Podcast
Questions and Answers
What are the two primary purposes of postural control?
What are the two primary purposes of postural control?
Stability and Postural Orientation
What does COM stand for in the context of postural control?
What does COM stand for in the context of postural control?
Postural orientation and equilibrium are always the same.
Postural orientation and equilibrium are always the same.
False
Name three sensory systems involved in postural control during steady-state balance.
Name three sensory systems involved in postural control during steady-state balance.
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What is the term for the point at which a person will change their base of support to maintain stability?
What is the term for the point at which a person will change their base of support to maintain stability?
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Which postural control mechanism involves the control of movements during external disturbances?
Which postural control mechanism involves the control of movements during external disturbances?
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Which postural control strategy involves primary movement around the ankle with legs and trunk moving in phase?
Which postural control strategy involves primary movement around the ankle with legs and trunk moving in phase?
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Reactive control strategies are always fixed and unchanging.
Reactive control strategies are always fixed and unchanging.
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What does APA stand for in relation to anticipatory postural control?
What does APA stand for in relation to anticipatory postural control?
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What is the primary role of the 'central set' in anticipatory control?
What is the primary role of the 'central set' in anticipatory control?
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Anticipatory postural control is not affected by individual constraints such as age and fatigue.
Anticipatory postural control is not affected by individual constraints such as age and fatigue.
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Give one example of a condition that might affect anticipatory postural control.
Give one example of a condition that might affect anticipatory postural control.
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Which of the following is NOT a common way clinicians can manipulate task demands to improve anticipatory control?
Which of the following is NOT a common way clinicians can manipulate task demands to improve anticipatory control?
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What is the term for a task involving more than one action or goal at the same time, such as a cognitive task combined with a motor task?
What is the term for a task involving more than one action or goal at the same time, such as a cognitive task combined with a motor task?
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Postural control is always heavily reliant on attentional resources, even in young adults.
Postural control is always heavily reliant on attentional resources, even in young adults.
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What is the term for a functional coupling of groups of muscles working together as a unit?
What is the term for a functional coupling of groups of muscles working together as a unit?
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Which part of the nervous system is primarily responsible for the quick change in muscle patterns needed for rapid adjustments in postural control?
Which part of the nervous system is primarily responsible for the quick change in muscle patterns needed for rapid adjustments in postural control?
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The vestibular system only contributes to postural control in situations where visual information is limited.
The vestibular system only contributes to postural control in situations where visual information is limited.
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What are two key ways that postural control is adaptable?
What are two key ways that postural control is adaptable?
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Clinical approaches to improving balance should only focus on modifying movement strategies.
Clinical approaches to improving balance should only focus on modifying movement strategies.
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What is the general term for a situation where the body's ability to control posture is significantly reduced due to the loss of multiple sensory inputs?
What is the general term for a situation where the body's ability to control posture is significantly reduced due to the loss of multiple sensory inputs?
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Which of the following is NOT a common condition that can lead to issues with sensory redundancy and selection?
Which of the following is NOT a common condition that can lead to issues with sensory redundancy and selection?
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Study Notes
Postural Control
- Postural control is defined in the context of task-oriented movement, encompassing motor and sensory strategies.
- Postural control strategies adapt to changes in individual, task, and environmental constraints.
- Postural control is related to clinical practice, linking motor and sensory strategies.
Defining Postural Control
- Postural control has two purposes: stability and orientation.
- Stability: maintaining the center of mass (COM) over the base of support (BOS). The center of gravity (COG) is the vertical projection of the COM and the center of pressure (COP) is the center of distribution of forces applied to the support surface.
- Orientation: maintaining appropriate relationships between body segments and the environment.
- Vertical orientation is essential for functional tasks; it requires multiple sensory inputs.
How is Postural Control Operating Here?
- Orientation and equilibrium are not the same.
- Postural orientation can sometimes involve sacrificing postural equilibrium.
COM is the Key Element in Postural Control
- The center of mass (COM) is a virtual point in space that relies on all body segments' positions.
- Variability in controlling the COM is a crucial aspect.
- The central nervous system (CNS) detects changes in the COM and has thresholds for acceptable variability to manage postural control accurately.
- The CNS recruits muscles throughout joints, with precision in force and timing dependent on the body segment configuration as well as the environment.
Biomechanical Analysis
- How the central nervous system (CNS) handles postural control challenges, particularly in the context of the mechanical system, can involve the concept of an inverted pendulum system.
Measurement of Postural Stability
- Postural stability comprises force plate measurements, including center of pressure (COP) and sway amplitude determined by body sensors.
Defining Systems of Postural Control
- A complex interplay exists between task, individual, and environment, impacting postural control.
- Multiple systems such as cognitive resources, musculoskeletal features, and sensory systems contribute to postural control.
Neural Components of Postural Control
- Action systems involve motor processes, including neuromuscular synergies.
- Perceptual systems involve the integration and organization of sensory information.
- Cognitive systems involve high-level processes, including attention, motivation, and intention affecting adaptive postural control.
Shumway Cook & Woollcott Normal Control Mechanisms
- Motor control of steady state balance
- Motor control during perturbations: Reactive Balance
- Perceptual System of Postural Control (Sensory organization)
- Motor control of Anticipatory Postural Control or Balance
- Cognitive systems in postural control
Control of Steady State Balance
- Postural sway involves small amounts of movement.
- Maintaining upright posture involves controlling factors like body alignment, muscle tone, and intrinsic muscle stiffness, with extensor muscles playing a role during upright posture.
Steady-State Balance
- Stability limits are variable points where postural configuration changes for stability.
