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- Crenshaw, Albert G., et al.
(författare)
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Reduced muscular oxygenation during computer mouse use with time pressure and precision demands
- 2004
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Ingår i: Conference proceedings at the American College of Sports Medicine (ACSM) 51st Annual Meeting. ; 35:5, s. S221-S222
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Konferensbidrag (refereegranskat)abstract
- Monitoring oxidative metabolic states may provide information on the mechanism behind computer use related musculoskeletal disorders. PURPOSE: To compare tissue oxygen saturation (Sat-O2) profiles in the forearm extensor carpi radialis (ECR) during computer mouse use with and without time pressure and precision demands. METHODS: Twenty-four healthy, right-handed subjects (12 females, 12 males; age 19-28 years) participated in the study. Subjects performed a 45-min mouse operated computer task on two occasions, separated by 3-5 days. The task consisted of painting squares that were presented on the screen. On one occasion, time pressure and precision demands were imposed by limiting the time available for painting a square and introducing a scoring system based on precision of painting (STRESS). On the other occasion, no such restraints were added (NON-STRESS). The order of the two task versions was randomized. During the task, Sat-O2 in the right ECR muscle was measured by near-infrared spectroscopy – NIRS (Inspectra, Hutchinson Technology). In addition, subjective ratings of tenseness and strain, and painting performance measures were recorded. RESULTS: A repeated measures ANOVA revealed a significant decline in Sat-O2 during the STRESS condition (p < 0.05), but no change for the NON-STRESS condition. A gender difference was apparent as females exhibited an overall lower Sat-O2 than males (p < 0.05); however, no interaction was found. Subjects’ ratings of tenseness and strain were significantly higher during the STRESS as compared to the NON-STRESS condition (p < 0.001). These data were paralleled by work pace (i.e. squares painted during STRESS = 119; NON-STRESS = 84, p < 0.001). Furthermore, accuracy of painting was greater for the STRESS as compared to the NON-STRESS condition (p < 0.01), i.e., number of times outside the square, STRESS = 2, NON-STRESS = 4. No gender differences in subjective ratings or performance variables were detected. CONCLUSIONS: Our finding of a change in local metabolic states under stressful conditions may shed light on the mechanism behind computer mouse related forearm muscular disorders. Furthermore, that females demonstrate a lower ECR Sat-O2 could give precedence to their higher incidence of disorders than males.
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- Dahlgren, Gunilla, et al.
(författare)
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Local oxygen saturation during computer work in patients with computer related disorders from the upper extremity : a pilot study
- 2003
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Ingår i: Conference proceeding at the 49th NAM conference (Nordiska Arbetsmiljömötet).
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Konferensbidrag (refereegranskat)abstract
- IntroductionAlong with increasing number of computer users in work organizations, upper extremity complaints become more and more common. Research has shown that increased exposure to repetitive keyboard and mouse use increases the risk of musculoskeletal disorders. However, the physiological mechanisms remain unclear. Pathological processes as the rate of the metabolism (energy crisis) can be conceivable as a cause of the symptoms and disability related to intensive computer work 1 . To date, there are no studies made upon local tissue oxygen (O2) saturation during computer work in patients suffering from computer related disorders in the upper extremity. In the present study, we examined local tissue oxygen (O2) saturation in m. trapezius and m. extensor carpi radialis brevis before and during mouse operated computer work in patients suffering from computer related disorders, and looked at relations between oxygen saturation, subjective ratings of pain, symptoms and disability.Material and methodFour right dominant female patient subjects (PS) aged 27 to 46 recruited through the company health care participated in the study. Their mean height was 166 cm and weight of three PS 55.8 kg (130 kg for the fourth PS). They had one or several diagnoses each, comprising of neck myalgia, diffuse forearm pain and lateral epicondylitis. All of them worked full-time and used computer with keyboard and mouse or mousetrapper device. Three PS used the computer for 7-8 hours per workday. The PS related their disorder to intensive computer work for long hours and high precision demands.Skin fold thickness was measured with a caliper at m. trapezius (TRAP) and m. extensor carpi radialis (ECRB) on the right side, and ranged from 2-6 mm. The mean skin temperature was 32.2° during rest and 32.7° following work on the ECRB (there was one missing post-value due to technical problems). The local tissue oxygen saturation was measured non-invasively with near-infrared spectroscopy, NIRS (Inspectra, Hutchinson Technology). One NIRS-electrode was placed at TRAP and the other on ECRB, both on the right side. After five minutes of rest, the PS performed a mouse operated computer task for 45 minutes with their right hand. The task consisted of painting squares presented on the screen, by using the mouse. Measurements of oxygen saturation were made throughout