Computer Time
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Eur J Appl Physiol (****) **: ** ***
O R I GI N A L A R T IC L E
M. Heiden E. Lyskov M. Djupsjobacka
F. Hellstrom A. G. Crenshaw
Effects of time pressure and precision demands during computer
mouse work on muscle oxygenation and position sense
Received: 19 May 2004 / Accepted: 19 November 2004 / Published online: 29 January 2005
Springer-Verlag 2005
in forearm muscle oxygenation, but did not a ect wrist
Abstract The present study investigated the e ects of
position sense accuracy. We attribute our changes in
time pressure and precision demands during computer
oxygenation more to increased oxygen consumption as a
mouse work on muscle oxygenation and position sense
result of enhanced performance, than to vasoconstric-
in the upper extremity. Twenty-four healthy subjects (12
tion.
males and 12 females) performed a 45-min standardized
mouse-operated computer task on two occasions. The
task consisted of painting rectangles that were presented Keywords Near infrared spectroscopy Forearm
on the screen. On one occasion, time pressure and pre- Proprioception Arousal Gender
cision demands were imposed (more demanding task,
MDT), whereas, on the other occasion, no such re-
straints were added (less demanding task, LDT). The
order of the two task versions was randomized. Tissue Introduction
oxygen saturation in the trapezius and extensor carpi
radialis muscles was recorded throughout, and the po- As the number of employees involved in computer or
sition-matching ability of the wrist was measured before visual display unit work increases, neck and upper
and after the tasks. In addition, measurements of auto- extremity complaints grow more common. Wigaeus
nomic nervous system reactivity and subjective ratings Tornqvist et al. (2000) reported that almost 90% of of-
of tenseness and physical fatigue were obtained. Per- ce employees in Sweden perform visual display unit
formance was measured in terms of the number of work. At the same time, the number of cases where
rectangles that were painted during the task. During computer work is considered to be the cause of muscu-
MDT, oxygen saturation in extensor carpi radialis de- loskeletal disorders increased by 20% from 1992 to 1998
creased (P
paralleled by increased electrodermal activity (P 0.05), paired t-tests were that 24 subjects would be su cient for detecting mini-
mum di erences of 2 in VE, 1.5 in AE, 5% in StO2,
used to test for di erences in initial measurements at the
3 beats min 1 in heart rate, 10 s2 in heart rate variabil-
occasions. F-tests of gender di erences and di erences
ity, 3 responses min 1 and 7 lS min 1 in EDA, 30
between task versions were obtained in full-factorial
arbitrary units (a.u.) min 1 in skin blood ow,
repeated-measures analyses of variance on VE and AE
101
2 breaths min 1 in respiration rate, 5 mmHg in blood 8
pressure, and 15 mm in VAS ratings, with statistical
power of at least 0.95. VAS ratings during the task were
analyzed by Wilcoxon s non-parametric tests. Skin MDT
Absolute error (degrees)
7
LDT
temperature and skin fold thickness were tested for
di erences by t-tests or Wilcoxon s non-parametric tests,
depending on distribution of data. In all tests, P4.88, P122.0, P>0.114] and fatigue [W>116.0,
P>0.052], or in painting performance [t(22)0.102].
60
Men
Women
Discussion
Rest Work Work
part 1 part 2
In the present study, we examined the e ect of time
Fig. 4 Mean values of %StO2 in extensor carpi radialis during rest,
pressure and precision demands during computer mouse
part 1 and part 2 of work for men (solid square) and women (open
work. VAS ratings of tenseness and physical fatigue
square). The bars represent 1 standard error of the mean. A
gender di erence in %StO2 was found during rest as well as during were higher during MDT than LDT, indicating an in-
the work (P2.83, P
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