KNR 352: Quantitative Analysis in Biomechanics Dr. Steve McCaw 227B438-3804 .

transcript

KNR 352: Quantitative Analysis in Biomechanics

Dr. Steve McCaw

438-3804

www.castonline.ilstu.edu/mccaw

Topics• Basic Operations required

• Dealing with vectors• Review from 282 (Basic Biomechanics)

• Kinematics• Calculations of basic quantities

• Displacement, velocity, acceleration

• Kinetics• Calculations

• GRF, CofP, JMF

• Energetics• Calculations

• Power, Work

Performance Injury

Task Factors

• Basic Skill• Walking • Jumping

• Take off & Landing• Running

• Take off & Landing• What joint actions are occurring?• What muscles are active?• What are the risks?

Task Factors

• Basic Skill• Complex Task

• Throw• Assembly Task• Curl up• Hitting a baseball• What joint actions are occurring?• What muscles are active?• What are the risks?

Performance Injury

Environment

Environmental Factors

• Weather/field/floor conditions• Friction====>stability, tissue loads

• Weather/field/floor conditions• Gravity

• space travel & platforms

• Weather/field/floor conditions• Gravity• Open/closed task

• dynamic vs. static environment

• Weather/field/floor conditions• Gravity• Open/closed task• Rules on the game/of the job

• # of players• field dimensions

• workplace layout• temporal constraints

Performance Injury

EnvironmentIndividual

Individual Factors

• Cognitive ability

Individual Factors

• Cognitive ability• Anthropometrics

Individual Factors

• Cognitive ability• Anthropometrics• Psychological state

Individual Factors

• Cognitive ability• Anthropometrics• Psychological state• Fitness & Health• Skill level

Performance Injury

Modulated by force: described by mechanics

Every structure that participates in the movement of the body does so according to physical and physiological principles.

Hamilton & Luttgens, Kinesiology: Scientific basis of Human Motion, 10th edition.

Mechanicsinfluence of force on bodies

• Biomechanics: force on biological organisms• biomechanics of fluids

• circulation (lung, blood, artery)

• Biomechanics: force on biological organisms• biomechanics of fluids• biomechanics of deformable solids

• bones, ligaments, tendons

• Biomechanics: force on biological organisms• biomechanics of fluids• biomechanics of deformable solids• biomechanics of rigid bodies

• body as “rigid links” at “frictionless hinges”

StaticsN o a cc le ra tio n P re se n t

Kinem aticsm o tio n p a tte rn s / m o tio n d e sc rip tio n s

Kineticss tu d y o f fo rce s ca u s in g m o tio n

Dynam icsA cce le ra tio n P re se n t

RigidBodies

Mechanics

• Kinematics• description of pattern of motion

• how far• how fast• how consistent

• Kinetics

Mechanics

• temporal aspects• durations• sequencing

• Kinetics

Mechanics

• Kinetics• study of forces that cause motion

Mechanics

• Kinetics• study of forces that cause motion

• magnitude• direction• line of action• point of application

F = m a

F = m aForce CAUSES acceleration

F = m aForce CAUSES accelerationForce CAUSES injury

Fundamental Concepts for Biomechanical Analysis

• Units of Measure: ISU (International system of Units, ie the Metric System)

Fundamental Concepts for Biomechanical Analysis

• Units of Measure: ISU (International system of Units, ie the Metric System)

• Base Units• length: meter (m)• mass: gram (g)• time: second (s)

Motion

• Change in position of a body with respect to time

Motion

• Change in position of a body with respect to time• quantify POSITION

• location in 3D space: P• three reference axes: X, Y, Z

• Cartesian system: axes at 90o

(orthogonal)

ISB Convention: 2D

Progression

ISB Convention: 3D

Vertical

Medio-Lateral

Anterior-Posterior

Scalars and Vectors

• Scalar quantity• described by magnitude alone

• mass• volume• distance• speed

• Vector quantity• requires description of magnitude and direction

• force• momentum• impulse• displacement• velocity• acceleration

Parallelogram Law forAddition of Vectors

• Sum of two vectors (resultant, R) equals the diagonal of the parallelogram with sides equal to the two vectors.• Draw on board, tail to tail• Triangle Rule: tip to tail

• commutative: R = A + B = B + A

• Polygon Rule: extends to 3 or more vectors

Review: Basic Trigonometry

• Right angle Triangle• naming conventions

• Pythagorean Theorem• Trig functions

• Sine, Cosine, Tangent (slope)

• Inverse Tangent

Coordinate Systems• Rectangular or Cartesian Coordinate System

• P = Px + Py

• Polar coordinate system• P = r and Ө

• Polar to rectangular • (use SOH and CAH)

• Rectangular to Polar• use Pythagorean Thereom and arctan

Examples: P to R: 270 N @ 23 degrees R to P: Fv= 1300 N & FA/P = 100 N

Adding Force (vectors) by Summing Components

• Force: magnitude & direction need to be calculated

• Force 1 = 50 N at -45 degrees• Force 2 = 30 N at 90 degrees

Solve for Resultant

• Force 1 = 50 N at -45 degrees• Force 2 = 30 N at 90 degrees• Force 3 = 75 N at 28 degrees• Force 4 = 15 N horizontal & 13 N vertical

Solve for Resultant

New & Useful Information

•Radian – the angle created by the arc on a circle with the length of the radius of the circle (~ 57.3 degrees)

Arc length = 1 radius

Calculate the resultant force from Coracobrachialis and Pectoralis Major

Coracobrachialis = 1200 N, PM = 1700 N

Effect of tension development on angle of muscle insertion and muscle activation level.

