biomechanics 2015 section 1:1 an introduction to biomechanics dr. moira mcpherson, school of...
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Biomechanics 2015Biomechanics 2015
Section 1:1Section 1:1
An Introduction to Biomechanics An Introduction to Biomechanics
Dr. Moira McPherson,Dr. Moira McPherson,
School of Kinesiology School of Kinesiology
AN INTRODUCTION TO THE STUDY AN INTRODUCTION TO THE STUDY
AND ANALYSIS OF HUMAN MOVEMENTAND ANALYSIS OF HUMAN MOVEMENT
During the past decade the term During the past decade the term BIOMECHANICS has emerged as an area BIOMECHANICS has emerged as an area of inquiry in the sport science of inquiry in the sport science domain. Biomechanics is based on domain. Biomechanics is based on NEWTON'S LAWS and involves the study NEWTON'S LAWS and involves the study of the motion of bodies and the of the motion of bodies and the interrelationships among the forces interrelationships among the forces acting on these bodies.acting on these bodies.
INTRODUCTION TO THE STUDY AND INTRODUCTION TO THE STUDY AND ANALYSIS OF HUMAN MOVEMENTANALYSIS OF HUMAN MOVEMENT
BIOMECHANICS: BIO = LIVINGBIOMECHANICS: BIO = LIVING MECHANICS = FORCES & EFFECTSMECHANICS = FORCES & EFFECTS The application of mechanics to the living The application of mechanics to the living organism organism
Involves the principles of anatomy and physics Involves the principles of anatomy and physics in the descriptions and analysis of movement.in the descriptions and analysis of movement.
Has many diverse applications to all Has many diverse applications to all biological systemsbiological systems
The study of biological structures, processes The study of biological structures, processes and functions by applying the methods and and functions by applying the methods and principles of mechanicsprinciples of mechanics
HAY, 1995HAY, 1995
THE SCIENCE THAT EXAMINES THE THE SCIENCE THAT EXAMINES THE INTERNAL AND EXTERNAL FORCES INTERNAL AND EXTERNAL FORCES ACTING ON THE BODY AND THE ACTING ON THE BODY AND THE EFFECTS PRODUCED BY THESE EFFECTS PRODUCED BY THESE FORCESFORCES
KINEMATICS & KINETICSKINEMATICS & KINETICS
Why learn about Biomechanics?
AREAS OF STUDY, AREAS OF STUDY, RESEARCH AND PRACTICERESEARCH AND PRACTICE
Sport and Exercise Sport and Exercise ScienceScience
CoachingCoaching ErgonomicsErgonomics Equipment DesignEquipment Design Gait & LocomotionGait & Locomotion Orthopedics - Orthopedics -
Rehabilitation -Rehabilitation -Physiotherapy, Physiotherapy, Occupational TherapyOccupational Therapy
Prosthetics and OrthoticsProsthetics and Orthotics Motor ControlMotor Control Computer SimulationComputer Simulation
Videotape Analysis: A Videotape Analysis: A Functional Capacity LiftFunctional Capacity Lift
Graphical AnalysisGraphical Analysis
MECHANICSMECHANICS
Rigid body mechanics are based Rigid body mechanics are based on the assumption that a solid on the assumption that a solid body is considered to be a body is considered to be a rigid body if the distance rigid body if the distance between the particles remains between the particles remains fixed when a force is applied.fixed when a force is applied.
Figure 2. ForceFigure 2. Force
SEGMENTAL ANALYSISSEGMENTAL ANALYSIS
We often make the We often make the assumption that the human assumption that the human skeleton can be skeleton can be represented as a series of represented as a series of links. Researchers have links. Researchers have used everything from cones used everything from cones to spheres to form the to spheres to form the links which best links which best approximated the approximated the complexity of the human complexity of the human body. However, by far the body. However, by far the most widely adopted and most widely adopted and simplest link system simplest link system representation is the representation is the stick man.stick man.
