S3_L5: Postural Control Flashcards
An unsupported posture in which a person attempts to sit up as straight as possible
Active erect sitting posture
A sudden cessation of muscular activity, as manifested by electrical silence of the back extensors during trunk flexion in either sitting of standing postures
Flexion relaxation phenomenon
Pressure caused by contact forces between the person’s body and the seat
Seat interface pressure
A compensatory posture where the head is positioned anteriorly and the normal anterior cervical convexity is increased with the apex of the lordotic cervical curve
Forward Head Posture
Source: Levangie & Norkin, 5th
A compensatory posture where hyperextension at the knee is usually caused either by limited dorsiflexion at the ankle or by a fixed plantarflexion position of the foot and ankle called equinus.
Genu recurvatum
Source: Levangie & Norkin, 5th
Postures that represent an attempt to either improve function or normalize appearance
compensatory postures
Source: Levangie & Norkin, 5th
TRUE OR FALSE: With more stability due to more muscle bulk, males are relatively more stable than females.
True
During pregnancy, the CoG shifts ___, challenging the stability. This results in an increase in the lordotic curves in the cervical and lumbar areas of the vertebral column, protraction of the shoulder girdle, and hyperextension of the knees.
Forward / anteriorly
TRUE OR FALSE: A taller individual has a higher CoG, which makes them more unstable
True
TRUE OR FALSE: A heavier individual is more stable and more difficult to perturb.
True
The sum of all of the external and internal forces and torques acting on the body and its segments must be equal to ____ for the body to be in equilibrium.
Zero
Any sudden change in conditions that displaces the body away from equilibrium. An eternal force applied, just one type of activity that is related to postural control.
Perturbation
TRUE OR FALSE: Proprioception is not just related to sensory perturbation, as it can also be activated in mechanical perturbation.
True
For balance control, there is an interaction between 3 systems. Enumerate all.
- Visual system
- Somatosensory system
- Proprioceptive / Vestibular system
Determine the corresponding descriptions of the perturbation types
- E.g. standing on soft or wobbly surface, push, nudge
- Alteration of visual input, environment cannot be seen
- Also addresses proprioception
- External force that challenges CoG to be maintained within the BoS
A. Sensory perturbation
B. Mechanical / Contact perturbation
- B
- A
- A
- B
When unable to see, an automatic mechanism that makes an individual slouch and ___ their arms. This is a safety mechanism in the absence of visual input.
Extend
Posture where the body and its segments are aligned and maintained in certain positions. E.g. sitting, standing, lying, kneeling.
Static posture
Posture where the body and its segments are moving. E.g. walking, running, jumping, throwing, and lifting.
Dynamic posture
An abnormal increase in the normal thoracic posterior convexity
Kyphosis
A stance where the body weight is distributed in UE & LE. It is composed of 1 whole kyphotic curve and this stance is to maintain a stable position.
Quadrupedal stance
A stance that is unique to humans. It increases the work of heart and stress on vertebral column, pelvis, and LE. The BoS is reduced with this stance and secondary curves and adjustments are a result.
(Erect) Bipedal Stance
Postural control where the individual reacts to an external force displacing the body’s CoM. A force came into contact with body thus changing the CoM outside of its equilibrium state.
Reactive / Compensatory
The nudge test is used for this postural control.
Reactive / Compensatory
Postural control where it responds to internally-generated anticipated destabilizing forces. The force has not come in contact with the body, and the body is only anticipating its arrival.
Proactive / Anticipatory
TRUE OR FALSE: The postural controls (proactive and reactive) are sequential in nature, not simultaneously occurring.
True
The ability to maintain an appropriate relationship between body segments, and between the body and the environment for a task. It is determined by alignment, relationship, and orientation.
Posture / Postural orientation
Determine the corresponding line of gravity of the following joints
- Atlanto-occipital
- Cervical
- Thoracic
- Lumbar
A. Anterior
B. Posterior
- A
- B
- A
- B
Determine the corresponding line of gravity of the following joints
- Sacroiliac joint
- Hip joint
- Knee joint
- Ankle joint
A. Anterior
B. Posterior
- A
- B
- A
- A
Determine the corresponding external moment the LoG produces on the following joints
- Atlanto-occipital
- Cervical
- Thoracic
- Lumbar
A. Flexion
B. Extension
C. Nutation
D. Counternutation
- A
- B
- A
- B
Determine the corresponding external moment the LoG produces on the following joints
- Sacroiliac
- Hip
- Knee
- Ankle
A. Flexion
B. Extension
C. Nutation
D. Counternutation
E. Dorsiflexion
- C
- B
- B
- E
With reference to the normal posture of the ankle joint, the ___ will exert a posterior pull and counter the external dorsiflexion moment, producing an internal plantarflexion moment.
