Iran Occupational Health

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  Background and aims : Long term working in a static and awkward posture is known as an important risk factorof work related musculoskeletal disorders in hand carpet weavers. Inappropriate workstation and awkward posture can increase the electrical activity and fatigue in muscles. The aim of this study was the measurement of muscle load and fatigue by surface electromyography and Borg CR-10 scale methods.

  Methods: Two typical carpet weaving workstations (A: seated with cross legged posture and B: seated on chair) were simulated in the laboratory and 12 women carpet weavers with mean age of 32.5 years, without any musculoskeletal problems in upper limb were invited to this study and they were asked to work in each workstation in separate days for 3 hours. Surface EMG signal recordings were done during these 3 hours for four muscles (bilateral trapezius and bilateral deltoid) andall subjects were asked to report shoulder region fatigue in Borg CR-10 rating scale. The RMS and MF values were extracted form row EMG signal to estimate the muscle activity and fatigue.

  Results: The result of this study shown that muscle activity in all muscles under the test in workstation A is higher than workstation B (P <0.05). In comparison between the muscles, the mean RMS of the trapezius is higher than bilateral deltoid (P<0.01). Joint analysis of spectral and amplitude for estimating the muscle fatigue shown that muscle fatigue incidence in workstation B is more than workstation A. In comparison between Borg CR-10 rating scale, there is no significant difference in two workstations.

  Conclusion: According to these results, it can be concluded that working in two workstations can increase the risk of work related musculoskeletal disorders in shoulder region and further studies and hence, designing the ergonomic workstation for carpet weavings is necessary

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Background and aims: Car seats have a significant impact on driver comfort and reduction of postural load on the low back of the driver. The purpose of this study was to compare three common types of car seat in Iran on the driver's fatigue and muscle discomfort.

Methods: Ten participants completed 2 hours of simulated driving for each of the three type of car seat in different days within a week. During driving task, the electrical activity of the lumbar erector spinae muscles were recorded every 15 minutes and discomfort rate measured every 30 minutes by a visual indicator. The RMS, mean frequency (MNF) and median frequency (MDF) were calculated and used to assess muscle load and fatigue. Repeated measure ANOVA was performed to assess the effect of car Seat on muscular activity and fatigue.

Results:  A significant difference found between various types of car seat with regards to subjective measure of discomfort data (p<0.05), MNF parameter of left erector spinae muscle showed approximately significant difference between car seats(p=0.07), however with regards to NRMS and MDF parameters, the difference between car seats is not significant during 2 hours driving in simulation context.

Conclusion: Although the level of activity and fatigue of erector spinae muscles showed no significant difference during two hours of driving, but self reported discomfort in low back muscles suggested a significant difference. Based on the findings of this study, it seems some type of car seats may cause discomfort however there was no significant difference between three types of car seat with regard to fatigue. In order to design of ergonomic car seat further studies recommended.

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Background and aims: The psychosocial work factors have a major impact on employees’ cognitive performance. The purpose of this study was to investigate the relationship between psychosocial work factors and cognitive failures among nurses.
Methods: In this study, 300 nurses who worked in educational hospitals were selected by simple random sampling method. The questionnaires that used for data collection included: demographics information,COPSOQ and CFQ questionnaires. To analyze the relationship between variables, independent t-test, ANOVA, Pearson correlation coefficient and linear regression analysis were used.
Results: There was a significant relationship between the majority of dimensions of psychosocial work factors such as role clarity, influence at work, job satisfaction, and insecurity at work, quantitative demands, emotional demands, total job demands and meaning of work with cognitive failures of nurses. Also, the dimensions of total job demands, meaning of work and influence at work with high and significant correlations had a good predictition of cognitive failure in nurses.                                                                                                                 
Conclusion: According to the results, some of the psychosocial work factors affects on the rate of cognitive failures. Therefore, organizational interventions must be considered in order to control important psychosocial work factors. Further studies are needed to identify other factors affecting nurses’ cognitive failures.