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Understanding Motor Skills. Introduction Focus: Response mechanism of the human body as the output of information processing “input—mediation—output” Knowledge bases from:. Biomechanics Kinesiology Psychology Neuroscience. Terms to Describe Body Movements. Three Anatomical Planes:

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Understanding Motor Skills

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Understanding Motor Skills

  • Introduction

    • Focus:

    • Response mechanism of the human body as the output of information processing

    • “input—mediation—output”

    • Knowledge bases from:





Terms to Describe Body Movements

  • Three Anatomical Planes:

  • Flexion —

  • Extension —

  • Abduction —

Frontal, Sagittal, Transverse

A movement of a segment of the

body causing a decrease in the

angle of the joint

A movement in the opposite

direction of flexion which causes

an increase in the angle at the joint

A movement of a body segment in the lateral (frontal) plane away from the midline of the body

Terms to Describe Body Movements

  • Adduction —

  • A movement of a body segment

  • toward the midline as when moving

  • the arm from the outward horizontal

  • position downward to the vertical

  • position.

  • Rotation —

  • Circumduction —

A movement of a segment around its

own longitudinal axis

A circular or cone-like movement of a

body segment

Control & Acquisition of Motor Responses

  • Skill - the ability to use the correct muscles with the exact force necessary to perform the desired response with proper sequence and timing (Jensen, Schultz, and Bangerter, 1983)

  • Three Aspects:

  • spatial-temporal precision

  • “doing the right thing at the right time”

  • adaptability to changing

    • environmental conditions

  • consistency of action from occasion to occasion

Types of Responses

  • Discrete Movements —

  • Repetitive Movements —

  • Sequential Movements—

involving a single reaching movement

to a stationary target; may or may not be visually guided

involving a repetition of a single

movement to a stationary target(s)

involving discrete movements to a

number of stationary targets regularly

or irregularly spaced

Types of Responses

  • Continuous movements —

  • Static positioning —

involving movements that require

muscular control adjustments of some

degree during the movement

consisting of maintaining a specific

position of a body member for a period

of time

Sensory Feedback

  • motor responses can be influenced by both internal and external feedback

    • Close-loop servocontrol model

  • feedback — ( high impact )

  • feedforward —

sensory information that is available

during or after the motor response

sensory info that is available prior

to the action that regulates and

triggers coordinated responses

Sensory Feedback

  • Sources of feedback

  • Kinesthesis (proprioception)

  • Receptors:

    • Muscle spindle for muscle length and rate of change

    • Golgi tendon organ for muscle force

  • Vision

  • Sound

Speed of Movements

Total Response



Reaction time

—>the time from onset

of a signal calling for

a response until the

beginning of the



Movement time

—>the time from the

beginning of the response

until its completion

Reaction Time

  • - under ideal conditions, simple reaction time is between 150 - 200 msec

  • Influences on reaction time :

  • stimulus modality

  • stimulus detectability

  • preparedness or expectancy of a signal

  • age

  • spatial frequency

  • stimulus location

Reaction Time

Reaction Time

  • Choice reaction time

    • this is an issue when one of several possible stimuli are presented, each of which requires a different response.

  • Some influences on choice reaction time :

  • compatibility between stimuli and

    • responses

  • practice

  • warning

  • type of movement

  • more than one stimulus

Movement Time

  • Direction of Movement

    • this affects the time to make the movement

    • controlled arm movements that are primarily based on a pivoting of the elbow take less time than those that require a greater degree of upper-arm and shoulder action

  • Distance and Accuracy Required

  • Fitt’s Law

Movement Time

Fitt’s Law

  • Fitt’s Law holds for :

    • movements of the head

    • movements of the feet

    • movements of the fingers

    • and more

MT = a + b log2 (2D/W)

  • where :

  • MT = movement time

  • a,b = empirically derived constants,

    • movement type dependent

  • D = distance of mvmt from start to target center

  • W = width of target

Accuracy of Movements

  • Often accuracy of a response is of greater importance than the response time, within limits

  • —Location

    • close-in, straight-ahead, below- shoulder positions reduce error (Fig. 9-11)

  • —Distance

    • overshooting short distance and undershooting long distance

    • (Fig. 9-12)

  • —Speed of Movement

    • Schmidt’s Law: W = a+b(D/MT)


  • “I saw her friend Jane today”

  • (1) Write the sentence 10 times with your preferred hand

  • (2) Write the sentence holding the pen

    • in your RIGHT HAND

    • in your LEFT HAND

    • in your MOUTH

  • What can you learn from this experiment?

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