# Kinesiology

Mechanics

Jul 18, 2012 (5 years and 10 months ago)

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NORMAL GAIT
NORMAL GAIT
Part A
Part A
(Patto
n)
(Patton)
￿
￿
Introduction
I
ntroduction
￿
￿
Gait measurement
Gait measu
rement
techniques
techniques
￿
￿
Force
Force
￿
￿
Motions
Motions
￿
￿
EMG
EMG
￿
￿
Other
Other
￿
￿
Terminol
ogy
Terminology
￿
￿
RLA
RLA
vs
vs
“traditional”
“traditi
onal”
￿
￿
Ph
ases of gait
Phases
of gait
￿
￿
Observational Gait
Observational Gait
Analysis
Part B
Part B
￿
￿
Mechanics
Mechanics
(Patton)
(Patton)
￿
￿
“Determi
nants
” of gai
t
“Determinants” of
gait
￿
￿
Kinematics
Kinematics
￿
￿
Kinetic Patterns
Kinet
ic Patte
rns
￿
￿
Ground reaction forces
Ground reaction forces
￿
￿
COP
COP
￿
￿
GRFV m
ethod
GRFV method
￿
￿
Inverse Dynamics method
Inve
rse Dynamics method
￿
￿
Calculat
ing joint p
ower
Calculating joint power
￿
￿
Muscle Torques
Muscle Torques
(Humphrey)
(Humphrey)
￿
￿
Specialized Gait
Specialized Gait
(Humphrey)
(Humphrey)
￿
￿
Pediatric
Pediatric
￿
￿
Geriatric
Geriatric
￿
￿
Running
Analysis
Runn
ing
(
Patton
)
slide#1
Review of Mechanics Terminology
Revi
ew of Mechanics Terminology
Mechanics:
Interaction of forces, motions, deformations, and flow.
Kinematics:
Movements (position, velocity, acceleration, j
oint angles, etc
.)
Kinetics:
Forces during movements (joint torque, GRF, etc.)
Forward Dynamics:
How forces cause
movements. We use dynamics to estimate
th
e
movements that result from forces and moments.
(a=F/m).
Inverse Dynamics:
Ho
w
movements requi
re
forces. We use inverse dynamics to
estimate
the forces that cause the motions we measure.
(F=ma)
.
Most labs
u
se measured forces and measured motions combined to
get a b
est estimate of joint torque and mu
scle actions.
(Patton)
slide#2
Mechanics & mechanical
Mechanics & mechanical
Patterns:
Patterns:
“streamlined research” gives
patterns & deviations
5.1
Center of mass motion
Determinants of Gait
5.2
K
inematics:
Sagittal, Frontal, Transverse, & Other
5.3
K
inetics
GRF’s, COP, “GRF vector method” for
estimating joint moments, inverse
dynamics, sagittal muscle torques
(Patton)
slide#3
Gait Phase Diagram:
Gait Phase Diagram:
100%
90%
80%
70%
60%
50%
40%
30%
10%
20%
0%
Midstance
(w
eight is over
stance leg)
Heel
off
Midswing
(Swing leg is
under the body)
Toe
off
Contra-
lateral
Foot off
Foot Flat
Heel
strike
Heel
strike
Loading
Response
Phase
EVENTS:
SUB-
PHA
SES:
PHA
SES:
RLA
terminology:
Traditional
terminology:
Tibia
is
vertical
Maximum knee
Flexion
Foot
off
Initial
contact
Initial
con-
tact
Double
S
upport
Phase
Gait cycle is 1
Stride (100%
)
Stance (6
0 to 62%
)
Swing (38 to 40%)
Mi
d
-
stance
Terminal
stance
Double
Support
Phase
Preswing
Phase
Termi
nal
swing
Phase
A
cceleration
phase
Mids
wing
Phase
RLA
terminology:
Traditional
terminology:
Initial
Sw
ing
Phase
(Jim Pat
t
on)
Deceleration
phase
Single Support Phas
e
Contra-
lateral
Foot strike
Contra-
lateral
Foot strike
kinesiology gait section, part1 (Patton)
5
kinesiology gait section, part1 (Patton)
6
Center of Mass (CM) motion:
Center of Mass (CM) motion:
Bipedal tradeoff: mobili
ty
vs
efficiency
￿
ADVANTAGES OF BIPEDAL GAIT:
￿
Bipedal gait frees our hands, elevates our head,
and allows us to move
on challenging terrain.
￿
DISADVANTAGE:
￿
Very hard for our CM
to
move in a straight line,
which would be the most
efficient. (like a wheel.)
￿
Instead, there is an arc-shaped pattern with
lateral sway.
￿
Maintaining a smoother trajectory of the CM plays
