Postural Control and Balance Strategies Quiz

Postural Control Overview

• Postural control involves two main functions: stability and orientation.
• Neural control mechanisms for posture include steady-state, reactive, and anticipatory postural adjustments.
• These mechanisms utilize motor synergies, sensory integration, and cognitive strategies.
• Postural control is task-specific and adapts to different demands.
• Attentional resources for balance depend on task difficulty and individual impairments.

Dynamic Systems Theory Perspective

• Postural control is a dynamic process, not a fixed set of responses.
• Center of mass (COM) is a virtual point that depends on the positions of all body segments.
• The central nervous system (CNS) detects changes in COM and adjusts muscles accordingly.
• This adjustment involves appropriate timing and force application by the targeted muscles in the system.
• Strategy for movement is based on current configuration of segments and relationship to the environment

Learning Objectives

• Define postural control within the task-oriented movement context.
• Identify motor and sensory strategies associated with postural control.
• Describe how these strategies adapt to changes in individual, task, and environmental constraints.
• Relate motor and sensory strategies to clinical practice.

Measurement of Postural Stability

• Force plates measure the center of pressure (COP).
• COP variability indicates postural changes in quiet standing.
• Sway amplitude, measured by body sensors, also indicates postural changes.

Defining Postural Control

• Stability involves controlling the center of mass (COM) over the base of support (BOS).
• COM is the vertical projection of the center of gravity (COG), while the COP is measured at the point of pressure distribution on the BOS.
• Postural orientation involves maintaining appropriate relationships between the body segments and the environment

Biomechanical Analysis

• Analysis helps understand how the CNS solves the problem of maintaining balance.
• The body/system can be modeled as an inverted pendulum

Neural Components of Postural Control

• Actions systems utilize motor processes and neuromuscular synergies
• Perceptual systems involve sensory process focusing on integration and sensory information organization
• Cognitive System involves high-level processes with cognitive influences such as attention, motivation and intention. This also involves adaptive postural control

Normal Control Mechanisms

• Motor control in steady-state balance.
• Reactive balance during perturbations.
• Sensory organization in postural control.
• Anticipatory postural control or balance

Control of Steady State Balance

• Small amounts of postural sway are normal.
• Body alignment, muscle tone, and intrinsic muscle stiffness help minimize the effect of gravity.
• Postural tone in extensor muscles needed for upright posture.

Steady State Balance

• Stability limits define the point at which a person adjusts their base of support (BOS) to maintain stability.
• Postural control isn't based only on physical limits, but also affected by perceptual (vision and sensation) and cognitive factors.

Ideal Alignment

• Ideal alignment minimizes muscular effort during static posture

Base of Support (BOS)

• Extending the BOS is a strategy to capture and counteract center of mass disturbances.
• This can occur through swaying movements or stepping responses.
• Using one's arms may also be a response to regulate postural control

Movement Strategies

• Inverted pendulum model provides insight into movement strategies for steady-state and reactive balance.
• Ankle strategies involve oscillations around the ankle.
• Low frequency strategies (<1 Hz) utilize hip movement.
• High frequency strategies (> 1 Hz) occur concurrently with hip movement.

Reactive Balance

• Feedback control mechanisms are utilized during reactive balance.
• Ankle, hip, and stepping strategies help individuals regain stability.

Anterior-Posterior Stability

• Ankle strategy is effective for maintaining stability during small, slow movements.
• Hip strategy is utilized for rapid, larger movements.

Testing Reactive Balance

• Methods for testing are presented

Other Planes of Movement

• Mediolateral control involves unloading/loading of legs and control of hip abductors and adductors
• Directional control involves EMG turning curves

Reactive Control Strategies

• Reactive strategies adapt when an individual’s posture is altered (by an external force).
• Body responses (muscle activation, compensatory movements) depend on various factors (e.g., start position, task specifications, support).

Effect of Practice

• Practice affects adjustments of the body in response to disturbances
• Improvements in reactive control noted over time.

