5.95 * Peso = 4422.2 N, aos 0.025 s
força normalizada
6
5
4
3
2
1
0
t apoio = paulo1 0.167 Paulo s componente vertical
t apoio = marisa1 0.154 Marisa s componente vertical
7
6
5
4
3
2
1
0
-1
0 20 40 60 80 100
tempo normalizado
Vertical:
Máx: 7.00 * Peso = 3797.0 N, aos 0.013 s
força normalizada
força normalizada
1
0
-1
-2
-3
-4
Força / Peso
-1
0 20 40 60 80 100
t norm
Força / Peso
-5
0 20 40 60 80 100
tempo normalizado
Antero-posterior:
Máx: 4.60 * Peso = 3419.2 N, aos 0.022 s
1
0
-1
-2
-3
-4
3
2
1
0
1
0
-1
-2
-3
-4
-5
-6
paulo1 Paulo componente antero-posterior
marisa1 Marisa componente antero-posterior
-5
0 20 40 60 80 100
tempo normalizado
Antero-posterior:
Máx: 4.38 * Peso = 2376.6 N, aos 0.015 s
Force plates
Naide Gomes - componente médio-lateral 3 passagens
Naide Gomes - componente antero-posterior 3 passagens
-7
0 20 40 60 80 100
t
norm
força normalizada
1
0.5
0
-0.5
Force plates
paulo1 Paulo componente médio-lateral
-1
0 20 40 60 80 100
tempo normalizado
Médio-lateral:
Máx: 0.91 * Peso = 675.2 N, aos 0.029 s
força normalizada
1.5
1
0.5
0
marisa1 Marisa componente médio-lateral
-0.5
0 20 40 60 80 100
tempo normalizado
Médio-lateral:
Máx: 1.17 * Peso = 636.4 N, aos 0.022 s
Stalker ATS
Dynamics
Force transducers
Force plates
v (m/s)
10
8
6
4
2
Naide_26Fev - speed vs. distance - 3 attempts
0
-40 -35 -30 -25 -20
d (m)
mean
-15 -10 -5 0

Stabilogrametry
Vilas-Boas, Carvalho, Lopes, Gonçalves, Sousa (2003). Biomechanical analysis of acute backpack load
consequences on children’s gait.
(Subj. 7)
0% 15% 30%
Dynamics Pressure transducers
Dynamic pressure transduction

Internal forces assessment
Intrusive measures vs. inverse dynamics
EMG
Provides
information
on:
timing
sequencing
relative intensity
of contraction
force (...???)
fatigue
Activity of
various
muscle
groups
EMG
Not a biomechanical
technique
That’s a bioelectrical
(biophysical)
technique
EMG
Sensors
(electrodes)
Data
processing
Data acquisition and processing
Conditioners
(amplifiers & filters)
A/D
converter
PC
Based on Soares, R. (2005)

EMG
Type
Derivation
Pre-
-amplification
Data acquisition and processing EMG Data acquisition and processing
Electrodes
kneel wire surface
mono-polar bipolar multi-polar
passive
active
Based on Soares, R. (2005)
Electrodes anatomical location
Electrodes oriented according the fibers arrangement, with detection surfaces perpendicularly oriented
1st third
Middle
3th third
Signal attenuation away from
the middle point
Middle point of the muscle length
Motor spot
Signal attenuation in the
muscle/ tendon union
0.0000 5.0000 10.000 15.000 20.000 25.000
seconds
Adapted from de Luca (1997)
EMG Data acquisition and processing
iEMG (AU)
1
0.8
0.6
0.4
0.2
0
N=40
4 subjects
0 20 40 60 80
Load (% máx.)
EMG
ABS
envelope
RMS
iEMG
Ângulo
iEMG
0.0000 5.0000 10.000 15.000 20.000 25.000
seconds
10.0000
5.00000
0.00000
-5.00000
-10.0000
10.0000
8.00000
6.00000
4.00000
2.00000
0.00000
3.00000
2.00000
1.00000
0.00000
5.00000
4.00000
3.00000
2.00000
1.00000
0.00000
2.50000
2.00000
1.50000
1.00000
0.50000
0.00000
-0.50000
120.000
100.000
80.0000
60.0000
40.0000
20.0000
2.50000
2.00000
1.50000
1.00000
0.50000
0.00000
-0.50000
mV
mV
mV
mV/sqrt(s)
mV.s
graus
mV.s