a large role in determining HOW
we walk
(Patton)
slide#7
Smoothing out CM Excursion
1)
Pelvic Rot
ation
2)
Pelvic List (Lateral Tilt) (Pelvic Drop)
3)
Stance Knee Flexion
4&5) Knee, Ankle & Foot Interactions
6)
Lateral Displacement from Hip
Adductors &
Genu Valgum
See Saunders (1953), Inman et. al, (1981). Modified slightly fr
om origi
nal.
(Patton)
slide#8
PELVIC ROTATION
￿
Pelvis moves
forward with swing
limb
￿
Trails
behind with
the following limb
￿
Flattens the Arc of
CM motion by
increasing the
effective leg-length
at these times
(Patton)
slide#9
PELVIC
LIST
￿
Pelvis dips down
on swing side
during swing
￿
Lowers CM and
flattens arc
Recently
disputed to be
not true
Recently
disputed to be
not true
(Patton)
slide#10
STANCE KNEE FLEXION
￿
Shortens the leg
during stance
￿
Flexion at the
beginning and
end of stance
smoothes the
abrupt changes
in CM
￿
Flattens the arc
(Patton)
slide#11
Recently disputed to be not true:
Gard, S. A. (19
96). "The influence of s
tance-phase knee
flexion on the
vertical displacement
of the
tr
unk during no
rmal walking." Journal of Biomechan
ics 29(
10): 1387-91.
KNEE, ANKLE & FOOT INTERACTIONS
Heel
Strike
Loading
Response
Terminal
Stance
Preswing
Recently disputed to be not true:
Kerrigan
DC, D
ella
Croce
U,
Marciello
M, Riley PO.
A refined
view of th
e determinants of gait: sign
ificance of heel ris
e.
Arch Phys Med
Rehabil
2000;81:1077-80.
￿
Heel-strike:
Knee is
extended and ankle is
dorsiflexed to lengthen the
leg
￿
Loading response (HS
to FF):
knee flexes, ankle
plantarflexes
, and foot
pronates
￿
Midstance to terminal
stance (FF to HO): Knee
extends, ankle dorsiflexes
￿
Preswing (HO to TO):
ankle plantarflexes to
lengthen the leg
(Patton)
slide#12
GENU VALGUM & HIP ADDUCTION
￿
￿
Valgus at the knee
Valgus at the knee
permits a narrower
permits a narrower
walking base, and
walking base, and
thus a smaller
thus a smaller
lateral shift
lateral shift
￿
￿
Tibia about vertical
Tibia about vertical
￿
￿
Femur articulates
Femur articulates
adducts to shift CM
adducts to shift CM
in the frontal plane,
in the frontal plane,
toward the line of
toward the line of
progression
progression
(Patton)
slide#13
￿
Averages 1 inch anterior to S2 on the
midline
￿
about 55% of body height up from the
floor.
￿
During gait, the CM still waves up and
down and side to side in a sinusoidal
trajectory that has about a 2 inch
amplitude
(Patton)
slide#14
kinesiology gait section, part1 (Patton)
15
Gait is Variable
Gait is Variable
539 strides of a “normal” subject
￿
Sagittal, lower extremity kinematics
dominate gait
￿
Gross motions and muscle groups
￿
Sometimes the only thing measured
￿
VARIABILITY MU
ST BE CONSIDERED
￿
People are variable
￿
Measurement techniques are variable
(Patton)
slide#16
-20
-10
0
10
20
30
40
0
2
04
06
08
0
1
0
0
Sagittal: Hip
Sagittal: Hip
degrees
% gait cycle
(Patton)
slide#17
Avg+std
avg
Avg-std
-10
0
10
20
30
40
50
60
70
0
20
40
60
80
100
Sagittal: Knee
Sagittal: Knee
degrees
% gait cycle
(Patton)
slide#18
Avg+std
avg
Avg-std
-25
-20
-15
-10
-5
0
5
10
15
0
20
40
60
80
100
Sagittal: Ankle
Sagittal: Ankle
degrees
% gait cycle
(Patton)
slide#19
Avg+std
avg
Avg-std
Loading Response Phase
(Heel Strike to Foot Flat)
(see also pg. 30 of
Observational Gait Analysis
)
￿
HIP:
25°
flexion
￿
KNEE: 0° ￿
15° flexion (Lowers CM)
￿
ANKLE: 0° ￿
10° plantar flexion
“1st rocker:”
Calcaneus
“1st rocker:”
Calcaneus
(Patton)
slide#20
Midstance Phase
(Foot Flat to “midstance event”)
￿
HIP: 25° flexion ￿

