Understanding Motor Skills

1
Understanding Motor Skills

• Introduction
• Focus
• Response mechanism of the human body as the
  output of information processing
• inputmediationoutput
• Knowledge bases from

Biomechanics Kinesiology Psychology Neuroscience
2
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
3
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
4
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

5
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
6
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
7
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
8
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

9
Speed of Movements
Total Response Time

Reaction time
gtthe time from onset of a signal calling for a
response until the beginning of the response

Movement time
gtthe time from the beginning of the
response until its completion
10
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

11
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

12
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

Fitts Law
13
Movement Time
Fitts Law
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

• Fitts Law holds for
• movements of the head
• movements of the feet
• movements of the fingers
• and more

14
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
• Schmidts Law W ab(D/MT)

15
Exercise

• 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?