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Influence of Time Pressure and Verbal Provocation on Physiological and Psychological Reactions during Work with A Computer Mouse

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The overall aim of this study was to investigate whether time pressure and verbal provocation has any effect on physiological and psychological reactions during work with a computer mouse. It was hypothesised that physiological reactions other than muscle activity (i.e. wrist movements, forces applied to the computer mouse) would not be affected when working under stressful conditions. Fifteen subjects (8 men and 7 women) participated, performing a standardised text-editing task under stress and control conditions. Blood pressure, heart rate, heart rate variability, electromyography, a force-sensing computer mouse and electrogoniometry were used to assess the physiological reactions of the subjects. Mood ratings and ratings of perceived exertion were used to assess their psychological reactions. The time pressure and verbal provocation (stress situation) resulted in increased physiological and psychological reactions compared with the two control situations. Heart rate, blood pressure and muscle activity in the first dorsal interosseus, right extensor digitorum and right trapezius muscles were greater in the stress situation. The peak forces applied to the button of the computer mouse and wrist movements were also affected by condition. Whether the increases in the physiological reactions were due to stress or increased speed/productivity during the stress situation is discussed. In conclusion, work with a computer mouse under time pressure and verbal provocation (stress conditions) led to increased physiological and psychological reactions compared to control conditions.
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ORIGINAL ARTICLE
J. Wahlstro
¨
m Æ M. Hagberg Æ P.W. Johnson
J. Svensson Æ D. Rempel
Influence of time pressure and verbal provocation on physiological
and psychological reactions during work with a computer mouse
Accepted: 20 February 2002 / Published online: 22 May 2002
Springer-Verlag 2002
Abstract The overall aim of this study was to investigate
whether time pressure and verbal provocation has any
effect on physiological and psychological reactions
during work with a computer mouse. It was hypothes-
ised that physiological reactions other than muscle ac-
tivity (i.e. wrist movements, forces applied to the
computer mouse) would not be affected when working
under stressful conditions. Fifteen subjects (8 men and 7
women) participated, performing a standardised text-
editing task under stress and control conditions. Blood
pressure, heart rate, heart rate variability, electromyog-
raphy, a force-sensing computer mouse and electrog-
oniometry were used to assess the physiological
reactions of the subjects. Mood ratings and ratings of
perceived exertion were used to assess their psychologi-
cal reactions. The time pressure and verbal provocation
(stress situation) resulted in increased physiological and
psychological reactions compared with the two control
situations. Heart rate, blood pressure and muscle ac-
tivity in the first dorsal interosseus, right extensor digi-
torum and right trapezius muscles were greater in the
stress situation. The peak forces applied to the button of
the computer mouse and wrist movements were also
affected by condition. Whether the increases in the
physiological reactions were due to stress or increased
speed/productivity during the stress situation is dis-
cussed. In conclusion, work with a computer mouse
under time pressure and verbal provocation (stress
conditions) led to increased physiological and psycho-
logical reactions compared to control conditions.
Keywords Stress Æ Electromyography Æ Input device Æ
Video display terminal Æ Physiological reactions
Introduction
Musculoskeletal symptoms of the neck and upper ex-
tremity associated with work with visual display units
(VDUs) are common. In 1999, approximately 60% of
the Swedish work force used a VDU in their profession
(Statistics Sweden 2000), and it is believed that this fig-
ure is increasing. It is thought that musculoskeletal
symptoms among VDU operators have a multi-factorial
aetiology. Non-neutral wrist, arm and neck postures,
workstation ergonomics, duration of computer work
and psychological and social factors such as time pres-
sure and high perceived work load, are believed to in-
teract in the development of these symptoms (Bongers
et al. 1993; Faucett and Rempel 1994).
Experimental studies have shown that mental stress
can induce muscle activity (Ekberg et al. 1995; Larsson
et al. 1995; Lundberg et al. 1994; Wærsted et al. 1991,
1994; Wærsted and Westgaard 1996). In some of these
experimental studies (Ekberg et al. 1995; Larsson et al.
1995; Lundberg et al. 1994), authors have used the
Stroop Color Word Test (CWT) as a stressor, and the
outcome has primarily been muscle activity in the tra-
pezius muscles. Other authors have used a complex two-
choice reaction-time task (Wærsted and Westgaard
1996; Wærsted et al. 1991, 1994) and focused on the
muscle activity in the trapezius muscle, but also mea-
sured muscle activity in other body regions. The CWT
and the two-choice reaction-time task require minimal
physical activity during performance and are not easily
transferred to real work situations using a VDU or a
computer mouse.
The aim of this study was to investigate whether time
pressure and verbal provocation have any effect on
Eur J Appl Physiol (2002) 87: 257–263
DOI 10.1007/s00421-002-0611-7
J. Wahlstro
¨
m(&) Æ M. Hagberg Æ J. Svensson
Department of Occupational Medicine,
Sahlgrenska University Hospital,
St. Sigfridsgatan 85, 412 66, Go
¨
teborg, Sweden
E-mail: jens.wahlstrom@ymk.gu.se
Fax: +46-31-409728
P.W. Johnson
Department of Environmental Health,
University of Washington, Seattle, WA, USA
D. Rempel
Ergonomics Program, Division of Occupational Medicine,
University of California, San Francisco, USA
physiological and psychological reactions when working
with a computer mouse. It was also hypothesised that
physiological reactions other than muscle activity (i.e.
wrist movements, forces applied to the computer mouse)
would not be affected when working under stressful
conditions.
Methods
Subjects
Fifteen subjects, 8 men and 7 women, volunteered to participate in
the study, which had been approved by the Ethics committee.
Subjects from various occupations were recruited from the
Sahlgrenska University Hospital, Go
¨
teborg, and former fellow
students of two of the authors (JS and JW). The mean age was
30 years (range 18–48 years), the mean body mass index (BMI) was
23.5 (range 20–28) and the median time with VDU work per week
was 10 h (range 2–80 h). The subjects were all experienced com-
puter mouse users and they all used their right hand to operate the
mouse. Prior to the study, subjects were given written and verbal
information explaining the experimental procedures. None of the
subjects used medication for hypertension or any other cardio-
vascular disease and they were all free of upper extremity muscu-
loskeletal disorders, as determined by an interview.
Experimental procedure
An adjustable VDU workstation was set up and the subjects ad-
justed the table and chair to fit their personal preferences. A
Macintosh computer with a 13-in (33 cm) colour display and a
standard keyboard was used. Before the measurements, subjects
practised at the experimental workstation to familiarise themselves
with the equipment and the task.
The subjects participated in a control situation (Control 1), a
stress situation (Stress) and, at the end of the experiment, a second
control situation (Control 2). In the control situations, subjects
edited eight, five-line paragraphs of text (two pages) with no time
constraints imposed. In each line, at a random location, one to four
characters were highlighted using coloured text. Subjects were in-
structed to highlight the coloured characters with the computer
mouse and then delete the characters by hitting the delete key on
the keyboard with the hand operating the computer mouse. Ap-
proximately 10–15 min later, in the stress situation, subjects were
asked to perform the same task but do twice the amount of work
(edit four pages). Here, subjects were asked to work ‘‘as fast as
possible’’ and a time constraint of 40 s was imposed to complete
each page of text editing. If the subjects could not complete editing
the page of text, they were verbally prompted to use the ‘‘page
down’’ key on the keyboard and continue with the text-editing task
on the next page. Subjects were also verbally provoked every 15th s
(e.g. ‘‘hurry up’’ or ‘‘come on, you can do it faster’’). The verbal
provocation was given by the same test leader throughout the
experiment (JS).