￿
KNEE: 15° flexion ￿
0° flexion
￿
ANKLE: 10° plantar flexion ￿
5° dorsi
flexion
“2n
d rocker:”
ankle
“2n
d rocker:”
ankle
(Patton)
slide#21
Terminal Stance Phase
(“midstance event” to Heel Off)
￿
HIP: 0° flexion ￿
20° extension
￿
KNEE: 0°
￿
ANKLE: 5° dorsi flexion ￿
10° dorsi
flexion
Continue “2nd rocker:” ankle
At end of terminal stance,
Begin “3rd rocker:” MTP
Continue “2nd rocker:” ankle
At end of terminal stance,
Begin “3rd rocker:” MTP
(Patton)
slide#22
Preswing Phase
(Heel Off to Toe Off)
￿
HIP: 20° extension
￿

￿
KNEE: 0° ￿
40° flexion
￿
ANKLE: 10° dorsi flexion ￿
20° plantar
flexion
“3rd rocker:”
MTP
“3rd rocker:”
MTP
(Patton)
slide#23
Swing Phase (Toe Off to Heel Strike)
￿
HIP: 0° ￿
30° flexion
￿
KNEE:
40° flexion ￿
60° flexion ￿

￿
ANKLE: 20° plantar flexion ￿

Note:
RLA divides swing into 3
sections, where we will not
cover it in this amount of detail.
Note:
RLA divides swing into 3
sections, where we will not
cover it in this amount of detail.
(Patton)
slide#24
Other motions
Pelvic tilt
￿
5° forward in early stance, then tilts 5° backward
in late stance, then tilts 5° forward again by late
swing
Arms
￿
Swing opposite to the legs (out of phase).
Smoothes the CM trajectory.
MTP
￿
0° ￿
30° ￿
60° dorsiflexion
ROM 5° and variable
ROM 5° and variable
(Patton)
slide#25
Hip & Pelvis
Hip & Pelvis
Pelvic Obliquity (Pelvic List)
Near midstance, the CM is high.
The swing side of the pelvis drops
down during swing to lower the CM.
Hip AB-Adduction
Hip adducts in early stance about 5°,
abducts in late stance about 5°, and
returns to
neutral in swing.
(Patton)
slide#26
Subtalar
Subtalar
In early stance, eversion
(pronation) unlocks the
midtarsal
j
oint, allowing shock
absorption.
In late stance, inversion
(supination) locks the
midtarsal
joint, allowing a rigid forefoot
lever for heel off.
(Not quite frontal)
Initial
Contact
Loading
Response
Terminal
Stance
(Patton)
slide#27
Hip, trunk & lower limb
Hip, trunk & lower limb
Pelvic Rotation
Pelvic Rotation
￿
the swing leg side of the pelvis rotates 10° with the

