Chapter 6 - Gait and Posture Analysis Flashcards
Main functions of Lower Kinetic Chain
- to provide a stable BOS in standing
- to propel body through space with gait (gait is controlled instability)
What are the 3 essential requirements for gait?
1) Progression
2) Postural Control
3) Adaptation
Progression
The “fall” that occurs at initiation of gait controlled by CNS, CNS computes in advanced the required size and direction of this fall
Postural Control
Dynamically maintained to properly position the body for efficient gait
Adaptation
Achieved by adjusting the central pattern to meet task and environmental demands
Stance Phase
60-65% of gait cycle
Foot is in contact with ground and the limb is bearing weight
Swing Phase
35-40% of gait cycle
Foot is not in contact with the ground
Weight Acceptance
Initial contact and loading response (first 10% of gait cycle)
Double support at this time, both feet are on the floor
Single Leg Support Intervals
Midstance, terminal stance, preswing
Midstance
- first half of single-leg support
- begins as one foot is lifted and continues until the body weight is aligned over forefoot
Terminal Stance
- second half of single-leg support
- begins with heel of weight-bearing foot lifting and continues until contralateral foot strikes ground
Preswing
-begins with initial contact of contralateral limb and ends with ipsilateral toe-off
Swing Phase Intervals
Initial swing, midswing, terminal swing
What are the primary sources of motion during swing phase?
Gravity and momentum
Initial Swing
-begins with lifting of the foot from the floor and ends when swinging foot is opposite the stance foot
Midswing
-begins as swinging foot is opposite stance limb and ends when swinging foot is forward and the tibia is vertical
Terminal Swing
-begins with vertical tibia of swing foot and ends the moment the foot strikes the floor
Step Width
Distance between both feet, normally 5-10 cm (2-4 in). Forms BOS (COG must be over BOS for equilibrium)
Step Length
Distance between point of initial contact of one foot and initial contact of other foot (average is 28 inches)
Stride Length
Distance between successive points of foot to floor contact of same foot (step length + step length = stride length) normal is 56 inches
Cadence
number of steps taken in a certain time (normal is 90-120/min)
Velocity
Distance a body moves in a given time
V = d/t
What causes the Vertical Ground Reaction Force?
- gravity
- body weight
- firmness of the ground
Where does the Vertical Ground Reaction Force peak during gait?
1st = maximum limb loading during loading response 2nd = during terminal stance
Why do women experience greater Ground Reaction Forces?
- shorter leg length than men (51.2% of body height vs 56%)
- women must strike ground more often to cover same distance
- women complete heel to toe gait in a shorter time than men
Gait involves…
- displacement of body weight in desired direction
- coordinated effort between joints of the trunk/extremities and the muscles that control or produce these motions
Five priorities for Normal Gait
1) Stability of weight bearing foot throughout stance phase
2) Clearance of NWB foot during swing phase
3) Appropriate prepositioning of foot during terminal swing
4) Adequate step length
5) Energy conservation
How to ensure that energy is conserved during gait
- COG must undergo MINIMAL displacement
- any displacement that elevates, depresses or moves COG beyond normal will waste energy
- any abrupt/irregular movement will waste energy
Six ways to reduce energy loss during gait
1) Lateral displacement of pelvis (1 to 2 inches)
2) Forward pelvic rotation on swing side
3) Vertical displacement of pelvis (no more than 2 inches)
4) Knee flexion in stance
5) Ankle mechanism (10 DF/20 PF)
6) Foot mechanism
Explain how trunk, thoracic and lumbar spine, pelvis and shoulders rotate during gait
-trunk twists about vertical axis
-t spine and pelvis rotate opposite
-l spine and pelvis rotate together
-shoulder and trunk rotate out of phase with each other
(if arm swing prevented, upper trunk and pelvis rotate same way)
What is the hips function during gait?
Extend the leg during stance phase
Flex the leg during swing phase
When is the force on the hip the greatest?
Midstance
What occurs at the hip during swing phase?
- adducts early in swing phase
- 30-35 degrees of hip flexion in late swing phase
- slight hip abduction at end of swing phase
What occurs at the hip during normal stride?
rotates 40-45 degrees
What occurs at the hip during toe-off?
10 degrees of extension
What are the functions of the knee during gait?
- bear weight and absorb shock
- reduce vertical displacement of the COG
- maintain the stride length
- allow the foot to move through its swing
What motions occur at the knee during gait?
Loading Response = 20 flexion
Terminal Stance = almost fully extended
Swing Phase = flexes again
Heel Strike = extends
60 degrees of motion required for clearance
