Advances in Physical Education
2012. Vol.2, No.3, 77-81
Published Online August 2012 in SciRes (
Copyright © 2012 SciRes. 77
Reliability and Sex Differences in a Coordination Test of a
Tracking Moving Target with the Center of Foot Pressure
Haruka Kawab at a1*, Shinichi Demura1, Masanobui Uchiyama2
1Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
2Akita Prefectural University, Akita, Japan
Email: *
Received April 30th, 2012; re vised Ma y 28th, 2012; accepted June 7th, 2012
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Keywords: Center of Pressure; Coordination; Tracking Test; Reliability; Sex Differences
Coordination is the ability to accurately accomplish physical
activity in a timely way, and is closely related to nerve function.
It is generally considered to consist of elements such as elabo-
ration, dexterity, accuracy, skill, and agility (Ferslew et al., 1982).
It is necessary to coordinate the exertion of muscle strength to
perform movements efficiently.
Coordina ti on Test
Upper limb movements such as using chopsticks and writing
require coordination. Hence, coordination tests such as the Pur-
due Pegboard test (Buddenberg & Davis, 2000) and the Moving
Beans with Tweezers test (Shigematsu et al., 2001) have been
developed (Ferslew et al., 1982; Noguchi et al., 2006; Nakafuji
& Tsuji, 2001). Nagasawa et al. (2002) developed a controlled
force exertion (CFE) test pursuing the changing demand values,
appearing as sinusoidal and quasi-random waveforms on a per-
sonal computer, by grip strength exertion. These tests evaluate
mainly upper limb coordination. However, since daily life and
sports activities are generally performed standing upright, they
require the coordination of the whole body. Visual, somatosen-
sory, and sensory motor system functions contribute to efficiently
perform movements. Moreover, in movements involving the
whole body, many skeletal muscles are needed to maintain
posture balance. However, not many tests have been developed
that rationally evaluate co o rdination of the whole body.
Recently, it has become possible to record the center of foot
pressure (COP), which is projected at the body center of gravity
on the plantar surface. As a result of the central nervous system
(CNS) receiving feedback from visual, vestibular, and somatic
sensations, the COP during standing always sways slightly. The
total length and area of body sway have been widely used an
index of balance function disorder and static balance ability.
According to previous studies on COP sway (Ekdahi et al.,
1982; Goldie, 1989; Hattori et al., 1992; Dickstein et al., 1993;
Yamaji et al., 2001), the reliability of the COP parameters dur-
ing standing is high. Recently, a balance measurement devive
has been developed that can follow a randomly moving target
by voluntary changes in COP. It is assumed that well-per-
forming individuals who can coordinate their entire body can
also meet their COP to a moving target on the above device. In
short, this device can evaluate the coordination of the whole
body. Yoshida et al. (1997) developed the test that tracks a
moving target by COP. However, in their test the target moves
linearly (back and forth, left and right) and constantly, the sub-
jects can predict the target’s movements. A test involving an
unpredictably moving target will be able to more accurately
evaluate the coordination of the whole body.
Reliability of the New Test and Sex Difference
On the other hand, when developing a new test, it is neces-
sary to establish the measurement method and to determine
appropriate evaluation parameters. In addition, it is essential to
examine the reliability of the parameters. The practice effect is
often found in coordination tests and performances improve
with every trial (Noguchi et al., 2009). Hence, the practice ef-
fect may also be found in a coordination test involving the
whole body tracking a moving target by the COP. In additional,
Nagasawa et al. (2002) clarified that males perform better than
females in the controlled force exertion (CFE) test for both
hands. Hence, they (Nagasawa et al., 2009: Nagasawa et al.,
2010) determined the standards of the CFE test according to sex.
The existence of standards is one important condition of a good
test. If sexual differences are found in the test, it is necessary to
make up a different standard according to each sex. Hence, it
also is important to examine whether a sex difference is found
in advance.
During movements using whole body, it is required to coop-
eratively exert many skeletal muscles of the whole body to keep
posture balance. However, tests that rationally evaluate coordi-
nation of the whole body have little been developed. Recently,
a balance measurement device, which can pursue voluntary the
randomly moving targets by the COP, has developed. It is as-
sumed that superior persons in coordination of whole body can
meet right the COP to a moving target on the above device. In
short, it is considered to be possible to evaluate coordination of
the whole body by a test using the above device.
*Corresponding author. However, a size of rel iability in this te st which is one import a nt
condition of the test is unclear. Hence, this study aimed to ex-
amine reliability and sex difference of the new coordination test
pursuing the randomly moving target by the COP.