Physiological Significance of Synergies

• Synergies in muscles are functional groupings that constrain muscles in the system to act as a unit.
  • Multiple muscles within a synergy may be different.
  • Muscle synergies have fixed weighting within a defined synergy.
  • A synergy has a defined direction of force.
  • Synergies add together to result in movement (force).

Importance to the Clinician

• Assessment and treatment must consider postural equilibrium in individuals exhibiting steady-state and reactive balance deficits.
• Control mechanisms may vary between individuals and require adaptability in treatment plans.
• Multiple synergies, not just one type, may be needed for optimal postural control.
• Individuals should be trained to modulate postural strategies to adapt to various, changing tasks and destabilizing forces.

Musculoskeletal Constraints

• Abnormalities in alignment (e.g., head forward, kyphosis, lordosis) can affect postural control.
• Crouched posture is a specific postural abnormality.

Perceptual Systems in Postural Control

• Vision, vestibular, and somatosensory inputs are essential for postural control during steady-state balance.
• Visual inputs are particularly important for maintaining vertical posture.

Six Sensory Conditions

• Sensory conditions are defined and assessed using the Sensory Organization Test (SOT).

Control Changes in Different Sensory Conditions

• Sway index measures postural sway and differences noted across varying sensory organization conditions.

CNS Adapts to Sensor Input

• CNS adapts to changing task and environmental demands, with or without impairments due to age or sensory problems
• CNS reweights sensory inputs as necessary
• Adaptation to new tasks is also performed by the CNS.

Loss of a Single Sense

• A loss of single sensory input (vision or vestibular) can impact balance.
• Individuals may compensate by utilizing other available senses such as vision and somatosensation.
• There is a possibility of postural impairment if compensatory mechanisms are unsuccessful

Loss of Sensory Redundancy

• Multiple sensory inputs are needed for effective postural control
• When multiple senses are lost, it impacts postural control significantly.
• Some individuals can handle the loss of a sense better if others remain (e.g., a stroke patient with residual vision might still maintain balance)

Clinical Importance

• Sensory input consideration, not just movement, is critical to treat stability problems in clinical settings.
• Task and environment conditions are part of postural control assessment.

Anticipatory Postural Control

• Preprogramming for voluntary movements (APAs).
• Movements are started 50-plus milliseconds in advance of intended action to minimize instability.
• This allows for postural adjustment prior to the planned movement.
• Predictive control or proactive control, central set.
• Sensory changes prepare the motor system.
• Automatic postural adjustments are context specific.

Example of Anticipatory Postural Adjustment

• Example showing anticipatory postural adjustments.

APA Flexibility during Arm Reaching

• Environmental constraints (additional load, target location).
• Task constraints (self-paced vs reaction time, unilateral vs bilateral tasks).
• Individual constraints (age, fatigue).

Anticipatory Control Problems

• Difficulty with anticipatory postural movements observed in specific neurological conditions.
• Various constraints within the individual can impair APA.

Clinical Importance (Anticipatory Postural Control)

• Information on anticipatory postural control can guide clinical interventions.
• Clinicians can adjust task and environmental demands to enhance anticipatory control.

Cognitive System in Postural Control

• Attentional demands are influenced by motor task complexity.
• Competition for resources affects postural control during dual tasks.
• Performance depends on the complexity of the added (secondary/additional) task.

Clinical Importance (Cognitive Factors)

• Young adults have less attentional demand during postural control.
• Individuals with neurological conditions require specific strategies for postural control.
• Practice of postural tasks with varying attentional demands is beneficial.

Distribution of CNS Control

• Systems involved in postural control (spinal cord, brainstem, basal ganglia, cortex, cerebellum).
• The systems interact via circuits and pathways to maintain stability.
• Sensory input from the body impacts the stability of the system

Summary (Conclusion)

• Postural system has stability and orientation functions
• Neural mechanisms involve steady-state, reactive, and anticipatory control.
• Postural control depends on the characteristics of the environment and the task.

Test your knowledge on postural control and balance strategies with this quiz. Explore key concepts such as reactive balance, sensory systems, and muscle synergies critical for maintaining equilibrium in patients. Assess your understanding of how various factors influence postural stability and control.