- Postural stability is not fixed; it's influenced by perceptual and cognitive factors.
Ideal Alignment minimizes muscular effort
- Ideal posture (anatomical alignment) reduces the needed muscle effort for maintaining balance.
Base of Support (BOS)
- Extending the BOS for postural control is a strategy to capture the center of mass (CoM).
Movement Strategies for Steady State and Reactive balance
- Inverted Pendulum: Ankle strategies (primary movement with legs and trunk in phase) are low frequency (<1Hz). Hip strategies (primary movement with legs and trunk out of phase) are low frequency (<1Hz) and high frequency (>1Hz).
Movement strategies to externally generated destabilization (perturbations)
- Reactive Balance – the process to respond to external forces, including feedback control strategies like ankle strategy, hip strategy, or stepping strategy.
Anterior-Posterior Stability for Reactive Balance
- Ankle strategy is employed when posture is relatively stable and the center of mass (COM) doesn't need to move quickly.
- Hip strategy is used when posture is unstable, and the COM needs to move quickly, more frequently associated with impairments.
How do you test for Reactive balance?
- Methods for testing reactive balance are not covered in this document.
Other Planes of movement need to be controlled
- Mediolateral strategies include unloading and loading of each leg, hip abductors and hip adductors, and the coordination between proximal and distal structures.
- Multidirectional control strategies depend on EMG.
Reactive Control Strategies are Adaptive
- The effectiveness of reactive control strategies adapting to various circumstances and initial conditions (e.g., initial stance position, width) is assessed.
Reactive Control Strategies Adapt With Practice
- Adaptive reactive control improves with practice, affecting muscle activity timing and magnitude.
Physiological significance of synergies?
- Synergies are functional couplings of muscles acting as a unit.
- Multiple muscles can participate in various synergies.
- Muscles within a synergy have fixed weighting.
- Synergies generate specific force directions.
Importance to the Clinician
- Maintaining postural equilibrium is crucial; clinicians utilize common postural control mechanisms and adapt training strategies.
- Multiple synergies are vital but require individualized attention and modulation based on changing task and destabilization force demands.
Musculoskeletal Constraints in Postural Control
- Abnormalities of alignment (e.g., head forward, kyphosis, lordosis, etc) and crouched posture can influence postural control.
Perceptual Systems in Postural Control
- Sensory organization in the perceptual system manages stability during posture maintenance.
- The roles of visual (perceiving surrounding objects and motions), vestibular (interpreting gravity and inertial forces), and somatosensory (relating body to surfaces) systems are vital for postural control.
Six Sensory Conditions of Sensory Organization
- Sensory conditions 1-6 illustrate variations in sensory information accuracy and reliance (or not) on vestibular, vision, and somatosensory input.
Control Changes as different Sensory Systems are Available Sensory Organization Test (SOT)
- The Sensory Organization Test (SOT) is a tool for assessing how postural control changes based on available sensory systems.
CNS Adapts the way it uses sensory Information
- Central nervous system (CNS) adaptively modifies the usage of sensory information based on environmental variables, aging effects, and new task learning.
Loss of a Single Sense
- Compensatory strategies depend on remaining systems' ability to sense body position and utilize environmental cues.
- Individuals can compensate for some sensory losses.
Example: Sensory loss of Single sensation
- This is a visual example of how different levels of sensory loss can influence sway index with a chart.
Loss of Sensory Redundancy and Selection
- Losing multiple sensory inputs leads to substantial loss of postural control, with studies examining this effect in various populations and conditions.
- Maintaining balance depends heavily on proper sensory input selection from available cues.
Clinical Importance
- Using accurate sensory inputs as a strategy for clinical practice is beneficial for maintaining postural control in different situations.
- Clinical approaches to improving balance should address sensory organization as well as movement strategies.
Anticipatory Postural Control
- Anticipatory postural control is the preparatory postural movement or activation in advance of voluntary movement by the CNS.
- Predictive control is the ability of the nervous system to prepare for future sensory changes.
Example of an Anticipatory postural control experiment
- There is an example of a subject performing a task requiring anticipatory control that demonstrates the process.
APA Flexibility during Arm Reaching
- APA flexibility adapts based on changing environment, task-specific requirements, and individual factors like age and fatigue.
Anticipatory Control Problems
- Postural synergies might be impaired or less evident in certain conditions like stroke or TBI; This is a known constraint in APA in certain clinical populations (e.g., individuals with neurological control impairments)
Clinical Importance
- Clinicians' understanding of anticipatory postural control is essential, as it offers options for improved postural control through task- and environment-specific adjustments.
Cognitive System in Postural Control
- Attention is an important aspect of postural control. In dual tasks (doing two tasks together), control is lost if the combined attentional demands exceed capabilities. The difficulty of the postural control task depends on the secondary task.
Clinical Importance
- Attentional demands for postural control are low in young adults, but clinicians need to consider the role of attention in patients with neurological deficits to distinguish between postural control and attentional issues.
Distribution of CNS Control
- A diagram depicting the various anatomical structures and their roles in CNS control of posture.
Summary
- The postural system has two main functions that are important for stability and orientation.
- The mechanism relies on various types of neural control, including steady states, reactive, and anticipatory motor synergies; sensory integration; and cognitive strategies.
- Attentional requirements and the interaction between task demands, individual constraints, and environmental contexts in relation to postural behavior are factors for successful balance maintenance.
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Description
Explore the concepts of postural control, emphasizing its role in task-oriented movement. This quiz covers definitions, stability, orientation, and the sensory inputs crucial for maintaining balance. Understand the relationship between postural strategies and clinical practice.