Physiological and psychological reactions
Heart rate and heart rate variability
Heart rate (HR) and heart rate variability (HRV) were measured
with the Polar Vantage NV heart-rate monitor and data were
analysed using Polar Precision Performance software version 2.0
(Polar Electro Oy, Kempele, Finland). The heart rate was
recorded ‘‘beat by beat’’ and then the data were filtered using an
automatic procedure contained within the Polar software system.
The low-frequency (LF) domain (0.04–0.15 Hz) and the high-
frequency (HF) domain (0.15–0.40 Hz) of the HRV power
spectrum were calculated using the Polar software system, and the
LF:HF ratio (LF/HF ratio) was calculated, together with the
mean HR. The HF component of the power spectrum reflects
parasympathetic activity and the LF component reflects sympa-
thetic activity with vagal modulation; mental stress has been
shown to lower HRV and effect an increase in the LF/HF ratio
(Kristal-Boneh et al. 1995).
Blood pressure
Systolic and diastolic blood pressure (SBP and DBP, respectively)
were recorded with an ambulatory blood pressure monitor (Car-
dioTens; Medikolt International AB, Ska
¨
rholmen, Sweden). This
equipment has been tested for validity and reliability (Barna et al.
1998), and the algorithm used in the apparatus adhered to the
recommendations of the Association for the Advancement of
Medical Instrumentation. SBP and DBP were recorded once during
the control situations midway through the task. During the stress
situation, SBP and DBP were measured approximately 1 min after
the start of the text-editing task.
Forces applied to the computer mouse
An instrumented Apple ADBII computer mouse was used to
measure the forces applied to the sides and button of the computer
mouse. The force-sensing computer mouse was fully operational,
and similar in weight, feel and appearance to an ordinary Apple
ADBII computer mouse. The design and measurement accuracy of
the force-sensing computer mouse has been validated, described
and discussed in detail elsewhere (Johnson et al. 1993, 1994). The
force data were analysed using a program written in Labview 4.0
(National Instruments, Austin, Texas, USA). The program iden-
tified each time the computer mouse was used (termed a grip epi-
sode), and kept track of idle periods, which were defined as any
period the mouse was not used for 1 s or longer. For each grip
episode the program calculated the mean force, peak force and grip
duration. At the end of the experiment, subjects were asked to
apply maximum voluntary contractions (MVCs) to the sides and
button of an Apple ADBII computer mouse equipped with load
cells.
Muscle activity
Muscle activity from four separate muscles was collected at 1 kHz
using a commercial electromyography (EMG) system (ME3000P4,
Mega Electronics, Kuopio, Finland). The muscles examined were
the right first interosseus (FDI), the right extensor digitorum (ED),
and the pars descendens of the right and left trapezius muscles. The
electrodes for the FDI and ED were placed as recommended by
Perotto (1994), and for the trapezius, as recommended by Mathi-
assen et al. (1995). Self-adhesive surface electrodes (M-00-S;
Medicotest, Ølstykke, Denmark) were placed in pairs with a 35-mm
inter-electrode distance. For the FDI muscle, the electrodes were
modified (cut), resulting in an inter-electrode distance of 25 mm.
Before attaching the electrodes, the skin was dry shaved and
cleaned with alcohol. At the beginning of the recordings the
subjects performed standardised MVCs to obtain the maximal
voluntary electrical activity (MVE) in the FDI and the ED. MVE in
the FDI and the ED was set with maximum static contraction
against manual resistance for a minimum of 3 s. Reference
voluntary electrical activity (RVE) in the right and left trapezius
muscles was set with the shoulders flexed to 90, thumbs up and a
1-kg dumb-bell held in each hand for a minimum of 3 s. The raw
data was recorded on-line using a portable PC and monitored in
real-time for quality control. The muscle activity was derived by
full-wave rectification and filtering of the EMG signal using a time
constant of 100 ms. Data were analysed using ME3000P software
version 1.5 (Mega Electronics), and the 50th percentile of the EMG
signal was calculated.
258
Wrist movements
A two-axis electrogoniometer (Model XM65, Penny and Giles Bio-
metrics, Blackwood, Wales, UK) and a data logger (Model DL 1001,
Penny & Giles) were used for recording flexion/extension (F/E) and
radial/ulnar deviation (R/U) movements in the right wrist. Goni-
ometry data were analysed using a program written in Labview 4.0.
The program calculated the mean velocity and the mean power
frequency (MPF) for both F/E and R/U. The MPF is defined as the
centre of gravity for the power spectrum (Hansson et al. 1996).
Mood ratings
To describe mood during work, a Swedish stress/energy question-
naire was used (Kjellberg and Iwanowski 1989; Kjellberg et al. 1996).
The checklist measures two factors, stress and energy, each com-
prising six items. Three adjectives within each factor are positively
loaded and three are negatively loaded. The following items are
included in the stress dimension: (positive) ‘‘rested’’, ‘‘relaxed’’ and
‘‘calm’’; (negative) ‘‘tense’’, ‘‘stressed’’ and ‘‘pressured’’, and the
following in the energy dimension: (positive) ‘‘active’’, ‘‘energetic’’
and ‘‘focused’’; (negative) ‘‘dull’’, ‘‘ineffective’’ and ‘‘passive’’. The
checklist uses a six-point scale (0–5) for each item, ranging from ‘‘not
at all’’ to ‘‘very much’’. High values indicate a high stress and energy
level, respectively. The means from the two different dimensions were
calculated and the ratings were made immediately after each test.
Ratings of perceived exertion (RPE) and comfort
Subjects rated perceived exertion after each condition for five dif-
ferent body locations [neck/shoulder (scapular), right shoulder
(upper arm), right forearm, right wrist and right hand/fingers] using
a modified 0- to 14-point Borg scale (Borg 1990). In the analysis,
ratings for the different body locations were summed and divided
into two different categories, proximal (neck/shoulder and shoul-
der) and distal (forearm, wrist and hand/fingers).
Productivity
When comparing productivity across all three conditions, the mean
duration of the time the computer mouse was gripped (grip episode
duration) and the ratio between the number of editing changes
made in the standardised text and the duration of the task, termed
speed, were assessed.
Statistics
The descriptive data are presented as mean (SEM). A repeated-
measures analysis of variance (RANOVA) was performed to test
the null hypothesis that condition did not have any effect on the
different variables assessed. The results from the RANOVAs are
presented with the exact F-statistic and the corresponding P-value.
Statistical significance was assumed for P £ 0.05.
