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KNR 352: Quantitative Analysis in Biomechanics
Dr. Steve McCaw
227B
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
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?
TASK
Performance Injury
Environment
Environmental Factors
• Weather/field/floor conditions• Friction====>stability, tissue loads
Environmental Factors
• Weather/field/floor conditions• Gravity
• space travel & platforms
Environmental Factors
• Weather/field/floor conditions• Gravity• Open/closed task
• dynamic vs. static environment
Environmental Factors
• Weather/field/floor conditions• Gravity• Open/closed task• Rules on the game/of the job
• # of players• field dimensions
• workplace layout• temporal constraints
TASK
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
TASK
Performance Injury
EnvironmentIndividual
TASK
Performance Injury
EnvironmentIndividual
TASK
Performance Injury
EnvironmentIndividual
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)
Mechanicsinfluence of force on bodies
• Biomechanics: force on biological organisms• biomechanics of fluids• biomechanics of deformable solids
• bones, ligaments, tendons
Mechanicsinfluence of force on bodies
• 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
• Kinematics• description of pattern of motion
• how far• how fast• how consistent
• temporal aspects• durations• sequencing
• Kinetics
Mechanics
• Kinematics• description of pattern of motion
• how far• how fast• how consistent
• temporal aspects• durations• sequencing
• Kinetics• study of forces that cause motion
Mechanics
• Kinematics• description of pattern of motion
• how far• how fast• how consistent
• temporal aspects• durations• sequencing
• 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
X
Y
0,0
Progression
ISB Convention: 3D
X
Y
0,0,0
Z
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
Adding Force (vectors) by Summing Components
• Force 1 = 50 N at -45 degrees• Force 2 = 30 N at 90 degrees
Solve for Resultant
Adding Force (vectors) by Summing Components
• 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
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
Principles of Recording
1. Maximize image size within field of view. Optimize calibrated volume.
Volume: Height x Width x Depth.
Principles of Recording
1. Optimize calibrated volume
2. Ensure always within field of view
Principles of Recording
1. Optimize calibrated volume
2. Ensure always within field of view Stay within calibrated volume
1. Landing
2. Run
3. Jump
Principles of Recording
1. Optimize calibrated volume
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
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
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
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
3. Ensure adequate pre and post recording Capture adequate pre-initial and post-final activityImportant for video processing
1. Smoothing process
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
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
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
3. Capture adequate pre-initial and post-final activity
4. Use as slow a video speed as feasible Set at 200 fps.
Ensure an even multiple of EMG or GRF (??)
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
3. Capture adequate pre-initial and post-final activity
4. Set at 200 fps.
5. Make shutter speed as short as possibleToo short: not enough light
Too long: “comets” rather than round markers
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
3. Capture adequate pre-initial and post-final activity
4. Set at 200 fps.
5. Make shutter speed as short as possibleToo short: not enough light
Too long: “comets” rather than round markers
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
3. Capture adequate pre-initial and post-final activity
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
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
3. Capture adequate pre-initial and post-final activity
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
Principles of Recording
1. Optimize calibrated volume
2. Stay within calibrated volume
3. Capture adequate pre-initial and post-final activity
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
• Change in position of a body with respect to time• quantify POSITION• quantify TIME
Linear Motion: translation rectilinear curvilnear
Motion
• Change in position of a body with respect to time• quantify POSITION• quantify TIME
Linear Motion: translation rectilinear: straight line curvilnear: curved line (parabolic)
Motion
• Change in position of a body with respect to time• quantify POSITION• quantify TIME
Linear MotionAngular Motion: rotation
Motion
• Change in position of a body with respect to time• quantify POSITION• quantify TIME
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
• Position: location in space• Displacement (distance)
• change of position
• Velocity (speed)• change of position with respect to time
• This is motion
Motion
• Position: location in space• Displacement (distance)
• change of position• Velocity (speed)
• change of position with respect to time• This is motion
• Acceleration• change of velocity = change of motion
Force
• Push or pull exerted by one body on another body that causes or tends to cause a change in motion of each body
Force
• 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
Mass
• 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