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
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

3
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
4
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
5
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
6
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

7
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
8
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

9
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
10
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

11
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)