Biomechanics *Gait/Balance/Posture* Flashcards
What is Step Depth?
The distance between successive heel contacts of the two different feet
What is Stride length?
The distance between two successive heel contacts of the same foot
What is Step Width?
The lateral distance between the heel centers of two consecutive foot contacts and is on average around 8-10 cm
What is Foot Angle?
The amount of “Toe-Out”, is the angle between the line of progression of the body and the long axis of the foot
What is normal walking speed?
1.37 m/sec (3 mph)
What is normal step rate?
1.87 steps/sec (110 steps/min)
What is normal step length?
72 cm (28in)
What are the two major systems in gait?
Traditional vs. Rancho Los Amigos (RLA)
Unless noted otherwise, which leg starts the gait cycle?
The gait cycle begins at Right heel strike (initial contact) and ends with the next R heel strike (Initial contact)
Why is the RLA system preferred in research then the traditional?
The phases of gait (Except for initial contact) are durations of time, not points in time
What is the Percent of Cycle in the Heel Strike (Initial Contact) phase?
In the () is RLA, outside is Traditional
0%
What is the Percent of Cycle in the Heel Strike to Foot Flat (Loading Response) Phase?
In the () is RLA, outside is Traditional
0 - 10%
What is the Percent of Cycle in the Foot Flat to Midstance (Midstance) Phase?
In the () is RLA, outside is Traditional
10 - 30%
What is the Percent of Cycle in Midstance to Heel Off (Terminal Stance) Phase?
In the () is RLA, outside is Traditional
30 - 50%
What is the Percent of Cycle in the Heel Off to Toe Off (Pre-Swing) Phase?
In the () is RLA, outside is Traditional
50 - 60%
What is the Percent of Cycle in the Early Swing (Initial Swing) Phase?
In the () is RLA, outside is Traditional
60 - 75%
What is the Percent of Cycle in the Midswing Phase?
75 - 85%
What is the Percent of Cycle in the Late Swing (Terminal Swing) Phase?
In the () is RLA, outside is Traditional
85 - 100%
What is the kinematic analysis for the hip? (In terms of Hip joint motion in degrees and phases of gait)
- In Initial contact the hip is flexed (0% gait cycle)
- The hip extends from 10-50% gait cycle (heel off)
- Flexes from 50-85% gait cycle
- Stays flexed from 85-100% gait cycle
What is the kinematic analysis for the Knee? (In terms of Knee joint motion in degrees and phases of gait)
- Knee is extended in Initial contact
- Knee flexes till 15% of gait cycle
- Extends till 40% of gait cycle
- Flexes till 75% of gait cycle
- Extends till 0% of gait cycle
What is the kinematic analysis for the ankle? (In terms of ankle joint motion in degrees and phases of gait)
- Neutral at 0% gait cycle
- Plan. Flexed till 10% gait cycle
- Dorsi. Flexed till 50% gait cycle
- Plan. Flexed till 65% gait cycle
- Dorsi. Flexed till 80% gait cycle
How do the does muscle activity work by group?
- Concentric contractions generate power
- Eccentric contractions absorb power
When are the Hip Extensors activated in gait?
- Concentric in early stance (Hip extension) for propulsion (0-50%, then 85-100%)
- Slight eccentric activation at terminal swing for deceleration (50-85%)
When are the Hip Flexors activated in gait?
- Firstly, Eccentric control of hip extension, after midstance (0-50%, then 85-100%)
- Then Concentric to flex hip at toe off (50-85%)
- Concentric during first half of swing
When are the Hip Abductors activated in gait?
- Eccentric on Initial contact to decelerate lower pelvis (BW) on same side (0-15%)
- Then concentric to move BW up and help extend hip. Remains active for first 40% cycle to control pelvis.
(15-65%) - 65-100% eccentric
When are the Hip Adductors activated in gait?
- Hip adductors stabilize hip through co-contraction with abductors
- May assist with hip extension at beginning of cycle, and with flexion after toe off
0-15%, then 65-100% Concentric
15-65% Eccentric
When are the Knee Extensors activated in gait?
- Upon contact, eccentric to control slight degree of knee flexion in the first 10% (~0-10%)(Then eccentric ~40-85%)
- Then concentric to extend knee to midstance (~10-40%)
- Finally concentric to flex hip at toe off (~85-95%)
When are the Knee Flexors activated in gait?
- Concentric in early stance (Hip extension)
- May assist with knee flexion in swing (Keep leg up, early swing phase)
- Eccentric at the knee in preparation for heel contact
(Terminal Swing Phase)
Concentric at (0-15%, then 40-80%)
Eccentric at (15-40%, then 80-100%)
When are the Plantar Flexors activated in gait?