Due to technical problems, the results from two male subjects
were excluded from the HR analysis, one female subject was ex-
cluded from the analysis of blood pressure and one male subject
was excluded from the analysis of wrist movements.
Results
The RANOVAs showed significant differences between
conditions on HR, SBP and DBP, but not on the LF/HF
ratio (Table 1 and Fig. 1). There was also a significant
Table 1. Means (SEM) of the
different parameters assessed in
the three conditions. A repeat-
ed-measures analysis of
variance (RANOVA) was
performed to test whether the
different conditions had any
effect on the outcome parame-
ters assessed. The exact F-sta-
tistic and the P-value are also
presented. (LF Low frequency,
HF high frequency, %MVC %
maximum voluntary contrac-
tion, %MVE % maximum
voluntary electrical activity,
%RVE % reference voluntary
electrical activity)
Parameter Recording condition RANOVA
Control 1 Stress Control 2 Exact F P-value
Blood pressure (n=14)
Systolic (mmHg) 130 (2.9) 136 (3.5) 128 (2.6) 12.20 0.0013
Diastolic (mmHg) 82 (1.3) 86 (1.6) 80 (1.3) 11.48 0.0016
Heart rate parameters (n=13)
Heart rate (beats/min) 77 (2.6) 82 (2.7) 77 (2.4) 4.59 0.036
LF/HF Ratio 1.9 (0.40) 3.0 (0.88) 2.5 (0.57) 0.87 0.45
Mood ratings (n=15)
Stress (scale step) 1.7 (0.18) 3.0 (0.25) 1.6 (0.13) 23.37 <0.0001
Energy (scale step) 3.1 (0.18) 3.4 (0.17) 3.1 (0.20) 3.09 0.078
Forces applied to computer mouse (n=15)
Side mean force (%MVC) 0.8 (0.08) 0.9 (0.11) 0.7 (0.08) 2.68 0.106
Side peak force (%MVC) 1.3 (0.14) 1.5 (0.19) 1.2 (0.11) 2.52 0.119
Button mean force (%MVC) 1.4 (0.14) 1.5 (0.15) 1.4 (0.13) 2.78 0.099
Button peak force (%MVC) 3.5 (0.38) 4.2 (0.46) 3.5 (0.33) 8.30 0.005
Wrist flexion/extension (n=14)
Mean power frequency (Hz) 0.72 (0.05) 0.96 (0.07) 0.74 (0.04) 12.73 0.0011
Mean velocity (/s) 16.5 (1.39) 21.9 (1.89) 18.3 (1.79) 19.12 0.0002
Wrist radial/ulnar deviation (n=14)
Mean power frequency (Hz) 0.44 (0.03) 0.58 (0.03) 0.41 (0.03) 18.41 0.0002
Mean velocity (/s) 9.9 (0.92) 11.8 (1.14) 11.3 (1.46) 18.68 0.0002
Muscle activity (n=15)
First dorsal interosseus (%MVE) 8.7 (2.14) 11.7 (2.83) 10.3 (3.23) 14.28 0.0005
Extensor digitorum (%MVE) 7.8 (0.55) 9.7 (0.78) 7.9 (0.60) 16.05 0.0002
Right trapezius (%RVE) 28.3 (5.92) 45.1 (10.1) 31.8 (5.58) 5.17 0.022
Left trapezius (%RVE) 10.9 (2.84) 20.4 (5.69) 12.9 (2.75) 1.85 0.20
Ratings of perceived exertion (n=15)
Proximal (scale step) 6.3 (1.24) 10.6 (1.51) 7.0 (1.05) 9.70 0.0026
Distal (scale step) 5.3 (1.40) 8.6 (1.58) 6.3 (1.36) 3.18 0.075
Productivity (n=15)
Speed 0.22 (0.007) 0.32 (0.015) 0.26 (0.007) 28.81 <0.0001
Grip duration (s) 3.1 (0.11) 2.2 (0.09) 2.6 (0.08) 44.59 <0.0001
259
effect of condition on the subjective ratings of stress and
RPE proximally, but not on ratings of energy or RPE
distally (Table 1).
The only force parameter that was affected by con-
dition was the button peak forces (%MVC) applied to
the computer mouse (Table 1 and Fig. 2). In the other
force parameters there was no significant effect of con-
dition, although the forces tended to be higher in the
stress condition compared to the two control situations
(Table 1). Muscle activity from the FDI, the ED and the
right trapezius muscle were all affected by condition
(Table 1 and Fig. 3). Condition also had a significant
effect on MPF and mean velocity of the wrist, both in
F/E and R/U deviation (Table 1 and Fig. 2). The mea-
sures of productivity (grip episode duration and speed)
were also affected by condition (Table 1 and Fig. 4).
Discussion
The intention of this study was to put subjects into
two different work situations and evaluate how their
physiological and psychological reactions changed from
relatively relaxed conditions to simulated stressful work
conditions. The time pressure and verbal provocation
(the stress situation) resulted in increased physiological
(HR and blood pressure) and psychological reactions
(mood ratings). These increases indicate that the time
pressure and verbal provocation met the objectives of
creating a stressful work situation.
There was not only an increase in muscle activity, but
also a more generalised increase, which included higher
forces applied to the button of the computer mouse and
more repetitive wrist movements when comparing the
stress situation to the control situations.
Based on decreases in grip episode duration and in-
creases in speed/productivity, part of the increases in the
physiological parameters could be attributed to the fact
that subjects worked faster in the stress condition com-
pared to the control conditions. The productivity in-
crease was approximately the same between the three
recording sessions, with the greatest productivity being
observed for the stress situation (Fig. 4). However, the
magnitude of the differences in physiological parameters
Fig. 1. Least-square (LS) means of systolic blood pressure
(mmHg; upper graph) and heart rate (beats per minute, BPM;
lower graph) in the control and the stress conditions
Fig. 2. LS means of button peak forces (% of maximal voluntary
contraction, %MVC; upper graph) applied to the computer mouse
and mean power frequency of the wrist in radial/ulnar deviation
(lower graph) in control and stress conditions
260
between the first and second control recordings was
much less than that observed between the control and
stress conditions (Figs. 1, 2, 3). Therefore, this indicates
that some of the increase in the physiological parameters
was stress related. HR and SBP were probably only af-
fected by stress, while the other physiological measures
(EMG, forces and wrist movements) were probably af-
fected by both stress and speed/productivity. Kohlisch
and Schaefer (1996) concluded that the impact of motor
activity on cardiac parameters (HR, blood pressure)
could be neglected during common computer tasks (i.e.
keystrokes at intervals of 300 ms or longer).
