The Measurement of Motor Performance Chapter 2 The Measurement of Motor Performance

Measuring Motor Skill Performance Performance outcome measures Category of motor skill performance that indicates the outcome or result of performing a motor skill (i.e., how far did they throw the ball?) Does not tell us about the behavior of the limbs or body that led to the outcome Does not provide information about the activity of various muscles involved

Measuring Motor Skill Performance, cont’d Performance outcome measures Category of motor skill performance that indicates the performance of specific aspects of the motor control system during the performance (i.e., EEG readings) Additional categories do exist, however, these two represent the motor skill performance measures found in the text

Reaction Time Common measure indicating how long it takes a person to prepare and initiate a movement The stimulus or go signal is the indication to act

Reaction Time, cont’d Types of RT situations Simple RT: one signal and one response Choice RT: more than one signal, each signal has a specific response Discrimination RT: more than one signal, only one response

RT Interval Components EMG enables one to fractionate RT Fractionate RT has two components Pre-motor: quiet interval of time between the onset of stimulus and beginning of activity Motor time: period from the increase in muscle activity until the actual limb movement

Pre-Motor and Motor RT Pre-motor RT Motor RT Signal Movement EMG

Use of RT in Research RT has a long history as a measuring tool for human performance It is used as a basis for inferring what a performer does Identifies the environmental context information a person may use while preparing for action Assess the capabilities of a person to anticipate a required action and determine when to initiate it

Relationship of RT to Movement Time and Response Time Warning Signal Go Signal Initiation of response Termination of the response Foreperiod Reaction Time Movement time Response Time

Error Measures Error measures allow us to evaluate performance for skills for which accuracy is the action goal

Assessing Error for One-Dimension Action Goals We can calculate three error measures to assess the general accuracy characteristics of performance over repeated performances Absolute error: absolute difference between the actual performance on each trial and the goal. Provides a general index of accuracy

Assessing Error for One-Dimension Action Goals, cont’d (three error measures, cont’d) Constant error: index of the person’s tendency to be directionally biased when performing the skill Variable error: measures performance consistency by calculating the standard deviation of the CE scores

Assessing Error for Two-Dimension Action Goals When the outcome of performing a skill requires accuracy in the vertical and horizontal directions Radial error measures general accuracy for the two-dimension situation Performance bias and consistency are difficult to assess than the one-dimension

Assessing Errors for Continuous Skills Continuous skills require accuracy Common error score for continuous skills is the Root-mean-Squared error (RMSE) An example of performing this continuous skill is pursuit tracking

Kinematic Measures Kinematics: description of motion without regard to force or mass Includes the following: Displacement (spatial position of a limb or joint over a period of time) Velocity (rate of change in an object position with respect to time) Acceleration (change in velocity during movement) Linear and angular motion (motion in a straight line or motion along the axis of rotation)

Kinetics vs. Kinematics Kinetics refers to the study of the role of force as a cause of motion Kinematics refers to descriptors of motion without concern for the cause of that motion Human movements involve both external and internal sources of force

Kinetics vs. Kinematics, cont’d All three of Newton’s laws of motion refer to force The effect of a force on rotation is known as joint torque (rotary force)

EMG Measures Movement involving electrical activity in the muscles Electrodes detect muscle activity Recordings can indicate when a muscle begins and ends activation

Measuring Coordination Measures complex skills The use of computer-based technology has furthered research involving complex skills

The Measurement of Motor Performance Chapter 2 The Measurement of Motor Performance