Motor Control Theory – ESPS 3002 Lecture 1
Overview of the Session
First content lecture for ESPS 3002 – Human Motor Learning & Performance.
Presenter: Dr. Rachel Ward (unit convener; delivers lectures + practical classes).
Primary focus: Motor Control Theory – what theories are, why they matter, and an introduction to the two dominant theoretical families.
Lecture aligns with Unit Learning Outcome 4: “Explain the common theoretical models used to explain motor control, motor learning & skill acquisition.”
Scientific Theory in the Research Process
Definition: A scientific theory unifies many related observations into a single coherent framework and is repeatedly confirmed by experiment/observation.
Must describe a large number of observations with only a few core propositions.
Must predict future outcomes/events.
Theory vs. Law:
Theory ⇒ explains why something happens (causal mechanism).
Law ⇒ describes what happens (empirical regularity).
Example used later: Fitts’ Law (descriptive) vs. theoretical accounts that explain why the speed–accuracy trade-off emerges.
Why Motor Control Theory Matters to Exercise & Sport Science Practitioners
Clarifies why humans behave/move the way they do, how skills are learned, and how control is exerted.
Functions for practitioners:
Identify performance problems.
Design interventions to solve those problems.
Predict effectiveness of chosen interventions.
Systematically enhance performance capabilities.
Invent new motor-skill strategies.
Evaluate effectiveness → close the practitioner “feedback loop.”
Ultimately guides evidence-based coaching, rehab, PE, and skill-acquisition programs.
Two Core Behavioural Questions Motor Control Theories Must Answer
Coordination
Definition: “Patterning of head, body, and limb movements relative to environmental objects & events.”
Two nested relationships:
Inter-segmental: arrangement of body parts relative to each other at a given time.
Task/Environment coupling: movement of the performer relative to objects, surfaces, opponents, implements, etc.
Theory must account for how such patterns emerge and are regulated across contexts.
Degrees of Freedom (DoF) Problem
Coined by Nikolai Bernstein.
System contains many independent components (≈ 600 muscles, ≈ 360 joints, multi-level neural elements).
DoF for a single joint = number of independent movement planes it permits (e.g., shoulder ≈ 3, finger IP joint ≈ 1).
Core challenge: How does the CNS reduce or exploit these DoF to achieve a stable, goal-directed movement?
“Solution” = constraining or coordinatively structuring DoF so that effective, efficient movement emerges.
Control System Typology: Open-Loop vs. Closed-Loop
Open-Loop Control
One-way information flow: Control Center → Movement Effectors; no feedback utilized during the execution.
Ideal for:
Very fast, discrete, ballistic skills (e.g., golf drive, throw, kick).
Situations requiring minimal attentional load once initiated.
Limitations:
Poor for unpractised or unpredictable environments.
Accuracy suffers when the performer is not highly trained (no online corrections possible).
Closed-Loop Control
Circular flow: Control Center → Effectors → Feedback → Control Center … (loop continuously updates command).
Advantages:
Suitable for unpractised, slow, or precision tasks (e.g., tracing a line, balancing, aiming archery shot).
Allows ongoing error‐correction; higher ultimate accuracy.
Disadvantages:
Greater attentional demand; slower overall due to processing time of feedback.
Continuum Concept: Skills sit between the poles depending on speed requirement & necessity for online sensory feedback.
Comparative Table (Advantages/Disadvantages)
Summarised in lecture slide; key points captured above.
Speed–Accuracy Trade-Off & Fitts’ Law
Everyday observation: increasing speed usually ↓ accuracy and vice-versa.
Formalised by Paul Fitts (1954). Classic reciprocal-tapping task:
Two targets separated by distance A (amplitude) with width W.
Index of Difficulty: ID = \log_2!\left(\dfrac{2A}{W}\right).
Movement Time: MT = a + b \times ID (constants a & b empirically fitted).
Practical tie-in: Lab class will replicate this tapping paradigm; students observe open- vs. closed-loop tendencies as target conditions change.
Two Major 20ᵗʰ/21ˢᵗ-Century Motor Control Theories
1. Motor Program-Based (Hierarchical) Theory
Assumes pre-structured commands (motor programs) stored in CNS.
Hierarchical organisation: higher centers issue generalized programs, lower centers handle execution specifics.
Cognitive, top-down orientation.
Strengths:
Explains rapid movements where feedback is too slow.
Accounts for invariance across different effectors (e.g., writing signature with hand or foot).
Challenges:
Storage problem (infinite programs?).
Novelty problem (how generate never-before-executed movement?).
2. Dynamical Systems (Ecological / Self-Organising) Theory
Movement patterns emerge from real-time interaction among:
Individual (intrinsic dynamics, morphology, fatigue state…)
Task (goal, rules, implements…)
Environment (surface, temperature, obstacles, social context…)
No single executive; control is distributed and emergent.
Key constructs: attractors, phase transitions, stability, self-organisation.
Strengths:
Naturally solves DoF via self-organisation.
Explains sudden “aha!” transitions in skill acquisition.
Challenges:
Hard to specify neural implementation explicitly.
Predictive precision sometimes lower without quantitative models.
Ethical, Philosophical & Practical Implications
Understanding control models guides safe & effective coaching (avoid overload, unnecessary constraints).
Shapes rehab protocols: e.g., closed-loop emphasised early post-injury for safe precision, then transition to open-loop speed work.
Affects human–machine interface design (wearables, exoskeletons, VR rehab systems): must respect speed–accuracy trade-offs and DoF constraints.
Highlights ethical duty to provide evidence-based interventions rather than intuition-only coaching.
Connections to Previous/Foundation Units
Functional Anatomy: joint DoF count, muscle lines of action underpin movement possibilities.
Neuroscience / Motor Physiology: motor unit recruitment & feedback pathways underpin theoretical constructs.
Biomechanics: kinematic chains & constraints directly relate to coordination patterns.
Example Scenarios (Elaborated from Lecture)
Throwing a javelin (high-speed, ballistic): predominantly open-loop; training builds internal motor program.
Archery aiming: closed-loop utilisation of visual & proprioceptive feedback for micro-corrections.
Novice vs. expert typist: novice relies on closed-loop (looking at keys), expert shifts to open-loop feed-forward control.
Lecture-End Summary (Consolidated)
Motor control theories explain why and how people produce skilled movement.
Two essential behavioural constructs: coordination & degrees of freedom problem.
Two foundational control systems: open-loop (no feedback) vs. closed-loop (feedback-based).
Fitts’ Law quantifies speed–accuracy trade-off; illustrates role of feedback demands.
Two dominant theoretical families:
Motor Program-Based (hierarchical, top-down).
Dynamical Systems (self-organising, interaction-driven).
Mastery of these ideas enables practitioners to diagnose, intervene, predict, and evaluate motor-skill performance.
Next steps: Future lectures will deep-dive into motor program hierarchy (e.g., GMP, invariant features, parameters) and dynamical principles (attractors, order parameters, control parameters). Practical classes will experimentally test Fitts’ Law and explore open- vs. closed-loop dominance in selected tasks.