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

2. Quantitative Domains Temporal Electromyography
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 x rate (b/min)
Instrumentation
Photocells and timers
Videography (1 frame = /30 second)
Metronome

4. Donovan Bailey sets world record (9
Donovan Bailey sets world record (9.835) despite slowest reaction time (0.174) of finalists

5. Electromyography Bortec system Noraxon system Delsys electrodes
Mega system

6. EMG of normal walking gait initiation strides rectus femoris
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch

7. EMG of normal walking rectus femoris vastus lateralis
rectus femoris contracts twice per cycle, once in early stance and once in late stance
rectus femoris
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch

8. 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

9. 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

10. EMG of normal walking
gastrocnemius has one long contraction throughout stance.
It is asynchronous with tibialis anterior.
rectus femoris
vastus lateralis
tibialis anterior
gastrocnemius
biceps femoris
heel switch

11. Kinematic Analysis Linear position Linear velocity Linear acceleration
Ruler, tape measure, optical, potentiometric
Linear velocity
radar gun, photo-optical timer
Linear acceleration
Accelerometry, videography
3D digitizer
radar gun
miniature accelerometers

12. Gait Characteristics - Walking

13. Gait Characteristics – Running/Sprinting

14. Motion Capture Cinefilm, video or infrared video
Basler charge-coupled device (CCD) camera
Cinefilm, video or infrared video
Subject is filmed and locations of joint centres are digitized
Panasonic videocamera
Vicon infra-red camera

15. Video Motion Capture (e.g., SIMI or APAS)
data
F-Scan
data
EMG data
3D motion
data
Force platform
data

16. Passive Infrared Motion Capture (e.g., M.A.C.)
Infrared video cameras
M.A.C.
system
Kistler force platforms

17. Active Infrared Motion Capture
NDI’s Optotrak
Infrared video cameras
Infrared emitting diodes

18. Computerized Digitizing (Vicon, SIMI, etc.)

19. Gait and Movement Analysis Lab (e.g., Vicon)
Vicon Nexus or Workstation
Vicon MX cameras
Kistler and AMTI force platforms
Bortec EMGs ( 8-channels) or Delsys Trigo (16 EMGs + 24 accelerometers)
Tekscan or Pedar in-shoe pressure mapping systems

20. Full-body 3D Marker Set

21. 3D Geometric Model (Visual3D)
from stick-figures to geometrical solids of revolution with known inertial properties
from markers to joint centres and stick-figure of body

22. 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)

23. Steps for Inverse Dynamics
Space diagram of the lower extremity

24. Divide Body into Segments and Make Free-Body Diagrams
Make free-body diagrams of each segment

25. Add all Known Forces to FBD
Weight (W)
Ground reaction force (Fg)

26. Apply Newton’s Laws of Motion to Terminal Segment
Start analysis with terminal segment(s), e.g., foot or hand

27. Apply Reactions of Terminal Segment to Distal End of Next Segment in Kinematic Chain
Continue to next link in the kinematic chain, e.g., leg or forearm

28. Repeat with Next segment in Chain or Begin with Another Limb
Repeat until all segments have been considered, e.g., thigh or arm

29. Compute Net Force and Moment Powers
Powers provided by the net moments of force can be positive (increasing mechanical energy) or negative (dissipation of mechanical energy), or can show transfer of energy across joint usually by muscles
Pmoment = M w
Powers provided by net forces show rates of transfer of energy from one segment to another through joint connective tissues (ligaments) and bone-on-bone (cartilage) contact
Pmoment = F  v

30. Normal Walking Example
Female subject
Laboratory walkway
Speed was 1.77 m/s (fast)
IFS = ipsilateral foot-strike
ITO = ipsilateral toe-off
CFS = contralateral foot-strike
CTO = contralateral toe-off

31. Ankle angular velocity, moment of force and power
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Time (s)
-200
-100
100
-10 10
Power (W) Moment (N.m) Ang. Vel. (rad/s)
Dorsiflexion
Plantar flexion
Trial: 2SFN3
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
CFS
ITO
IFS
CTO
CFS
ITO

32. Knee angular velocity, moment of force and power
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Time (s)
-200
-100
100
-10 10
Power (W) Moment (N.m) Ang. Vel. (rad/s)
Extension
Flexion
Trial: 2SFN3
Ang. velocity
Negative work by flexors to control extension prior to foot-strike
Moment
Power
Extensors
Flexors
Burst of power to cushion landing
Concentric
Negative work by extensors to control flexion at push-off
Eccentric
CFS
ITO
IFS
CTO
CFS
ITO

33. Hip angular velocity, moment of force and power10
Flexion
-10
Extension
Trial: 2SFN3
Ang. velocity
Moment
Positive work by flexors to swing leg
Power
100
Flexors
Power (W) Moment (N.m) A ng. Vel. (rad/s)
Positive work by extensors to extend thigh
Extensors
-100
Concentric
100
Negative work by flexors to control extension
Eccentric
-100
-200
CFS
ITO
IFS
CTO
CFS
ITO
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Time (s)

34. Solid-Ankle, Cushioned Heel (SACH) Prostheses

35. Power dissipation during weight acceptance and push-off
Ankle angular velocity, moment of force and power of SACH foot prosthesis
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Time (s)
-200.
-100. 0.
100.
-10.
10.
Power (W) Moment (N.m) Angular vel. (/s)
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

36. FlexFoot Prostheses (Energy Storing)
Original model
FlexFoot Prostheses (Energy Storing)
Recent models

37. Power returned during push-off
Ankle angular velocity, moment of force and power of FlexFoot prosthesis
-100. 0.
100.
-10.
10.
Power (W) Moment (N.m) Angular vel. (/s)
Dorsiflexing
Trial: WB13MH-F
Plantar flexing
Ang. velocity
Net moment
Dorsiflexor
Power
Power 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)

38. Power at push-off is increased to compensate for other side
Ankle angular velocity, moment of force and power of person with hemiplegia (normal side)
10.
Dorsiflexing 0.
-10.
Trial: WPN03EG
Plantar flexing
Ang. vel.
Net moment
100.
Dorsiflexor
Power 0.
Power at push-off is increased to compensate for other side
Power (W) Moment (N.m) Angular vel. (/s)
-100.
Plantar flexor
100.
Concentric 0.
-100.
Eccentric
IFS
CTO
CFS
ITO
IFS
-200.
0.0
0.2
0.4
0.6
0.8
Time (s)

39. Reduced power during push-off due to muscle weakness
Ankle angular velocity, moment of force and power of person with hemiplegia (stroke side)
0.0
0.2
0.4
0.6
0.8
Time (s)
-200.
-100. 0.
100.
-10.
10.
Power (W) Moment (N.m) Angular vel. (/s)
Dorsiflexing
Trial: WPP14EG
Plantar flexing
Ang. vel.
Net moment
Dorsiflexor
Power
Reduced power during push-off due to muscle weakness
Plantar flexor
Concentric
Increased amount of negative work during stance
Eccentric
IFS
CTO
CFS
ITO
IFS

40. Above-knee Prostheses

41. Questions?
Answers?
Comments?