hpe 660 lecture 6 - intro to gait
TRANSCRIPT
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ADVANCEDBIOMECHANICS
HPE 660
Luke Hopper
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Introduction to Gait Analyses
Temporal parameters of the gait cycle
General kinematics and kinetics
Treadmill gait analysis
Today’s Lecture and Lab
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Evolutionary Adaptations for Human Endurance Running
Anatomical adaptations Bipedalism places COM directly over
base of support Tendon length and size enable energy
storage Longitudinal foot arch for shock
absorption and energy storage Enlarged knee joint articular surfaces Gluteus maximus size
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Evolutionary Advantages for Human Endurance Running
Bramble & Lieberman, 2004. Endurance running and the evolution of Homo. Nature, 432, 345-52
Relatively slow max speed Human jogging range beyond trot to gallop transition
of small to medium quadripeds
Quadriped panting capacity
reduced during galloping Hunting success may have
improved over long distance
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Walking
Inverted pendulum model Translation strategy of movement Energy and force dissipated through
bones and joint tissue COM height increases
during mid stance
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RunningMass spring model Leg obeys stiffness properties
of a spring
Stiffness = Force/distance = Nm-1
Compression of leg reacts to opposing JRF and GRF
VGRF and braking forces result in spring compression and energy storage
COM vertical displacement behaves in opposition to walking
Blickhan, 1989. The spring-mass model for running and hopping. Journal of Biomechanics. 22 (11-12), 1217-27.
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Human gait cycle
Stance phaseFoot contact (footstrike) until foot leaves the
ground (toe-off) Swing phase
Toe-off to footstrike Stride
Toe-off to ipsilateral toe-off Step
Toe-off to contra lateral toe-off (footstrike to contra lateral footstrike)
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Human gait cycle
Walking:Alternating single
and double leg support
Running:Alternating
sequences of support and non-support
Data from Vaughan 1984.
Notice stance phase decreases as speed increases
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Temporal-Spatial Parameters (TSP’s) Walking speed
Distance/time(Cadence x stride length)/ 120
CadenceNumber of steps per minute (divide by 120
to get strides/second) Stride length
(120 x speed)/cadenceSpeed x stride time
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Normative data for “TSP”
Other factors which influence TSP:Shoes vs No shoes
○ Longer support barefootAgeTreadmill
○ Stride length ↓○ Cadence ↑
Speed (m/s) Cadence (steps/min)
Stride length (m)
Men 1.3-1.6 110-115 1.4-1.6
Women 1.2-1.5 115-120 1.3-1.5
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Effect of speed on time, phase & stance
Implications for force development?
(b) Adapted from J. Nilsson and A. Thorstensson 1987.
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Kinematics of running speed... SL for initial
increase in speed SR later SL increases
require less energy Trained athletes are
able to maximise SL Data from Saito et al. 1974.
Trained
Untrained
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Kinematics with speed...
Knee joint kinematics change with speed increase
Greater flexion during swing and at IC
Consider walking and running models
Data from C.L. Vaughan 1984.
Shaded area = stance phase (IC to TO
0 rad = extension at knee
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General kinematics and muscle activation during walking
Whittle, M. (2007). Gait analysis: an introduction. Philadelphia: Elsevier.
Kirtley, C. (2006). Clinical gait analysis: Theory and practice. Philadelphia: Elsevier.
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2-D Analysis of gait kinematics Can give some
quick valuable information but the downfalls include:Parallax error
○ Movement away from the optical axis of the camera
○ Increase toward periphery
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2-D Analysis of gait kinematics (2)
Perspective errorOut-of-plane movement causes an apparent change in
lengthReduced by increasing camera distance and zooming in
to compensate for subject size
Segment length (l) is reduced by amount (e) when it moves distance (d)
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GRF during normal walking gait Rise and fall above or
below BW = extra accelerationA = IC rises quicklyB = above BW early in
stance phaseC = below BW in mid-
stanceD = terminal support,
transfer to contra lateral limb
E= swing phase Winter, 1991
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Shear components during normal gait
Be familiar with shearing forces FAP
○ Smaller than vertical○ Posterior (braking) for
1st 50% of stance and anterior (propulsive) late stance
FML
○ Medially in response to lateral motion of body
○ Size proportional to stride width
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Speed and AP shear force Closely related to stride length Braking AP shear (in % BW) = 31 – normalized SL x 8.36 Propulsive AP shear = 30 x normalized SL – 6.4
r2 = 0.99
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The double support phase Sum of GRF from
each side Normally smooth
pattern is irregular in double support
GRF of L and R are not necessarily symmetrical even in healthy populations