Muscle activity increased in three of the muscles
(FDI, ED and the right trapezius) during the stress
condition. Birch and co-workers (2000) have also in-
vestigated the effect of time pressure during simulated
computer work and found that high time pressure
combined with low precision and low mental demands
resulted in higher EMG activity in the trapezius, infra-
spinatus, deltoid and ED muscles, but high precision
and high mental demands did not result in any change in
muscle activity. Perhaps with low precision and low
mental demands subjects worked faster and this in-
creased the muscle activity, but with high precision and
high mental demands, subjects had a slower overall
work pace and this was counterbalanced any increase in
EMG. This indicates the importance of having some
measure of productivity. Laursen and co-workers (1998)
investigated the effect of increased speed and increased
precision and found that the muscle activity in the
shoulder muscles increased as the speed demand in-
creased (four different levels of speed). In the study
presented here, the results from the right trapezius
muscle showed a tendency to increase as the speed/
productivity increased (Fig. 3). However, the trend was
much less marked in the ED muscle (Fig. 3). The muscle
activity in the ED was 2% MVC higher in the stress
situation than in the control conditions. This increase in
muscle activity, which was probably due to a combina-
tion of stress and increased speed/productivity, could
Fig. 3. LS means of muscle activity in the extensor digitorum (%
maximum voluntary electrical activity, %MVE; upper graph) and
in the right trapezius muscles (% reference voluntary electrical
activity, %RVE; lower graph) in control and stress conditions
Fig. 4. LS means of computer mouse grip duration (seconds;
upper graph) and speed (ratio between the number of editing
movements and the duration of the task; lower graph) in the
control and stress conditions.
261
imply that individuals with poor psychosocial working
conditions could be more prone to develop muscular
fatigue. In the long run, this might be associated with an
increased risk of developing discomfort and musculo-
skeletal symptoms in the forearm region.
The peak forces applied to the button of the com-
puter mouse increased by 0.7% MVC during the stress
situation compared to the control situations. Since there
was only a small difference in applied force between the
two control recording sessions, despite the difference in
speed/productivity, the increase in applied forces ob-
served in the stress situation is most likely an effect of
stress. Whether the increase in applied forces (0.7%
MVC) during the stress situation has any clinical rele-
vance is uncertain; previous studies have reported dif-
ferences between men and women in applied forces
ranging from 0.5% to 1.7% MVC (Johnson et al. 2000;
Wahlstro
¨
m et al. 2000), and intense computer mouse
work may induce muscle fatigue in the forearm muscles
(Johnson 1998). This could imply that individuals in-
volved in intense computer mouse work and adverse
psychosocial working conditions (i.e. stress, time pres-
sure) could be at higher risk of experiencing fatigue and
discomfort in the forearm. The increase in applied force
to the computer mouse may also explain some of the
increase in muscle activity in the hand and forearm (i.e.
FDI and ED) and perhaps some of the increased muscle
activity in the trapezius muscle.
The MPF and velocities from the mouse-operating
wrist increased in the stress situation. This result could
be expected since subjects worked faster, although it
might have some practical implications since MPF has
been associated with a higher prevalence of musculo-
skeletal disorders in female industrial workers (Hansson
et al. 2000). The mean values of MPF during control
situations were high compared to those reported in other
studies of VDU work (Karlqvist et al. 1995; Lindega
˚
rd
et al. 2001). The higher values of MPF, both in F/E and
R/U deviation, in this study were probably due to the
repetitive nature of the text-editing task. However, there
was an increase in MPF of about 0.2 Hz in F/E devia-
tion and of about 0.15 Hz in R/U deviation. In a study
of industrial workers who perform repetitive tasks,
where an exposure/response relationship was found be-
tween wrist movements (MPF) and musculoskeletal
wrist/hand disorders, the difference in MPF between the
high and low exposure groups was about 0.25 Hz
(Hansson et al. 2000). This could imply that subjects
who perform VDU work under stressful conditions are
at greater risk of developing wrist/hand disorders.
Limitations and implications
Whether the stressors used in this study are comparable
with stressors that individuals are exposed to during
daily work is uncertain, but the reactions to the stressors
could mirror the reactions to different stressors en-
countered during ordinary work. It is also likely that the
combination of stress and increased speed/productivity
appears in combination in occupational settings. Since
the order of the two different situations was not
randomised, the increases in physiological and psycho-
logical reactions and physical load during the stress
situation could be an effect of subjects working faster or
an effect of time or learning. However, as discussed
earlier, it is indicated that the increases in physiological
and psychological reactions in the stress situation were
stress related to at least some degree, and previous
studies have shown that stress may increase muscle ac-
tivity (Ekberg et al. 1995; Larsson et al. 1995; Lundberg
et al. 1994; Wærsted and Westgaard 1996; Wærsted et al.
1991, 1994). There was most likely a learning effect, since
the subjects performed the text-editing task faster during
the second control recording session. This increase in
speed/productivity in the second control recording ses-
sion may explain the general pattern of the physiological
reactions being slightly higher compared to those ob-
tained in the first control recording session. We chose
not to perform Bonferroni adjustments of P-values,
although we made multiple comparisons, since the out-
come parameters were not chosen at random. The
decision as to whether or not to use Bonferroni adjust-
ments remains a matter of controversy, some authors
being of the opinion that adjusting statistical significance
for the number of tests may create more problems than
it solves (e.g. Perneger 1998). Finally, one potential
limitation of this study was that the data collection for
the two situations was made over a period of less than
5 min, which is a short time of exposure to a stressor.
Future studies should investigate further these effects
and extend the data collection time.
Conclusions
Work with a computer mouse under time pressure and
verbal provocation (stress situation) led to increased
physiological and psychological reactions compared to
control conditions.
Acknowledgements The authors are grateful to Anna Ekman for
her advice and assistance with the statistical analysis and to Pro-
fessor Roland Kadefors for his valuable comments on the manu-
script.
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... Inexperienced drivers and those who drive infrequently, are most strongly affected, displaying higher subjective stress responses, as well as higher physiological stress (Dogan et al., 2012;Scott-Parker, 2017). Experimental studies have shown that mental stress, induced by computer tasks, leads to negative changes in physiological parameters, including increases in arterial blood pressure (Hjortskov et al. 2004;Wahlström et al., 2002), increases in cardiovascular stress as indicated by reductions in heart rate variability (HRV) (Hjortskov et al. 2004;Wahlström et al., 2002), and increases in salivary stress hormones concentrations (i.e. salivary cortisol levels) (Bakke et al. 2004). ...
... Inexperienced drivers and those who drive infrequently, are most strongly affected, displaying higher subjective stress responses, as well as higher physiological stress (Dogan et al., 2012;Scott-Parker, 2017). Experimental studies have shown that mental stress, induced by computer tasks, leads to negative changes in physiological parameters, including increases in arterial blood pressure (Hjortskov et al. 2004;Wahlström et al., 2002), increases in cardiovascular stress as indicated by reductions in heart rate variability (HRV) (Hjortskov et al. 2004;Wahlström et al., 2002), and increases in salivary stress hormones concentrations (i.e. salivary cortisol levels) (Bakke et al. 2004). ...
... suggest a decrease in autonomic nervous system modulation, particularly a reduction in parasympathetic modulation of the heart, which aligns with our findings of a decrease in SDNN and RMSSD in response to the discourteous drive. Previous work has shown that mental stress induced by computer tasks (Hjortskov et al. 2004;Wahlström et al., 2002), self-reported stress experiences (Michels et al., 2013) or perceived job stressors (Kageyanna et al., 1998), are associated with acute reductions in HRV. The sympathetic nervous system is fast responding and therefore it is likely that the observed change in heart rate variability parameters reflect the short term acute increase in stress during the discourteous condition. ...
