Postural Control (9/18a) [Integrative Care] Flashcards Preview

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Postural control

Involves controlling the body’s position in space for the dual purpose of stability and orientation


Postural orientation (posture)

Ability to maintain an appropriate relationship:
1) Between different body segments (alignment)
2) Between the body and the environment for a task

How your mass is centered over your base of support impacts alignment


Postural stability (balance)

Ability to control the center of mass in relationship to the base of support

COM does not necessarily stay within the BOS


Base of support (BOS)

the area of the body in contact with the support surface


BOS relationship

Wide BOS: more stability

Narrow BOS: less stability


Center of mass (COM)

the point at the center of the total body mass

COM is a point in 3-dimensional space, usually around L2 in standing


COM relationship

Higher the COM: lesser stability

As COM shifts upward the object/subject becomes more “top-heavy”

Lower the COM: greater stability


Maintaining vs Controlling COM

Maintaining - COM always stays within BOS

Controlling - COM can move outside BOS but you don't lose stability


Center of gravity (COG)

vertical projection of the COM

COG is vertical projection of COM on 2-dimensional plane, usually the ground


COG relationship

COG is within the BOS: greater stability

COG is outside the BOS: lesser stability


Center of pressure (COP)

the center of the distribution of total forces applied to the support surface

Represents the average “location” of the ground reaction force vector but NOT the forces themselves → it is a point on a 2- D plane


COP and COM relationship

For static equilibrium- COP must be directly under the COM (perfectly aligned with COG)

Standing isn't static, so rarely aligned

CNS activates muscles to change the location of COP to align it close to COM

If COM goes well beyond the COP, then BOS is changed to ensure that COP and COM are close


Static balance (steady-state balance)

ability to maintain COG within the supporting base while standing or sitting


Dynamic balance

maintaining an upright position while COG and base of support are moving and the COG is moving outside of the supporting base


Functional balance

ability to perform daily movement tasks requiring balance and involves static and dynamic balance


Stability vs Orientation relationship

Requirements depend on task, and one may hav to be compromised (complicated relationship)

Postural orientation affects postural stability

Postural orientation is altered to regain postural stability


Stability limits

boundaries of the combined COM velocity and position possible without the need to change the base of support


Stability limits result from

the interaction between the position and velocity of COM


Feedback control (Compensatory or reactive postural responses)

Sensory feedback from unexpected external perturbations triggers postural responses

Response depends on multiple factors:
Amount of perturbation, Properties of support surface, Speed of perturbation, Pathology, Pain

Can test by pushing patient, taking away sensory systems, etc


Feedforward control (Anticipatory postural control)

Postural responses are made prior to voluntary movement that is potentially destabilizing in order to maintain stability during the movement

Can test with sit to stand, stepping on toes, etc