Motor behavior chapter 10

Postural Control

-The maintenance of body alignment and spatial orientation in order to put the body in a position to enable effective movement

Alignment

-Biomechanical positioning of body segments and limbs to one another

• Includes whole body alignment (aka “posture”) and

  segment alignment

Orientation

-The spatial positioning of the body to the environment at any given moment in time

Stability 

-A position that is resistant to disturbance or returns to its normal state after disruption

Joint level control

-Maintains structural integrity of the joint while still permitting motion

Segmental level control

-The anchoring and stabilizing of body parts to provide a firm foundation upon which other body parts can move

Whole-body level control

-orients the body to prevent or prepare for falls, and is better known as balance

Muscle tone

-Base level of muscle activity for postural control

Tone

-The force with which the muscle resists lengthening, that is, its stiffness

Tone regulates?

-The storage and release of elastic energy

-Force dampening

Dampening

-Helps smooth out movements

Stiffness

-Regulates the storage and release of elastic energy

Muscle tone is dependent on what two factors?

-Passive and active tone 

Passive tone 

-Viscoelasticity of the muscle and tendon tissue

Active tone

-The level of neural activation of the muscle tissue

Range of muscle tone

-Hypotonia: low tone/ muscles are less stiff/ less ready to respond

-Normal: balanced level of muscle readiness and stiffness

-Hypertonia: high tone/ muscles are overly stiff / resistant to movement

What are the 4 systems that provide Postural Control?

-Sensory/reflexive systems

-Neuromuscular components

-Musculomechanical components

-CNS components

What system is associated with feedforward control?

-Visual systems

What system is associated with synergies?

-Neuromuscular components

What system is associated with conscious control?

-CNS

Proactive posture

-Postural control prepares the body for an anticipated postural disturbance

Reactive posture

-Postural control occurs in response to postural disturbances

The 4 systems together contribute to what 3 levels of postural control?

-Reflexive

-Autonomic

-Voluntary

Reflexive

-Sensory systems and musculomechanical systems

Autonomic

-Sensory systems, musculomechanical systems, neuromuscular systems, CNS systems

Voluntary

-CNS systems

Quiet stance

-The posture of standing upright with minimal movement while maintaining balance.

Perturbation

-Any external or internal force that disturbs posture or balance, requiring the body to make a corrective response to maintain stability.

Ankle strategy

-(Dorsi-plantar flexion) provides the quickest way to maintain balance under normal circumstances.

Hip strategy

-Enables more correction and affords a different biomechanical profile than an ankle strategy

• Does not rely as much on foot friction with the support surface

Suspensory strategy

-Involves going into a crouched flexed position to lower the center of mass

• More common in those afraid to fall or when in an unfamiliar environment

Fixed point is?

-Ankle, hip, and suspensory

Change in support is?

-Stepping and reaching

Proactive postural control comes in what two basic forms?

-Upcoming or expected environmental circumstances or bodily actions

-Anticipatory postural adjustments (APAs)

How do we measure postural control?

-EMG

-Plumb line

-Timmed sawy

EMG

-Evaluate muscle activation patterns of postural support muscles during goal-directed movements, perturbed movements, or during quiet stance.

Plumb line

-Comparing the body’s position to a vertical reference line created by gravity

Timed sway

-A person stands in quiet stance and the amount of body sway is timed or observed over a set period.