the computer work. Furthermore, subjective ratings of tiredness and strain were recorded on a 10 cm long VAS-scale. Symptoms and disability of the hand, arm and shoulder was rated with the DASH questionnaire, which contains the areas activities of daily living (ADL) and work 3. Descriptive statistics of the oxygen saturation comprised average and standard deviation of StO2 values in %. Comparison of the local tissue oxygen was made with the subjective ratings.Results and discussionTable 1. Local tissue oxygen (during 5 minutes rest and 45 minutes of computer work) and subjective ratings in PS.The mean saturation value for ECRB during rest was 52.6 (SD 20.2), work 46.7 (SD 14.7), and for TRAP during rest 58.8 (SD 21.2) and work 61.2 (SD 21.7). Skin fold thickness and skin temperature did not show any obvious interaction with the tissue oxygen values. Neither did comparisons of PS´s subjective ratings of tiredness and strain, symptoms, disability and the oxygen saturation, or severity of ratings and oxygen saturation. This might be due to the small amount of subjects and/or that the subjective ratings were not sensitive enough or do not fully reflect the state of art of computer related disorders from the upper extremity. One of the PS in our study reported intense delayed onset of pain 24 hours after the computer work. It is important to be aware that this can occur. The group of PS in this study had lower mean tissue oxygen saturation than healthy female subjects in another study that used the same device and performed an identical mouse operated computer task2. More research is needed for a better understanding of the mechanisms behind upper extremity disorders and the extent to which local tissue oxygen saturation reflects their symptoms and disability.References1. Boushel, R.; H., L.; Olesen, J.; Gonzales-Alonzo, J.; Bulow, J.; and Kjaer, M.: Monitoring tissue oxygen availability with near infrared spectroscopy (NIRS) in health and disease. Scand J Med Sci Sports, 11: 213-22, 2001.2. Heiden, M.; Dahlgren, G.; Lyskov, E.; Crenshaw, A.; and Johansson, H.: Effects of time pressure and precision demands during computer mouse work on muscle oxygenation and position sense. In Nordiska arbetsmiljömötet. Edited, Nyslott, Finland, 2003.3. http://iwh.on.ca/dash.html.
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| 4. |
- Heiden, Marina, 1974-, et al.
(författare)
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Effects of time pressure and precision demands during computer mouse work on muscle oxygenation and position sense
- 2003
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Ingår i: Conference proceeding at the 49th NAM conference (Nordiska Arbetsmiljömötet).
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Konferensbidrag (refereegranskat)abstract
- IntroductionAs the number of employees involved in computer work increases, neck and upper extremity complaints grow more common. Tight deadlines lead to high time pressure, which, in combination with precision demands, may increase the risk of musculoskeletal disorders. The physiological manifestation of such demands, however, is not entirely clear. In the present study, we examined local tissue oxygen saturation in the upper extremity as well as subjective stress responses during computer mouse work with and without time pressure and precision demands, and investigated whether these working situations have different effects on wrist position sense.Material and methodsTwenty-four healthy, right-handed subjects (12 females, 12 males; age 19-28 years) participated in the study. Except for one subject who reported using a computer for 480 minutes per day, their average daily computer use was 84 minutes (SD 65 minutes). Subjects performed a 45-min mouse operated computer task on two occasions, separated by 3-5 days. The task consisted of painting squares that were presented on the screen. On one occasion, time pressure and precision demands were imposed on the task by limiting the time available for painting a square and introducing a scoring system based on precision of painting. On the other occasion, no such restraints were added. The order of the two task versions was randomized. During the task, tissue oxygen saturation in trapezius and extensor carpi radialis on the right arm was measured non-invasively by near-infrared spectroscopy, NIRS (Inspectra, Hutchinson Technology). In addition, subjective ratings of tenseness and strain, painting performance measures, and skin temperature were recorded. The position matching ability of the wrist was measured before and after the computer task. In the position matching tests, subjects attempted to actively reproduce target positions of horizontal movements about the right wrist joint. From a starting position of 30° of extension, target positions were randomized between 0° and 30° of flexion. The absolute value of the difference between presented target and reproduced position (AE) was used as outcome measure. Skin fold thickness at the locations of the NIRS electrodes was measured with a caliper at the beginning of the experiment.Repeated measures analyses of variance were used to test for differences in oxygen saturation throughout the task, and for testing differences in position sense, as estimated by position matching ability, before and after the task. Subjective ratings during the task were analyzed by Wilcoxon’s non-parametric tests. Remaining parameters were tested for differences by t-tests or Wilcoxon’s non-parametric tests, depending on distribution of data. In all tests, p<0.05 was considered significant.ResultsA significant decline in oxygen saturation during mouse work