Biomechanics of Locomotion

1
Biomechanics of Locomotion

• D. Gordon E. Robertson, PhD, FCSB
• Biomechanics, Laboratory,
• School of Human Kinetics,
• University of Ottawa, Ottawa, Canada

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Quantitative Domains

• Temporal
• phases (stance/swing) and events (foot-strike,
  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

3
Temporal Analysis

• 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

4
Donovan Bailey sets world record (9.835) despite
slowest reaction time (0.174) of finalists
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Electromyography
Noraxon system
Bortec system
Delsys electrodes
Mega system
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EMG of normal walking
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EMG of normal walking
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EMG of normal walking
rectus femoris
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch
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EMG of normal walking
rectus femoris
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch
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EMG of normal walking
rectus femoris
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch
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Kinematic Analysis

• Linear position
• Ruler, tape measure, optical
• Linear velocity
• radar gun, photo-optical timer
• Linear acceleration
• Accelerometry, videography

radar gun
miniature accelerometers
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Motion Capture

• Cinefilm, video or infrared video
• Subject is filmed and locations of joint centres
  are digitized

Panasonic videocamera
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Gait Characteristics - Walking
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Gait Characteristics Running/Sprinting
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Motion Capture(e.g., SIMI or Vicon)
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Passive Infrared Motion Capture (e.g., Vicon or
M.A.C.)
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Active Infrared Motion Capture

• NDIs Optotrak

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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

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3D Geometric Model(Visual3D)
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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)

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Normal Walking Example

• 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

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Results
Dorsiflexion
Trial 2SFN3
Plantar flexion
Ang. velocity
Moment
Power
Dorsiflexors
Plantar flexors
Concentric
Eccentric
IFS
CTO
CFS
ITO
CFS
ITO
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Ankle angular velocity, moment of force and power
Dorsiflexion
Trial 2SFN3
Plantar flexion
Ang. velocity
Moment

• Dorsiflexors produce dorsiflexion during swing

Power
Dorsiflexors
Plantar flexors

• Plantar flexors control dorsiflexion

Concentric

• Large burst of power by plantar flexors for
  push-off

Eccentric
IFS
CTO
CFS
ITO
CFS
ITO
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Knee angular velocity, moment of force and power
Extension
Trial 2SFN3
Flexion

• Negative work by knee flexors to control knee
  extension prior to foot-strike

Ang. velocity
Moment
Power
Extensors
Flexors

• another to cushion weight-acceptance

Concentric

• Negative work by knee extensors to control
  flexion at push-off

Eccentric
IFS
CTO
CFS
ITO
CFS
ITO
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Hip angular velocity, moment of force and power
10
Flexion
0
Trial 2SFN3
Extension
-10
Ang. velocity

• Positive work by hip flexors to swing thigh
  flex knee

Moment
Power
100
Flexors
0
Power (W) Moment (N.m)
A ng. Vel. (rad/s)
Extensors

• Positive work by hip extensors to extend hip in
  early stance

-100
Concentric
100
0
Eccentric
-100

• Negative work by hip flexors to control extension

IFS
CTO
CFS
ITO
CFS
ITO
-200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Time (s)
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Solid-Ankle, Cushioned Heel (SACH) Prostheses
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Ankle angular velocity, moment of force and power
of SACH foot prosthesis
Dorsiflexing
Trial WB24MH-S
Plantar flexing
Ang. velocity
Net moment
Dorsiflexor
Power

• Power dissipation during weight acceptance and
  push-off

Plantar flexor
Concentric

• No power produced during push-off

Eccentric
ITO
IFS
CTO
CFS
ITO
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FlexFoot Prostheses(energy-storing)
Original model
Recent models
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Ankle angular velocity, moment of force and power
of FlexFoot prosthesis
Dorsiflexing
Trial WB13MH-F
Plantar flexing
Ang. velocity
Net moment
Dorsiflexor
Power

• Some energy returned during push-off

Plantar flexor
Concentric
250.
0.
-250.
Eccentric
ITO
IFS
CTO
CFS
ITO
-500.
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Time (s)
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Above-knee Prostheses
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Running Prostheses