Transcript Kinetics versus kinematics for analyzing coordination

Kinetics versus Kinematics
for Analyzing Locomotor
Coordination
D. Gordon E. Robertson, Ph.D.
School of Human Kinetics,
University of Ottawa, Ottawa, CANADA
Kinematic Analysis
• linear position, velocity and
acceleration of markers
• linear position, velocity and
acceleration of body segments
• angular position, velocity and
acceleration of body segments
• total body or limb kinematics
Advantages of Kinematics
• easy to obtain with automated
motion analysis systems
• accuracy is easy to determine
• requires little operator expertise
• immediate feedback possible
Disadvantages of Kinematics
• only describes motion
• not indicative of causes
• difficult to discriminate
important variables from
idiosyncratic variables
Kinetic Analysis
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forces and moments of force
work, energy and power
impulse and momentum
inverse dynamics derives forces
and moments from kinematics
and body segment parameters
Advantages of Kinetics
• defines which structures cause
the motion (i.e., coordination)
• can be used to simulate motion
and describe resulting kinematics
• can be validated against external
force measurements
Disadvantages of Kinetics
• may require synchronization of
several data acquisition systems
(e.g., videography with force
plates)
• special training to interpret
• more expensive and less developed
software
• invasive for direct internal
measurements (muscle, ligament,
or bone forces)
Inverse Dynamics is Partial
Solution to Invasive Measurements
• noninvasive with videography
• kinematics are determined
• direct measurements of external
forces are often necessary (i.e.,
force platforms)
• can be applied at several joints,
simultaneously
Limitations of Inverse
Dynamics
• results apply to conceptual structures
not true anatomical structures
• cannot partition results into
contributions by individual anatomical
structures
• no direct means of validating
• modeling permits partitioning of
forces and moments
Sprint Analysis Example
• swing phase of one leg
• world-class male sprinter
• 50 m into 100 m competitive
race (t=10.06 s)
• analysis of hip and knee
only (ankle forces not
significant during swing)
Hip angular
velocity,
moment of
force and
power during
sprinting
• initial burst of
power to
create swing
• latter burst to
drive leg down
20.
Flexing
0.
Extending
-20.
300.
0.
Flexor
Extensor
-300.
Concentric
2000.
0.
Eccentric
-2000.
-4000. Toe-off
0.0
0.1
0.2
Time (s)
Touch-down
0.3
0.4
Hip Moment
• causes rapid hip and knee flexion
immediately after toe-off
• causes hip and knee to extend in
preparation for touch-down
Knee angular
velocity,
moment of force
and power
during sprinting
• initial burst of
power to stop
flexion
• small burst for
extension
• final burst to
stop extension
20.
Extending
0.
-20.
Flexing
300.
Extensor
0.
-300.
Flexor
2000.
Concentric
0.
-2000.
Eccentric
-4000. Toe-off
0.0
0.1
0.2
Time (s)
Touch-down
0.3
0.4
Knee Moment
• not used to cause flexion or
extension during swing
• stops knee flexion before midswing
• prevents hyper-extension
(locking) prior to touch-down
Hip angular
velocity,
moment of
force and
power during
kicking
• initial burst of
power to
create swing
• negative work
to create whipaction of leg
and foot
20.
Flexing
0.
-20.
Trial: SL2CF
Extending
200.
Flexor
0.
-200.
1000.
Extensor
Concentric
0.
-1000.
Eccentric
-2000.
CFS
0.0
Hit Off
0.1
Time (s)
0.2
0.3
Knee angular
velocity,
moment of force
and power
during kicking
• initial power to
stop flexion,
bumper effect
• negative power
prior to contact
to prevent
hyperextension
20.
Extending
0.
-20.
Trial: SL2CF
Flexing
200.
Extensor
0.
-200.
1000.
Flexor
Concentric
0.
-1000.
Eccentric
-2000.
CFS
0.0
Hit Off
0.1
Time (s)
0.2
0.3
Normal Walking Example
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athletic male subject
laboratory setting
speed was 1.75 m/s
IFS=ipsilateral foot-strike
ITO=ipsilateral toe-off
CFS=contralateral foot-strike
CTO=contralateral toe-off
Ankle angular
velocity, moment
of force and
power during
walking
• large burst of
power by plantar
flexors for pushoff
• dorsiflexors allow
gentle landing
and flexion
during swing
10.
Dorsiflexing
0.
-10.
Trial: WN02DRMP
Plantar flexing
100.
Dorsiflexor
0.
-100.
Plantar flexor
250.
Concentric
0.
-250.
-500.
-750.
Eccentric
IFS CTO
0.0
CFS ITO
0.2
0.4
0.6
Time (s)
IFS
0.8
1.0
Knee angular
velocity, moment
of force and
power during
walking
• initial burst of
power to cushion
landing
• positive work to
extend knee
• negative work by
extensors to
control flexion at
push-off
10.
Extending
0.
-10.
Trial: WN02DRMP
Flexing
100.
Extensor
0.
-100.
250.
Flexor
Concentric
0.
-250.
-500.
Eccentric
-750. IFS CTO
0.0
0.2
0.4
CFS ITO
0.6
Time (s)
0.8
IFS
1.0
Hip angular
velocity, moment
of force and
power during
walking
• some cushioning
at landing
• large amount of
negative work by
flexors
• positive work by
flexors to swing
leg
10.
Flexing
0.
-10.
Trial: WN02DRMP
Extending
100.
Flexor
0.
-100.
250.
Extensor
Concentric
0.
-250.
-500.
Eccentric
-750. IFS CTO
0.0
0.2
0.4
CFS ITO
0.6
Time (s)
0.8
IFS
1.0
Questions?
Answers?
Thank you.