Chapter 2
…Measurement
Why measure?
• Without measurement, how can you reliably
assess progress in…
– Learning?
– Recovery?
– …or even assess current performance strengths and
weaknesses?
• Idea behind this bit is to introduce some
assessment methods used in motor learning and
performance
Two measures of performance
• Performance outcome measures
– FG%; QB rating; Time for 40m dash
– Result only – do not indicate movement used to
achieve the result
• Performance production measures
– Joint angle changes, position-time graphs, EMG
traces
– Focus on descriptors of the movement used to
achieve the result
• See table 3.1, p. 24
Performance outcome measures
• Reaction time
– Time from presentation (“onset”) of stimulus
to the start (“initiation”) of the movement
• Initiation refers to observed or measured physical
movement, and is usually particular to the
measurement device
• Example:
– 100m sprint
Performance outcome measures
• Reaction time
Warning
signal
“Go”
signal
Initiation of
response
Termination of
response
Fore period
Time
Reaction time
Movement time
Response time
Performance outcome measures
• Reaction time (RT)
– 1 signal, 1 action: simple RT
– More than 1 signal, more than one action:
choice RT
– More than 1 signal, only one requiring a
response: discrimination RT
Performance outcome measures
• Reaction time (RT)
– Fractionated (with EMG):
• Pre-motor Time: Perceptual & cognitive processes
• Motor Time: Muscle vs. inertia
Performance outcome measures
• Error Scores
– Who is best?
A.
B.
C.
Performance outcome measures
• Error Scores
– Who is best?
• Depends on whether you’re talking about
Accuracy
Bias
Consistency
Performance outcome measures
• Error Scores – 1-dimensional versions
– Accuracy – absolute error (AE)
• Average of positive deviations from the target
Thrower
Throw attempts
So AE = the average length of
these lines
Target line
Performance outcome measures
• Error Scores – 1-dimensional versions
– Bias – constant error (CE)
• Average deviation (+/- both count)
Thrower
So CE = average position – either a “bit” short
or a “bit” long
Throw attempts
Target line
Performance outcome measures
• Error Scores – 1-dimensional versions
– Consistency – variable error (VE)
• Grouping - how close are throws to each other?
Thrower
So VE = clustering
Throw attempts
Target line
Performance outcome measures
• Error Scores – 2-dimensional versions
– Radial error & others
• Same general thing, but computationally more
tricky – similar concepts of bias, consistency, and
accuracy
Accuracy
Bias
Consistency
Performance outcome measures
• Error Scores – continuous skills
– Root-mean-square-error (RMSE)
• Like a longer version of AE
Target line
Path
taken
The RMSE is
roughly the
average
length of all
the vertical
lines
Performance production measures
• Kinematics
3-d
reconstruction
of joint angles
Performance production measures
• Kinematics
Position-time
plot
Performance production measures
•
http://www.usc.edu/dept/LAS/kinesiology/exsc408l/powerpoint/sldaniela/complete/sld001.htm
Performance production measures
•
http://www.usc.edu/dept/LAS/kinesiology/exsc408l/powerpoint/sldaniela/complete/sld001.htm
Velocitytime chart
Performance production measures
•
http://www.usc.edu/dept/LAS/kinesiology/exsc408l/powerpoint/sldaniela/complete/sld001.htm
Angle-angle
diagram
Performance production measures
• Our diagrams – both for a free throw at
basketball
Performance production measures
Elbow
Extension
Knee
1
8
6
3
4
Knee
5
7
2
Flexion
Flexion
Elbow
Extension
Joint angle (radians)
3.5
3
2.5
2
Elbow - FT
Knee - FT
1.5
1
0.5
0
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31
Ball
release
Time
2.9
Knee (radians)
Position-time plot
Finish
2.4
Start
Angle-angle
diagram
1.9
0.5
1
1.5
2
Elbow (radians)
2.5
3
Summing up…
• Go over those last few slides enough
times to allow yourself to “get it”…if you
still don’t, then try mapping out a few
movements yourself, or move on to the
online discussion.
• OK?