Download - Mechanics of human movement
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Mechanics of human movementMechanics of human movement
M. Foidart-Dessalle (Prof. FM, ULg)S. Cescotto (Prof. FSA, ULg)
F. Pascon (FNRS)
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Structures implied in movementStructures implied in movement
Bones and JointsBones and Joints: : Moving StructuresMoving Structures
Motor forcesMotor forces: : Gravity, Gravity, muscle contractionsmuscle contractions, , friction forces, friction forces, ground reaction, aquatic, …. ground reaction, aquatic, ….
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KinematicKinematic conventionsconventions
Kinematics (descriptive analysis)Kinematics (descriptive analysis)displacement, velocity, displacement, velocity, accelerationacceleration
Kinetics (causal analysis)Kinetics (causal analysis)forcesforces
Necessary to analyze human motion
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LES CHAINONS
OSSEUX
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Schematic representation of jointsSchematic representation of joints
Joints (rotation centers) are represented as pointsIt is a necessary approximation Rotation centers are between 18.9 (scapula) and 12 (elbow) square mm
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Schematic model of human bodySchematic model of human body
Segments joining points:mechanical axis# of anatomic axis
Either all body, either part of it: limb, part of it
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KinematicsKinematics
Position = localization in spaceGlobal reference frame neededUse a “human reference frame”Movements wrt the “human reference frame”Relative movements of the limbs
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« Humanreference frame »
3 reference planes
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Examples of movements that could be described wrt the “human reference frame”
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Examples of relative movements between limbs
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Classification of diarthroses withconcordant surface
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KinematicKinematic analysisanalysis: position/: position/timetime
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Numeric and graphic analysisNumeric and graphic analysis
For complex movementsvelocity and acceleration
can be calculated from positioncan be calculated from position--time time data obtained with high precision data obtained with high precision cameras and chronometerscameras and chronometers
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Graphic resolutionGraphic resolution
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Graphic resolutionGraphic resolution
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Historical:Chronophotography – running man
Measurement techniquesMeasurement techniques
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Historical:Chronophotography – walking man
Measurement techniquesMeasurement techniques
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Measurement techniquesMeasurement techniquesHistorical:
Chronophotography
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Measurements techniques Measurements techniques Stroboscopic flashStroboscopic flash
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Measurement techniques Measurement techniques ElectrogoniometryElectrogoniometry
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camera
platform for force measurement
Measurement techniquesMeasurement techniques
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Electrodes inside the muscles for precise measurements of
muscle activity
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hip curve and numerical walk
3D and numerical walk
Electrodes on the muscle for simple measurements of
muscle activity
Reflecting spheres to capture the movement by 5 cameras
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Anthropometric requirementsAnthropometric requirements
Length of the segmentsWeight and density of whole body and segmentsThe center of mass locationMoment of inertia and radius of giration
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Length of segmentsLength of segments
Necessary determination to represent Necessary determination to represent the body and its segments at the right the body and its segments at the right scalescale
Direct measure is preferableDirect measure is preferable
Data from tables give length of segments Data from tables give length of segments as fractions of whole body heightas fractions of whole body height
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Useful in determination of mass centers Useful in determination of mass centers and moments of inertiaand moments of inertia
In the past it was measured on cadavers/ In the past it was measured on cadavers/ then on segments volumes with tables /then on segments volumes with tables /nowadays on crossnowadays on cross--sections obtained by sections obtained by scanning the segments at regular intervalsscanning the segments at regular intervals
Whole body densityWhole body density
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Measurements with tablesDirect measurements with
accelerometers:
quick release experiment
Determination of mass centers Determination of mass centers and moments of inertiaand moments of inertia
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Whole body densityWhole body density
