Postural Control in Neurologic Dysfunction
Learning Objectives
Discuss changes to steady state, anticipatory, and reactive control following neurologic dysfunction.
Describe the effects of sensory and cognitive dysfunction and the impact on postural control.
Analyze movement and differentiate task demands and factors contributing to postural control dysfunction.
Impaired Postural Control Responses in Neurologic Dysfunction
Impairments related to postural control can lead to:
Slips
Trips
Falls
History/Background Information Considerations
Key Patient and Family Reports:
Main difficulties related to balance.
Experience of falls or near-falls.
Activities that induce instability and specific conditions under which this occurs.
Impact of balance problems on daily activities and quality of life (QOL).
Initial Observations
Task Demands Assessment: Identify if the task is steady state, anticipatory, or reactive.
Base of Support (BOS) and Alignment: Determine the patient's alignment within their BOS and whether excessive sway or other movement issues are present.
Stability in Self-Initiated Movement (Anticipatory Control): Assess ability to maintain balance when BOS is decreased or modified and evaluate weight shifting towards limits of stability (distance and symmetry).
Reactive Control: Analyze how the patient responds to external perturbations, including strategy effectiveness.
Increase challenge by altering task demands, sensory inputs, and cognitive demands.
Postural Control Motor Dysfunction
Categories of Postural Control:
Steady State Control:
Decreased stability limits, altered alignment, motor recruitment, and coordination leading to instability recovery difficulties.
Anticipatory Control:
Impaired muscle activation prior to voluntary movements, leading to reduced movement amplitude and velocity, decreased EMG activation in the affected extremity.
Reactive Control:
Difficulty recovering stability post-perturbation, ineffective motor responses due to impaired timing and coactivation, and inability to adapt to changing demands.
Impaired Steady State Control
Reduced Stability Limits:
Alignment relationships among body segments in relation to the BOS, support surface, and gravity.
Determines effort needed to support body against gravity and influences movement strategies.
Increased Postural Sway:
Refers to the amount of execution and trajectory of the center of mass (COM) within the BOS.
Impaired Anticipatory Postural Control
Issues with preparatory activation of postural muscles leading to:
Delayed responses.
Reduced movement amplitude and velocity.
Lower EMG activation of key postural muscle groups in affected limbs.
Impaired Reactive Control
Challenges include:
Delayed and ineffective response to external perturbations.
Muscle Coactivation: Can lead to ineffective strategies.
Difficulty in adapting postural responses to dynamic task and environmental demands.
Increased Response Latency: Resulting in poor control of the COM and trunk stability.
Assessments of Reactive Balance
Question types for assessing reactive balance include:
Types of Responses: Evaluating generated responses and their effectiveness.
Sensory Dysfunction and Postural Control
Impacts:
Absent/inaccurate sensory inputs can lead to functional limitations and poor adaptability to task demands.
Increased reliance on visual inputs can lead to increased sway and limits on stability, particularly when somatosensory inputs are compromised.
Sensory Dysfunction in Reactive Control
Sensory inputs from lower extremities are essential for accurate motor responses.
Impairments can lead to ineffective motor activation across balance control types.
Impaired Cognitive Systems
Balance self-efficacy is determined by:
Risks for falls, willful avoidance of activity, and prediction of community mobility post-stroke.
Dual Task Interference: Increased cognitive demands can exacerbate sway and motor response delay, prompting "posture first" strategies.
Evaluating Results from Studies
Timed Up-and-Go (TUG): Analyzing mean times with single and dual task conditions post-stroke vs. healthy controls, indicating increases in cognitive-motor interference with complexity in tasks.
Intervention Approaches in Postural Control
Always prioritize safety during interventions.
Considerations for Effective Interventions:
Attention: Focus on task goals to enhance performance.
Motivation: Promote autonomy and enhance expectancies.
Training Conditions: Should involve real-life tasks, progressively adapting to skill changes involving active participation.
Task-Oriented Approach to Postural Control Interventions
Identify impacted tasks and suboptimal control types.
Determine contributing factors including motor control and sensory integration.
Select appropriate outcome measures to evaluate functional task-specific interventions.
Example Training Techniques
Retraining Steady State Control: Focus on orientation and alignment to restore COM within the BOS.
Backward Walking Training: Enhances postural demand and requires sensory reweighting for movement planning.
Anticipatory Control Balance Training: Engage patients in step training with various targets and cognitive tasks.
Reactive Balance Training**
Externally applied mechanical perturbations to encourage rapid reaction for stability.
Training protocols should focus on unpredictable perturbations to enhance reactive stepping.
Task Complexity and Dual Task Training
Implement dual task training to improve cognitive resource allocation under dual-task conditions (e.g., TUG with verbal fluency tasks).
Improvements in Balance: Studies show significant improvements have occurred in dual task conditions over time.
Impact of Assistive Devices on Postural Control
Changes in base of support and COM may enhance or hinder dynamic motor activation patterns.
Forward and Lateral Weight Shifting
Increase demand through unstable surfaces, speed, or cognitive challenges like verbal fluency tasks during balance training.
Conclusion
Future discussions will revolve around fall risk and prevention strategies, emphasizing the importance of effective training interventions.