The measurement of motor performance PDF

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Lecture 2: The Measurement of Motor Performance Part 1: The Measuring of Motor Performance Serving a Tennis Ball -

Potential measurements? o Count the # of serves inside vs. outside the court o Speed of the ball o Proper form?

Relearning How to Walk After a Stroke -

Potential measurements? o Count the # of steps o The distance the patient can walk unassisted o Posture & balance assessment  measure balance using force plate o Gait analysis

Performance Measurements Are Essential for: -

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Performance assessment o Overall evaluation of capabilities & limitations o Determinant of progress o Inferring areas disability/dysfunction Motor learning & control research o Quantitative analysis of movements o Studying basis of human motor control Need a value to compare Look at goal as a marker to improve/recognize improvement  gentiles taxonomy Motivated or not etc.

The Measurements of motor Performance -

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There are a variety of ways to measure motor skill performance Can categorize using different levels of analysis o Actions, movements, & neuromotor processes  Neuromotor process action potentials created in brain & which way it fired to achieve that task 2 categories of measurements: 1) Performance outcome measures 2) Performance production measures

Performance Outcome Measures

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Indicates the outcome or result of performing a motor skill o Ex. Distance ball thrown, slap shot speed, batting average, marathon time, running speed o Concerned w/ accomplishment of task However… o Does not indicate the specific movements used to accomplish goal o Does not provide info about the activity of various muscles involved (neuromotor processes) Get a score based on how well they performed the overall task/outcome Rehab  based on outcome of movement accomplished Downside  gives value to compare to individual people doesn’t give idea of movements person did to complete task or neuromotor process used to achieve that goal

Performance Production Measures -

Measurements that relate to the performance characteristics which produced the outcome Describes the different movements used to achieve task goal Indicates the activity of specific aspects of the motor control system during performance (neuromotor processes) Looks specifically at movement involved in doing task or neuromotor process Look at how person produces a motor skill

Part 2: Performance Outcome Measures Performance Outcome Measures -

Reaction time o Common measure indicating how long it takes a person to prepare & initiate a movement o Measured as the interval of time b/w onset of a signal (stimulus) & the initiation of movement o Most common to use o Go signal eg. sprinter in a race, swimmer  delay b/w go signal & time to move, more someone has to process = longer rxn time which can alter characteristics of person, environment & task o Brian has to process more before initiating a movement if change in environment o CLINICAL: What is the minimum reaction time allowed for a legal start the 100m sprint?  A reaction time less than 100ms (0.1s) is illegal  Has led to multiple rule changes over the time

Reaction Time (RT) -

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RT has a long history as an “index” of specific aspects of human performance o Has been used extensively in motor control research RT is used to: o Infer what a performer does to prepare an action o Identify the environmental context info a person uses to prepare an action o Assess the capabilities of a person to anticipate a required action & determine when to initiate it Regulatory  affect way things move Non-regulatory  affect conditions in the environment but not the way things move eg. changing the colour of volleyball (still serve the same way), change a light Types of RT situations 1) Simple RT: involves on 1 signal & requires only 1 response  Sprinter starting a race  1 movement/rxn related to the stimulus 2) Choice RT: involves more than 1 signal & each signal requires its own specified response  Traffic light at intersection  Each stimulus/choice requires different response  based on # of choices, the rxn time increases 3) Discrimination RT: involves more than 1 signal; but only 1 signal requires a response  The other signals do not require a response  Multiple signals but only response, increases rxn time

RT interval components o EMG enables researchers to fractionate RT to obtain more specific info  Allows study of action preparation o 2 component parts:

1. Pre-motor time – quiet interval b/w the onset of stimulus & beginning of activity  Represents CNS processing & transmission 2. Motor time – interval from the initial increase in muscle activity until the actual limb movement  Small lag time from onset of motor time (EMG) to actual muscle contraction and movement Fractionated RT -

Premotor  happens in brain Motor  time takes AP to run through & contract More accurate measurement of rxn time