under time pressure and precision demands was seen for extensor carpi radialis (F=4.68, p=0.036). This pattern was not present when mouse work was performed under more relaxed conditions. For trapezius, no difference in oxygen saturation between task versions was seen (F=0.01, p=0.932), although a general increase in saturation during work was found (F=10.35, p=0.002). Gender differences were apparent for extensor carpi radialis as well as for trapezius. Females showed an overall lower oxygen saturation in extensor carpi radialis than men (F=4.81, p=0.034). Furthermore, they showed a significantly different trend in trapezius oxygen saturation during work than men (F=6.27, p=0.016). Somewhat surprisingly, these gender differences could not be explained by differences in skin fold thickness at electrode positions (extensor carpi radialis: t=0.77, p=0.449; trapezius: t= 1.34, p=0.193). Subjects’ mean skin temperature changes during work was +0.41°C (SD 0.83°C).AE measured before the computer task did not significantly differ between occasions (paired t-test: t=0.08, p=0.940), indicating that the time period between occasions was long enough for effects of work to wash out. A significant increase in AE was seen following the task (F=15.59, p<0.001), irrespective of task version (F<0.01, p=0.968). No gender differences in AE were found (F=0.08, p=0.774). Subjects’ ratings of tenseness and strain were significantly higher during work under time pressure and precision demands (Wilcoxon’s signed-ranks test: Z>3.41, p<0.001), compared to work without such demands. This is in agreement with the fact that subjects increased their work pace (squares painted in work with demands: 119, without demands: 84, paired t-test: t=8.38, p<0.001), and made an effort to paint as accurate and precise as possible (no. of times outside the square in work with demands: 2, without demands: 4, paired t-test: t=3.68, p=0.001) during the more demanding task version. No gender differences in subjective ratings (Mann-Whitney U-test: Z<2.14, ns) or performance variables (t-test: t<1.71, ns) were found.DiscussionSubjects’ showed diminished oxygen saturation in extensor carpi radialis when working under time pressure and precision demands. This could be attributed to an increased mental load and/or a higher work intensity associated with this working situation. In support of this, subjective ratings of tenseness and strain scored higher during the more demanding task. It was also shown that subjects painted squares at a higher rate during the task. The fact that no differences in trapezius oxygen saturation between task versions was found might suggest that the physical strain associated with the work, being more prominent in extensor carpi radialis, could be a major contributor to oxygen saturation changes. Subjects’ tenseness ratings, however, would argue against it. Position sense, although poorer following work, was not affected by work type. One may speculate that physiological mechanisms involved in our measurement of position sense are not affected by local tissue oxygen saturation in extensor carpi radialis. The present data show considerable gender differences in oxygen saturation during rest as well as computer mouse work, that does not seem to be caused by skin fold thickness or painting performance.
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| 9. |
- Wilén, Jonna, et al.
(författare)
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Electromagnetic field exposure and health among RF plastic sealer operators
- 2004
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Ingår i: Bioelectromagnetics. - New York : Alan R. Liss, Inc.. - 0197-8462 .- 1521-186X. ; 25:1, s. 5-15
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Tidskriftsartikel (refereegranskat)abstract
- Operators of RF plastic sealers (RF operators) are an occupational category highly exposed to radiofrequency electromagnetic fields. The aim of the present study was to make an appropriate exposure assessment of RF welding and examine the health status of the operators. In total, 35 RF operators and 37 controls were included. The leakage fields (electric and magnetic field strength) were measured, as well as induced and contact current. Information about welding time and productivity was used to calculate time integrated exposure. A neurophysiological examination and 24 h ECG were also carried out. The participants also had to answer a questionnaire about subjective symptoms. The measurements showed that RF operators were exposed to rather intense electric and magnetic fields. The mean values of the calculated 6 min, spatially averaged E and H field strengths, in line with ICNIRP reference levels, are 107 V/m and 0.24 A/m, respectively. The maximum measured field strengths were 2 kV/m and 1.5 A/m, respectively. The induced current in ankles and wrists varied, depending on the work situation, with a mean value of 101 mA and a maximum measured value of 1 A. In total, 11 out of 46 measured RF plastic sealers exceeded the ICNIRP reference levels. RF operators, especially the ready made clothing workers had a slightly disturbed two-point discrimination ability compared to a control group. A nonsignificant difference between RF operators and controls was found in the prevalence of subjective symptoms, but the time integrated exposure parameters seem to be of importance to the prevalence of some subjective symptoms: fatigue, headaches, and warmth sensations in the hands. Further, RF operators had a significantly lower heart rate (24 h registration) and more episodes of bradycardia compared to controls.
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