The stick man uses straight sticks to The stick man uses straight sticks to represent each of the links. In any case, represent each of the links. In any case, regardless of the shapes which are used regardless of the shapes which are used we also make the assumption that the we also make the assumption that the human link system is a system of rigid human link system is a system of rigid
bodies connected at the jointsbodies connected at the joints
Figure 3. Figure 3.
Rigid Body Mechanics
kinematics kinetics
linear curvilinear statics dynamics
angular parabolic
KINETICSKINETICS examines the causes of motion, examines the causes of motion, the internal and external the internal and external forces that cause motion or forces that cause motion or cause a body to remain at rest, cause a body to remain at rest, and the interactions between and the interactions between these forces. There are two these forces. There are two branches of kinetics; STATICS branches of kinetics; STATICS and DYNAMICSand DYNAMICS
KINEMATICSKINEMATICS Describes the Describes the motion of a body motion of a body without without reference to the reference to the forces causing forces causing it. Kinematics it. Kinematics examines how, examines how, when, and where when, and where a body moves. a body moves.
For example, variables such as For example, variables such as the displacement of a ball, the the displacement of a ball, the velocity of a skater, and the velocity of a skater, and the acceleration of the free leg acceleration of the free leg all describe motion, and are all describe motion, and are kinematic variables.kinematic variables.
We classify the kinematic We classify the kinematic motion according to the motion according to the pathway it takes. Movement pathway it takes. Movement may be may be LINEAR, CURVILINEAR,LINEAR, CURVILINEAR, or a combination of the two. or a combination of the two. Curvilinear motion can be Curvilinear motion can be further specified as further specified as ANGULAR ANGULAR or or PARABOLIC.PARABOLIC.
LINEAR MOTIONLINEAR MOTION
Linear motion is the Linear motion is the movement of a body in a movement of a body in a straight line or along a straight line or along a straight pathway. Linear straight pathway. Linear motion is also produced motion is also produced when external forces are when external forces are applied directly through applied directly through the centre of mass of an the centre of mass of an body. body.
CURVILINEARCURVILINEAR: Motion along a : Motion along a curved pathcurved path
ANGULARANGULAR: Angular motion takes : Angular motion takes place when a body moves along a place when a body moves along a circular path about some AXIS circular path about some AXIS in space. This axis is known as in space. This axis is known as the axis of rotation. Angular the axis of rotation. Angular motion is produced when forces motion is produced when forces are applied away from the axis are applied away from the axis of rotation of a body. of rotation of a body.
Our body limbs are able to Our body limbs are able to rotate about the joints because rotate about the joints because all of our muscles are attached all of our muscles are attached at some distance from the at some distance from the centre of the joints.centre of the joints.
PARABOLICPARABOLIC: : Bodies which are Bodies which are projected into projected into the air will the air will assume a assume a PARABOLIC PATHPARABOLIC PATH and are governed and are governed by the laws of by the laws of projectile projectile motion.motion.
STATICSSTATICS: Statics refers to : Statics refers to situations where the body or situations where the body or object remains at rest, or is object remains at rest, or is moving at a constant speed in a moving at a constant speed in a state of equilibrium. state of equilibrium. Equilibrium is a balanced state Equilibrium is a balanced state in which there is no in which there is no acceleration. acceleration.
DYNAMICSDYNAMICS: Dynamics deals with : Dynamics deals with the changes in motion brought the changes in motion brought on by unbalanced forces. on by unbalanced forces.