Reaction Time -

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Movement time (MT): interval of time b/w the initiation of movement & completion of an action o Dependent on the task (no typical MT) o How fast the movement/how long took to perform a movement Response time: interval of time b/w the stimulus & the completion of the specific task o RT + MT The speed/accuracy tradeoff: o Responding or moving very fast can (usually) result in increased errors o Precise movement  move slower o Faster move = less accurate Event of time intervals of RT & MT

Performance Outcome Measures -

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Error measures o Error measures allow us to evaluate performance for skills that have spatial or temporal accuracy action goals o Certain error measures can also infer performance problems  When evaluating a series of repetitions researchers can assess bias & consistency  Less error = performed better  More error = performed worse 3 mains outcome error measures: 1) Absolute error – absolute value of difference b/w the actual performance on each trial & the criterion for each trial  AE = ∑|(performance – criterion)| / no. of trials  Provides a general index of performance accuracy  AE  rhythm , take absolute errors (not positive or negative) with how much error there was in achieving a skill, everything is positive (looking at magnitude of the error) 2) Constant error – index of tendency to be directionally biased when performing skill  CE = ∑(performance – criterion) / no. of trials  Provides an index of performance bias  Tendency to overshoot or undershoot goal  CE  positive or negative (either overshoot or undershoot rhythm task) eg. caffeine causes undershoot b/c moving too quickly 3) Variable error – the standard deviation of the CE scores  Provides an index of performance consistency or variability  Variable  standard deviation of error when achieving a task, mean or median, allows to understand if person is being consistent Error for two-dimension accuracy goals 1) Radial error – general 2D accuracy measure  AE calculation using hypotenuse  Performance bias & consistency more difficult to assess

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Can obtain a qualitative assessment of bias & consistency o How would you assess the performance of the following 2 golf putt examples? o Golfer A  variable/inconsistent, if averaged it may be in the middle o Golfer B  biased to the right, motor control is good b/c consistent Assessing errors for continuous skills o Many continuous skills require accuracy over a period of time  Driving a car on a highway o Root-mean squared error: common accuracy measure used in research to evaluate continuous skills  AE for continuous skills  Amount of area not in contact w/ the target  Add up amount of time/distance that person was away from the target  root mean square/error

Part 3: Performance Production Measures

Performance Production Measures -

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Remember: production measures are used to describe the specific movements & neuromotor processes utilized in motor skill performance Examples: o Kinematics  Displacement, velocity, & acceleration o Kinetics  Force & moments o Neural measures  EMG & brain activity measures (brain & muscle) Not looking at the outcome

Kinematic Measures -

Kinematics o Describes motion w/o regard to force or mass which produced the movement o Involves motion analysis  Research has developed numerous technologies to assess kinematics  Eg. photography, goniometers, accelerometers, mechanical systems, magnetic systems, optoelectric devices o Motion cameras: digital (passive)  problem b/c too many markers , computer gets confused o Optotrak (active)  no real markers, motion = 1 light going on at once, more expensive & accurate o Displacement  Change in position of a limb or joint over time o Velocity  Rate of change of displacement (i.e. speed)  V= displacement/time o Acceleration  Rate of change of velocity  A = velocity/time

Co-ordination: Angle-angle Diagrams -

Measuring coordination o Assess how one limb/joint moves relative to another o Quantitative measurement of angle-angle diagrams  Cross-correlation technique  Relative phase

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Angle – angel diagram o Look at one angle for a long period of time, how closely related to expert one

Kinetic Measures -

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Kinetics: is the study of forces as a cause of motion Human movements organized by external & internal forces Use of biomechanics o angular & linear forces o kinetic values can be calculated using kinematic measures Studies involve use of force plates, forces transducers & strain gauges

Part 4: Neural Measures -

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Neural measures: o Indicate how the brain & CNS are involved in planning & executing movements o Analyze electrical activity (in brain or nerves of the muscles) Examples: o Muscle activity measures o Brain activity measures