Article
Prior studies into road safety have concentrated largely on studying unsafe forms of driving behaviour such as aggressive, stressed, and risky driving. Little attention has been given to ‘positive’ driving behaviour, such as how pro-social driving may help to promote cooperation with other road users and decrease incidences of aggressive and stressful driving. This study aimed to compare the impact of courteous and discourteous driving on the immediate physical health of other drivers (blood pressure, heart rate, and markers of stress) whilst controlling for other recognized factors responsible for driver stress such as road infrastructure (e.g. roadworks, traffic lights, freeways) and driving maneuvers (e.g. merging, tail-gaiting, navigating roundabouts). Using actors in a deception study, a naturalistic driving scenario was created in a lab-based simulation. All participants (n = 10; 39 ± 14.5 years) drove the same route in a simulator and engaged with the same driving behaviours and other virtual road users on two separate occasions separated by 7 days. The difference between conditions was whether the participant interacted with other drivers who displayed: a) courteous or b) discourteous behaviours. Blood pressure, heart rate variability and salivary hormone concentrations (cortisol and alpha amylase) were measured before and immediately after each simulated drive. After interacting with the discourteous drivers, participants experienced significantly higher mean arterial blood pressure, systolic and diastolic pressure, central systolic and diastolic pressure, and heart rate, and lower heart rate variability (indicative of acute stress) compared to interacting with the courteous drivers. Conversely, these markers of stress were reduced after interacting with the courteous drivers. The results support courtesy on the road to provide short-term benefits for the recipient of the action, while also increasing road safety more generally.
... Stressful situations are common in everyday human life. For example, stress may arise when we are struggling with time pressure (Wahlström, Hagberg, Johnson, Svensson, & Rempel, 2002) with respect to being late for appointments (Zimring, 1981) or when our performance is evaluated (Zeidner, 1998). Some evidence even points to stress-related emotions that emerge during environmental navigation (Lawton, 1994) and may be associated with anxiety of becoming lost or disoriented (Bryant, 1982). ...
... However, immediate threats are not the only situations that manifest in physiological responses. Prior research has demonstrated that physiological stress reactions can be caused by social pressure (Kirschbaum, Pirke, & Hellhammer, 1993), time pressure (Wahlström et al., 2002), and many other situations or stimuli. ...
... Concerning the relation between self-reported stress states and working memory impairment, (Matthews & Campbell, 2010) demonstrated consistent positive relation between higher distress ratings and poorer working memory performance. Among other aspects of everyday navigation, stress might occur when we are struggling with time pressure (Wahlström et al., 2002). Psychological stress and high arousal have been associated with inattention to global landmarks and negative effects on working memory functioning (Section 2.7). ...
Article
In a fast-paced digital society, individuals increasingly rely on computerized location-based services to efficiently find their way through unfamiliar environments. However, scientific evidence is increasingly showing that despite digital navigation assistance helping people to find their way, it can cause wayfinders to become “mindless” of the traversed environment, thus acquiring no or very little spatial knowledge in the long term. It is still not entirely clear what causes these impairments or how the design of navigation devices can be improved to counteract such undesirable effects. The objective of this thesis is to gain empirical insights into the role of stressful navigation conditions for potential spatial learning impairments, and to identify the features in the environment for which it is particularly important that wayfinders’ pay attention to and thus increase their spatial knowledge even when experiencing stress. Building on existing work in spatial cognition, cognitive geography, and stress research, the studies of this thesis investigate whether and how highly visible landmarks can improve memory of large spaces like cities, and how that may be influenced by navigators’ stress states. It is widely accepted that landmarks serve a key role for the development of spatial knowledge, and there has been increasing interest in integrating landmarks into automated navigation instructions in recent decades. Specifically, recent studies have pointed to a potential advantage of so-called global landmarks that are visible from several locations in an environment for spatial orientation and route learning. However, there has been little research on the difference in mentally encoding and learning the locations of global landmarks as compared to landmarks that are only visible locally. In this thesis, I conducted two virtual reality experiments that assessed human participants’ capability to acquire spatial knowledge from local or global landmark configurations in situations with and without stress. Insights from this work can help designers of future navigation systems, and industry decision makers, to reconsider which and when landmarks should be presented in navigation systems. For example, future navigation assistance may dynamically adapt the display of local and global landmarks according to the contextual demands of the wayfinder. In Study I, I investigated the role of time pressure in learning the spatial relations among local landmarks (e.g., a shop along the route) as compared to global landmarks (e.g., a tower in the distance) during navigation through virtual cities. During this navigation, participants used a navigation aid and had explicit learning instructions for the different local or global landmark configurations. Participants’ performance in a survey knowledge test after navigation suggests that global landmark configurations were not represented more accurately than local landmark configurations, and that survey knowledge acquisition was not impaired under time pressure. In contrast to prior findings, the results of Study I indicate no advantage of distant global landmarks for spatial knowledge acquisition. In Study II, I investigated the role of working memory in acquiring survey knowledge from sequentially (locally) or simultaneously (globally) visible landmark configurations during navigation through virtual cities. As in Study I, participants navigated routes through virtual cities, but both local and global landmarks were located along these routes. Moreover, one group of participants performed a concurrent spatial task that aimed to interfere with the active processing of information in working memory. I expected that an increase in spatial working memory demands would impair survey knowledge for sequentially visible local landmarks more than for simultaneously visible global landmarks. I also assessed individuals’ working memory capacity, because I expected greater capacity to be beneficial for the sequential integration of local landmarks over time. My findings show a negative effect of concurrent task demands for both local and global landmark learning. Furthermore, the data indicates that participants had improved spatial knowledge of globally visible landmarks as compared to locally visible landmarks along the route. Finally, Study II revealed that individual working memory capacity moderates the accuracy of acquiring spatial knowledge of global landmarks. Only participants with greater working memory capacity are able to benefit from globally visible landmarks. In summary, this work has identified a number of cognitive and contextual conditions that impair users’ ability to take advantage of globally visible landmarks for spatial learning. Based on these conditions, the present work provides design guidelines for future learning-aware navigation systems. For example, my analysis of participants’ learning performance indicates that users with greater working memory capacities have the necessary cognitive resources available to take advantage of global landmarks for spatial learning. While this might imply that the navigation systems of tomorrow need to be aware of users’ spatial abilities to optimize information display, future research should also identify means to support navigators with low working memory capacity.
... Hernandez et al showed a higher contact area with the surface of a capacitive mouse under stressful conditions compared to relaxed conditions [6]. Wahlstrom et al [27] showed that muscle activity in the right extensor digitorum (ED) and right trapezius muscles were greater in stressed situations evoked by time pressure and verbal provocation while working with a computer mouse. Carneiro et al [28] showed that acceleration and mean and maximum intensity (aka, pressure) of touch when interacting with touchscreen devices were higher under stressful conditions. ...
... However, the absolute level of muscle activity in the FDI during trackpad usage is low compared to that in the bigger trapezius muscle during computer mouse usage [29,30]. As a result, it could be hard to rely on muscle tension and stiffness to infer stress using trackpad versus mouse data [4,27]. ...