swing leg.
Trunk Rotation
Trunk Rotation
￿
Lower trunk (below T7/T8 ) rotates with the pelvis.
￿
Upper Trunk rotates opposite to this (180° out of
phase)
Femoral/
Femoral/
Tibial
Tibial
Rotation
Rotation
￿
internal r
o
t
ation until foot flat, then externally
rotates until toe off, then internally rotates through
swing.
(Patton)
slide#28
Talo
Talo
-
-
crural
crural
&
&
Talo
Talo
-
-
calcaneal
calcaneal
joints act as a
joints act as a
torque converter
torque converter
Pronation at heel-strike is
converted to internal
tibial
(and subsequently
femoral) rotation.
External rotation of the
femur between midstance
event and toe-off is
converted into supination
of the f
o
ot.
(Patton)
slide#29
Ground Reaction Forces (GRF)
Ground Reaction Forces (GRF)
￿
The equal-and-opposite
force the floor exerts on
the body during stance
￿
Best measured with a
force plate
￿
Forces are typically
resolved into:
￿
Vertical Compression (z)
￿
Anterior-Posterior Shear (y)
￿
Medial-Lateral Shear (x)
(Patton)
slide#30
0
20
40
60
80
100
120
140
0
2
04
0
6
08
0
1
0
0
￿
“M” shaped curve
￿
There can be a
spike at heel
contact
￿
Hump during
loading response
￿
Valley at
midstance
￿
Hump in
preswing
% body weight
% gait cycle
Vertical GRF
Vertical GRF
(Patton)
slide#31
Avg+std
avg
Avg-std
-20
-15
-10
-5
0
5
10
15
20
25
30
0
2
04
06
08
0
1
0
0
Anterior
Anterior
-
-
Posterior Shear Force
Posterior Shear Force
￿
Friction is
required to walk
normally
￿
Often an anterior
spike at heel
contact
￿
Braking hump in
loading response
￿
Acceleration
hump in
preswing
response
% body weight
% gait cycle
(Patton)
slide#32
Avg+std
avg
Avg-std
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
0
2
04
0
6
08
0
1
0
0
Medial
Medial
-
-
Lateral Shear Force
Lateral Shear Force
% body weight
% gait cycle
￿
Highly
variable
￿
CM is
usually
medial to
the foot, so
odds are it
is a lateral
force
(Patton)
slide#33
Avg+std
avg
Avg-std
Kinetics:
Cen
ter Of Pressure (COP)
Center Of Pressure (COP)
GRF
COP
￿
Represents the centroid of
foot forces on the floor
￿
This is an idealization,
because pressures are
distributed all over
￿
It is important, because we
want to know where
the
GRF is applied to the body
￿
When measured by a force
plate, it is more correctly
called the
point of
application of the GRF
(Patton)
slide#34
￿
Plotting the COP as it
mov
es under the
foot:
￿
Normal Path: Center of the
calcaneus or slightly lateral,
curving laterally and then
medial (pronation) and ending
between the 1st and second
toes
￿
Variable: Normal individuals
can hav
e many COP
trajectories, just by changing
their gait style.
(Patton)
slide#35
kinesiology gait section, part1 (Patton)
36
kinesiology gait section, part1 (Patton)
37
(see website f
or these)
(Patton)
slide#38
(Patton)
slide#38
plantar
flex
flex
flex
do
rsi
do
rsi
do
rsi
zero
exten
exten
exten
flex
flex
zero
do
rsi
LR
MSt
Mid
stance
event
TSt
PSw
T
his is Ex
ternal torque
(torque demand)
vs

