Journal of Ergonomics

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Introduction: Musculoskeletal disorders (MSDs) represent one of the leading causes of occupational injury and disability in the developed and industrially developing countries. This study was conducted to investigate the prevalence of MSDs and evaluate the risk of these disorders among welders of a steel manufacturing industry.

 

Materials and Methods: This descriptive-analytical study was achieved on all 243 welders employed in a steel manufacturing industry. Nordic Musculoskeletal Questionnaire (NMQ) was used to study the prevalence of MSDs. Meanwhile, QEC technique was employed to evaluate the risk of exposure to these disorders. For data analysis, central statistical indices, T-test and Chi-square test were used.

 

Results: The results suggested the highest prevalence of symptoms of musculoskeletal disorders in low back, trunk and knees, respectively. QEC technique showed a high and very high risk of exposure to MSDs in 64.6 % of welders.

Conclusion: This study demonstrated that the prevalence of WMSDs in welders under study was high. Based on the obtained results, the most significant ergonomic problems in welders were found to be awkward postures, manual material handling and back bending and twisting. Furthermore, the results suggested that QEC can present reliable findings in evaluating the risk level of exposure to WMSDs. Normal 0 false false false EN-US X-NONE AR-SA

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Introduction: The development of the industry has led to an increased incidence of muscle-skeletal disorders. The disorders increased caused by factors such as type of job, repetition of work, intensity and duration of the work. Food industries, including industries that are doing the type of job that involves repetitive movements, this study examined was conducted the role of stress and other psychosocial factors on musculoskeletal disorders. Methods: The present cross-sectional study to determine the prevalence of musculoskeletal disorders in different organs and factors affecting food production was one of the workers. According to a random sample of 215 workers were studied with an average age of 39 years. To evaluate the prevalence of musculoskeletal disorders was used of the Nordic questionnaire, also for of occupational stress was used OSIPOW questionnaire the data obtained are analyzed by SPSS 16 software and processing of data with the descriptive statistics and Pearson correlation test. Results: The results showed that the study population in the past 12 months the most common symptoms of lower back 69.8%. We were founded between stress and musculoskeletal discomfort in the neck, shoulder, wrist, upper back, a significant relationship (P<0.05). We were founded between smoking and low back pain (P <0.05), shoulder pain (P = 0.023), leg pain (P = 0.008) statistical test significant. As well as we were found between the average working hours per day and work experience, with musculoskeletal symptoms, fatigue, and BMI also a significant relationship. Conclusions: The results obtained in this study shows that job stress, work experience, BMI, the number of working hours and fatigue is considered a risk factor for upper extremity musculoskeletal disorder.

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Abstract Background: Heat exposure is one of the harmful agents at work environments. Workers in high temperature environments are susceptible to heat strain. The purpose of this study was to evaluate the performance of Iranian cooling vests containing phase change material in hot and humid conditions in the Persian Gulf. Materials and Methods: This interventional study carried out on 6 subjects of oil tanker ship's engine room staff in summer in 2013. The Heat Strain Score Index (HSSI), oral temperature and blood pressure measured with and without the cooling vest wearing for two hours, and data were analyzed by paired t test. Results: The mean oral temperature were 36.98± 0.22 °C (without cooling vest) and were 36.68± 0.68°C (cooling vest) at 30th minutes in heat exposure. The mean oral temperature were 37.06± 0.25 °C (without cooling vest) and were 36.78± 0.16°C (cooling vest) at 60th minutes in heat exposure. (p <0.042) and also HSSI was 12.72 ±3.03 (without cooling vest) and 8.65 ±2.9 (with cooling vest) (p <0.039) but the mean systolic and diastolic blood pressure were not significant statistically with and without the use of cooling vests (p>0.05). Conclusion: Our findings showed that cooling vests with phase change material packs reducing heat strain (oral temperature and perceptual heat) in hot and humid climates in Persian Gulf

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Introduction: The incidence of heat stress is one of the most common problems in work environments as well as many different industries. The exposure of workers to heat results in heat strain. The purpose of the present study was to validate the Perceptual Strain Index through determining its relationship to the Physiological Strain Index and the Wet Bulb Globe Temperature Index under hot laboratory conditions.

Materials and Methods: The present cross-sectional study was conducted on 15 men in five different temperature conditions (21, 24, 27, 30 and 35ºC) in a climate chamber and on the treadmill with three different activity levels –light (2.4km/h), medium (4.8km/h) and heavy (6.3km/h). Participants' heart rate and oral temperature were measured in order to calculate the Physiological Strain Index, and their thermal sensation and the rate of perceived exerted activity were measured for calculating the Perceptual Strain Index. The correlations between the indices were then evaluated using Pearson's correlation test and the regression analysis.

Results: Pearson's correlation test showed a significant correlation between the Perceptual Strain Index and the Physiological Strain Index (P=0.001 and r=0.94). The Perceptual Strain Index was also found to have a significant correlation with oral temperature and heart rate (p=0.001 and r=0.78 (p=0.001 and r=0.90). In addition, a significant correlation was found between the Perceptual Strain Index and the Wet Bulb Globe Temperature Index (p=0.001 and r=0.71) however, no relationship was observed between the Perceptual Strain Index and the Body Mass Index (p=0.79 and r=0.0009).

Conclusion: The findings of the study showed that the Perceptual Strain Index can be used for evaluating heat strain in the absence of access to other methods of evaluating heat stress as it has an acceptable correlation with valid indices of heat stress.

 

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Introduction: Concurrent pain in the knee joint and its-related muscles is expectable in patients with sacroiliac dysfunction. However, the association between the severity of knee pain and the level of sacroiliac dysfunction is still unclear. The present study aimed to determine the association between the severity of sacroiliac dysfunction and the severity of pain due to involvement of knee compartment. 

