Theories of Control

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What do theories of control explain?
How we effectively control various muscles to work effectively and efficiently
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What is motor control an interaction between?
Task, individual and environment
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Who came up with 4 aspects of motor control that all theories must take into account?
Sheridan
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What year did Sheridan develop the 4 aspects of control?
1984
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What 4 approaches try to explain theories of control?
Reflex, hierarchical, dynamical and ecological
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What researchers developed hierarchical theories of control?
Adams (71), Keele (68) and Schmidt (75)
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What researchers developed dynamical theories of control?
Berenstein (67), Kelso (83) and Turvey (77)
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What are the 4 aspects of motor control?
Motor equivalence, uniqueness of action, modifiability of action and stability/consistency of action
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What is motor equivalence?
The motor systems has the ability to achieve functionally the same end result via different movements, using different muscles and joints
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What is uniqueness of action?
Movements are never exactly repeated
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What is modifiability of action?
Action is capable of amendment as a consequence of changing contexts or information to performer
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What is stability/consistency of action?
There is stability and consistency in both the temporal and spatial structure of movement
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What do the 4 aspects of motor control suggest?
They highlight the number of problems the motor system has to overcome
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What is the main idea of the reflex theory?
That reflexes are the fundamental unit of motor control
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What is a reflex?
When a stimulus creates a movement response
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How are reflexes used to generate movement?
They are combined to constitute a movement through reflexive chaining
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Reflex theory fails to explain what 4 things?
Fast sequential actions, novel actions, actions without sensory stimuli, or how one stimulus can result in various responses
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Does reflex theory support Sheridan's 4 aspects of control?
No as it does not explain that movement can change depending on environment
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What is the idea of hierarchical theories?
That all commands originate from highest control centres, and they are responsible for all aspects of movement planning and execution
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Do hierarchical theories take into account feedback?
Yes (especially in Adams closed/open loop theory)
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What does feedback allow?
Communication between units, and therefore they can be controlled and adjusted as necessary
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When did Adams develop the closed and open loop theory?
1971
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How is movement initiated in Adams (71) theory?
Command centre issues command to effectors
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How is movement controlled in Adams (71) theory?
Feedback is responsible for execution and completion of movement
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What is a closed loop system?
When there is feedback to control centres to adjust/monitor movement
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What is an open loop system?
When there is no feedback, the movement is preprogrammed and cannot be adjusted
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When might open systems be used?
In fast ballistic movements, when there is little control e.g. sprint starts
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When might closed systems be used?
During slower movements, to allow for correction and control e.g. penalty shot
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When did Keele develop his motor program theory?
1968
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What is a motor program?
A set of muscle commands that a structured before a movement begins, to be used as a plan of action
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How are motor programs stored?
In the memory
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What is the major issue with Keele's motor program theory?
There must be limited storage capacity, so how to we keep all programs
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When did Schmidt develop the motor program theory further?
1975
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How did Schmidt develop the motor program theory further?
It became the generalised motor program theory
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What is a generalised motor program?
Generalised set of muscle commands that can be used in various and novel environments
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Why is GMP better than motor program theory?
More adaptable to different contexts, while also having fewer storage issues
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What are 3 examples of families of movements?
Locomotion, self help, upper limb function
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What is an issue with Schmidt's GMP?
It still has storage issues, however not as many as Keele's
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When did Bernstein develop his theory?
1967
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What is the idea of Bernstein's theory?
How do we control the multiple degrees of freedom without overloading the system?
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What are degrees of freedom?
Many structures that have to be controlled at any one time, the possible movements of each joint
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What are some examples of degrees of freedom?
Joints, muscles, alpha-gamma linkages, motor units
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What changing contexts and conditions does movement also take place in, which makes it more complicated to control?
Anatomical, mechanical and physiological variability
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How did Bernstein put forward that the number of DOF could be reduced?
By linking elements together
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What year did Kelso develop his theory?
1983
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What is the idea Kelso (83)?
Synergies can reduce the number of DOF
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What is a synergy?
Linking together 2 elements, which means their position is dependant on each other
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What effect does a synergy have on the number of degrees of freedom?
It reduces DOF
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What experiment demonstrates synergies?
Kelso (83) moving hands separately from A to B and C to D, then together only to find out they sync time it takes to move
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In what year did Turvey develop the dynamical theory of control further?
1977
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What idea did Turvey (77) put forward?
Coordinative structures help to control a number of movement variables in a variety of movement contexts
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What is a coordinative structure?
A group of muscles spanning several joints, that are constrained to act as a single functional unit
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What do coordinative structures exhibit?
4 self organising principles
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What are the 4 self organising principles of coordinative structures?
1. Integration, 2. Ability to change level, 3. Not context specific, 4. Self correcting
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How to coordinative structures integrate?
They can combine with others to appear to act in unison as a single unit
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How do coordinative structures change level?
Can change from one organisation to another automatically, like gait
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How is a coordinative structure self correcting?
It will automatically adjust to achieved its final desired state
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How are coordinative structures non-context specific?
They can acquire desired outcome with varied initial conditions
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What is self organisation?
Intrinsic structural patterns that occur spontaneously as they self organise to create specific stable pattern of behaviour due to certain conditions
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What is the idea of the ecological theory of control?
Perception and action coupling
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What is perception and action coupling?
The interaction between perceptual and movement variables that results in specific movement dynamics in accordance with perceptual variables
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What is perception?
The process of obtaining sensory information and making it available for action
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What receives sensory information about movement?
Visual, auditory and proprioreceptors
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How do sensory receptors work together?
They constantly talk and inform each other to help maintain accuracy
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What is proprioception?
Muscles and tendons are filled with mechanical receptors that stretch and compress which tells us about body position and movement in space
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What are 4 examples of proprioception?
Muscle spindles, Golgi tendon, joint receptors, vestibular system
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How do muscle spindles work?
Stretch in receptors increase rate of afferent fibres which sends message to contract and shorten
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What do Golgi tendon organs do?
They are activated by stretch and act as a brake against excessive contractions
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What do joint receptors do?
They give information about joint angles and fire at extreme angles
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What does the vestibular system do?
Monitors angular and linear accelerations of the head, which helps posture/balance and gives stable visual image
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Card 2

Front

What is motor control an interaction between?

Back

Task, individual and environment

Card 3

Front

Who came up with 4 aspects of motor control that all theories must take into account?

Back

Preview of the front of card 3

Card 4

Front

What year did Sheridan develop the 4 aspects of control?

Back

Preview of the front of card 4

Card 5

Front

What 4 approaches try to explain theories of control?

Back

Preview of the front of card 5
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