QUANTITATIVE VS QUALITATIVEQUANTITATIVE VS QUALITATIVE
Both kinematics and kinetics can be analyzed Both kinematics and kinetics can be analyzed using a quantitative or qualitative approachusing a quantitative or qualitative approach
A quantitative analysis requires a numerical A quantitative analysis requires a numerical evaluation of an individual’s movementevaluation of an individual’s movement
Qualitative analysis involves a systematic Qualitative analysis involves a systematic analysis of movement based on biomechanical analysis of movement based on biomechanical concepts but without actual measurementconcepts but without actual measurement
METHODS OF ACQUIRING METHODS OF ACQUIRING DATADATA
1. VIDEO ACQUISITION1. VIDEO ACQUISITION 2 D or 3D2 D or 3D Points are digitized manually or by Points are digitized manually or by attaching reflective markers and digi attaching reflective markers and digi autoauto
2. 3 D OPTICAL ACQUISITION2. 3 D OPTICAL ACQUISITION 3D in controlled environment3D in controlled environment Marker only system that uses 2 – 12 Marker only system that uses 2 – 12 cameras and infra red lights to cameras and infra red lights to collect 3D coordinatescollect 3D coordinates
3. ANALOG ACQUISITON3. ANALOG ACQUISITON analog sampling from force analog sampling from force platforms, EMG or other devices.platforms, EMG or other devices.
Can be integrated with video or 3D Can be integrated with video or 3D opticaloptical
VIDEOGRAPHYVIDEOGRAPHY
Fax
SOME QUESTIONS that SOME QUESTIONS that may require may require
quantitative video quantitative video analysis?analysis? 1. An objective of prescribing an 1. An objective of prescribing an
orthosis is usually to improve the orthosis is usually to improve the function of the patient. How can we function of the patient. How can we determine if the use of a foot determine if the use of a foot orthotic is correcting for the severe orthotic is correcting for the severe pronation exhibited by a patient? pronation exhibited by a patient?
Video tape, digi and compare joint Video tape, digi and compare joint angular displacement throughout angular displacement throughout stridestride
Hydro workersHydro workers
Hydro workers are required to lean Hydro workers are required to lean out of a lift to repair the out of a lift to repair the lines. The action of leaning and lines. The action of leaning and working from a distance puts working from a distance puts dangerous loads on the lower back dangerous loads on the lower back – injury.– injury.
How can the lift be modified to How can the lift be modified to reduce the risk of injury?reduce the risk of injury?
EMGEMG
BASED ON RELATIONSHIP BETWEEN BASED ON RELATIONSHIP BETWEEN FORCE AND THE ELECTRICAL FORCE AND THE ELECTRICAL ACTIVITY ACROSS THE MUSCLE ACTIVITY ACROSS THE MUSCLE MEMBRANEMEMBRANE
EXAMPLE: Which exercise is EXAMPLE: Which exercise is best for rehabilitation of a best for rehabilitation of a particular muscle?particular muscle?
ELECTROMYOGRAPHY-EMGRaw EMG
Full wave Rectify
Linear Envelope
Integrate over contraction
Fy Fz
FORCE ANALYSISFORCE ANALYSIS
FX
How much force is applied in theHorizontal direction?
JOINTJOINTREACTIONREACTIONFORCESFORCES
QUALITATIVE ANALYSISQUALITATIVE ANALYSIS
Qualitative analysis involves a Qualitative analysis involves a systematic analysis of movement systematic analysis of movement based on biomechanical concepts based on biomechanical concepts but without actual measurementbut without actual measurement
What does the QA What does the QA process include?process include?
Is there a technique error?Is there a technique error? What are the mechanical What are the mechanical concepts concepts that govern specific parts of the that govern specific parts of the skillskill??
What the critical features of the What the critical features of the performance?performance?
What is the best observation What is the best observation strategy?strategy?
How do you detect errors in How do you detect errors in performance and remediate? performance and remediate?
Sally, a powerful outside hitter on a Sally, a powerful outside hitter on a high school volleyball team, has been high school volleyball team, has been out for two weeks with mild shoulder out for two weeks with mild shoulder bursitis, but has recently received bursitis, but has recently received her physicians clearance to return to her physicians clearance to return to practice. The coach notices that practice. The coach notices that Sally’s spikes are traveling at a Sally’s spikes are traveling at a slow speed and are being easily slow speed and are being easily handled by the defensive players????? handled by the defensive players?????
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