Materials and Methods: One hundred consecutive patients who visited an orthopedic clinic with the primary complaint of knee pain were recruited. According to specific diagnostic tests, 50 had sacroiliac dysfunction and 50 had no history of sacroiliac dysfunction. The severity of knee pain was determined using the Anterior Knee Pain Scale (AKPS). T-tests were then performed to compare the two groups in terms of AKPS scores.

Results: The mean AKPS score was 33.2 ± 12.1 in patients with sacroiliac dysfunction and 62.6 ± 18.6 in those without sacroiliac dysfunction (p < 0.001). Moreover, anterior knee pain was more frequent in the first group (56% vs. 10% p < 0.001). 

Conclusion: There is a significant association between the severity of anterior knee pain and severity of sacroiliac dysfunction. This association may be due to involvement of knee extensor muscles following the progression of sacroiliac dysfunction.

       

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Introduction: Water and paraffin are well-known phase change materials used in the manufacturing of cooling vests. The present study was conducted to design and make a cooling vest using commercial paraffin compounds and ice and to then examine their effect on thermal strain parameters in hot climate conditions in a climate chamber.

Materials and Methods: A cooling vest was first made with polyester fabric and containing 17 aluminum packs. Each aluminum pack was filled with 72 g of water and 65 g of prepared paraffin. A total of 10 male students then performed a treadmill exercise in hot climate conditions in a climate chamber (ambient temperature (TA) = 40 ⁰C and relative humidity (RH) = 40%) once with and once without wearing the cooling vest and at two levels of exercise intensity, including a light intensity (2.8 kph) and a moderate intensity (4.8 kph) exercise. Each stage of the experiment involved 30 minutes of rest and 30 minutes of exercise on the treadmill. Participants’ heart rate, oral and skin temperature and sweat rate were measured throughout the study.

Result: The latent heat of the prepared paraffin was 108 kJ/kg and the peak melting point was 30 °C. Significant differences were observed between participants’ mean heart rate, oral and skin temperature and sweat rate at both exercise intensities and both with and without the cooling vest (P<0.05).

Conclusion: The use of a cooling vest containing paraffin and ice can reduce thermal strain through reducing the heart rate, oral and skin temperature and sweat rate.

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Introduction: Job burnout can have negative effects on organizations and their employees. This study tried to investigate the relationships between job burnout and occupational stress, the four dimensions of organizational justice, personality characteristics, role clarity, and role overload.

Material and Methods: All full-time employees of the Regional Electric Company of Kerman (n = 200) were selected as the study sample. Finally, 138 usable questionnaires were collected. Previously designed questionnaires were used to measure work overload, occupational stress, role calrity, and organizational justice and respect. Maslach Burnout Inventory and NEO were also administered. Pearson’s correlation and multiple regression analyses were applied to analyze the data. All analyses were performed using SPSS 16.0.

Results: Job burnout was significantly related with occupational stress, distributive justice, extraversion, role clarity, role overload, organizational respect. Multiple regression analysis suggested distributive justice, overload, procedural justice, and occupational stress as the best predictors of job burnout. These factors explained 48% of the variance in burnout.

Conclusion: According to the results of this study, policymakers and planners of the organization are recommended to pay more attention to parameters contributing to job burnout. This will prevent job burnout among the personnel and promote organizational efficiency.

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Introduction: This study aimed to investigate the effects of cooling vests on heat strain and reaction time while wearing protective clothing against chemical, biological, and radioactive contamination.

Materials and Methods: Twelve male students with the mean age of 25 ± 2 years and mean body mass index (BMI) of 23.0 ± 1.5 kg/m2 were recruited in this experiment. Each student was asked to run on a treadmill at a speed of 2.4 km/h for 20 minutes. The experiments were performed at 35 °C and 30% relative humidity. Physiological strain index score, oral temperature, heart rate, reaction time, and number of errors were measured at the end of the two phases. The findings were analyzed by SPSS.

Results: According to Wilcoxon test, exercising with and without the cooling vest resulted in significantly different physiological strain index scores (P = 0.02), oral temperature (P = 0.02), reaction time (P = 0.02), heart rate (P = 0.02), and errors (P = 0.03). The mean physiological strain index score was 4.038 ± 0.882 without the cooling vest and 1.42 ± 0.435 with the cooling vest. The mean reaction times with and without the cooling vest were 0.539 ± 0.977 and 0.769 ± 0.0972, respectively.

Conclusion: The results of this study showed that using a cooling vest reduced the physiological strain, reaction time, and error rates in workers.

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Introduction: Few studies were conducted to determine the effects of lighting on cognitive performance. However, they could not reach a decisive conclusion. This study investigated cognitive performance of university students exposed to different levels of lighting under laboratory conditions.

Methods: In this experimental study, 33 subjects (age range 19-26 years) performed cognitive tests. Participants were exposed to three levels of lighting (200, 500 and 1500lux) in laboratory conditions while performing CPT tests to investigate percentage of attention and reaction time machine that measures reaction time.

Results: The results of this study showed that the maximum percentage of attention (99.75%) belonged to lighting of 1500 (lux) and the minimum percentage of attention was related to 500(lux) (99.36%). statistical analysis showed significant differences in percentage of attention in different levels of lighting (P=0.004). In addition, results of data analysis showed that increase in intensity of  lighting can make a significant change in the average response time (P˂0.001), correct response (P=0.004), commission error (P=0.001) and omission error (P=0.017). With increasing the lighting intensity, reaction time has decreased. The reaction time showed significant differences  at all levels of lighting (P˂0.001)

Conclusion: According to the findings of this study, lighting causes a decrease in reaction time and increase in attention. Thus, the lighting should be taken into account while designing of job and tasks which need attention or reaction time.

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