principles of motion and stability

Motor Control Perspectives

  • Overview of motor control perspectives that aid in understanding motor behavior.
    • Maturational Perspective
    • Ecological Model
    • Dynamic Systems Model (part of the ecological model)
    • Information Processing Model
    • Perception Action Model

Motor Program Model

  • Complements information processing perspective.
  • Brain and spinal cord form preprogrammed movements known as schemas.
    • Advantage: Explains how complex movements are executed quickly and accurately.
    • Limitations:
    • Questions arise about how movements and schemas are stored.
    • Challenges in creating new movements remain, given the rigidity of these schemas.
  • Adjustments can be made based on sensory input despite schemas being less reliant on it.

Central Pattern Generators (CPGs)

  • Located within the spinal cord and lower brain centers.
  • Responsible for rhythmic motor outputs (e.g., chewing, swallowing, walking).
  • Example of chewing:
    • Normal chewing does not require high brain function unless an unexpected crunch is encountered.
  • Specific pattern generators exist for different functions:
    • Lower extremities: Stepping pattern generator for walking.
    • Upper extremities: Generators for reaching and swimming motions.
  • Patients with spinal cord injuries can relearn walking movements due to inherent spinal and CPG functions.

Systems Model

  • Comprised of three components: distribution, body systems, and feedback.
  • Suggests cooperation between brain and spinal centers in controlling posture and movement.
    • Complexity of tasks governs where control occurs within the nervous system.
    • Differentiation of motor control locations:
    • Basic movements may involve lower brain structures (brain stem, spinal cord).
    • Higher-level skills require cortical control.
  • Body systems contributing to movement:
    • Muscle, skeletal, cardiovascular, and respiratory systems are all involved.
    • Example: Endurance and muscular strength limit running capabilities, not just nervous system issues.

Feedback Mechanisms

  • Definition: Sensory/perceptual information collected during or after movement.
    • Types of feedback:
    • Intrinsic Feedback: Interoceptive sensory feedback internal to the body (e.g., proprioception, vestibular, visual knowledge).
    • Extrinsic Feedback: External information sources (e.g., coaches, video analysis).
  • Distinction between feedback types based on temporality and source.
    • Closed Loop Feedback:
    • A cyclical process of perception and output generating responses that refine movements over time.
    • Best for slower, precise action execution (e.g., dribbling a basketball).
    • Open Loop Feedback:
    • Final execution of an action without modification based on real-time feedback (e.g., shooting a basketball).
  • Modifications based on feedback and context, e.g., sprinting dynamics.

Stages of Motor Control

  1. Mobility:
    • Characterized by the erratic nature of infant movements.
    • Joint motion required to progress to higher levels of control.
  2. Stability:
    • Ability to maintain balance and equilibrium.
    • Involves tonic holding; muscle groups engaged for position stability.
  3. Controlled Mobility:
    • Integration of stable postures with joint movements.
    • Example: Moving an arm while maintaining upright balance.
  4. Skill:
    • Mastery of controlled mobility leads to specific skilled actions (e.g., throwing).

Postural Control System

  • Integrative system involving:
    • Visual System
    • Vestibular System
    • Proprioceptive System (Kinesthetic Awareness)
  • Relationship between posture, movement, and balance:
    • Balance refers to maintaining center of mass (COM) within base of support (BOS).
    • Larger BOS increases stability (e.g., assistance devices promote balance).
    • Examples of body alignment and stability are discussed (e.g., pyramidal vs. skyscraper stability).
  • Developmental progression in posture, stability, and control:
    • Head-to-tail development and proximal to distal functional grasping.

Sensory Role in Stability

  • Visual Dominance:
    • Most influential between ages 0-3 for stability.
  • Vestibular System:
    • Located in the inner ear, essential for spatial orientation, relative to gravity.
    • Crystals within the labyrinth play a role in balance and stability.
  • Somatosensory Integration:
    • Touch and proprioception become more dominant in adults compared to infants.

Aging and Balance

  • Changes in sensory perceptions and motor outputs due to aging.
    • Intrinsic changes include sensory receptor modifications and muscle weakness.
    • Potential psychosocial factors (e.g., depression, dementia) affecting processing.
  • Extrinsic environmental factors contributing to risks (e.g., stairs, lighting).
  • Alterations in musculoskeletal structure affect balance strategies:
    • Positional changes or deformities can disrupt established balance metrics.

Conclusion

  • Complex interplay of sensory systems governs balance and movement control.
  • Understanding these systems aids in addressing mobility and balance issues across age brackets and rehabilitation.