46 terms

KIN 3330 | Motor Learning - Chapter 3

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motor control theory
describes and explains how the nervous system produces coordinated movement during motor skill performance in a variety of environments and conditions

1. coordination
2. control
3. degrees of freedom problem
coordination
process of organizing all physical elements into an efficient movement pattern to achieve a goal
control
manipulation of variables within movement to meet demands of given situation
degrees of freedom (df)
number of independent elements in a system multiplied by the ways each element can act
df problem
how to control the df to make a complex system act in specific way (helicopter)
df problem for control of movement
how does the nervous system control the many df of muscles, limbs, and joints to enable a person to perform an action as intended?

two types of systems
open loop
does not use feedback

control center provides all information for effectors to carry out movement

does not use feedback to continue and terminate movement

- effective, effector, no comparator or feedback, quick, no error detection, no mods during movement
open loop control
higher centers
->
spinal level
->
lower level
->
movement

it's an all or nothing system:
- brain plans all movement in advance and sends this information to spinal cord
- 'go' signal is given to the muscles from the spinal cord
- muscles execute movements as planned
closed loop
uses feedback

control center issues information to effectors sufficient only to initiate movement

relies on feedback to continue and terminate movement
closed loop control
higher centers
<->
spinal level
<->
lower level
<->
movement

(eg. furnace/heather/cooler)
motor program theories
command center in the brain thought to make all decisions regarding movement
dynamic systems theories
a command center could not account for all variations and adjustments in skilled movement

movements results from interaction of body, environment, and skill (experience)
early motor program theories

adam's closed loop theory of motor control




henry's memory drum theory
- memory starts the action which is adjusted during the movement
- fb effects clearly shown in slow and continuous tasks
- error correction and movement modifications well documented

- open loop control emphasis
theory proposals









problems with theories
for each movement, a separate motor program existed and was stored in memory

when a specific action was required, the program was retrieved from memory and executed

storage requirements and production of new movements
what is necessary in motor programs to control movement?
specific muscles to produce action

order of muscle activation

force on various muscle contractions

timing/sequencing

duration of contractions
problems with motor program theory?
storage space

novel tasks are not explained

one solution is generalized motor program
generalized motor program
hypothesized memory based mechanism responsible for adaptive and flexible qualities of human movement

proposed that each GMP controls a class of actions which are identified by common invariant characteristics
schema concept
develops as result of accumulated experiences

directs decision making

each movement attempt gives learner information to guide future attempts
recall schema
responsible for ORGANIZING motor program
recognition schema
responsible for EVALUATING movement attempt
GMP
gmp defines class of actions or movement patterns that can be modified to yield various outcomes
invariant features
relatively fixed

define the motor program itself

some underlying features of a movement remain constant
3 possible features:

1. sequence of actions or components
2. relative timing
3. relative force

(eg. relative time of the components of a skill (eg. % of total time each component uses during performance))
(eg. rhythm of beat)
parameters
more flexible

define the program's execution

some features of a movement are flexible and are easily modified from one performance to the next
4 basic parameters:

1. overall duration
2. overall force
3. movement direction
4. muscle selection

(eg. overall amount of time taken to perform a skill)

(eg. tempo - speed)
cerebral challenge
one technique is to practice when athlete is fatigued
dynamic systems theory
movement patterns emerge, or self organize, as a function of interactions among various constraints:

learner, environment, task
ecological perspective
examples of naturally emergent properties:

snowflakes, crystals, tree canopy, waterflows, change of H2O temp
constraints
all of the factors-limiting/enabling-within the practice environment that influence skill aquisitiona nd performance

types:
individual, environmental, task
self organization
a specific pattern of limb movement emerges from the certain conditions that characterize the situation

this pattern of movement self organizes within the characteristic of environmental conditions and limb dynamics
examples of SO
gait transitions:
person walking on treadmill at slow speed

speed increases gradually

person shifts to running

same effect if person begins running on treadmill - shifts to walk
emergence of movement patterns
a function of a system self organizing and compressing available degrees of freedom into a single unit designed to carry out a specific task

movement pattern is the result of the constraints imposed by a given situation
order parameters (collective variables)
variables that define the overall behavior of the system (similar to invariant features of gmp theory)

enable a coordinated pattern of movement that can be reproduced and distinguished from other patterns

relative phase is the most prominent/observable of order parameters, and represents the movement relationship between 2 or more movement segments
control parameter
when increased/decreased, it will influence stability and charactor of order parameter

important to identify since it can be the variable that manipulates the order parameter

provides basis for determining attractor states for patterns of limb movement
attractor
stable state of the motor control system that leads to behavior according to preferred coordination patterns (e.g. walking)
characteristics of attractor
identified by order parameters

control parameters influence order parameters

minimum trial to trial performance variability

stability - retains present state despite perturbation

energy efficient compared to non-preferred coordination patterns
shallow vs deep attractors
attractors function much like basins (holes, divets) in which observable behaviors pool; their depth is an indication of the stability of the system:
- deep attractor basins: stable systems, difficult to change
- shallow basins: less stable, more susceptible to change
changes in movement behavior
result from series of transitions in system's state of stability

- shallow attractor state: a phase shift can occur abruptly
- deep attractor state: intervention strategies have to cause instability, which leads to an increase in movement variability

with training overtime, any pattern can reorganize, and the new technique will take over, then a phase shift will occur to a new attractor state
coordinated structures
functional synergies of muscles and joints of a person's nervous system which act cooperatively to produce an action

develops through practice, experience, or naturally

can be intrinsic (walking) or developed through practice
perception-action coupling
linking together (coupling) of information/movements
perception
detection and utilization of critical info for the control of action
action
various movements that are regulated by perceived info
example
when walking, time to contact object in pathway determines when you initiate stepping over the object

your action is coupled with your visual perception of object
non-linear pedagoy and constraints-led approach
...
non-linear pedagogy
learner searches through a range of potential movement solutions for the optimum strategy

perceptual-motor workspace
constraints-led approach
purposeful manipulation of key constraints in an effort to acquire movement skills and decision making behaviors

hands off practitioner
practical implications
strategies for creating effective learning environments are limited only by the practitioner's imagination

emphasize game and context-related skills

encourage learners to:
- hone decision making skills
- develop functional movement patterns
- adapt movement behaviors to meet task requirements
present state of control theory issue
motor program based theory and dynamic pattern theory are the predominant behavioral theories addressing how nervous system produces coordinated movement

theory of control cannot focus exclusively on movement info that is specified by CNS

task/environmental characteristics must be taken into account

speculation of hybrid on a compromise theory could emerge, to explain the control of coordinated movement