Internal torque
(muscle torque)
This is Ex
ternal torque
(torque demand)
vs

Internal torque
(muscle to
rque)
The “GRF Vector Method”
The “GRF Vector Method”
Estimating
Estimating
external
external
joint
joint
torques
torques
NOTE: This method is
dynamically
inaccurate
& can give WRONG r
esults.
(Patton)
slide#
39
GRF Vector Method:
GRF Vector Method:
Why this is NOT correct
Why this is NOT correct
￿
Dynamics are neglected
￿
The faster the gait, the m
ore error
￿
Accuracy is fair for distal joints (ankle
and sometimes knee)
￿
Neck example: if we use this to
estimate the neck moment, we end up
with an outrageous value.
￿
GRF Vector Method says all moments
during swing are zero, whi
ch is not true
￿
(see Winter,
1990)
￿
What is the c
orrect way?
INVERSE DYNAMICS
(Patton)
slide#40
Muscle torques:
Muscle torques:
What are the
What are the
muscles
muscles
doing in gait?
doing in gait?
￿
An external (GRF) force :
￿
can cause motion
OR,
￿
can be countered by gravity
OR
,
￿
it can be resisted by muscle
OR,
￿
any com
bination of
the above
￿
Inverse dynamics
:
￿
tell us the net effect of the muscles
￿
￿
Example:
Example:
“The muscles crossing the
ankle are generating a
“The muscles crossing the
ankle are generating a
NET torque of 70 Newton*meters at heel rise”
NET torque of 70 Newton*meters at heel rise”
(Patton)
slide#41
Cause & Effect
Cause & Effect
accelerations
torques
muscle
tension
s
motor-
neurons
mixing
converging
& mixing
converging
MOTION
Dynamic
equations
Dynamic
equations
Why can’t we get the actual muscle tensions?
It is difficult to estimate the actual muscle forces from to
rques, because many
muscles can make the same torque (due to “converging” of muscles
to torques)
(Patton)
slide#42
kinesiology gait section, part1 (Patton)
43
gives the parts
gives the parts
gives the parts
Torques caused b
y moti
ons
(I￿)
Inv
ers
e
Dynam
ics
GRF & COP
LEFTOVERS
: Net torques
caused by
muscles and other
passive st
ructures su
ch as
ligame
nts, ski
n, etc. (RJT)
RJT
M
I
:
IDA
L
￿
￿
￿
￿
￿
￿
RJT
M
:
GRFVM
L
￿
￿
￿
Kinematics
(pos
itions
, velocit
ies,
and
accelerations
)
Torques caused b
y grav
ity
(ML)
(Patton)
slide#43
Disadvantages of Inverse
Disadvantages of Inverse
Dynamics
Dynamics
￿
No information on co-contraction
￿
No information on elastic storage
￿
No information on passive structures
(ligament, skin, clothing)
￿
No information on what role bi-articular
muscles are playing
(Patton)
slide#44
SAGITTAL muscle torq
ues:
SAGITTAL muscle torques:
ANKLE
ANKLE
3
1
0
-1
Plantarflexion
(+)
Dorsiflexion (-)
the fo
llowing s
lides
a
re all muscle
torque
s obtained
usin
g invers
e
dyna
mics.
Compare
thes
e tor
q
ues to
tho
s
e
est
imated
from the G
RF
method in
Observational Gait
Analysis
`
the fo
llowing s
lides
a
re all muscle
torque
s obtained
usin
g invers
e
dyna
mics.
Compare
thes
e tor
q
ues to
tho
s
e
est
imated
from the G
RF
method in
Observational Gait
Analysis
`
2
moment
Nm/KG
(Patton)
slide#45
SAGITTAL muscle torq
ues:
SAGITTAL muscle torques:
KNEE
KNEE
2
1
moment
Nm/KG
0
-1
Extension (+)
Flexion (-)
(Patton)
slide#46
SAGITTAL muscle torq
ues:
SAGITTAL muscle torques:
HIP
HIP
2
1
moment
Nm/KG
0
-1
Extension (+)
Flexion (-)
(Patton)
slide#47
Simply multip
ly
Simply multip
ly
torque
torque
times
times
velocity
velocity
Hip
Hip
Knee
Knee
Ankle
Ankle
Joint
Joint
Power
Po
wer
(Watts/Kg)
(Wa
tts/K
g)
%
%
Gait
Gait
Cycle
Cycle
% Gait Cycle
% Gait Cycle
% Gait Cycle
% Gait Cycle
(F/E)
(F/E)
(F/E)
(F/E)
(D/P
)
(D/P)
Concentric (+)
Concentric (+)
Eccentric (
Eccentric (-
-)
)
￿
UNITS (for angular power):
(Newton*meters/sec) = watts
￿
Positive: prime mover is concentric
￿
Ne
gative: prime mover is eccentric
￿
Does not show co-contraction
￿
3D is problematic
(Patton)
slide#48
Where to get more info
Where to get more info
￿
Books:
￿
Gage, James R.
Gait analysis in
cerebral palsy
. Clinic
s in
developmental medicine; no.121. London: Mac Keith, 1991.
￿
Inman, VT, Ralst
on, HJ, Todd, F. (1981) ,
Huma
n Walking
,
Baltimore: Williams and Wilkins
￿
Inman & Saunders,
Human
Walking
(
2nd Edition).
￿
Perry,
Jacquelin.
Gait analysis: normal and pathological
function
.
Thorofare, N.J:
SLACK, 1992.
￿
Vaughan, CL.
Gait analysis laboratory an interactive book &
software package.
[kit]. Champaign, Ill: Human Ki
netics
Publishers, 1992.
￿
Vaughan C.L., B.L. Davis, a
nd J.C. O'Connor, "Dynamics of
Human Gait", 1st edition, H
um
an Kinetics Publishers, 1992
￿
Vaughan, Christopher L.
Biomechanics of
human gait: an
annotated bibliography
. 2nd ed. Champaign, Ill.: Hum
an
Kinetics P
ublishers, 1987.
￿
Weber, Wilhelm
Eduard.
Mechanics of the h
uman walking
apparatus
. Berlin: Springer-Verlag, 1991.
￿
Whittle, Michael.
Gait analysis: an introduction
. Oxford:
Butterworth
-Heineman
n, 1991.
￿
Winter, David A.
The biomechanics and motor co
ntrol of
human gait: normal, elderly and pathological.
2nd ed.

