Transcript Biomechanics of Locomotion

Biomechanics of
Locomotion
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 (footstrike, toe-off), stride rate
• Electromyography
– muscle activation patterns
• Kinematic (motion description)
– stride length, velocity, ranges of motion,
acceleration
• Kinetic (causes of motion)
– ground reaction forces, pressure patterns,
joint forces, moments of force, work, energy
and power
Temporal Analysis
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Stride time (s)
Stride rate = 1/time (/s)
Stride cadence = 120 × rate (b/min)
Instrumentation
– Photocells and timers
– Videography (1 frame =
1/30 second)
– Metronome
Donovan Bailey sets
world record (9.835)
despite slowest
reaction time (0.174)
of finalists
Electromyography
Bortec system
Delsys electrodes
Noraxon system
Mega system
EMG of normal walking
rectus femoris
vastus lateralis
gait
initiation
strides
tibialis anterior
gastrocnemius
biceps femoris
heel switch
EMG of normal walking
rectus femoris
vastus lateralis
rectus femoris
contracts twice per
cycle, oncetibialis
in earlyanterior
stance and once in
late stance
gastrocnemius
biceps femoris
heel switch
EMG of normal walking
rectus femoris
vastus lateralis
biceps femoris has one
longer contraction in
late swing and early
stance, synchronous
with one burst of
rectus femoris
tibialis anterior
gastrocnemius
biceps femoris
heel switch
EMG of normal walking
tibialis anterior has
two bursts of activity
one in mid-swing
and one during early
stance. It is very
active at initiation.
rectus femoris
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch
EMG of normal walking
gastrocnemius has one
long contraction
throughout stance.
rectus femoris
It is asynchronous
with tibialis anterior.
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch
Kinematic Analysis
• Linear position
– Ruler, tape measure, optical
• Linear velocity
– radar gun, photo-optical timer
• Linear acceleration
– Accelerometry, videography
miniature
accelerometers
radar gun
Motion Capture
• Cinefilm, video or
infrared video
• Subject is filmed and
locations of joint
centres are digitized
Basler charge-coupled
device (CCD) camera
Panasonic
videocamera
Vicon
infra-red
camera
Gait Characteristics Walking
a
walking
stride length
b
stance phase,
left foot
swing phase,
left foot
step length
one gait cycle
left foot
right foot
double-support
left foot-strike
right toe-off
left toe-off
right foot-strike
single-support
time
Gait Characteristics –
Running/Sprinting
a
running/sprinting
stride length
b
stance phase,
left foot
swing phase,
left foot
step length
one gait cycle
left foot
right foot
flight phase
right foot-strike
left foot-strike
right toe-off
left toe-off
time
Video
data
Motion Capture
(e.g., SIMI or Vicon)
EMG data
Force platform
data
F-Scan
data
3D motion
data
Passive Infrared Motion Capture
(e.g., Vicon or M.A.C.)
Infrared
video
cameras
M.A.C.
system
Kistler force platforms
Active Infrared Motion Capture
• NDI’s Optotrak
Infrared
Infrared
video
emitting
cameras
diodes
Gait and Movement
Analysis Laboratory
• Motion capture
system for marker
trajectories
• Force platforms for
ground reactions
• Electromyography
for muscle activity
• Pressure mapping
systems for in-shoe
pressure patterns
3D Geometric Model
(Visual3D)
from markers to
joint centres and
stick-figure of
body
from stick-figures to
geometrical solids
of revolution with
known inertial
properties
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)
Normal Walking Example
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Female subject
Speed was 1.77 m/s (fast)
IFS = ipsilateral foot-strike
ITO = ipsilateral toe-off
CFS = contralateral foot-strike
CTO = contralateral toe-off
Results
• Angular velocity
tells whether joint is
flexing or extending
• Moment of force
records whether
flexors or extensors
are performing work
10
Dorsiflexion
0
-10
100
Trial: 2SFN3
Ang. velocity
Moment
Power
Dorsiflexors
0
-100
100
• Power quantifies
whether work done
was positive or
negative
Plantar flexion
Plantar 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
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
• Plantar flexors
control dorsiflexion
Plantar flexion
100
Plantar flexors
Concentric
0
• Large burst of
power by plantar
flexors 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
• Negative work by
knee flexors to
control knee
extension prior to
foot-strike
• another to cushion
weight-acceptance
• Negative work by
knee extensors to
control flexion at
push-off
10
Extension
0
-10 Flexion
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
hip flexors to swing
thigh & flex knee
• Positive work by
hip extensors to
extend hip in early
stance
100
Trial: 2SFN3
Ang. velocity
Moment
Power
Flexors
0
-100
Extensors
Concentric
100
0
-100
• Negative work by
hip flexors to
control extension
Extension
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.
• Some energy
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
Above-knee Prostheses
Running Prostheses