Soleus muscle
Additional: Gastrocnemius can also help (Levangie & Norkin, 2011)
With reference to the normal posture of the knee joint, the ___ and ___ will counteract hyperextension (external knee extension moment produced by LoG).
Soleus and hamstrings
TRUE OR FALSE: The LoG passes anterior to the midline of the knee and posterior to the patella.
True
With reference to the normal posture of the hip joint, the ___ will produce an internal flexion moment at the hip to prevent hip hyperextension.
Iliopsoas
Source: Levangie & Norkin, 5th
TRUE OR FALSE: When the LoG passes directly through a joint axis, no external gravitational torque is created around that joint. However, if the LoG passes at a distance from the axis, an external gravitational moment is created.
True
Additional: This causes rotation of the superimposed body segments around that joint axis unless it is opposed by a counterbalancing internal moment (a muscle contraction)
What muscle is the active opposing force counteracting the nutation moment caused by the LoG at the sacroiliac joint?
Transversus abdominis
A head stabilizing strategy where the anticipatory change in head position is together with the trunk. They act as one unit.
Head Stabilization on Trunk (HST)
A head stabilizing strategy where the anticipatory change in head position is independent of the trunk. It is modification of head position in anticipation of displacements of the body’s CoG.
Head Stabilization in Space (HSS)
TRUE OR FALSE: Maintenance and control of posture depend on the integrity of the central nervous system, visual system, vestibular system, and musculoskeletal system.
True
The ability to maintain the body in equilibrium at rest (static posture) or in motion (dynamic posture). It is a dynamic process involving establishing equilibrium among various forces.
Postural stability / Balance
Enumerate the 3 muscles that counteract the external flexion moment caused by the LoG passing anterior to the thoracic spine
- Thoracic erector spinae
- Trapezius
- Temporalis
A strategy where the body will react to prevent too much dorsiflexion & the muscles behind will be reacting.
Ankle strategy
Additional: Discrete bursts of muscle activity on either the anterior or posterior aspects of the body that occur in a distal-to-proximal pattern in response to forward and backward movements of the support platform, respectively (Levangie & Norkin, 2011)
TRUE OR FALSE: The magnitude of the gravitational moment of force increases as the distance between the LoG and the joint axis increases.
True
Muscles that counteract the extension moment, hyperextension, and excessive lumbar lordosis brought about by the LoG passing posteriorly to the lumbar spine
Abdominals
TRUE OR FALSE: Breathing can displace the CoM
True
This happens in response to shifts in either the BoS or the entire body as in the tether release system. It moves or enlarges the body’s BoS so that it remains under the body’s CoM.
Change-in-support strategies
Discrete bursts of muscle activity in a proximal-to-distal pattern of activation. This may be used primarily in situations in which change-in-support strategies (stepping or grasping synergies) are not possible.
Hip strategy
Patterns of muscle activity in which the BoS remains fixed during the perturbation and recovery of equilibrium. Stability is regained through movements of parts of the body, but the feet remain fixed on the BoS.
Fixed support strategies
Where is the Center of Mass in the body?
An inch anterior to S2
It is always a vertically directed downward force where gravity is passing through
Center of gravity
A point at the center of the total body mass representing the weighted average of the CoM of each body segment. The point/center of an object where we can actually balance it
Center of mass
Area of the object that is in contact with the support surface
Base of support
A person’s ability to maintain stability of the body and body segments in response to forces that threaten to disturb the body’s equilibrium
Postural control
Source: Levangie & Norkin, 5th
Point of application of the ground reaction force vector (GRFV)
Body’s center of pressure (CoP)
Additional: It is located in the foot in unilateral stance and between the feet in bilateral standing postures
TRUE OR FALSE: The ground reaction force vector (GRFV) is equal in magnitude but opposite in direction to the gravitational force in the erect static standing posture.
True
A force exerted by the ground whenever the body contacts it. It is the composite (or resultant) force that represents the magnitude and direction of loading applied to one or both feet.
Ground reaction force
A constant swaying motion of the body in erect standing posture. It is the natural sway of CoG forward and backward and even sideways, because of external forces from inertia and gravity.
Postural Sway / Sway Envelop
It is a protective reaction of holding onto something when in disequilibrium to catch the body and prevent injuries.
Grasping response
It is a response where the individual steps forward to be able to catch the CoG within the BoS
Stepping strategy
