1.3 Postural Control

Postural control

Process of CNS controlling the body's position in space for purposes of orientation and stability.

Orientation (posture)

Ability to maintain an appropriate relationship between the body segments and between the body and environment for a task.

Stability (balance)

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

Center of mass

Point at the center of total body mass.

Center of gravity

Vertical projection of center of mass.

Base of support

Area of the body in contact with support surface.

Center of pressure

Center of the distribution of total force applied to the supporting surface.

Postural reactions

Maturational motor skills that develop during the first year of life and form the basis for attainment of functional motor skills.

Righting reactions

Support positioning of the head vertically in space, alignment of head and trunk, and alignment of trunk and limbs.

Head righting

Aligns the eyes with the horizon and the head with the trunk.

Body righting

Contributes to movement around the body axis.

Equilibrium reactions

Provide balance when the center of gravity is disturbed.

Counter-rotation of head and trunk

More mature responses to regain balance than righting reactions.

Development of equilibrium reactions

Higher centers of CNS have to mature for equilibrium reactions to develop.

Maturation of postural reactions

Not mastered in 1st year; ongoing maturation until about age 7.

Response to stimuli

Postural reactions respond to more global stimuli than the primitive reflexes seen early in life.

Impact of neurological pathology

After neurological pathology/injury, these NORMAL postural reactions can be absent or be severely impaired/delayed.

Anti-gravity positions

Both body and head righting are necessary to assume anti-gravity positions.

Disturbance of center of gravity

Equilibrium reactions include counter-rotation of head and trunk away from the direction of displacement.

Use of extremities in balance

Equilibrium reactions include the use of extremities to regain balance.

Protective reactions

Required to prevent injury if equilibrium reactions are unable to restore balance in timely manner.

Individual constraints on motor and postural control

Factors including cognition, attention, perception, arousal, sensory integrity, flexibility, muscle performance, muscle tone, and movement patterns/motor function.

Task classifications

Motor and postural control processes differ for each task.

Open task

Variability and flexible; changing environment with greater difficulty to plan movement.

Closed task

Fixed, habitual patterns with minimal variation and lower demand on information processing systems.

Regulatory features

Shape the movement itself, such as weight, size, shape, and type of surface.

Non-regulatory features

Affect performance, such as background noise and distractions.

Steady state postural control

Ability to control CoM relative to BoS in predictable conditions.

Anticipatory postural control

Ability to activate muscles in legs and trunk for balance in advance of potentially destabilizing voluntary movements.

Reactive postural control

Ability to recover a stable position following an unexpected perturbation.

Adaptive postural control

Ability to modify sensory and motor systems in response to changing task and environmental demands.

Compensatory phase

Postural muscles activated again after primary movers to further stabilize body.

Sequence of activation

Task-specific order of muscle activation during postural adjustments.

Central set

State of nervous system that is influenced by context of a task.

Postural movement strategies

Includes fixed base of support strategies like ankle and hip strategies.

Stepping strategy

Used when CoM is moved outside BoS and is considered more complex.

Multi-directional stability

Complex central organization for muscle recruitment to control stability over a 360-degree continuum of perturbations.

Sensory processes

Visual, vestibular, and somatosensory systems contribute to postural control.

Perception of verticality

Ability to maintain orientation with respect to gravity.

Pusher syndrome

Condition in which patients lean and actively push toward the hemiplegic side with no attempt to compensate.

Cognitive processes

Impaired dual task ability can indicate cognition as a factor in postural control.

Anticipatory postural adjustments

Do not only include activation of postural muscles in advance of a skilled movement but also use adjustments when scaling the amplitude of postural adjustments.

Development of anticipatory postural control

4-5 months old show postural muscle activation prior to reaching in sitting.

Clinical implication of anticipatory postural control

Conditions that require anticipatory adjustments include speed, weight of load to be moved, and support.

Reactive postural adjustments

Can occur sooner than reaction time volitional step.

Visual system

Reports position and motion of head with respect to surrounding objects.

Vestibular system

Responsible for position and motion of head with respect to gravity and inertial forces.

Somatosensory system

Fastest and most sensitive to balance disturbance, providing information about body position in relation to supporting surfaces.

What are the key components examined in postural control?

Underlying sensory, motor, and cognitive impairments; sensory and motor strategies for maintaining postural control; functional skills requiring postural control.

What is steady state postural control based on?

It starts with alignment, which includes ideal alignment and muscular activity.

What aspects are observed when documenting posture?

Self-selected posture and fixed alignment, midline alignment (head, trunk, pelvis, limbs, and Base of Support), verticality, and symmetry.

What is postural stability?

The ability to control body position in space for movement and balance, including observing postural sway and documenting time maintaining midline and upright position.

What are the limits of stability in degrees for anterior, posterior, and medio-lateral directions?

Anterior: 8 degrees; Posterior: 4 degrees; Medio-lateral: 16 degrees.

What is anticipatory postural control and how is it assessed?

It involves APA recruitment, with activation patterns differing in sitting and standing. Assessment includes weight shifting, lifting objects, marching in place, and reaching.

What muscles are most active during reactive postural control in response to instability?

Abdominals are most active for backward instability, extensors for anterior instability, and trunk muscles are used if legs are dangling.

How does postural control differ in children with cerebral palsy (CP) compared to typically developing children?

Children with CP have a reversed recruitment order (top down vs bottom up), difficulty modulating muscle activity, and high co-activation in antagonist muscles.

What is the maximum score for the Berg Balance Scale and what does a score below 45 indicate?

Max score is 56; a score below 45 indicates moderate fall risk.

What is the purpose of the Dynamic Gait Index?

To assess balance problems in individuals, particularly in conjunction with the Berg Balance Scale.

What does the Functional Gait Assessment (FGA) measure?

Postural stability during various walking tasks, with a cutoff of 22/30 indicating fall risk.

What is the HiMAT designed for?

To assess high-level balance and mobility problems, particularly for individuals who can walk independently for over 20 meters.

What does the Mini-BEST assess and what are its cutoffs for chronic stroke and Parkinson's disease?

It assesses balance impairments in six contexts; cutoff for chronic stroke is <17.5 and for Parkinson's disease is 20/32.

What does the Falls Efficacy Scale (FES) measure?

Patient perspective on their own balance during specific functional activities, with higher scores indicating greater confidence.

What is the significance of sensory inputs in postural control?

Vision, somatosensation (cutaneous sensation, proprioception), and vestibular function are crucial for maintaining posture and alignment.

At what age does somatosensory control become the main control for balance?

By age 3, with adult-like sensory adaptation not presenting until age 7.

What challenges do children under 7 face regarding postural control?

They have reduced ability to adapt their senses for postural control when sensory inputs are inaccurate or removed.

What is the role of anticipatory postural control in functional tasks?

It prepares the body for movement by activating muscles in anticipation of postural demands.

How does reactive postural control differ in individuals with a CVA compared to age-matched controls?

Individuals with CVA use reach-to-grasp strategies for small perturbations, while controls can use in-place strategies.

What are the implications of optimizing trunk support in children with moderate to severe CP?

It can lead to the emergence of reactive control in the head and neck.

What factors influence the activation of anticipatory postural adjustments (APA)?

APA activation decreases with increased body support and increases with task speed or load.

What is the importance of documenting postural reactions during assessments?

It helps evaluate the timeliness and appropriateness of postural responses to maintain stability.

What types of movements are assessed in reactive postural control exams?

Self-initiated movements, perturbations, and responses to sudden stops or changes in direction.