- Active during most of stance except for first 10%
- From 10% to heel off, eccentric control of Dors. Flexors
- Concentric at push off (Between heel off and toe off)
Concentric at (0-10%, then 45-65%, then again at 85-95%)
Eccentric at (10-45%, then 65-85%, then again at 95- 100%)
When are the Dorsi Flexors activated during gait?
- Strong eccentric at heel contact to avoid “Foot slap”
- From heel contact to foot flat, eccentric deceleration of foot pronation
- Concentric in swing to clear foot from ground
In gait, if there is an impairment of the ankle plantar flexion contracture, what would be the compensation?
- Knee hyperextension (mid-stance)(Ipsilateral side) : Forward trunk lean (terminal stance)
In gait, if the patient has foot drop, what would be the compensation?
Excessive knee and hip flexion on ipsilateral side
In gait, if the patient has reduced knee flexion, what would be the compensation?
Vaulting of contralateral ankle
In gait, if there is an impairment of the knee flexion contracture, what would be the compensation?
Exaggerated knee and hip flexion of contralateral limb
In gait, if the patient has reduced knee flexion and/or lack of ankle dorsiflexion, what would be the compensation?
Hip circumduction
In gait, what would happens if the hip extensors are weak?
- There will be a posterior trunk lean in early stance
- Moves GRF (Ground Reaction Force) posterior to hip joint
In gait, what would happen if the hip flexors are weak?
- There would be rapid hip extension in stance
- Circumduction during swing
In gait, what would happen if the hip abductors are weak?
- Contralateral pelvic drop or lateral lean during stance
In gait, what would happen if the hip adductors are weak?
- They become flexors when the hip is extended
- They become extensors when the hip is flexed
- They may demonstrate some combination of gait deviations typical of hip flexors and/or extensors
In gait, what would happen if the knee extensors are weak?
No knee flexion during loading response
In gait, what would happed if the knee flexors are weak?
There would be rapid knee extension during terminal swing (whip)
In gait, what would happed if the Plantar Flexors are weak?
There would be a “Roll-off” instead of push off
In gait, what would happen if the Dorsi Flexors are weak?
-initial contact with foot flat or foot slap during loading response
- Excessive hip and knee flexion during swing
What is the Operational Definition of Posture?
Relative position of segments
- Relative advantages and disadvantages
What is the Operational Definition of Stability? What is Static Stability?
Defined as resistance to change in state
- Balance is the ability to maintain an upright posture by keeping the Center Of Mass (COM) above the BOS
- Sometimes called Static Stability
Static Stability is when the line of gravity falls within the BOS
What is Line of gravity?
Force vector of gravity
- Always vertical in a static model
What is BOS?
A polygon formed by the most peripheral contact points of the body with the ground
What is Center Of Pressure (COP)?
- The average location of foot to floor forces
- The point of contact between the GFR and the ground
How can a cane increase Static stability?
- Increase size of BOS
- Increase “Margin of stability”
(The distance from COP to nearest edge of BOS)
How can a cane decrease stability?
- Might be used incorrectly; if provides no help if its pulled not pushed
- Increases computational load; may result in deterioration of motor control
What are the components of neurological system for balance? (3)
- Visual
- Vestibular
- Sensory-Motor
What is the difference between Feed-Forward vs. Feed-Back?
Feed-Forward: Is based on previous learning
- Basis for ‘anticipatory’ strategies
Feed-Back: Is based on current sensations
- Basis for ‘reactive strategies’
For Posture and Balance, Feed-back control of balance requires 3 steps, what are the steps?
- Sensing
- Processing
- Responding
What takes part in the ‘Sensing’ step for Feedback control of balance?
- Sensors-Mechanoreceptors (proprioceptors): Joint capsules and ligaments, muscles, skin (especially feet), and fastest subsystem to respond
- Sensors-Vision: Relationship to surface geometry, head position, reports to visual cortex
- Sensors-Vestibular:Orientation of the head, coordinates with visual system, reports to cerebellum
What takes part in the ‘Processor’ step for Feedback control of balance?
- CNS
- Though experiment
“Walking while chewing gum”
What takes part in the ‘Responding’ step for Feedback control of balance?
- Muscle activation
(This is dependent of ROM, strength, joint structure and function)
(Often impaired by: pain and inflammation)
What are Perturbations? What are strategies to respond to perturbations?
Perturbations are sudden mechanical changes threatening stability
(Stratagies)
- Proactive (anticipatory)
Feedforward Control
- Reactive
Feedback Control
As perturbations become greater, what is the feedback based strategy?