The Motor Unit -

Measured by using electrodes

Muscle Activity Measures a) Electromyography (EMG): recording of muscle electrical activity o Common use is to determine when a muscle begins & ends activation o Indicates degree of activation of muscles being studied

o Used in fractionated RT o More reading = more muscle is contracting b) Whole Muscle Mechanomyography (wMMG): displacement of muscle belly after stimulation o Potential to estimate muscle fibre composition o How much muscle belly moves c) Near Infrared Spectroscopy (NIRS): level of oxygenation in the muscle (or brain) o Portable o Can be used to measure cerebral cortex - Study o Gripping and contraction of rotator cuff muscles Brain Activity Measures -

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Brain activity measures: now more widely used by motor control & learning researchers to investigate the relationship b/w brain activity & the performance of motor skills a) Electroencephalography (EEG): measures electrical activity in brain  Active brain regions produce electrical activity  Can only measure top layer/surface of the skull, need to know the whole brain b) Transcranial magnetic stimulation (TMS): method of assessing brain activity by exciting or inhibiting activity of the cortex  Assess motor skills performance to infer function of brain regions  Uses wand to affect part of the brain, doesn’t record anything Brain scanning techniques a) Positron Emission Topography (PET): Neuroimaging technique that measures blood flow in the brain (flow increases in active regions)  Marker on blood (how much blood in which areas & how flow changes when doing a task  Same as fMRI b) Functional Magnetic Resonance Imaging (fMRI): Neuroimaging technique that measures blood oxygenation levels  Looks at oxygenation levels (blood flow in the brain – one part being utilized more) c) Magnetoencephalography (MEG): Measures magnetic fields created by neuronal activity  Directly measures activity NOT metabolism  Looks at magnetic field in all the brain, register all electrical potentials of every neurone in the brain

Part 5: Motor Abilities

Ability & Motor Ability -

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Ability o General gait or capacity of a person o Relatively enduring characteristic o A determinant of a person’s achievement potential for the performance of specific skills Motor ability o An ability that is specifically related to the performance of a motor skill o Each person has a variety of motor abilities

Abilities as Individual Difference Variables -

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Motor abilities establish achievement potential for specific motor skills o Each motor skill requires specific motor abilities to successfully perform it o Given identical practice, instruction, & motivation; motor abilities will influence the level of performance success an individual can achieve Two hypotheses o General motor ability hypothesis – motor abilities are highly related to each other o Specificity of motor ability hypothesis – motor abilities are relatively independent in an individual

Controversy About Relationship Among Motor Abilities -

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General motor ability hypothesis o All motor abilities are highly related to each other o A person can be described as having an overall amount of general motor ability Specificity of motor abilities hypothesis o All motor abilities are relatively independent o Each person varies in the amount of each ability o A person’s motor ability can be described only by a profile of amounts of each specific motor ability

Abilities as Individual Differences Variables -

Research evidence supports SPECIFICITY HYPOTHESIS o Consistent correlations could not be found b/w motor abilities  Initial research compared rxn time & movement time o Recent research investigated whether variations of a motor ability represents one ability 1. Balance (postural stability) as a motor ability  2 types – static & dynamic

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Rose et al. (2002): Children with CP showed balance problems while walking but not while standing  Static and dynamic balance are distinct independent abilities 2. Timing as a motor ability  2 types – External vs. Internal timing  External – movement based on external source (hitting a baseball)  Internal – timing based on individual’s internal representation of timing (dancer keeping rhythm and tempo)  Research also demonstrated distinct timing abilities that are skill specific Identifying Motor Abilities -

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Fleishman’s Taxonomy of Motor Abilities o Describes 2 broad categories of motor abilities 1. Perceptual motor abilities 2. Physical proficiency abilities o Indicated people differ in amount of each ability o Goal was to define the “fewest independent ability categories in describing performance in a wide variety of tasks” CLINICAL: tests for motor abilities can be used for: o The prediction of future performance of a motor skill or activity o Evaluation & assessment of the effectiveness of an intervention program (rehab & occupational therapy settings)...