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BACKGROUND Stress is a risk factor associated with physiological and mental health problems. Unobtrusive, continuous stress sensing would enable precision health monitoring and proactive interventions, but current sensing methods are often inconvenient, expensive, or suffer from limited adherence. Prior work has shown the possibility to detect acute stress using biomechanical models derived from passive logging of computer input devices. OBJECTIVE Our objective is to detect acute stress from passive movement measurements of everyday interactions on a laptop trackpad: (1) click , (2) steer , and (3) drag and drop . METHODS We built upon previous work, detecting acute stress through the biomechanical analyses of canonical computer mouse interactions and extended it to study similar interactions with the trackpad. A total of 18 participants carried out 40 trials each of three different types of movement—(1) click , (2) steer , and (3) drag and drop —under both relaxed and stressed conditions. RESULTS The mean and SD of the contact area under the finger were higher when clicking trials were performed under stressed versus relaxed conditions (mean area: P =.009, effect size=0.76; SD area: P =.01, effect size=0.69). Further, our results show that as little as 4 clicks on a trackpad can be used to detect binary levels of acute stress (ie, whether it is present or not). CONCLUSIONS We present evidence that scalable, inexpensive, and unobtrusive stress sensing can be done via repurposing passive monitoring of computer trackpad usage.
... Hernandez et al showed a higher contact area with the surface of a capacitive mouse under stressful conditions compared to relaxed conditions [6]. Wahlstrom et al [27] showed that muscle activity in the right extensor digitorum (ED) and right trapezius muscles were greater in stressed situations evoked by time pressure and verbal provocation while working with a computer mouse. Carneiro et al [28] showed that acceleration and mean and maximum intensity (aka, pressure) of touch when interacting with touchscreen devices were higher under stressful conditions. ...
... However, the absolute level of muscle activity in the FDI during trackpad usage is low compared to that in the bigger trapezius muscle during computer mouse usage [29,30]. As a result, it could be hard to rely on muscle tension and stiffness to infer stress using trackpad versus mouse data [4,27]. ...
Article
Full-text available
Background: Stress is a risk factor associated with physiological and mental health problems. Unobtrusive, continuous stress sensing would enable precision health monitoring and proactive interventions, but current sensing methods are often inconvenient, expensive, or suffer from limited adherence. Prior work has shown the possibility to detect acute stress using biomechanical models derived from passive logging of computer input devices. Objective: Our objective is to detect acute stress from passive movement measurements of everyday interactions on a laptop trackpad: (1) click, (2) steer, and (3) drag and drop. Methods: We built upon previous work, detecting acute stress through the biomechanical analyses of canonical computer mouse interactions and extended it to study similar interactions with the trackpad. A total of 18 participants carried out 40 trials each of three different types of movement—(1) click, (2) steer, and (3) drag and drop—under both relaxed and stressed conditions. Results: The mean and SD of the contact area under the finger were higher when clicking trials were performed under stressed versus relaxed conditions (mean area: P=.009, effect size=0.76; SD area: P=.01, effect size=0.69). Further, our results show that as little as 4 clicks on a trackpad can be used to detect binary levels of acute stress (ie, whether it is present or not). Conclusions: We present evidence that scalable, inexpensive, and unobtrusive stress sensing can be done via repurposing passive monitoring of computer trackpad usage.
... Although not suitable for use in driving tasks, it shows that hand muscle tonus measurement has the potential to be an indication of stress. Wahlström et al. (2002) examined the effect of stressors (e.g., time pressure and verbal provocation) on various factors, including the grip force upon a computer mouse. Grip force increased when stressors were used. ...
Article
Full-text available
Driver performance is crucial for road safety. There is a relationship between performance and stress such that too high or too low stress levels (usually characterized by stressful or careless driving, respectively) impair driving quality. Therefore, monitoring stress levels can improve the overall performance of drivers by providing either an alert or intervention when stress levels are sub-optimal. Commonly used stress measures suffer from several shortcomings, such as time delays in indication and invasiveness of sensors. Grip force is a relatively new measure that shows promising results in measuring stress during psychomotor tasks. In driving, grip force sensor is non-invasive and transparent to the end user as drivers must continuously grip the steering wheel. The aim of the current research is to examine whether grip force can be used as a useful measure of stress in driving tasks. Twenty-one participants took part in a field experiment in which they were required to brake the vehicle in various intensities. The effects of the braking intensity on grip force, heart rate, and heart rate variability were analyzed. The results indicate a significant correlation between these three parameters. These results provide initial evidence that grip force can be used to measure stress in driving tasks. These findings may have several applications in the field of stress and driving research as well as in the vehicle safety domain.
... Human-computer interactions with ubiquitous digital devices could be used for real-time monitoring of work-related stress. In particular, it has been shown that the computer mouse responds to changes in muscular activity as a result of stress [3][4][5][6]. Thus, previous studies have investigated the association between stress and the use of the computer mouse [7][8][9][10][11], for instance, by analyzing computer mouse movements [8,10,11]. ...
Article
Full-text available
Background: Work stress affects individual health and well-being. These negative effects could be mitigated through regular monitoring of employees’ stress. Such monitoring becomes even more important as the digital transformation of the economy implies profound changes in working conditions. Objective: The goal of this study was to investigate the association between computer mouse movements and work stress in the field. Methods: We hypothesized that stress is associated with a speed-accuracy trade-off in computer mouse movements. To test this hypothesis, we conducted a longitudinal field study at a large business organization, where computer mouse movements from regular work activities were monitored over 7 weeks; the study included 70 subjects and 1829 observations. A Bayesian regression model was used to estimate whether self-reported acute work stress was associated with a speed-accuracy trade-off in computer mouse movements. Results: There was a negative association between stress and the two-way interaction term of mouse speed and accuracy (mean −0.32, 95% highest posterior density interval −0.58 to −0.08), which means that stress was associated with a speed-accuracy trade-off. The estimated association was not sensitive to different processing of the data and remained negative after controlling for the demographics, health, and personality traits of subjects. Conclusions: Self-reported acute stress is associated with computer mouse movements, specifically in the form of a speed-accuracy trade-off. This finding suggests that the regular analysis of computer mouse movements could indicate work stress.
... Human-computer interactions with ubiquitous digital devices could be used for real-time, early detection of workrelated stress. In particular, it has been shown that the computer mouse responds to changes in muscular activity as a result of stress [3][4][5][6]. Previous studies have thus tried to use the computer mouse in order to detect stress [7][8][9][10][11], for instance, by analyzing computer mouse movements (CMMs) [8,10,11]. ...
