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)
– 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
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Stride time
Stride rate = 1/rate
Stride cadence = 120 x rate (b/min)
Instrumentation
– Photocells and timers
– Videography (1 frame =
1/30 second)
– Metronome
Motion Analysis Tools
EMG
Force platform
Cine
or
Video
camera
Electromyography
Bortec system
Delsys electrodes
Noraxon system
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
• Linear position
Manual goniometer
– Ruler, tape measure, optical
• Angular position
– Protractor, inclinometer,
goniometer
• Linear acceleration
– Accelerometry, videography
• Angular acceleration
– 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 (Fg)
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
10
Dorsiflexion
0
-10
• Dorsiflexors
produce dorsiflexion
during swing
100
Trial: 2SFN3
Ang. velocity
Moment
Power
Dorsiflexors
0
-100
• Plantiflexors
control dorsiflexion
Plantar flexion
100
Plantar flexors
Concentric
0
• Large burst of
power by
plantiflexors for
push-off
-100
Eccentric
-200CFS ITO
0.0
0.2
IFS CTO
0.4
0.6
Time (s)
CFS ITO
0.8
1.0
1.2
Knee angular
velocity, moment
of force and
power
10
Extension
0
-10 Flexion
• Negative work by
flexors to control
extension prior to
foot-strike
• Burst of power to
cushion landing
• Negative work by
extensors to control
flexion at push-off
100
Trial: 2SFN3
Ang. velocity
Moment
Power
Extensors
0
-100
100
Flexors
Concentric
0
-100
Eccentric
-200CFS ITO
0.0
0.2
IFS CTO
0.4
0.6
Time (s)
CFS ITO
0.8
1.0
1.2
Hip angular
velocity, moment
of force and
power
10
Flexion
0
-10
• Positive work by
flexors to swing leg
• Positive work by
extensors to extend
thigh
• Negative work by
flexors to control
extension
100
Extension
Trial: 2SFN3
Ang. velocity
Moment
Power
Flexors
0
-100
Extensors
Concentric
100
0
-100
Eccentric
-200CFS ITO
0.0
0.2
IFS CTO
0.4
0.6
Time (s)
CFS ITO
0.8
1.0
1.2
Solid-Ankle, Cushioned Heel
(SACH) Prostheses
Ankle angular
velocity, moment
of force and
power of SACH
foot prosthesis
10.
Dorsiflexing
0.
-10.
Plantar flexing
100.
• Power dissipation
during weight
acceptance and
push-off
• No power
produced during
push-off
Dorsiflexor
Trial: WB24MH-S
Ang. velocity
Net moment
Power
0.
-100.
100.
Plantar flexor
Concentric
0.
-100.
Eccentric
-200.
ITO
0.0
IFS CTO
0.2
0.4
0.6
0.8
Time (s)
CFS ITO
1.0
1.2
1.4
FlexFoot Prostheses
(Energy Storing)
Recent models
Original model
Ankle angular
velocity, moment
of force and
power of FlexFoot
prosthesis
10.
Dorsiflexing
0.
-10.
Plantar flexing
100.
Dorsiflexor
Trial: WB13MH-F
Ang. velocity
Net moment
Power
0.
• Power returned
during push-off
-100.
250.
Plantar flexor
Concentric
0.
-250.
Eccentric
-500.
ITO
0.0
IFS CTO
0.2
0.4
0.6
Time (s)
CFSITO
0.8
1.0
1.2
Ankle angular
velocity, moment
of force and
power of person
with hemiplegia
(normal side)
10.
Dorsiflexing
0.
-10.
Plantar flexing
100.
Dorsiflexor
Trial: WPN03EG
Ang. vel.
Net moment
Power
0.
• Power at push-off
is increased to
compensate for
other side
-100.
Plantar flexor
100.
Concentric
0.
-100.
-200.
Eccentric
IFS CTO
0.0
0.2
CFS
0.4
Time (s)
ITO
IFS
0.6
0.8
Ankle angular
velocity, moment
of force and
power of person
with hemiplegia
(stroke side)
• Reduced power
during push-off due
to muscle weakness
• 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)
IFS
0.6
0.8
Questions?
Answers?
Comments?