The subjects were 30 healthy people consisting of 15 males
(age 23.9 ± 4.7 yrs, height 171.5 ± 4.0 cm, weight 66.9 ± 8.1 kg)
and 15 females (age 20.7 ± 3.1 yrs, height 161.1 ± 5.5 cm, weight
54.6 ± 5.3 kg). No participant reported previous leg injuries or
nerve disorder of lower limbs. Prior to measurement, the pur-
poses and procedures of this study were explained in detail, and
written informed consent was obtained from all subjects. The
protocol of this study was approved by the Kanazawa Univer-
sity Department of Education Ethical Review B oard.
Test of Whole Body Coordination by Tracking a
Moving Target with COP
In the motor task of pursuing the randomly moving target
with the COP, various nervous controls were needed by the
subjects. First, after the motor area and the cerebellum deter-
mined the tactics that make the COP track a moving visual
target, they transfer the commands coordinating the contracture
of muscles of each part of the body through spinal cord and
alpha motor neurons, and determine speed, duration, and accu-
racy of the motion (Hanatsch & Langer, 1985). Body balance is
maintained by the involuntary postural control derived from the
brain stem, in addition to the above stated voluntary control. In
short, since tracking by the COP is performed coordinately by
voluntary movements of the whole body and involuntary move-
ments that maintain balance, it was assumed that whole body
coordination can be evaluated by the tracking task. Hence, it is
judged that subjects with a smaller tracking error between their
COP and the moving target are able to better match their COP
to a moving target. In this study, subjects with a smaller total-
error, within a certain time, were assumed to have superior
coordination of the whole body.
Experiment Equipment
The measuring device used in this study was G-620 (Anima
Corp., Japan). It consists of the force platform containing three
sensors for the vertical load, an amplifier, and feedback display
(size: 15.6 inch; resolutions: 1366 × 768). By using this device,
subjects receive visual feedback information regarding their C O P
position through the device’s monitor. Thus, they can track the
randomly moving visual target on the monitor and compare it
to their COP. In addition, since it can record the subject’s COP
position during standing on the force platform over time, the
errors between the moving target and the subject’s COP can be
Experimental Condition
In this study, COP position was recorded for one minute with
sampling frequency 20 Hz (Demura et al., 2008) in each trial.
The monitor for the visual feedback was placed at 1.5 m. in
front of the subject and at eye level. The moving target ran-
domly moved within a range of 10 cm. from the coordinate ori-
gin on an x-y plane of the visual feedback monitor. The target
positions in the y and x directions were programmed to fluctu-
ate along with the substantially sinusoidal waveform (period:
12 ± 5 sec; amplitude: 5 ± 5 cm).
Test and Test Procedure
The subjects stood on the platform bare-footed, with their
arms held comfortably at the side of the body and their eyes
open (Figure 1). The randomly (by period and amplitude) mov-
ing target and the subject’s COP position were shown on the
feedback monitor in front of them. Then, they were instructed
to track the moving target with their COP (Figure 2). After one
practice trial, subjects carried out five trials with a break of one
minute between each trial. To exclude the influence of meas-
urement errors immediately after the first and the final phases,
COP data obtained from the first 20 sec. and the last 10 sec.
were omitted, in accordance with previous studies on CFE (Na-
gasawa et al., 2002; Riviere & Thakor, 1996). In short, data from
30 seconds were used as an evaluation parameter.
Statistical Analysis
A two-way analysis of variance (ANOVA) was used to test
mean differences of trial and sex factors. Mean differences a mo ng
trials was tested by one-way analysis of variance. Intra class
correlation coefficient was calculated to examine reliability of
the test. The level of significance was set a priori to .05.
Table 1 shows the means and standard deviations of five tri-
als according to sex. A result of two-way ANOVA showed in-
significance in main effect of trial and sex factors. The whole
mean of 5 trials was 1444.0 ± 277.6 in males and 1481.6 ±
313.2 in females, and significant sex difference was not found.
Figure 3 shows the means, standard deviations, one-way
ANOVA, and ICC of all five trials and of the first three trials
based on data pooled of males and females. The mean of five
trials showed insignificant difference, and the ICC of the above
trials was 0.68 and 0.75, being somewhat higher in the latter.
Table 2 shows the means of three trials after excluding maxi-
Figure 1.
Posture of the subject during the test.
Copyright © 2012 SciRes.
Figure 2.
Screen during the test and t e s t results.
Table 1.
The errors between moving target and COP.
Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 1-5 Trials ANOVA
Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Max Min F p ICC
Male (n = 15 ) 1487.2 265.4 1413.3267.5 1476.3 328.51396.0276.21447.4250.41444.0277.61723.0 1239.5 0.68 0.610.66
Female (n = 15) 1518.0 331.1 1493.5299.7 1472.4 271.81457.3281.91467.0381.41481.6313.21952.5 1313.8 0.30 0.880.71
Note: *p < .05, Mean (cm), SD: Standard Deviation, ICC: Intraclass correlation coeffic ient.
mum and minimum values among the five trials. An insignifi-
cant mean difference among trials was found and the ICC was
0.86, being somewhat higher than the above two ICCs.
