Gait Analysis Flashcards
What is gait?
- the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate
- most animals use a variety of gaits, selecting gait based on speed, terrain, the need to maneuver, and energetic efficiency
- human examples: walking, running, sprinting, crawling
normal gait sequence maintains:
- weight-bearing stability
- conserving energy
- absorbing the shock of floor impact
Why should we measure walking gait?
1) to find out how we walk
- what is normal? why?
- evaluate the function of walking
2) to use walking as a baseline measure to understand differences between:
- healthy and unhealthy populations
- ages
- genders
- races
Gait analysis involves the measurement of:
kinetics, kinematics, and EMG
EMG
electromyography: a technique for evaluating and recording the electrical activity produced by skeletal muscles
Kinematics can be recorded by:…
- passive marker systems: reflective markers and multiple cameras (usually 6-8)
- Active marker systems: similar to passive, but use “active” markers that are triggered to illuminate
- electromagnetic systems: track the position (X, Y, Z) and orientation of small sensors attached to the body
- electrical goniometers: measures joint angles, simple to use and relatively inexpensive compared to motion capture systems
- accelerometers, gyroscopes, and magnetometers can also be used
Passive marker systems
reflective markers and multiple cameras (usually 6-8, to ensure that we can digitize each marker and determine its 3D location, from these 3D digitized markers we can derive joint kinematics)
Kinetics can be recorded by:
- pressure mats and insoles: determine a basic estimate of force and centre of pressure movement
- force plates embedded in floors or treadmills: most detailed info about contact kinetics
Combining kinematics and kinetics can allow us to…
use inverse dynamics to calculate joint forces, torques, and muscle forces
Phases of Gait
- Stance phase (62% of gait cycle)
- first double support
- single limb stance
- second double support
- swing phase (38% of gait cycle)
Initial contact
0%
- instantaneous point when leading foot touches the ground
loading response
(0-10%)
- body weight transferred onto stance limb
midstance
(10-30%)
- contralateral foot leaves the ground (OT) and body weight travels along the length of the foot until aligned over the forefoot
Terminal Stance
(30-50%)
- begins with heel rise (HR), ends when opposite foot contacts the ground (OI)
Preswing
(50-60%)
- it begins with opposite foot contact, ends with ipsilateral toe off (TO)
- stance limb unloaded and body weight transferred onto opposite limb
Terminal Contact (TO)
- instant when foot leaves the ground
Initial swing
(60-70%)
- begins the moment the foot leaves the ground and continues until maximum flexion of the knee occurs
midswing
(70-80%)
- begins following maximum knee flexion and ends when the tibia is in a vertical position
Terminal swing
(85-100%)
- the tibia passes beyond perpendicular and the knee full extends in preparation for heel contact
timing of peak muscle activity tells us about muscle function
Glutes: hip extension during loading response
Quads: knee extension during loading response
Calves: ankle plantarflexion during heel rise in terminal stance
illiopsoas: hip flexion during pre and initial swing
hamstrings: hip extension to decelerate limb during terminal swing
TA: ankle dorsiflexion during swing phase to allow foot clearance and during loading response to maintain foot position
timing of limb kinematics can tell us about limb segment orientation during gait…
Hip: changes from extension to flexion just before TO
Knee: changes from max flexion to extension during swing
Ankle: changes from plantarflexion to dorsiflexion just after TO
Centre of pressure
the instantaneous point of application of the ground reaction force
- measuring foot CofP movement during walking can tell us about the point of pplication of the GRF vector and how we use our feet while walking
walking can be broken down into 3 functional tasks
1) weight acceptance
- the demand for immediate transfer of body weight onto the limb as soon as it contacts the ground requires: initial limb stability, shock absorption, and momentum of progression preservation
2) single-limb support
- the body weight is exclusively supported on the stance limb; forward progression while maintaining stability
3) limb advancement
- the stance limb leaves the ground and advances forward to posture itself in preparation for the next initial contact
inverted pendulum model
- a mechanical analogy of how we walk
- during single limb support the body vaults over the extended limb with little energy expenditure
- during double limb support there is a redirection of the whole body over the other extended limb and the inverted pendulum continues on the other side
- the only major energy expenditure is during redirection
best way to conserve energy while walking?
minimize unnecessary movement of the CofG
6 determinants of gait
1) pelvic rotation
2) pelvic obliquity
3) knee flexion in stance phase
4) ankle mechanism
5) foot mechanism
6) lateral displacement of body
Pelvic Rotation
the pelvis rotates so that the length of the stride does not come from just hip flexion and extension. it also reduces the angle of hip flex/ext which reduces vertical movement of the hip
Pelvic Obliquity
the vertical movement of the trunk is less than that of the hip due to pelvic tilt about an anteroposterior axis
Knee Flexion, Ankle Mechanism, Foot Mechanism
knee flexion shortens the leg in midstance; backward projection of the heel at initial contact lengthens the leg; so does forward projection of the forefoot during the preswing
Lateral Displacement of Body
if feet are placed on the ground far apart:
- large side-to-side movements of the CofG would be necessary to maintain balance
having them closer together
- reduces the size of side-to-side sway
Common, simple measures that can be used to compare individuals or provide information
changes in swing stance ratio
- step length is too short there may be an underlying abnormality
- inadequate push-off/pull-off, pain
left/right asymmetry
squatting below 90 degrees is bad
False! it actually relives pressure in your knees by transferring it to your hips
