Two-segment Model of the Foot for Gait Analysis D. Gordon E. Robertson, Ph.D. Alison Cronin...
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Two-segment Model of the Foot for Gait Analysis D. Gordon E. Robertson, Ph.D. Alison Cronin Biomechanics Laboratory, School of Human Kinetics, University of Ottawa, Ottawa, CANADA
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Solution use two force platforms Gerber & Stuessi (1987) developed equations to combine multiple force plates (available at biomech/csb/archives/ kistler.pdf) arrange plates end-to- end
Transcript of Two-segment Model of the Foot for Gait Analysis D. Gordon E. Robertson, Ph.D. Alison Cronin...
Two-segment Model of the Footfor Gait Analysis
D. Gordon E. Robertson, Ph.D.Alison Cronin
Biomechanics Laboratory,School of Human Kinetics,University of Ottawa, Ottawa, CANADA
Introduction
• Stephanyshn & Nigg (1997) showed negative work done by MP plantar flexors for running
• used EMED insole pressure system to partition floor reactions into two components
• pressure systems have no ability to distinguish components of a force only the magnitude of the resultant
• a single force platform cannot distinguish among several applied forces
• force plates computes a single resultant force--its components and centre of pressure
Solution
• use two force platforms• Gerber & Stuessi (1987)
developed equations to combine multiple force plates (available at www.health.uottawa.ca/
biomech/csb/archives/ kistler.pdf)
• arrange plates end-to-end
Solution
• subject lands foot across both plates
• in most cases little or no force occurs midstance
• can evaluate the subject using one or two ground reaction forces
Methods
• two male subjects• video taped at 60 fields/second• five trials of stance phase of walking at self-
selected speed• ground reaction forces sampled at 250 Hz
from two Kistler force plates• two conditions:
– one segment foot– two segment foot
Free-body diagram of one-segment foot
Free-body diagrams oftwo-segment foot
Methods
• mechanical energy and rate of change of energy computed (E/t)
• inverse dynamics to calculate net forces (F) and moments of force (M)
• force powers: Pf = F . v• moment powers: Pm = M • total power: Pt = Pf + Pm• power imbalance:Pi = E/t - Pt
Results (subject 1)
• pause to show animation
Ang. velocity, moment and power of the ankle joint
(WN01GR)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Time (s)
-500.
-250.
0.
250.
-100.
0.
100.
-10.
0.
10.
Pow
er (W
)
M
omen
t (N
.m)
Ang
ular
vel
. (/s
)
Trial: WN01GRAng. vel.Net momentPower
IFS IHO ITO
Dorsiflexing
Plantar flexingDorsiflexor
Plantar flexorConcentric
Eccentric
Ang. velocity, moment and power of the ankle joint
(WN01GR2)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Time (s)
-500.
-250.
0.
250.
-100.
0.
100.
-10.
0.
10.
Pow
er (W
)
M
omen
t (N
.m)
Ang
ular
vel
. (/s
)
Trial: WN01GR2Ang. vel.Net momentPower
IFS IHO ITO
Dorsiflexing
Plantar flexingDorsiflexor
Plantar flexorConcentric
Eccentric
Ang. velocity, moment and power of the MP joint
(WN01GR2)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Time (s)
-500.
-250.
0.
250.
-100.
0.
100.
-10.
0.
10.
Pow
er (W
)
M
omen
t (N
.m)
Ang
ular
vel
. (/s
)
Trial: WN01GR2Ang. vel.Net momentPower
IFS IHO ITO
Dorsiflexing
Plantar flexingDorsiflexor
Plantar flexorConcentric
Eccentric
Foot powers(WN01GR)
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70Time (seconds)
-2000.
-1500.
-1000.
-500.
0.
500.
1000.
1500.
2000.
Pow
er (W
)
Trial: WN01GRFloor powerForce powerMoment powerTotal powerEnergy ratePower imbalance
IFS IHO ITO
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70Time (seconds)
-2000.
-1500.
-1000.
-500.
0.
500.
1000.
1500.
2000.
Pow
er (W
)
Trial: WN01GR2Floor powerMP force powerMP moment powerFf total powerFf energy rateFf power imbalance
IFS IHO ITO
Forefoot powers(WN01GR2)
Rearfoot powers(WN01GR2)
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70Time (seconds)
-2000.
-1500.
-1000.
-500.
0.
500.
1000.
1500.
2000.
Pow
er (W
)
Trial: WN01GR2MP force powerMP moment powerAnkle force powerAnkle moment powerRf total powerRf energy rateRf power imbalance
IFS IHO ITO
Results (subject 2)
• pause to show animation
Ang. velocity, moment and power of the ankle joint
(WN01JS)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Time (s)
-500.
-250.
0.
250.
-100.
0.
100.
-10.
0.
10.
Pow
er (W
)
M
omen
t (N
.m)
Ang
ular
vel
. (/s
)
Trial: WN01JSAng. vel.Net momentPower
IFS IHO ITO
Dorsiflexing
Plantar flexingDorsiflexor
Plantar flexorConcentric
Eccentric
Ang. velocity, moment and power of the MP joint
(WN01JS2)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Time (s)
-500.
-250.
0.
250.
-100.
0.
100.
-10.
0.
10.
Pow
er (W
)
M
omen
t (N
.m)
Ang
ular
vel
. (/s
)
Trial: WN01JS2Ang. vel.Net momentPower
IFS IHO ITO
Dorsiflexing
Plantar flexingDorsiflexor
Plantar flexorConcentric
Eccentric
Ang. velocity, moment and power of the ankle joint
(WN01JS2)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Time (s)
-500.
-250.
0.
250.
-100.
0.
100.
-10.
0.
10.
Pow
er (W
)
M
omen
t (N
.m)
Ang
ular
vel
. (/s
)
Trial: WN01JS2Ang. vel.Net momentPower
IFS IHO ITO
Dorsiflexing
Plantar flexingDorsiflexor
Plantar flexorConcentric
Eccentric
Foot powers(WN01JS)
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90Time (seconds)
-2000.
-1500.
-1000.
-500.
0.
500.
1000.
1500.
2000.
Pow
er (W
)
Trial: WN01JSFloor powerForce powerMoment powerTotal powerEnergy ratePower imbalance
IFS IHO ITO
Forefoot powers(WN01JS2)
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90Time (seconds)
-2000.
-1500.
-1000.
-500.
0.
500.
1000.
1500.
2000.
Pow
er (
W)
Trial: WN01JS2Floor powerMP force powerMP moment powerFf total powerFf energy rateFf power imbalance
IFS IHO ITO
Rearfoot powers(WN01JS2)
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90Time (seconds)
-2000.
-1500.
-1000.
-500.
0.
500.
1000.
1500.
2000.
Pow
er (W
)
Trial: WN01JS2MP force powerMP moment powerAnkle force powerAnkle moment powerRf total powerRf energy rateRf power imbalance
IFS IHO ITO
Conclusions
• adding MP joint reduces error at foot-strike and toe-off
• plantar flexor moment at MP joint does both negative and positive work, but mainly negative
Questions?
Answers!
Where to go next?
Thank you
