Motor Learning and Control

⛹️‍♂️Motor Learning and Control Unit 14 – Postural Control and Balance

Postural control and balance are crucial for maintaining stability and preventing falls. This unit explores the neurological basis, sensory systems, and biomechanics involved in keeping us upright. Understanding these concepts is essential for assessing and improving balance in various populations. The unit covers balance assessment techniques, factors affecting postural control, and strategies for improvement. From clinical tests to virtual reality training, it provides practical applications for enhancing balance in older adults, athletes, and individuals with neurological conditions.

Key Concepts and Definitions

  • Postural control involves maintaining equilibrium and orientation of the body in space
  • Balance refers to the ability to maintain the center of mass within the base of support
  • Static balance maintains a stationary position while dynamic balance maintains stability during movement
  • Center of mass (COM) is the point around which the body's mass is equally distributed
  • Base of support (BOS) is the area beneath an object or person that includes every point of contact that provides support
  • Center of pressure (COP) is the point on the ground where the resultant force vector is applied by an object
  • Limits of stability (LOS) represent the maximum angle the body can sway without losing balance or changing the BOS
    • LOS are affected by factors such as height, size of the BOS, and joint range of motion

Neurological Basis of Balance

  • The central nervous system (CNS) integrates sensory input and generates motor output for postural control
  • The cerebellum plays a crucial role in balance by processing vestibular, visual, and proprioceptive information
    • It coordinates and fine-tunes motor commands for smooth, accurate movements
  • The brainstem contains vestibular nuclei that receive input from the vestibular system and project to the spinal cord
  • The basal ganglia contribute to postural control by regulating muscle tone and initiating postural adjustments
  • The motor cortex is involved in planning and executing voluntary movements that affect balance
  • Descending pathways, such as the reticulospinal and vestibulospinal tracts, transmit commands for postural control
  • Spinal reflexes, including the stretch reflex and crossed extensor reflex, help maintain balance by rapidly responding to perturbations

Sensory Systems Involved

  • The vestibular system detects head position and movement using semicircular canals and otolith organs
    • Semicircular canals sense angular acceleration while otolith organs sense linear acceleration and head tilt
  • The visual system provides information about the environment, body position, and movement relative to surroundings
    • Visual cues help maintain balance by providing a reference frame for vertical orientation
  • Proprioception, the sense of body position and movement, is detected by muscle spindles, Golgi tendon organs, and joint receptors
    • Proprioceptive input helps the CNS determine limb position and make appropriate postural adjustments
  • Cutaneous receptors in the skin, particularly in the feet, provide information about contact with the support surface
  • The somatosensory system integrates proprioceptive and cutaneous input to create a body schema for postural control
  • Sensory integration involves weighting and prioritizing input from different sensory systems based on the situation
    • For example, in a well-lit environment, vision may be weighted more heavily than vestibular input

Biomechanics of Posture

  • Postural alignment refers to the optimal positioning of body segments to maintain balance and minimize energy expenditure
  • The musculoskeletal system provides the framework and forces necessary for maintaining posture
  • Antigravity muscles, such as the erector spinae and leg extensors, work to counteract the pull of gravity
  • Co-contraction of agonist and antagonist muscles helps stabilize joints and maintain posture
  • Postural sway refers to the small, continuous movements of the body while standing still
    • Sway can be measured using force plates or motion capture systems
  • Postural strategies, such as the ankle strategy and hip strategy, are used to maintain balance in response to perturbations
    • The ankle strategy involves using ankle muscles to control sway, while the hip strategy involves larger movements at the hips and trunk
  • Anticipatory postural adjustments (APAs) are made prior to voluntary movements to maintain stability
    • For example, before raising an arm, trunk muscles activate to counteract the expected shift in the COM

