Transcript INTRODUCTION TO BIOMECHANICS

Biomechanics 2015
Section 1:1
An Introduction to Biomechanics
Dr. Moira McPherson,
School of Kinesiology
AN INTRODUCTION TO THE STUDY AND
ANALYSIS OF HUMAN MOVEMENT
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During the past decade the term
BIOMECHANICS has emerged as an area of
inquiry in the sport science domain.
Biomechanics is based on NEWTON'S LAWS and
involves the study of the motion of bodies and
the interrelationships among the forces acting
on these bodies.
INTRODUCTION TO THE STUDY AND ANALYSIS
OF HUMAN MOVEMENT
BIOMECHANICS: BIO = LIVING
 MECHANICS = FORCES & EFFECTS
 The application of mechanics to the living organism
 Involves the principles of anatomy and physics in the
descriptions and analysis of movement.
 Has many diverse applications to all biological systems
 The study of biological structures, processes and
functions by applying the methods and principles of
mechanics
HAY, 1995
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THE SCIENCE THAT EXAMINES THE
INTERNAL AND EXTERNAL FORCES
ACTING ON THE BODY AND THE EFFECTS
PRODUCED BY THESE FORCES
KINEMATICS & KINETICS
Why learn about Biomechanics?
AREAS OF STUDY, RESEARCH
AND PRACTICE
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Sport and Exercise Science
Coaching
Ergonomics
Equipment Design
Gait & Locomotion
Orthopedics - Rehabilitation Physiotherapy, Occupational
Therapy
Prosthetics and Orthotics
Motor Control
Computer Simulation
Videotape Analysis: A
Functional Capacity Lift
Graphical Analysis
MECHANICS
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Rigid body mechanics are based on the
assumption that a solid body is considered
to be a rigid body if the distance between
the particles remains fixed when a force is
applied.
Figure 2. Force
SEGMENTAL ANALYSIS
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We often make the assumption
that the human skeleton can
be represented as a series of
links. Researchers have used
everything from cones to
spheres to form the links
which best approximated the
complexity of the human body.
However, by far the most
widely adopted and simplest
link system representation is
the stick man.
The stick man uses straight sticks to represent each of
the links. In any case, regardless of the shapes which
are used we also make the assumption that the human
link system is a system of rigid bodies connected at the
joints
Figure 3.
Rigid Body Mechanics
kinematics
linear
angular
kinetics
curvilinear
parabolic
statics
dynamics
KINETICS
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examines the causes of motion, the
internal and external forces that cause
motion or cause a body to remain at rest,
and the interactions between these forces.
There are two branches of kinetics;
STATICS and DYNAMICS
KINEMATICS
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Describes the motion
of a body without
reference to the
forces causing it.
Kinematics examines
how, when, and
where a body moves.
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For example, variables such as the
displacement of a ball, the velocity of a
skater, and the acceleration of the free leg
all describe motion, and are kinematic
variables.
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We classify the kinematic motion
according to the pathway it takes.
Movement may be LINEAR,
CURVILINEAR, or a combination of
the two. Curvilinear motion can be
further specified as ANGULAR or
PARABOLIC.
LINEAR MOTION
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Linear motion is the
movement of a body in a
straight line or along a
straight pathway. Linear
motion is also produced
when external forces are
applied directly through the
centre of mass of an body.
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CURVILINEAR: Motion along a curved
path
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ANGULAR: Angular motion takes place
when a body moves along a circular
path about some AXIS in space. This
axis is known as the axis of rotation.
Angular motion is produced when
forces are applied away from the axis of
rotation of a body.
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Our body limbs are able to rotate about
the joints because all of our muscles are
attached at some distance from the centre
of the joints.
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PARABOLIC: Bodies
which are projected
into the air will
assume a
PARABOLIC PATH
and are governed by
the laws of projectile
motion.
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STATICS: Statics refers to situations
where the body or object remains at rest,
or is moving at a constant speed in a state
of equilibrium. Equilibrium is a balanced
state in which there is no acceleration.
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DYNAMICS: Dynamics deals with the
changes in motion brought on by
unbalanced forces.
QUANTITATIVE VS QUALITATIVE
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Both kinematics and kinetics can be analyzed
using a quantitative or qualitative approach
A quantitative analysis requires a numerical
evaluation of an individual’s movement
Qualitative analysis involves a systematic
analysis of movement based on biomechanical
concepts but without actual measurement
METHODS OF ACQUIRING
DATA
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1. VIDEO ACQUISITION
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2. 3 D OPTICAL ACQUISITION
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2 D or 3D
Points are digitized manually or by attaching
reflective markers and digi auto
3D in controlled environment
Marker only system that uses 2 – 12 cameras and
infra red lights to collect 3D coordinates
3. ANALOG ACQUISITON
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analog sampling from force platforms, EMG or
other devices.
Can be integrated with video or 3D optical
VIDEOGRAPHY
Fax
SOME QUESTIONS that may
require quantitative video
analysis?
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1. An objective of prescribing an
orthosis is usually to improve the
function of the patient. How can we
determine if the use of a foot orthotic is
correcting for the severe pronation
exhibited by a patient?
Video tape, digi and compare joint
angular displacement throughout stride
Hydro workers
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Hydro workers are required to lean out of
a lift to repair the lines. The action of
leaning and working from a distance puts
dangerous loads on the lower back –
injury.
How can the lift be modified to reduce the
risk of injury?
EMG
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BASED ON RELATIONSHIP BETWEEN
FORCE AND THE ELECTRICAL ACTIVITY
ACROSS THE MUSCLE MEMBRANE
EXAMPLE: Which exercise is best for
rehabilitation of a particular muscle?
ELECTROMYOGRAPHY-EMG
Raw EMG
Full wave
Rectify
Linear
Envelope
Integrate over
contraction
FORCE ANALYSIS
FX
Fy
Fz
How much force is applied in the
Horizontal direction?
JOINT
REACTION
FORCES
QUALITATIVE ANALYSIS
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Qualitative analysis involves a systematic
analysis of movement based on
biomechanical concepts but without actual
measurement
What does the QA process
include?
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Is there a technique error?
What are the mechanical concepts that
govern specific parts of the skill?
What the critical features of the
performance?
What is the best observation strategy?
How do you detect errors in performance
and remediate?
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Sally, a powerful outside hitter on a high
school volleyball team, has been out for
two weeks with mild shoulder bursitis, but
has recently received her physicians
clearance to return to practice. The coach
notices that Sally’s spikes are traveling at
a slow speed and are being easily handled
by the defensive players?????
TEXT BOOK
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