Preprint
Background: Work stress afflicts individual health and well-being. These negative effects could be mitigated through regular monitoring of employees’ stress. Such monitoring becomes even more important as the digital transformation of the economy implies profound changes of working conditions. Objective: To investigate whether the computer mouse can be used for continuous monitoring and early detection of work stress in the field. Methods: We hypothesized that stress is associated with a speed-accuracy tradeoff in computer mouse movements (CMMs). To test this hypothesis, we conducted a longitudinal field study at a large business organization, where CMMs from regular work activities were monitored over seven weeks (70 subjects, n=1,829 observations). A Bayesian regression model was used to estimate whether self-reported acute work stress was associated with a speed-accuracy tradeoff in CMMs. Results: There was a negative association between stress and the two-way interaction term of mouse speed and accuracy (mean = −0.36, lower = −0.66, upper = −0.08), which means that stress was associated with a speed-accuracy tradeoff. The estimated effect was not sensitive to different processing of the data and remained negative after controlling for the demographics, health, and personality traits of subjects. Conclusions: Self-reported acute stress can be inferred from CMMs, specifically in the form of a speed-accuracy tradeoff. This finding suggests to use regular analysis of CMMs for the early and scalable detection of work stress on the job and thus promises more timely and effective stress management.
... Power posing may also change the affective experience; however results with respect to behavioral (more risk-taking) and hormonal responses (i.e., increased testosterone and decreased cortisol level) are controversial (Carney et al., 2010;Ranehill et al., 2015;Simmons and Simonsohn, 2017). In the same vein, EMG activity increases in many muscles and muscle groups in stressful situations (Lundberg et al., 1994;Wahlström et al., 2002;Krantz et al., 2004;Luijcks et al., 2014), and it is possible to reduce stress and anxiety through relaxation techniques (e.g., progressive relaxation, autogenic training), which operate (at least partially) through the systematic relaxation of muscles (Kanji et al., 2006;Rausch et al., 2006). Finally, Cacioppo et al. (1993) showed that the activation of arm flexor muscles activates the approach system, which biases the judgment of neutral stimuli to the positive direction. ...
Article
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Interoception in the broader sense refers to the perception of internal states, including the perception of the actual state of the internal organs (visceroception) and the motor system (proprioception). Dimensions of interoception include (1) interoceptive accuracy, i.e., the ability to sense internal changes assessed with behavioral tests, (2) confidence rating with respect to perceived performance in an actual behavioral test, and (3) interoceptive sensibility, i.e., the self-reported generalized ability to perceive body changes. The relationship between dimension of cardioceptive and proprioceptive modalities and their association with affect are scarcely studied. In the present study, undergraduate students (N = 105, 53 males, age: 21.0 ± 1.87 years) filled out questionnaires assessing positive and negative affect (Positive and Negative Affect Schedule), interoceptive sensibility (Body Awareness Questionnaire), and body competence (Body Competence Scale of the Body Consciousness Questionnaire). Following this, they completed a behavioral task assessing cardioceptive accuracy (the mental heartbeat tracking task by Schandry) and two tasks assessing proprioceptive accuracy with respect to the tension of arm flexor muscles (weight discrimination task) and the angular position of the elbow joint (joint position reproduction task). Confidence ratings were measured with visual analog scales after the tasks. With the exception of a weak association between cardioceptive accuracy and the respective confidence rating, no associations between and within modalities were found with respect to various dimensions of interoception. Further, the interoceptive dimensions were not associated with state and trait positive and negative affect and perceived body competence. In summary, interoceptive accuracy scores do not substantially contribute to conscious representations of cardioceptive and proprioceptive ability. Within our data, non-pathological affective states (PANAS) are not associated with the major dimensions of interoception for the cardiac and proprioceptive modalities.
Article
Using a patient lift to assist in transfer can alleviate physical burden and reduce the risk of lower back disorders. However, it requires more time than applying manual transfer techniques, often resulting in caregivers opting out of its use. This study used two experiments to examine the lifting and lowering velocities experienced by caregivers and residents when using a patient lift during nursing care. In experiment 1, the usability, subjective assessment of velocity, heart rate (HR), electromyography (EMG), working time, and so on were measured at eight lift velocities (ranging from 0.01 to 0.15 m/s in 0.02 m/s intervals) during the transfer task of 10 female students in a laboratory. In experiment 2, the same measured parameters as in experiment 1 except for HR and EMG were measured at four lift velocities (ranging from 0.03 to 0.09 m/s in 0.02 m/s intervals) during the transfer task of six elderly residents by 12 caregivers at an elderly care facility. The residents and caregivers rated 0.05–0.09 m/s as appropriate velocities in both experiments. Specifically, the best velocities for lowering the lift without the resident, lifting with the resident, and lowering were 0.07–0.09 m/s, 0.05–0.07 m/s, and 0.05 m/s, respectively. We conclude that the studied velocities are appropriate when the lift is used by caregivers at an elderly care facility. Since the appropriate velocity is different for each transfer subtask, we suggest that manufacturers should program suitable velocities into lifts according to the subtasks deemed important by the caregivers.
Conference Paper
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Stress in students may be a useful indication for when a student is struggling and in need of academic intervention. Investigating differences in student behaviour in stressful and comparatively less stressful environments could be helpful in understanding the processes involved in learning to code, and combatting the high levels of drop-out and failure in undergraduate computer science. In this paper we will discuss the mouse movement data gathered from Maynooth University Learning Environment (MULE), our in-house, browser-based pedagogical environment for novice programmers, during the time period February to May of 2019. This included 5 supervised, scheduled lab sessions and two inlab examinations. The data was used to examine 21 different measurements of student behaviour, for example, by measuring efficiency of the mouse path, or the time between mouse click-down and mouse click-up. These features were used to build a Deep Neural Net that classifies sequences of mouse movements as being either from a more stressful environment or a less stressful one by training the classifier on data from examination situations and regular weekly lab situations, with the goal of comparing how students behave in environments with different levels of student comfort. The classifiers had an average accuracy of 61.9% but was more successful with students who performed poorly in their lab examinations. To further examine this connection between mouse movement, stress and student outcome, a second classifier was built to classify students as being in the high or low 50% of lab-exam grades in the module, with an accuracy of 69%.
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Subjective fatigue and reaction time performance were measured in a group of 24 aeroplane mechanics, during 1 week of high noise exposure and 1 week of low noise exposure. Subjective ratings were collected before and after each work day. On the last day of each week subjects also completed a reaction time task before and after work. The mechanics felt more sleepy and less energetic during the high noise week. This effect was most evident towards the end of the day and there was a build-up of the effect during the week. Reaction times were prolonged during the high noise week. Possible confounding factors are discussed and found to be less likely explanations of the effects.
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PW. Differences between work methods and gender in computer mouse use. Scand J Work Environ Health 2000;26(5):390-397. Objectives The aim of this study was to investigate whether gender or different methods of operating a computer mouse have an effect on pelfo~mance and lnusculoskeletal load in the use of a computer mouse. Methods Thirty experienced computer mouse users, 15 men and 15 women, participated in the study. Electromy-ography (right first dorsal interossei, right extensor digitorum and right and left trapezius), a force-sensing mouse, and subjective ratings were used to register muscular load. An electrogoniometer was used to register the wrist movements. The subjects worked with 3 different methods, their own, a wrist-based method and an arm-based method. Gender comnparisons were made when the subjects used their own method. Results The women worked with greater extension and range of motion and tended to work with a greater ulnar deviation of the wrist. They also applied higher forces to the mouse when expressed as a percentage of a maximum voluntary contraction and had higher muscular activity in the right extensor digitomm. When using the arm-based method, the subjects worked with greater wrist extension, had higher muscular activity in the right and left trapezius muscles, and had the highest ratings of perceived exertion in the neck and shoulder. The wrist-based method resulted in higher forces being applied to the sides of the mouse and the highest ratings of perceived exertion in the wrist and hand-fingers. C O ~ C I U S ~ O ~ S Gender differences were found for musculoskeletal load, and for most of the measured variables the women worked with higher loads than the men. The work method affected performance and musculoskeletal load. Finally, subjective measures appeared to have some utility in characterizing muscular load.