Waterloo, Ont.: University of Waterloo Press, 1991.
￿
Winter, David A.
A.B.C. (a
natomy, biome
chanics, control)
of balance during standing and walking
. Waterloo, Ont.:
Waterloo Bio
mechanics,
1995.
￿
Gait: an ant
hology. [United States]
: American Physical
Therapy Association
,
1981.
￿
Winters and Woo (eds),
Multiple Muscle Systems
, Springer
Verlag, 1990.
￿
Craik and Oatis
(eds),
Gait analysis: Theory and
application.
Mosby-Yearboo
k,
St
.
Luis, 1995.
Yo
res
th
on
e
￿
Local Labs/Clinical Facil
ities:
￿
NU/Rehab. In
stitute (RIC):
Dudley Childress, Scott Delp.
￿
Chicago Childre
n’s Hospital Clinical Gait Lab
￿
U. Of Illinois at Chicago and Rush Presbyterian St. Luke’s
￿
VA/Hine’s
Hospital
￿
Key Journal Articles:
￿
Ounpuu,
S., (1994) The biomechanics of walking and
running
Clinics in Sports Medicine,
13(
4) 843
-863.
￿
Saunders, J. B.
,
V. T
.
Inman, H. D.
Eberhardt (1953)
The
major determinants in nor
mal and pathological gait.
The
Journ
al of Bone and
Joint Surgery. 35-
A
:543
-558.
￿
Wi
nter, D. A. (1984
) Kinematic and Kinet
ic pattern
s in
Human Gait: Variability and Compensating Effects. Human
Move
ment Science. 3:51-76
.
￿
Kirtley
C, Whitt
le MW & Je
fferson RJ
(
1985
) Influence of
Walking Speed on Gait Parameters Journal of Biomedical
Engineering 7(4): 282-8.
￿
Gait Journals:
￿
Gait & Posture
￿
Journal of Biomechanics
￿
Human Movement
Scien
ce
￿
Web/Internet:
￿
Clinical G
ait Analysis Web Page and
Listserver:
http:
//www.curtin.edu.au/curtin/dept/physio/pt/s
taff/kirtley
/cga/
￿
Biomechanics Listserver:
http:
//www.k
in.ucalgary.ca/isb/bio
mch-l.h
tml
￿
http:
//www.
linder.com/muybridge.html
￿
http:
//165.124.30.88/jim/
k
inesiolo
gy_
gait
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ponsible fo
e material
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r

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