Sex Difference
This study examined sex difference and reliability of a novel
whole-body coordination test where the COP is used to follow
a randomly moving target. Nagasawa et al. (2000) examined a
sex difference in controlled force exertion (CFE) of mid-
dle-aged and elderly subjects, and reported that the males per-
formed better than the females. Kawabata et al. (2011) reported
that in the pursuit rotor test, young men performed significantly
better than young women. York & Biederman (1990) reported
that males performed better in tests that require dexterity of the
hands and fingers. On the other hand, Haward and Griffin (2002)
reported that a significant sex difference was found in the ma xi-
mum grip strength test, but not in the Purdue Pegboard test.
In the CFE test, subjects pursue the target presented on the
computer screen by grip strength exertion. In a pursuit rotor test,
they track the rotating target with a metalrod (Ferslew et al.,
1982; Nakafuji & Tsuji, 2001). These tests evaluate the accu-
racy of grip and manipulation of upper limb movements that are
frequently used in daily life, and they generally show functional
lateral dominancy (Chi & Dooling, 1977; Touwen, 1972; Nogu-
chi et al., 2009; Kawabata et al., 2011). In the cases of the above
tests, exercise experience in the past and use frequency in the
present life environment may largely affect measurements.
A sex difference was not found in the tracking test by the
COP used in this study. If strength and agility (speed) relate
largely to the test motion, a sex difference could have been
found since males are generally superior in these abilities. The
novel test presented here is performed in a standing position,
and since the task involved both legs, burden imposes on both
legs almost evenly. From the test content, a large exertion of
strength and agility is not required. Hence, it is inferred that a
sex difference was not found.
Reliability between Trials
Since a sex difference was not found, reliability was exam-
ined by using pooled data of males and females. A practice
effect is generally found in coordination tests (Noguchi et al.,
2009), but an insignificant difference was found among means
of five trials. A possible explanation is that the present coordi-
nation test is performed in static standing posture and does not
require special techniques. In addition, stable data for 30 sec-
onds excluding data of the first 20 seconds and the last 10 sec-
onds (see Methods) was used for statistical analysis. For a stan-
dard of reliability, ICC over 0.60 by Landis and Koch, (1997)
and .70 by Portney & Watkins (1983) have been reported and
widely accepted. Hence, reliability of the present test is consid-
ered to be guaranteed in both the five trials (.68) and first three
trials (.75). However, the latter ICC was somewhat higher. When
performing the task of pursuing the moving target with COP for
one minute, subjects need considerable tension, responsiveness
and concentration. In addition, it takes about 10 minutes to
perform the five trials, including the instructions and one prac-
tice trial. Hence, even if subjects had enough rest between trials,
it is inferred that the stability of measurements in the latter
trials decreased due to concentration loss and fatigue. From the
present results, when considering practical application, it may
be appropriate to administer three trials and use that mea n a s ar e
presentative of value.
On the other hand, in the whole body reacti on time te st, there
are cases when subjects respond predictively before the signal,
or their reaction is delayed abnormally due to missing the signal
or the response timing. In short, it is possible that abnormal
values are measured accidentally. When using these abnormal
values as measured values, means and standard deviations are
greatly affected. Considering this problem, a mean excluding
the maximum and minimum values after performing five or
seven trials is generally used during the whole body reaction
time test. Nagasawa and Demura (2004) reported that the mean
Copyright © 2012 SciRes. 79
Figure 3.
Posture of the subjec t d u ring the test.
Table 2.
The means of 3 trials excluding maxim um and minimum values 5 trial s .
1 2 3 3 Trials ANOVA
Mean SD Mean SD Mean SD Mean SD F p ICC
1479.4 291.7 1444.0 282.6 1419.7 252.6 1447.7 275.6 2.77 0.07 0.86 0.07
after excluding maximum and minimum values among seven
trials was high in the pursuit rotor test. The ICC (.86) of three
trials calculated in this study based on the above exclusion
practice was higher than the other ICCs. This method may also
be effective in ensuring high reliability. Previous studies on the
pursuing test using the COP (Yoshida et al., 1997; Yamamoto
et al., 1997; Hamann et al., 1990) evaluate the ability to follow
a linearly and constantly moving target along longitudinal and
lateral directions. In that test, subjects can predict target move-
ments and adjust easily. In order to adequately evaluate whole
body coordination ability, pursuing a randomly moving target
as used in this study is considered to be valid.
In conclusion, this test of whole body coordination shows in-
significant sex difference and has high reliability. From a per-
spective of practicality, it may be useful to use the mean of the
three trials as an evaluation parameter after one practice trial.
When prioritizing high reliability, it will be appropriate to use
data excluding the maximum and minimum values.
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