Postural Control and Balance Strategies Quiz

Postural Control: Dynamic Systems Theory Perspective

• The dynamic systems theory perspective views postural control as a complex interplay of multiple interacting systems.
• Postural control is defined in the context of task-oriented movement.
• Motor and sensory strategies associated with postural control are adaptable to changes in individual, task, and environmental constraints.
• Understanding motor and sensory strategies is crucial for clinical practice.
• Evidence-based practice focuses on research and clinical practice to understand normal and impaired balance.
• Methods (tests and measures) examine balance to develop treatment strategies.

Defining Postural Control

• Stability involves controlling the center of mass (COM) over the base of support (BOS).
• The center of gravity (COG) is the vertical projection of the COM.
• The center of pressure (COP) measures the center of distribution of forces applied to the support surface.
• Postural orientation involves maintaining appropriate relationships between body segments and the environment.
• Maintaining vertical orientation is critical for most functional tasks.
• Several sensory systems are essential to maintain vertical orientation.

How is Postural Control Operating Here?

• Orientation and equilibrium are separate but related processes.
• Postural orientation can sometimes require sacrificing postural equilibrium.
• Proper assessment and consideration of postural orientation and equilibrium are crucial for therapists.

COM is the Key Element in Postural Control

• The center of mass (COM) is a virtual point in space.
• Its position depends on all body segments.
• The central nervous system (CNS) needs sensory systems to detect changes in the COM.
• The CNS also has established thresholds for acceptable COM variability.
• The CNS controls the muscles (around joints) with appropriate force and timing to maintain balance.

Biomechanical Analysis (Patla, Ishac, and Winter, 2002)

• The CNS manages the mechanical problem of balance.
• The question of whether the system is an inverted pendulum is relevant to the understanding of balance issues.

Measurement of Postural Stability

• Force plates measure distance and variability of the center of pressure (COP) changes.
• Changes in COP during quiet standing are assessed, including sway amplitude data.

Defining Systems of Postural Control

• Task, individual, and environmental factors interact to influence posture.

Neural Components of Postural Control

• Action systems encompass the motor processes (neuromuscular synergies) required for controlling posture.
• The perceptual system integrates sensory information about the body and the environment.
• The cognitive system involves higher-level processes like attention, motivation, and intention that play a role in adaptive postural control, including anticipatory postural adjustments.

Normal Control Mechanisms (Shumway-Cook & Woollcott)

• Motor control of steady-state balance and reactive balance are discussed.
• The perceptual system is critical in postural control and helps organize sensory input data
• Anticipatory postural control or balance is also relevant.

Control of Steady-State Balance or Postural Control

• Postural sway involves small movements.
• Body alignment, muscle tone, and intrinsic muscle stiffness play a role in minimizing gravity's effect on posture.
• The tone of extensor muscles is particularly crucial for upright posture maintenance.

Steady-State Balance

• Stability limits describe the point when a person adjusts their base of support to maintain stability.
• Perceptual and cognitive factors influence stability limits.
• Ideal alignment (Figure 7.6) minimizes muscular effort in maintaining posture.

Movement Strategies for Steady State and Reactive Balance

• Inverted pendulum strategies involve ankle and hip strategies.
• Ankle strategies involve primary movements (oscillations) with legs and trunk moving in phase.
• Low-frequency strategies involve hip movements, with legs and trunk out of phase.
• High-frequency strategies involve more complex movements.

Reactive Balance

• Feedback mechanisms are critical in controlling reactive balance.
• Ankle, hip, and stepping strategies are used in reactive balance during different conditions

Anterior-Posterior Stability for Reactive Balance

• Ankle and hip strategies play important roles in reactive balance.
• The degree of stability depends on the individual and possible impairments.

How do You Test for Reactive Balance?

Other Planes of Movement

• Mediolateral control involves unloading and loading of legs, hip abductors, and adductors.
• Proximal-to-distal control is also involved.
• Multidirectional control involves EMG (electromyography) turning curves.

Reactive Control Strategies are Adaptive

• The effectiveness of reactive strategies depends on initial position, stance width, and support type.

Effect of Practice

Physiological Significance of Synergies

• Synergies are functional muscle groupings that act as a unit to provide stability during movement.
• Multiple muscles are combined in various synergies.
• Synergies have fixed muscle weighting patterns.
• They produce a defined direction of force.
• Synergies combine different force vectors.

Importance to Clinicians

• Clinicians need to understand postural equilibrium and control mechanisms, including how they may interchange
• Multiple synergies are needed to adapt to changes in task demands and destabilization forces.

Musculoskeletal Constraints

• Abnormalities of alignment contribute to biomechanical constraints.

Perceptual Systems in Postural Control (Sensory Organization)

• Visual system considerations
• Vestibular system involvement
• Somatosensory system assessment

Six Sensory Conditions of Sensory Organization (Figure 7.15)

• Accurate organization of sensory data from various systems is crucial for postural control.
• Individuals with less accurate sensory input organization may have difficulty with balance.

Control Changes as Different Sensory Systems are Available

• The Sensory Organization Test (SOT) measures how different sensory systems affect postural control.

Adaptations with the CNS

Loss of a Single Sense

• Compensatory strategies depend on available sensory information from other systems.
• Postural control is affected when multiple sensory systems are absent.

Loss of Sensory Redundancy and Selection

• Loss of multiple sensory inputs can lead to significant loss of postural control.
• There are differences in the loss of sensory cues for different people.

Clinical Importance

• Organizing and selecting appropriate sensory inputs contributes to and maintains postural stability.
• Identifying environmental and task demands helps to improve postural control, including sensory organization and movement strategies.

Anticipatory Postural Control

• This process involves programming posture before voluntary movement.
• It helps in minimizing instability before movement.

Example of Anticipatory Postural Adjustment

• The example illustrates anticipatory postural adjustments for volitional movements.

APA Flexibility During Arm Reaching

• Task, environment, and individual constraints affect anticipatory control, including flexibility.

Anticipatory Control Problems

• Understanding anticipatory control problems is crucial in clinical settings.

Clinical Importance: Anticipatory Control

• Clinical practice should incorporate tasks and environments designed to improve anticipatory control.
• Timing of anticipatory postural adjustments may change with repeated practice.

Cognitive System in Postural Control

• Postural control attentional requirements depend on the complexity of motor tasks.
• Dual tasking can affect attentional resources.

Clinical Importance: Cognitive System

• The attentional demand for postural tasks differs depending on the individual.

Distribution of CNS Control

• Describing the pathways by which the central nervous system (CNS) controls postural responses based on the different levels in the nervous system.

Summary

• The postural system has two critical roles.
• Several neural mechanisms contribute to postural control.
• Attentional resources are important in postural tasks, particularly with complex tasks.
• Postural control strategy adaptation depends on factors like task complexity and impairment levels.

Test your knowledge on postural control and the various reactive balance strategies employed. This quiz covers concepts such as muscle synergies, sensory integration, and stabilization techniques essential for maintaining equilibrium. Challenge yourself to see how well you understand these critical aspects of balance.