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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
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
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 movements3
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
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
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 responses6
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
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 feedback8
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
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
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 time11
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
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 time13
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
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?