Chapter 12 Flashcards
What are the requirements for mobility?
progression
postural control
adaptability
Progression:
the ability to generate a rhythmic stepping pattern to move the body forward
initiate and terminate movement
Postural Control:
the ability to ensure both orientation and stability
Adaptability:
the ability to adapt gait to changing tasks and environmental requirements
Progression for stance:
stabilizing limb for weight bearing and generating forces to move the body for continued motion
Progression for swing phase:
advancement of the swing leg to reposition the limb (in preparation for weight acceptance), and make sure toes clear the ground
Postural Control stance phase:
vertical forces support the body mass against gravity
Postural Control swing phase:
repositioning of the limb in preparation for weight acceptance
Adaptability stance phase:
changes in speed and direction or alterations (e.g., uneven terrain) in the support surface
Adaptability swing phase:
avoidance of obstacles by swing foot
Temporal parameters
Stance/swing time Single-limb support time Double-limb support time Stride time Step time Cadence Speed/Velocity
Spatial parameters
Stride length
Step length
Step width
Toe-out angle
Stance/swing time
time in stance/swing on a given limb
Single-support time
time elapsed in which the body is supported by a single limb
Double-support time
time elapsed in which both feet are in contact with the ground
Stride duration
time required to complete one stride
Step duration
time required to complete one step
Velocity
rate of linear movement (meter/second in research vs. 40 feet or for 6 minutes in clinic)
Cadence
(a frequency unit): the number of steps within a unit time, often denoted as steps/minute (e.g., 80 steps/min)
Step length
distance between the contralateral foot strikes
Stride length
distance from one foot strike to the next for the same (or ipsilateral) foot (~ twice the step length in normal gait).
Step Width
linear distance between midpoint of the heel of ipsilateral and contralateral feet
Degree of Toe-Out (DTO)
Angle of foot formed by each foot’s line of progression
Components of stance:
initial contact loading response mid stance terminal stance preswing
Components of swing:
initial swing
mid swing
terminal swing
Functional tasks of gait:
weight acceptance
single limb support
swing limb advance
Initial contact
0-2%
moment when leading limb touches floor
Objectives of initial contact
Start stance with heel rocker
Impact deceleration
Loading response
2-12%
first period of double stance
body weight to leading leg
trailing leg in preswing
Objectives of loading response:
shock attenuation,
weight-bearing,
forward progression
Mid Stance
12-31%
first half of single limb stance
When does mid stance begin?
toe off of trailing limb
When does mid stance end?
Weight aligned over the leading/supporting limb
Objectives of mid stance?
1) forward progression over the stationary foot;
2) weight bearing (limb and trunk Stability)
Terminal stance?
31-50%
When does terminal stance begin?
Heel rise initiates second half of single-limb support
When does terminal stance end?
Non-support limb (blue) strikes the ground
Objectives of terminal stance?
(1) Progression of body beyond support limb (red);
2) weight bearing (limb and trunk Stability
Pre-swing:
50-62%
A rapid unloading of the limb occurs as weight is transferred to the contralateral (lead) limb.
Unweighting allows limb to prepare for swing
When does pre-swing being?
Initial contact of contralateral (swing) limb
When does pre-swing end?
Ipsilateral limb (support) toe off
Objectives for pre-swing?
(1) Position the limb for swing phase,
(2) accelerate progression (propulsion)
Initial swing:
62-75%
Contralateral limb is in mid-stance
Foot lifts from ground during first third of swing
Advances to opposite stance foot.
When does initial swing begin?
ipsilateral limb (red) leaves floor
When does initial swing end?
ipsilateral is opposite stance foot
Objectives of initial swing?
(1) Foot clearance of the floor, (2) advancement of the limb from its trailing position
When is foot drop most evident?
initial swing
Mid swing
75-87%
Contralateral limb is in late mid-stance
Limb advances during the middle third of the swing until tibia achieves vertical (i.e., hip and knee flexion postures are equal).
When does mid swing begin?
end of initial swing
When does mid swing end?
ipsilateral limb advances anterior of the body
What are the objectives of mid swing?
(1) limb advancement,
(2) Foot clearance of the floor,
Terminal swing
87-100%
Tibia advances during final third of swing, and limb advancement is completed as the leg (shank) moves ahead of the thigh
When does terminal swing begin?
end of mid-swing
When does terminal swing end?
ipsilateral limb initial contact
What are the goals of terminal swing?
(1) Complete limb advancement;
(2) Prepare for stance phase
Ground force reaction:
Force applied back on the individual (Newton’s 3rd law)
Goals of stance limb:
to support the body (postural control) and propel the body forward;
Goals of swing limb:
foot clearance and limb advancement
Muscle activation for loading response
hip: extensors
knee: GFR posterior to knee; knee extensors contract
ankle: GFR anterior to joint
Muscle activation for mid stance
hip: plane abductors
knee: GFR anterior to knee; mostly hamstrings
ankle: PF eccentric
Muscle activation for terminal stance:
hip: GFR posterior to joint; extension moment
knee: initial flexor activity
ankle: PF, gastroc, soleus, FDL, FHL
Muscle activation preswing
hip: flexor activity
knee: rectus femoris
ankle: PF strong initially
Muscle activation mid swing:
hip: flexors first, them extensors
knee: flexor activity
ankle: DF (toe clearance)
Muscle activation for terminal swing:
hip: increasing extensor activity
knee: flexors, then extensors to stabilize
ankle: increasing DF at end of phase
Highest point of vertical displacement of COM?
midstance
Lowest point of vertical displacement of COM?
double support
What is the average vertical displacement?
5 cm
Lateral limit of COM?
mid stance