In approximate order:
- Fixed BOS: Ankle strategy and Hip strategy
- Changing BOS: Stepping and Grasping
- Changing Height of COM: Squatting
*Feedback strategies are automatic in people free of impairments
What is the Romberg’s Test? What are the different variations of Romberg’s? What is used to assess this test?
- Checking balance in bilateral stance with eyes closed for 1 min.
variations:
- Tandem (1 foot in front of the other)
- Single limb
- With perturbations
- With and without vision
- With and without proprioception
- Force Plate
What is the difference between Static Posture and Dynamic Posture?
Static posture is the condition of staying in the same posture or position for extended periods
Dynamic posture for examples is walking and running
Ideal Posture is considered ideal because it is optimized for what?
- Minimal muscle force
- Minimal stress on joints and CT
- Maximal stability
If a person is sitting slumped, what happens to their LOG relative to the axes of rotation?
In the slumped position, the LOG is relatively distant from the axes of rotation of the head, neck and trunk
What would anyone choose less than idea posture?
- Atypical bony shape
- Pain avoidance (antalgic posture)
- Weakness
- LOM
- Difficulty maintaining balance
- Psycho-social issues
What is Ideal standing Posture?
(Sagittal Plane)
- Location of the combined action line formed by the ground reaction force vector (GRF) and line of gravity (LoG) in the optimal standing posture
- The location of the LOG relative to
Apex of spinal curves and Joint centers - Minimal Distance of LOG
(Minimal moment arm length and minimal external moment.)
What is External Moment?
This is due to gravity re-counteracted via internal moments from ligaments or large muscles
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Atlanto-Occipital Joint?
LOG: Anterior
External Moment: Flexion
Passive Opposing forces: ligaments that limit flexion
Active opposing forces: Neck extensors
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Cervical spine?
LOG: Posterior
External Moment: Extension
Passive Opposing forces: ALL and lig. that limit Ext.
Active Opposing forces: Deep flexor muscles
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Thoracic spine?
LOG: Anterior
External Moment: Flexion
Passive Opposing forces: PLL, surpa and interspinous lig.
Active Opposing forces: Erector Spinae muscles
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Lumbar spine?
LOG: Posterior
External Moment: Extension
Passive Opposing forces: ALL and Iliolumbar lig
Active Opposing forces: Abdominal muscle (EO,IO,RA)
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Sacroiliac Joint?
LOG: Anterior
External Moment: Nutation
Passive Opposing forces: Sacrotub. and spinous, iliolumbar and ant. SI lig.
Active Opposing forces: Transverse abdominis
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Hip Joint?
LOG: Posterior
External Moment: Extension
Passive Opposing forces: Iliofemoral lig
Active Opposing forces: Iliopsoas
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Knee Joint?
LOG: Anterior
External Moment: Extension
Passive Opposing forces: Posterior joint capsule
Active Opposing forces: Hamstrings, gastroc
In terms of alignment is the sagittal plane of standing posture, what is the LOG, External moment, Passive Opposing forces and Active Opposing forces for the Ankle Joint?
LOG: Anterior
External Moment: Dorsiflexion
Passive Opposing forces: n/a
Active Opposing forces: Soleus and gastroc
In terms of alignment, what are some possible effects of an Excessive Anterior Pelvic Tilt Deviation? (Compression, Distraction, Stretching, and shortening)
Compression: Posterior aspect of vertebral bodies
Distraction: Lumbosacral angle increased; shearing at L5-S1
Stretching: Abdominal muscles
Shortening: Iliopsoas, lumbar extensors
In terms of alignment, what are some possible effects of an Excessive Lumbar Lordosis Deviation? (Compression, Distraction, Stretching, and shortening)
Compression: Posterior vertebral bodies and facet jts.
Distraction: Anterior Annulus fibers
Stretching: ALL
Shortening: PLL and interspinous lig.
In terms of alignment, what are some possible effects of an Excessive Dorsal Kyphosis Deviation? (Compression, Distraction, Stretching, and shortening)
Compression: Anterior vertebral bodies
Distraction: Facet joint capsules and posterior annulus fibers
Stretching: Dorsal back extensors, posterior ligaments
Shortening: ALL, upper abdominal muscles
In terms of alignment, what are some possible effects of an Excessive Cervical Lordosis Deviation? (Compression, Distraction, Stretching, and shortening)
Compression: Posterior vertebral bodies and facet jts.
Distraction: Anterior Annulus fibers
Stretching: ALL
Shortening: Posterior ligaments and Neck extensors
What is Scoliosis?
- Curvature of the spine in the frontal plane
–Almost all deviations in the frontal plane result in or are caused by scoliosis
What are the effects of a Longer lower extremity?
If its the right:
- Right pelvic elevation
- Increase in amount of lordosis and kyphosis
- Scoliosis
