Transcript Kinetics versus kinematics for analyzing coordination
Biomechanics of Walking D. Gordon E. Robertson, PhD, FCSB
Biomechanics, Laboratory, School of Human Kinetics, University of Ottawa, Ottawa, Canada
Quantitative Domains
• • •
Temporal
–
Phases (stance/swing) and events (foot-strike, toe-off), stride rate Kinematic (motion description)
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stride length, velocity, ranges of motion, acceleration Kinetic (causes of motion)
–
ground reaction forces, joint forces, moments of force, work, energy and power
Temporal Analysis
• •
Stride time Stride rate = 1/rate
• •
Stride cadence = 120 x rate (b/min) Instrumentation
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Photocells and timers
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Videography (1 frame = 1/30 second)
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Metronome
EMG
Motion Analysis Tools
Cine or Video camera Force platform
Bortec system
Electromyography
Noraxon system Delsys electrodes Mega system
Kinematic Analysis
• • •
Study of motion without consideration of its causes Motion description Based on Calculus developed by Newton and Leibnitz
Isaac Newton, 1642-1727
Kinematic Analysis
Manual goniometer • • • •
Linear position
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Ruler, tape measure, optical Angular position
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Protractor, inclinometer, goniometer Linear acceleration
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Accelerometry, videography Angular acceleration
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Videography
Miniature accelerometers
•
Motion Analysis
High-speed cine-camera
Cinefilm, video or infrared video
•
Subject is filmed and locations of joint centres are digitized
Videocamera Infra-red camera
Computerized Digitizing (APAS)
Stick Figure Animation
Kinetic Analysis
• • • •
Causes of motion Forces and moments of force Work, energy and power Impulse and momentum Inverse Dynamics derives forces and moments from kinematics and body segment parameters (mass, centre of gravity, and moment of inertia)
Force Platforms
Kistler force platforms
Steps for Inverse Dynamics
•
Space diagram of the lower extremity
Divide Body into Segments and Make Free-Body Diagrams Make free-body diagrams of each segment
Add all Known Forces to FBD
•
Weight (W)
•
Ground reaction force (F g )
Apply Newton’s Laws of Motion to Terminal Segment Start analysis with terminal segment(s), e.g., foot or hand
Apply Reactions of Terminal Segment to Distal End of Next Segment in Kinematic Chain Continue to next link in the kinematic chain, e.g., leg or forearm
Repeat with Next segment in Chain or Begin with Another Limb Repeat until all segments have been considered, e.g., thigh or arm
Normal Walking Example
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Female subject Laboratory walkway
• • • • •
Speed was 1.77 m/s (fast) IFS = ipsilateral foot-strike ITO = ipsilateral toe-off CFS = contralateral foot-strike CTO = contralateral toe-off
Ankle angular velocity, moment of force and power
•
Dorsiflexors produce dorsiflexion during swing
•
Plantiflexors control dorsiflexion
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Large burst of power by plantiflexors for push-off 10 Dorsiflexion 0 -10 Plantar flexion 100 Dorsiflexors 0 -100 Plantar flexors Trial: 2SFN3 Ang. velocity Moment Power 100 Concentric 0 -100 Eccentric -200 CFS ITO 0.0
0.2
IFS CTO 0.4
0.6
Time (s) 0.8
CFS ITO 1.0
1.2
Knee angular velocity, moment of force and power
•
Negative work by flexors to control extension prior to foot-strike
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Burst of power to cushion landing
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Negative work by extensors to control flexion at push-off 10 Extension 0 -10 Flexion 100 Extensors 0 -100 Flexors Trial: 2SFN3 Ang. velocity Moment Power 100 Concentric 0 -100 Eccentric -200 CFS ITO 0.0
0.2
IFS CTO 0.4
0.6
Time (s) 0.8
CFS ITO 1.0
1.2
Hip angular velocity, moment of force and power
•
Positive work by flexors to swing leg
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Positive work by extensors to extend thigh
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Negative work by flexors to control extension 10 Flexion 0 -10 Extension 100 Flexors 0 -100 Extensors 100 Concentric Trial: 2SFN3 Ang. velocity Moment Power 0 -100 Eccentric -200 CFS ITO 0.0
0.2
IFS CTO 0.4
0.6
Time (s) 0.8
CFS ITO 1.0
1.2
Solid-Ankle, Cushioned Heel (SACH) Prostheses
Ankle angular velocity, moment of force and power of SACH foot prosthesis
•
Power dissipation during weight acceptance and push-off
•
No power produced during push-off 10.
Dorsiflexing 0.
-10.
100.
Plantar flexing Dorsiflexor 0.
-100.
100.
Plantar flexor Concentric Trial: WB24MH-S Ang. velocity Net moment Power 0.
-100.
Eccentric -200.
0.0
ITO 0.2
IFS CTO 0.4
0.6
Time (s) 0.8
1.0
CFS ITO 1.2
1.4
FlexFoot Prostheses (Energy Storing)
Original model Recent models
Ankle angular velocity, moment of force and power of FlexFoot prosthesis
•
Power returned during push-off 10.
Dorsiflexing 0.
-10.
100.
Plantar flexing Dorsiflexor Trial: WB13MH-F Ang. velocity Net moment Power 0.
-100.
250.
Plantar flexor Concentric 0.
-250.
Eccentric -500.
0.0
ITO 0.2
IFS CTO 0.4
0.6
Time (s) 0.8
CFSITO 1.0
1.2
Ankle angular velocity, moment of force and power of person with hemiplegia (normal side)
•
Power at push-off is increased to compensate for other side 10.
Dorsiflexing 0.
-10.
100.
Plantar flexing Dorsiflexor 0.
Trial: WPN03EG Ang. vel.
Net moment Power -100.
100.
Plantar flexor Concentric 0.
-100.
-200.
0.0
Eccentric IFS CTO 0.2
CFS 0.4
Time (s) ITO 0.6
IFS 0.8
Ankle angular velocity, moment of force and power of person with hemiplegia (stroke side)
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Reduced power during push-off due to muscle weakness
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Increased amount of negative work during stance 10.
Dorsiflexing 0.
-10.
Plantar flexing 100.
Dorsiflexor Trial: WPP14EG Ang. vel.
Net moment Power 0.
-100.
Plantar flexor 100.
Concentric 0.
-100.
Eccentric -200.
IFS CTO 0.0
0.2
CFS ITO 0.4
Time (s) 0.6
IFS 0.8
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