Density of the whole body depends on Density of the whole body depends on respective density of bone (>1.8), muscle respective density of bone (>1.8), muscle ((≤≤1), fat (<1)1), fat (<1)
Ponderous index in metric units Ponderous index in metric units c = c = h/wh/w : kg/m: kg/m
Whole body density Whole body density d = 0.69 + 0.9 cd = 0.69 + 0.9 c
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Segment densitiesSegment densities
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Segments weight ratiosSegments weight ratios
Upper body part / Lower body part: 5/3Upper body part / Lower body part: 5/3Head and trunk / both upper limbs: 4/1Head and trunk / both upper limbs: 4/1Head / trunk: 1/6Head / trunk: 1/6Arm / forearm and hand: 1/1Arm / forearm and hand: 1/1Hand / Forearm: 1/3Hand / Forearm: 1/3Thigh / leg and foot: 5/3Thigh / leg and foot: 5/3Leg / foot: 3/1Leg / foot: 3/1
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Muscles anthropometric dataMuscles anthropometric data
Physiological Cross sectional Area (PCA) of a Physiological Cross sectional Area (PCA) of a muscle is a measure of the numbers of muscle is a measure of the numbers of sarcomerssarcomers(contractile units) parallel to the angle of pull of the (contractile units) parallel to the angle of pull of the muscle. In muscle. In pennatepennate muscles, only the parallel muscles, only the parallel component in effective. component in effective. PCA = m PCA = m coscos θθ / D l / D l θθ = = pennationpennation angle angle m = mass D = density l = lengthm = mass D = density l = lengthForce/unit cross section area ranges from 0.20 to Force/unit cross section area ranges from 0.20 to 1MPa 1MPa (0.70 MPa in quadriceps during running andjumping)
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5 deg25 cm²6.8 cm180 gVastus intermedius
5 deg26 cm²7.2 cm200 gVastus medialis
5 deg30 cm²6.7 cm210 gVastus lateralis
5 deg12.5 cm²6.8 cm90 gRectus femoris
5 deg9.1 cm²7.3 cm70 gTibialis anterior
15 deg21 cm²2.4 cm55 gTibialis posterior
15 deg30 cm²4.8 cm158 gGastrocnemius
30 deg58 cm²3.0 cm215 gSoleus
04.4 cm²16 cm75 gSemitendinosus
015.8 cm²9 cm150 gBiceps femoris
01.9 cm²38 cm75 gSartorius
Pennation anglePCAFiber lengthMassMuscle
5 deg25 cm²6.8 cm180 gVastus intermedius
5 deg26 cm²7.2 cm200 gVastus medialis
5 deg30 cm²6.7 cm210 gVastus lateralis
5 deg12.5 cm²6.8 cm90 gRectus femoris
5 deg9.1 cm²7.3 cm70 gTibialis anterior
15 deg21 cm²2.4 cm55 gTibialis posterior
15 deg30 cm²4.8 cm158 gGastrocnemius
30 deg58 cm²3.0 cm215 gSoleus
04.4 cm²16 cm75 gSemitendinosus
015.8 cm²9 cm150 gBiceps femoris
01.9 cm²38 cm75 gSartorius
Pennation anglePCAFiber lengthMassMuscle
Physiological Cross-section Area of some muscles
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Moments of musclesMoments of muscles
Depend on the force and on the moment Depend on the force and on the moment arm length (i.e. the normal line from the arm length (i.e. the normal line from the joint center to the muscle force vector).joint center to the muscle force vector).
Change with the joint angleChange with the joint angle
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Calculation of human movementCalculation of human movement
Get the anthropometric data
Get the mechanical properties of materials
Define the acting forces
Define the boundary conditions
Solve the equations of movement
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ExampleExample showingshowing thethe complexitycomplexity ofofanthropometricanthropometric datadata
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Example of presence of biomaterials in the tissues
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Forces acting on the kinetic chainsForces acting on the kinetic chains
GravityGravity : : fall, walking, divingfall, walking, divingFrictionFriction:resistance:resistance to body progression in air, to body progression in air, water...water...Muscle forceMuscle force under nervous system control:under nervous system control:push off in walking, push off in walking, antigravificantigravific, antagonist, , antagonist, agonistagonistInternal linking forces Internal linking forces (tension developed by (tension developed by ligaments and/or transmitted by contact surfaces)ligaments and/or transmitted by contact surfaces)Ground reaction, impact with obstaclesGround reaction, impact with obstacles
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Forces acting on the kinetic chainsForces acting on the kinetic chains
O2
uptake
CO2
expired
EXTERNAL WORK
maintenance heatheat of contraction, activation, labile stable, shortening
Metabolic energyMetabolic energy
Mechanical energyMuscle tension
Mechanical energyMuscle tension
loss due to cocontractionor absorption by muscles at another joint
Increase in segment energies
Increase in segment energies
The main difficulty is the force delivered by the muscle !!!
Scheme of energy flow through the muscles
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Equations of movementEquations of movement
Based on the classical laws of mechanicsBased on the classical laws of mechanicsDifferent levels of complexityDifferent levels of complexity
rigid body mechanics with jointsrigid body mechanics with joints(body decomposed into rigid elements with (body decomposed into rigid elements with kinematickinematicconstraints)constraints)
deformable solid mechanics with jointsdeformable solid mechanics with joints(the different elements of the body model can deform with (the different elements of the body model can deform with kinematickinematic constraints) constraints)
Use of Use of softwaressoftwares to solve the equationsto solve the equations