Normal and pathological gait Flashcards
Human gait is bipedal, reciprocating, upright and terrestrial. What are the functional requirements of gait?
Shock absorption
Stability
Propulsion
Energy conservation
How is shock absorption achieved?
Through controlled “shortening” of the limbs during gait e.g. knee flexion. It is required to prevent damage to the joints
What 3 types of stability are considered?
Joint stability - prevent buckling of joints against gravity
Global stability - keep centre of mass within base of support (speed, step length, foot position)
Foot clearance - Prevents stumbling (knee flexion and ankle dorsiflexion)
How is gait inherently efficient?
Little muscle force to resist gravity
Efficient exchange between potential and kinetic energy
What is the normal toe-clearance in walking?
1.2 +/- 0.4 cm
Why is gait measurable?
It is cyclic and repeatable
What is the stride length equal to?
Stride length = Right step length + Left step length
What is cadence?
The rate at which a person walks in steps per minute
How much of the gait cycle is stance phase and how much is swing?
Stance = 60% Swing = 40%
Task phases of the gait cycle?
Weight acceptance
Single support
Limb advancement
What is the basic lower body model for clinical gait analysis?
Consists of 3 rigid segments connected by pin joints with 3 degrees of motion
Use markers on segments to calculate angles at joints as they walk
Can analyse in 3 planes of motion
For info - look at graphs of motion for each joint
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Phases of the gait cycle?
Initial contact Loading response Mid stance Terminal stance Pre swing Initial swing Mid swing Terminal swing
3 factors of kinetics to consider in the gait cycle?
Forces
Moments
Powers
Gait involves body acceleration and therefore relies on an external force (Newton’s 1st law). What external forces acts on the body during gait?
Ground reaction force
What is the vertical force of gait?
It refers to the vertical acceleration of the centre of mass during gait.
There are also Ant-Post forces and Med-Lat forces
Moment refers to the turning effect about a point. What is its equation?
M = F.d
Moments are balanced by muscles. Why do muscle tend to have to apply a greater force than the applied external force?
Because the moment arms of muscles tend to be small as they are close to the centre of rotation of the joint
Equation for power?
P = Moment x angular velocity
Generation of power when moment arm and angular velocity are acting in the same direction
Absorption of power when they are acting in opposite directions
Concentric vs eccentric muscle contractions?
A concentric contraction causes muscles to shorten, thereby generating force. Eccentric contractions cause muscles to elongate in response to a greater opposing force
