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Motor Programming Theories of Motor Control

Learning Outcomes

  • Unit Learning Outcome (ULO) 4 focus: Explain common theoretical models for motor control, motor learning & skill acquisition.
    • Identify fundamental features of a motor program.
    • Describe the information-processing model in movement planning & execution.
    • Define a Generalized Motor Program (GMP).
    • Distinguish between invariant features & parameters of a GMP.
    • Explain schema formation & its role in motor-skill learning.

Motor Programming Theory – Core Idea

  • Cognitive-based, top-down approach: CNS houses pre-structured neural commands (motor programs) that drive effectors (muscles, joints).
    • Commands stored in Long-Term Memory (LTM) as “rules for action.”
    • Execution path: cognition → descending pathways → musculoskeletal response → afferent feedback returns.
  • Treats skilled movement as the retrieval & execution of a stored program, triggered by intention & sensory input.

The Information-Processing (IP) Model

  • Movement production viewed as a sequence of central cognitive stages:
    1. Sensory Input (stimulus identification)
    • External (environment) + internal (proprioceptive) data enter CNS.
    1. Perceptual Stage
    • Attentional selection: decide which sensations to prioritise.
    • Meaning extraction based on prior experience.
    1. Decision-Making Stage
    • Choose a course of action using memory traces.
    1. Programming Stage
    • Prepare & organise motor commands that realise the decision.
    1. Response Output
    • Signals descend spinal cord → muscles → observable movement.
  • Key emphasis: cognition (perception, memory, decision) shapes every downstream motor command.

Classical Motor Program Theory – Two Major Criticisms

  • Storage Problem
    • If each context-specific movement has its own program, memory capacity requirements become “countless.”
  • Novelty Problem
    • Completely new actions would be impossible because no pre-existing program exists to retrieve.

Generalized Motor Program (GMP)

  • Proposed by Richard Schmidt (1975) to address storage & novelty issues.
  • Concept: One abstract program represents an entire class of similar actions (e.g., all forms of over-arm throwing).
  • Each execution = GMP’s invariant structure + context-specific parameters.

Invariant Features (do NOT vary across executions)

  1. Order of Events
    • Fixed sequencing of muscle activations/joint motions.
  2. Relative Timing
    • Proportional timing of sub-phases remains constant regardless of total duration.
      • Example figure (hypothetical): 30\% phase 1, 20\% phase 2, 40\% phase 3, 10\% phase 4 → sums to 100\% in both fast & slow throws.
  3. Relative Force (or Amplitude)
    • Proportional contribution of different muscle groups remains stable even when overall force changes.

Parameters (CAN vary to fit the situation)

  • Overall Force: how much total muscular effort/impulse.
  • Overall Duration: absolute movement time.
  • Muscles Selected: which specific effectors are recruited.
  • Parameters blend with invariant structure to customise the action to current goals/environment.

Schema Theory (Schmidt, 1975)

  • A schema = set of rules that link parameter values to desired outcomes for a given GMP.
  • Generates movement commands when faced with novel or varying conditions by adjusting parameters.

Four Information Sources in Schema Formation

  1. Initial Conditions
    • Body position, current state, environmental context.
  2. Response Specifications
    • Intended movement plan (chosen parameters).
  3. Sensory Consequences (Expected)
    • Predicted what one should feel/see during execution.
  4. Response Outcome (Actual)
    • Feedback on success, errors & real sensory input.
  • Repeated practice updates the schema: comparison of expected vs. actual consequences refines the parameter-outcome mapping.

Execution-Feedback Loop (Simplified)

  • Retrieve GMP + select parameters via current schema → produce movement → sense actual outcome → store in Short-Term Memory → update schema in LTM for next trial.

Practical & Pedagogical Implications

  • Emphasises variability of practice: exposing learners to numerous parameter combinations strengthens the schema, enhancing adaptability.
  • Clinicians & coaches can design drills that vary force, speed, and context to build robust schemas rather than rote programmes.
  • Ethical note: Cognitive-centric models prioritise higher-order planning; practitioners must accommodate individuals with cognitive impairments when applying GMP-based interventions.

Connections & Comparisons

  • GMP/Schema sits in the motor program family of theories (top-down, central representation).
  • Contrasts with the Dynamical Systems Theory (DST) – bottom-up, self-organisation, context-driven (to be covered next lecture).

Key Takeaways

  • Motor Programming Theory: movement = retrieval of CNS-stored commands.
  • Information-Processing Model: perceiving → deciding → programming → acting.
  • Classical view struggled with storage & novelty; Schmidt’s GMP answers both via abstraction.
  • Invariant features define a movement class; parameters customise each attempt.
  • Schema = experiential rule set that links parameters to outcomes, refined through practice.
  • Understanding GMP & schema guides effective skill acquisition, rehabilitation, and coaching strategies.