Balance Assessment Techniques

  • Clinical tests, such as the Berg Balance Scale and Timed Up and Go test, assess functional balance in various tasks
    • These tests are often used to screen for fall risk and evaluate the effectiveness of interventions
  • Posturography involves measuring postural sway using force plates or motion capture systems
    • Static posturography assesses sway during quiet standing, while dynamic posturography assesses responses to perturbations
  • Sensory organization tests (SOTs) evaluate the contribution of different sensory systems to postural control
    • SOTs manipulate visual, vestibular, and somatosensory input to assess sensory integration and reliance
  • Electromyography (EMG) can be used to measure muscle activation patterns during balance tasks
  • Gait analysis assesses balance during walking using motion capture, force plates, or pressure-sensitive walkways
  • Virtual reality and gaming systems, such as the Nintendo Wii Balance Board, can be used for balance assessment and training
    • These systems provide engaging, interactive environments that challenge balance and provide feedback

Factors Affecting Postural Control

  • Age-related changes, such as decreased muscle strength, sensory function, and reaction time, can impair balance
    • Older adults often exhibit increased postural sway and a higher risk of falls
  • Neurological conditions, such as Parkinson's disease, multiple sclerosis, and stroke, can disrupt postural control mechanisms
    • These conditions may cause muscle weakness, sensory deficits, or impaired motor planning and execution
  • Musculoskeletal disorders, such as arthritis, back pain, and ankle instability, can affect postural alignment and stability
  • Vestibular disorders, such as benign paroxysmal positional vertigo (BPPV) and vestibular neuritis, can cause dizziness and imbalance
  • Visual impairments, such as cataracts, glaucoma, and diabetic retinopathy, can reduce the quality of visual input for balance
  • Medications, particularly those that cause drowsiness, dizziness, or orthostatic hypotension, can increase fall risk
  • Environmental factors, such as uneven surfaces, poor lighting, and clutter, can challenge balance and increase fall risk
    • Adapting to different surface conditions, like sand or foam, requires adjustments in postural strategies

Strategies for Improving Balance

  • Balance training exercises, such as single-leg stands, tandem walking, and reaching tasks, can improve postural control
    • Progressively increasing the difficulty of exercises by altering sensory input or surface conditions enhances adaptability
  • Resistance training can increase muscle strength and power, which are essential for maintaining balance
    • Targeting key postural muscles, such as the core, hip, and ankle muscles, is particularly beneficial
  • Flexibility exercises, such as stretching and yoga, can improve joint range of motion and postural alignment
  • Sensory-specific training, such as visual-vestibular habituation exercises, can enhance sensory integration and reduce dizziness
  • Tai Chi, a mind-body exercise that emphasizes slow, controlled movements and weight shifts, has been shown to improve balance and reduce falls
  • Biofeedback training using visual or auditory cues can help individuals learn to control postural sway and improve balance
  • Assistive devices, such as canes, walkers, and ankle-foot orthoses, can provide support and stability for individuals with balance impairments
    • Proper device selection and training are essential for optimal benefits and safety

Practical Applications and Case Studies

  • Fall prevention programs for older adults often include balance training, environmental modifications, and education
    • The Otago Exercise Program, which combines strength and balance exercises, has been shown to reduce falls by up to 35%
  • Balance training is a key component of rehabilitation for individuals with neurological conditions
    • For example, after a stroke, patients may practice weight shifting, stepping, and walking with assistive devices to regain balance
  • Athletes, particularly those in sports requiring rapid changes of direction or landing from jumps, benefit from balance training
    • Plyometric exercises, stability ball training, and single-leg balance drills can enhance sports-specific balance and reduce injury risk
  • Occupational therapists assess and address balance issues in the context of daily activities, such as dressing, bathing, and cooking
    • Environmental modifications, such as installing grab bars and removing tripping hazards, can improve home safety
  • Virtual reality balance training has shown promise for improving balance in various populations
    • For instance, the Nintendo Wii Fit has been used to improve balance in older adults, individuals with Parkinson's disease, and stroke survivors
  • Case study: A 72-year-old woman with a history of falls undergoes a comprehensive balance assessment and training program
    • The intervention includes strength training, balance exercises, and education on fall prevention strategies, resulting in improved balance scores and reduced fall risk
  • Case study: A soccer player with chronic ankle instability participates in a balance training program using a wobble board and single-leg balance exercises
    • After 6 weeks of training, the athlete demonstrates increased postural stability and returns to play without further ankle injuries


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© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.