Transcript Understanding Motor Skills

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:
Biomechanics
Kinesiology
Psychology
Neuroscience
Understanding Motor Skills
Terms to Describe Body
Movements
Three Anatomical Planes:
Frontal, Sagittal, Transverse
Flexion —
A movement of a segment of the
body causing a decrease in the
angle of the joint
Extension —
A movement in the opposite
direction of flexion which causes
an increase in the angle at the joint
Abduction —
A movement of a body segment
in the lateral (frontal) plane away
from the midline of the body
Understanding Motor Skills
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 —
A movement of a segment around its
own longitudinal axis
Circumduction —
A circular or cone-like movement of a
body segment
Understanding Motor Skills
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
Understanding Motor Skills
Types of Responses
Discrete Movements —
involving a single reaching movement
to a stationary target; may or may not
be visually guided
Repetitive Movements —
involving a repetition of a single
movement to a stationary target(s)
Sequential Movements—
involving discrete movements to a
number of stationary targets regularly
or irregularly spaced
Understanding Motor Skills
Types of Responses
Continuous movements —
involving movements that require
muscular control adjustments of some
degree during the movement
Static positioning —
consisting of maintaining a specific
position of a body member for a period
of time
Understanding Motor Skills
Sensory Feedback
motor responses can be
influenced by both internal
and external feedback
Close-loop servocontrol model
feedback — ( high impact )
sensory information that is available
during or after the motor response
feedforward —
sensory info that is available prior
to the action that regulates and
triggers coordinated responses
Understanding Motor Skills
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
Understanding Motor Skills
Speed of Movements
Total Response
Time
=
Reaction time
—>the time from onset
of a signal calling for
a response until the
beginning of the
response
+
Movement time
—>the time from the
beginning of the response
until its completion
Understanding Motor Skills
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
Understanding Motor Skills
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
Understanding Motor Skills
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
Understanding Motor Skills
Movement Time
Fitt’s 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
Fitt’s Law holds for :
movements of the head
movements of the feet
movements of the fingers
and more
Understanding Motor Skills
Accuracy of
Movements
Often accuracy of a response is
of greater importance than the
response time, within limits
—Location
close-in, straight-ahead, belowshoulder 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)
Understanding Motor Skills
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?