Article
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Mental stress was induced by the Stroop colour word task (CW task) and the effects on the micro-circulation and electromyography (EMG) in the upper portion of the trapezius muscle were studied during a series of fatiguing, standardized static contractions. A lowered blood flow of the skin recorded continuously by laser-Doppler flowmetry (LDF) was used as a stress indicator in addition to an elevated heart rate. Muscle blood flow was recorded continuously by LDF using a single optical fibre placed inside the muscle, and related to surface EMG. A group of 20 healthy women of different ages was examined. Recordings were made during a 50-min period in the following sequence: a 10-min series of alternating 1-min periods of rest and stepwise increased contraction induced by keeping the arms straight and elevated at 30, 60, 90 and 135 with a 1-kg load carried in each hand; a 10-min recovery period without load; a repeated contraction series with simultaneous performance of the CW task; a second 10-min recovery period, and a second contraction series without CW task. Signal processing was done on line by computer. The LDF and root mean square (rms)-EMG values were calculated, as well as the EMG mean power frequency (MPF) for fatigue. The CW-task added to the contraction series caused an increase in the heart rate accompanied by a decrease in the blood flow to the skin and a 30% increase in the blood flow in the exercising muscle. Both returned to normal during the subsequent recovery period and showed normal levels during the final contraction series without CW. The rms-EMG showed a 20% increase that persisted during the final contraction series performed without CW. There was no influence on MPF. This CW has previously been shown to evoke an increased secretion of adrenaline from the adrenal medullae to the blood. The increased blood flow in the exercising muscle would therefore appear to have been caused by -adrenoceptor vasodilatation, and the fall in the blood flow in the skin by -adrenoceptor vasoconstriction. The findings may have implications for work situations characterized by repetitive static loads to the shoulder muscles and psychological stress.
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In studies on work it is important to assess various subjective symptoms, complaints, and annoyances. To measure such symptoms, psychophysical ratio scales may be used, as along with simpler category rating scales. In this paper some of the basic concepts and methods of psychophysics have been described. In the field of heavy physical work and the perception of effort and exertion, one of the most popular methods is the rating of perceived exertion. This scale has been presented together with a new category ratio scale, commonly referred to as the CR-10 scale. Some situations in which it is important to obtain measurements of perceived exertion have also been described in the paper.
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Beat-to-beat fluctuations in heart rate (HR) or instantaneous HR is mainly determined by activity of the cardiac sympathetic and parasympathetic systems. Despite the need for standardization in methodology to facilitate the interpretation and comparison of results, the data presented in this review clearly show that there are individual differences in heart rate variability (HRV) and that these differences partly reflect differences in the degree of parasympathetic and sympathetic stimulation of the heart. HRV and its spectral components can be easily and noninvasively assessed and can provide valuable information to the occupational physician. Measurements of HRV and the quantification of its spectral components are powerful predictors of cardiovascular morbidity and mortality. Therefore, it may help assess the return to work of patients with ischemic heart disease. Studies in the workplace can also indicate the effects of various stresses of the work environment on such patients and even on asymptomatic workers.
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The aim of this study was to evaluate whether psychological stress causes increased muscle activity, especially static muscle activity, in the trapezius muscles of the neck and shoulder. A pilot and a main study were carried out with 10 males and 20 females, respectively. The subjects performed a VDU data entry task under psychologically stressful and non-stressful conditions. Stress reactions were measured by different methods: heart rate and heart rate variability, hormonal excretion, and subjective ratings of mood and body symptoms. The stress condition caused an increase in heart rate. The low-frequency variability increased and the high-frequency variability decreased. Ratings of motivation and relaxation decreased, and subjects felt more activated. Pain and discomfort from the stomach increased. Adrenaline and noradrenaline in urine were unaffected. The majority of the subjects showed moderately increased static and median EMG levels during the stress condition. The interindividual variation in muscular reactions was large. Statistically significant increases were obtained for the myoelectric activity of the left (resting) trapezius muscle when pooling the two groups. It appears that the increase in muscle activity due to this type of mental stress is small, and factors other than ‘attention-related’ load may be more important. The results indicate that some individuals may be more prone to general muscle tension, making them more likely to develop symptoms and musculoskeletal pain.
Article
Studied the association between psychosocial work factors and musculoskeletal disease, via a qualitative review of the epidemiologic literature. It is concluded that monotonous work, high perceived work load, and time pressure are related to musculoskeletal symptoms. The data also suggest that low control on the job and lack of social support by colleagues are positively associated with musculoskeletal disease. Perceived stress may be an intermediary in this process. In addition, stress symptoms are often associated with musculoskeletal disease, and some studies indicate that stress symptoms contribute to the development of this disease. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Video display terminal (VDT) operators (n = 150) in the editorial department of a large metropolitan newspaper participated in a study of day-to-day musculoskeletal symptoms. Work posture related to the VDT workstation and psychosocial work factors were also investigated for their contributions to the severity of upper body pain, numbness, and stiffness using a representative subsample (n = 70). Self-report measures included Karasek's Job Content Instrument and the author-designed Work Interpersonal Relationships Inventory. Independent observations of work posture were performed using techniques similar to those reported by Sauter et al. [1991]. Pain during the last week was reported by 59% (n = 88) of the respondents, and 28% (n = 42) were categorized by symptom criteria potentially to have musculoskeletal disorders. More hours per day of VDT use and less decision latitude on the job were significant risk factors for potential musculoskeletal CTDs. Head rotation and relative keyboard height were significantly related to more severe pain and stiffness in the shoulders, neck, and upper back. Lower levels of co-worker support were associated with more severe hand and arm numbness. For both the region of the shoulders, neck, and upper back and the hand and arm region, however, the contributions of relative keyboard and seat back heights to symptom severity were modified by psychological workload, decision latitude, and employee relationship with the supervisor. Alternative explanations for these findings are discussed.
Article
This paper evaluates task complexity as a task-related factor causing the development of psychologically mediated ('psychogenic') shoulder muscle tension. Eighteen subjects performed an experimental work session, responding to simple and complex reaction time tasks which were presented on a VDU screen. Most subjects generated low-level static muscle tension during the tests. On a group level the two tasks did not have a differential effect on muscle tension. However, a subgroup of eight subjects which consistently generated higher muscle tension in the complex tests, was identified. It is argued that for these subjects the difference in muscle tension is due to an increased mental effort invested, because of the higher computational demands in the complex task.