Motor Learning Ch5 Motor Control Theories

Chapter 5: Motor Control Theories

  • Theories about how we control coordinated movement differ in terms of the roles of central and environmental features of a control system.

Objectives

  1. Introduction

    • Overview of motor control theory and its issues.

    • Introduction to the OPTIMAL motor control theory.

  2. Memory-based Motor Control Theory

    • Define a generalized motor program (GMP) and describe its invariant features and parameters.

  3. Dynamical Perspective Motor Control Theory

    • Define key terms:

      • Order parameters

      • Control parameters

      • Self-organization

      • Coordinative structures

      • Perception-action coupling

      • Affordances

Theory and Professional Practice

  • What is a theory?

    • Accurately describes observations, making predictions about future results (Hawking, 1996).

  • Motor learning and control theories focus on:

    • Explaining human movement behavior.

    • Understanding why people perform skills as they do.

    • Predicting outcomes of training methods.

  • Relevance of theory to practice:

    • The theory provides a rationale for practitioners' actions

    • Helps predict effectiveness of interventions, identify performance problems, and evaluate strategies.

Motor Control Theory

  • Explains how the nervous system produces coordinated movement in various environments.

  • Two key terms:

    • Coordination

    • Degrees of freedom problem.

Coordination

  • Defined as the patterning of body and limb motions relative to environmental objects and events (Turvey, 1990).

  • Consider two aspects:

    • Relationships among joints and body segments at specific moments.

    • Relationship between coordination patterns and the environment.

Coordination in a Soccer Kick

  • Angle-Angle Diagram: Illustrates various phases of motion during a soccer kick.

    • Prepractice and postpractice performance can be analyzed using this diagram.

Degrees of Freedom Problem

  • Degrees of freedom (df): Number of independent elements in a system and how they can act.

  • The challenge is controlling these degrees of freedom to achieve specific movements.

  • Example: Control of a helicopter’s flight highlights this problem.

Two General Types of Control Systems

  1. Open-loop Control System:

    • Movement instructions are sent from the control center without feedback.

  2. Closed-loop Control System:

    • Movement instructions are sent with feedback mechanisms to adjust actions.

Major Theories of Motor Control

  1. Motor Program-based Theory:

    • Memory-based mechanism controlling coordinated movement.

  2. Dynamical Systems Theory:

    • Emphasizes environmental information and the body’s mechanical properties.

  3. The OPTIMAL Theory of Motor Learning:

    • New framework focusing on performance expectancies, learner autonomy, and external focus of attention.

Motor Program-Based Theory (1)

  • Schema Theory (by Schmidt, 1988):

    • GMP is a memory-based mechanism for adaptive and flexible movement.

    • Each GMP controls a class of actions identified by invariant characteristics.

Motor Program-Based Theory (2)

  • GMP Characteristics:

    • Invariant Features: Do not vary across performances and define the GMP signature.

    • Parameters: Specific features added to invariant features to adapt to situations.

Motor Program-Based Theory (3)

  • Invariant Features and Parameters:

    • Example of invariant feature: Relative time in a skill (e.g., proportion of time each component uses).

    • Example of parameter: Overall time taken in a skill.

    • Analogy to music: Rhythm remains stable whereas tempo may vary.

Testing Relative Time Invariance

  • Study by Shapiro et al. (1981):

    • Analyzed gait characteristics to assess if walking and running belong to one or two classes of action based on relative time invariance.

Dynamical Systems Theory

  • Focuses on how environmental information and dynamic properties control movement.

  • Identifies laws governing human coordination patterns.

Concepts Based on Non-Linear Dynamics

  • Behavioral changes can be sudden and not always linear.

  • Behavior emerges through interactions among task, environmental, and organismic constraints.

Attractors

  • Defined as a stable state of a motor control system representing preferred coordination patterns.

  • Characterized by order and control parameters, minimum performance variability, stability, and energy efficiency.

Order and Control Parameters

  1. Order Parameters:

    • Collective variables defining system behavior, such as relative phase.

  2. Control Parameters:

    • Variables that influence the stability and nature of order parameters, manipulated to assess stability and determine attractor states.

Self-Organization

  • Behavior emerging from constraints: No single constraint dominates how behavior is organized.

Examples of Self-Organization (1)

  • Gait Transitions: A gradual increase in treadmill speed prompts a shift from walking to running.

Examples of Self-Organization (2)

  • Swim Stroke Transitions: Changes in swim velocity lead to distinct arm coordination patterns.

Coordinative Structures (Muscle Synergies)

  • Groups of muscles acting as functional units.

  • These structures adapt through practice or experience.

Perception-Action Coupling (1)

  • Describes the integration of information and actions, where perception informs movement decisions.

Perception-Action Coupling (2)

  • Example: The timing of stepping over an object is determined by visual perception of its approach.

Affordances

  • Defined as possibilities for action based on the interaction between the person and environment.

Current State of Control Theory

  • Both motor program-based and dynamical systems theories are predominant.

  • Motor control must consider CNS movement information as well as task and environmental characteristics.

  • Speculation on a hybrid theory emerging to explain coordinated movement.