Given: Muscle force = 90 N /cm2 x-sectional areaX-sectional area = 4 cm2

Muscle Ө relaxed = 50°Muscle Ө active = 85°Required: 150 N force along tendonCalculate: Percentage of max muscle force developed to produce the 150 N of force.

Additional Problems

Available from web

Motion

• Change in position of a body with respect to time• quantify POSITION• quantify TIME

Motion-capture systems

Motion Capture

• Pre 1985: Film• RedLake Locam: 500 fps• ~ $125 roll (film + developing)• Working in the “dark”

• Record• Send for processing• Hope it all turns out ok.

• All black, badly focused, missed critical event • Manual Digitizing

Motion Capture

• Pre 1985: Film• Post 1985: High speed video

• Immediate feedback• Easy to adjust• Reduced cost (once system paid for)• Auto Digitizing Available

Example Video

Reflective Markers

Motion Capture

• Pre 1985: Film• Post 1985: High speed video • Post 1990: Active Marker Systems

• No visible recording of performer• Tracks x,y coordinates of markers only• FAST.• $$$$

Principles of Recording

1. Maximize image size within field of view. Field of view: rectangular area recorded

Field Height

Field Width

Field Depth

Photographic Dimensions

1. Maximize image size within field of view. Optimize calibrated volume.

Volume: Height x Width x Depth.

1. Optimize calibrated volume

2. Ensure always within field of view

2. Ensure always within field of view Stay within calibrated volume

1. Landing

2. Run

3. Jump

2. Stay within calibrated volume

3. Ensure adequate pre and post recordingTorry’s 16 mm thesis recording

1. Landing: air time, post max knee (max extension)

2. Lifting (bench & squat): before descent, post ascent

Video Tapes are Cheap

3. Ensure adequate pre and post recordingTorry’s 16 mm thesis recording Capture

adequate pre-initial and post-final activity1. Landing: air time, post max knee (max extension)

2. Lifting (bench & squat): before descent, post ascent

Server space is Cheap

3. Ensure adequate pre and post recording Capture adequate pre-initial and post-final activityImportant for video processing

1. Smoothing process

3. Capture adequate pre-initial and post-final activity

4. Use as slow a video speed as feasible• Standard video: 30 frames per second• High speed: 60, 120 2000 fpsLo speed = Improved quality of recordingHi speed = capture more frames of activity

4. Use as slow a video speed as feasible Set at 200 fps.

Ensure an even multiple of EMG or GRF (??)

4. Set at 200 fps.

5. Make shutter speed as short as possibleToo short: not enough light

Too long: “comets” rather than round markers

4. Set at 200 fps.

5. Make shutter speed as short as possibleToo short: not enough light

Too long: “comets” rather than round markers

4. Set at 200 fps.

5. Make shutter speed as short as possible

6. Depth of field1. Is 2D an appropriate assumption?

2. ISU Lab: record 3D even if 2D is of interest

4. Set at 200 fps.

5. Make shutter speed as short as possible

6. Depth of field1. Is 2D an appropriate assumption?

2. ISU Lab: record 3D even if 2D is of interest

4. Set at 200 fps.

Pilot Test

Calibration

• Real Life recorded on Video• Scale video dimensions to real life

• 2D: set up camera, record known length in plane of action• Perpendicular alignment is critical• Scaling factor

• Digitize recording of ruler• Sf = actual length (m) / digitized length (arbitrary units)

Calibration

• Real Life recorded on Video• Scale video dimensions to real life

• 2D: set up camera, record known length in plane of action

• 3D: set up cameras, record calibration Wand and calibration triangle on Force Platform.

Marker Selection• Where to put the

reflective markers?• What are you

measuring? • Segments & joints

of interest• Lower Body?• Upper Body?• Trunk?

Stick figure of landing in sagittal plane

Marker Selection• Where to put the

reflective markers?• What are you

measuring? • Segments & joints

of interest• Lower Body?• Upper Body?• Trunk?

Stick figure of landing in sagittal plane

Marker Selection

• Where to put the reflective markers?• What are you

looking at? • Landmarks defining

segment endpoints

Marker Selection

• Where to put the reflective markers?• What are you

looking at? • Landmarks defining

segment endpoints

ISU Lab• All landings on force platform• Spatially synchronized within

calibration grid• No need for markers on floor

Motion

Linear Motion: translation rectilinear curvilnear

Motion

Linear Motion: translation rectilinear: straight line curvilnear: curved line (parabolic)

Motion

Linear MotionAngular Motion: rotation

Motion

Linear MotionAngular Motion

General motion

Motion

• Change in position of a body with respect to time• quantify POSITION: from motion tracker• quantify TIME ?

Linear MotionAngular Motion

General motion

Time in Video Analysis

• 200 images per second• 1 second / 200 frames = 0.005 seconds

between frames

Motion

• Position: location in space• Displacement (distance)

• change of position

Motion

• change of position

• Velocity (speed)• change of position with respect to time

• This is motion

Motion

• change of position• Velocity (speed)

• change of position with respect to time• This is motion

• Acceleration• change of velocity = change of motion

• Push or pull exerted by one body on another body that causes or tends to cause a change in motion of each body

• a derived unit in mechanics• body: mass• change in motion: acceleration

• new location in space and time

1 newton = 1 N = 1 kg • m / s / s

• Quantifies linear inertia • resistance of a body to a change in linear

motion

• Anthropometry• measure of body dimensions

• ht, wt, girth, segment length, density

• Body Segment Parameters• mass, center of mass (gravity), radius of gyration

KNR 352: Quantitative Analysis in Biomechanics Dr. Steve McCaw 227B438-3804 .

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