gait (pmr)
TRANSCRIPT
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UNDERSTANDING NORMAL GAIT
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Gait Cycle - Definitions:►Normal Gait =
Series of rhythmical , alternating movements of the trunk & limbs which result in the forward progression of the center of gravity
series of ‘controlled falls’
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Gait Cycle - Definitions:
► Gait Cycle = Single sequence of functions by one limb Begins when reference foot contacts the
ground Ends with subsequent floor contact of the same
foot
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Gait Cycle - Definitions:
► Step Length = Distance between corresponding successive
points of heel contact of the opposite feet Rt step length = Lt step length (in normal gait)
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Gait Cycle - Definitions:
► Stride Length = Distance between successive points of heel
contact of the same foot Double the step length (in normal gait)
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Gait Cycle - Definitions:
► Walking Base = Side-to-side distance between the line of the
two feet Also known as ‘stride width’
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Gait Cycle - Definitions:►Cadence =
Number of steps per unit time Normal: 100 – 115 steps/min Cultural/social variations
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Gait Cycle - Definitions:
► Velocity = Distance covered by the body in unit time Usually measured in m/s Instantaneous velocity varies during the gait cycle Average velocity (m/min) = step length (m) x
cadence (steps/min)
► Comfortable Walking Speed (CWS) = Least energy consumption per unit distance Average= 80 m/min (~ 5 km/h , ~ 3 mph)
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Normal Development
Walking begins at about 12 - 15 months of age.
Children have shorter legs, so cadence is increased (170 st/min at age 1 yr to 140 st/min at 7y) Stride length is roughly the same as height (stature), so a child 0.5 m tall will have an expected stride length of about 0.5 m Velocity is roughly 1 stature/s, so a child 0.5 m tall will have an expected walking velocity of about 0.5 m/s Walking pattern more flexed than adult, especially at hip and knee, becomes adult at 7 yrs, and gait parameters stabilise by 16 - 18 yrs (when long bones stop growing) Elderly people gradually shorten stride length after about 65 yrs, but cadence remains relatively constant
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Gait Cycle - Components:
► Phases:(1)Stance Phase: (2) Swing Phase:
reference limb reference limb in contact not in contact with the floor with the floor
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Gait Cycle - Components:
► Support:(1) Single Support: only one foot in contact with
the floor(2) Double Support: both feet in contact with floor
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Gait Cycle - Subdivisions:
A. Stance phase:1. Heel contact: ‘Initial contact’2. Foot-flat: ‘Loading response’, initial contact of forefoot w.
ground3. Midstance: greater trochanter in alignment w. vertical
bisector of foot4. Heel-off: ‘Terminal stance’5. Toe-off: ‘Pre-swing’
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Gait Cycle - Subdivisions:
B. Swing phase:1. Acceleration: ‘Initial swing’2. Midswing: swinging limb overtakes the limb in
stance 3. Deceleration: ‘Terminal swing’
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Gait Cycle
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► Time Frame:A. Stance vs. Swing:
►Stance phase = 60% of gait cycle
►Swing phase = 40%B. Single vs. Double support:
►Single support= 40% of gait cycle
►Double support= 20%
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► With increasing walking speeds:►Stance phase: decreases►Swing phase: increases►Double support: decreases
► Running:►By definition: walking without double support►Ratio stance/swing reverses►Double support disappears. ‘Double swing’
develops
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Path of Center of Gravity►Center of Gravity (CG):
midway between the hips Few cm in front of S2
►Least energy consumption if CG travels in straight line
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Path of Center of Gravity
A. Vertical displacement:► Rhythmic up & down
movement► Highest point: midstance► Lowest point: double support► Average displacement: 5cm► Path: extremely smooth
sinusoidal curve
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Path of Center of Gravity
B. Lateral displacement:► Rhythmic side-to-side
movement► Lateral limit: midstance► Average displacement: 5cm► Path: extremely smooth
sinusoidal curve
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Path of Center of Gravity
C. Overall displacement:► Sum of vertical &
horizontal displacement► Figure ‘8’ movement of
CG as seen from AP view
Horizontalplane
Verticalplane
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Determinants of Gait :►Six optimizations used to minimize
excursion of CG in vertical & horizontal planes
►Reduce significantly energy consumption of ambulation
►Classic papers: Sanders, Inman (1953)
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Determinants of Gait :
(1) Pelvic rotation: Forward rotation of the pelvis in the horizontal plane
approx. 8o on the swing-phase side Reduces the angle of hip flexion & extension Enables a slightly longer step-length w/o further lowering
of CG
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Determinants of Gait :
(2) Pelvic tilt: 5o dip of the swinging side (i.e. hip adduction) In standing, this dip is a positive Trendelenberg sign Reduces the height of the apex of the curve of CG
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Determinants of Gait :
(3) Knee flexion in stance phase: Approx. 20o dip Shortens the leg in the middle of stance phase Reduces the height of the apex of the curve of CG
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Determinants of Gait :
(4) Ankle mechanism: Lengthens the leg at heel contact Smoothens the curve of CG Reduces the lowering of CG
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Determinants of Gait :
(5) Foot mechanism: Lengthens the leg at toe-off as ankle moves from
dorsiflexion to plantarflexion Smoothens the curve of CG Reduces the lowering of CG
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Determinants of Gait :
(6) Lateral displacement of body: The normally narrow width of the walking base
minimizes the lateral displacement of CG Reduced muscular energy consumption due to
reduced lateral acceleration & deceleration
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“ Don’t walk behind me, I may not lead. Don’t walk ahead of me, I may not
follow. Walk next to me and be my friend.”
Albert Camus
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THANK YOU