مجله ارگونومی
سال سوم شماره 3 (پاییز 1394)

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. 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. 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). 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.

There is a dearth of information available on psychological job demands and control in the job (decision latitude) and their relationship with musculoskeletal disorders (MSDs) among Iranian nurses. The present study was conducted to investigate psychological job demands and control in the job and their relationship with the prevalence of MSD symptoms among nurses in hospitals affiliated with Shiraz University of Medical Sciences (SUMS). The present cross-sectional study was conducted on 385 nurses at SUMS hospitals selected through systematic random sampling. Data were collected using the Persian version of the Job Content Questionnaire (P-JCQ), the standardized Nordic Musculoskeletal Questionnaire (NMQ) and a demographic questionnaire. The data obtained were then analyzed in SPSS-11.5 using descriptive statistics and logistic regression. The mean (SD) of the different dimensions of psychological job demands and control in the job were calculated as 38.19 (5.14) and 58.15 (6.50). The results revealed psychological job demands to be high and control in the job to be low. A total of 29.1% of the nurses suffered from a high job strain (a high demand and low control). Regression modeling showed that the chance of suffering from lower extremity disorders among the nurses placed in the cells indicating a high job strain cell was 2.35 times higher than those placed in the cells indicating a low job strain. The demand-control model placed the majority of the nurses in the cells indicating a high job strain. Any interventional program designed for preventing MSDs among nurses should focus on increasing their control and changing their job conditions from a high strain condition to a low strain or active one.

Musculoskeletal disorders are among the top 10 injuries accounting for absence from work. The Extended Nordic Musculoskeletal Questionnaire (NMQ-E) is one of the many tools used to examine these disorders. The present study was conducted to translate and localize the NMQ-E and to evaluate the face validity and test-retest reliability of its Persian version. The present non-empirical methodological study used the International Quality Of Life Assessment (IQOLA) approach to translate the NMQ-E into Persian. The face validity of the Persian version was examined in a sample of 15 patients with musculoskeletal disorders (MSDs) and its absolute and relative test-retest reliability were examined in a sample of 48 patients using the Standard Error of Measurement (SEM) and the Intra-class Correlation Coefficient (ICC). The Kappa coefficient was also used to measure the inter-rater agreement for nominal variables. The translation and localization of the NMQ-E was deemed easy and acceptable. All the items of the questionnaire had an acceptable face validity. The Intra-class Correlation Coefficient and the Standard Error of Measurement of the Persian version of the NMQ-E were deemed acceptable (SEM=0.56-1.76 and ICC>0.7) and the Kappa coefficient was calculated as 0.78-1.00. The Persian version of the Extended Nordic Musculoskeletal Questionnaire showed an acceptable validity and test-retest reliability for assessing musculoskeletal disorders in Iranian patients.

Driver’s fatigue is a major factor contributing to the prevalence of road accidents. A vast number of city dwellers in most countries use public transport bus services to move around the city. Driver’s fatigue causes job burnout and affects the risk of a traffic accident injuring the public. Several methods have been used to date for evaluating mental fatigue; however, using questionnaires tends to be a less time-consuming and more accessible technique. The present study was therefore conducted to develop a mental fatigue questionnaire for public transport bus drivers. The study was conducted based on the criteria used for qualitative research. Semi-structured interviews were held with public transport bus drivers using probing questions and data were collected until their saturation so as to enable access to a direct description of mental fatigue by the bus drivers. Data saturation occurred with 30 interviews and sampling was then discontinued. The analysis of the interviews led to the extraction of the themes and an initial list of questionnaire items was then developed. The psychometric properties of the questionnaire were then evaluated through examining the content validity and internal consistency of the items. The content validity of the items was calculated using Lawshe’s table. A minimum CVR of 0.99 and a minimum CVI of 0.75 denoted an acceptable content validity for the items. To determine the internal consistency of the items, 200 bus drivers completed the final version of the questionnaire. The data obtained were then analyzed in SPSS-16 using Cronbach's alpha to measure the reliability of the questionnaire and considering an acceptance level of 0.7. The interviews conducted at the beginning of the study with 30 drivers led to the emergence of an initial list with 26 items. A total of 9 items with a CVR less than 0.99 were omitted from the list and 17 items with adequate simplicity, clarity and correlation between them and which had a minimum CVI of 0.75 were kept. The questionnaire had a Cronbach's alpha value of 0.87 and was therefore considered a reliable tool. The questionnaire developed in this study has a good validity and reliability and can therefore be used to assess mental fatigue in public transport bus drivers.

An important measure for ensuring safety in the operation of industrial machinery is to install proper guards that prevent machine hazards and protect operators. The design of industrial machine guards is a key issue in ergonomics and worker safety and has become a focus of research in hand anthropometry.The present study was conducted to assess the different hand anthropometric dimensions of employees in an industrial unit and to design a fixed mesh guard in the shape of a rectangle for industrial machines and to use the collected data for the standardization of industrial machine guards in Iran to help prevent machine hazards. Thirteen right hand anthropometric dimensions of 97 male and female employees of an industrial unit were examined. To design a standard fixed guard, the length dimensions of the 99th percentile of men and the thickness (diameter) and width of the 1st percentile of women were calculated. According to the data obtained, a standard fixed guard creates a safe distance of 196.61 mm with the hazardous components of the machine, a gap length of 10.19 mm and a gap width of 8.29 mm. Comparison of 6 parameters, including DIP, PIP, MCP, TE, DPC and WR, with the OSHA regulations showed that PIP and WR had decreased, MCP, DIP and TE had increased and DPC could not be analyzed given the lack of sufficient information on the parameter in the OSHA. The design of machine guards that help prevent industrial hazards is an integral part of workplace safety. The analysis of DIP, PIP, MCP, TE, DPC and WR in the present study and in a study conducted by Vaillancourt et al. showed some of the parameters to have increased and some to have decreased compared with the OSHA regulations. This study also reveals the need for revising ISIRI 11800, a standard published by the Institute of Standards and Industrial Research of Iran.

Power and pinch hand grip strengths are major clinical and ergonomic parameters contributing to the hand muscle power. The data on hand grip strength measurements can have many benefits, including application in the design of hand tools. The present study was conducted to measure power hand grip strength among male and female students aged 19 to 36 using a Jamar Dynamometer and to compare their measurement data with the data obtained from other groups of the population. The present cross sectional study was conducted on 234 male and female students aged 19-36 in Urmia University of Medical Sciences. Hand grip strength was measured using Jamar hand dynamometer and according to the Southampton protocol for adult grip strength measurement. The mean (±standard deviation of) hand grip strength calculated was 44.39 (±9.71) in the male students 20.48 (±5.86) in the female students. A high correlation was observed between the power hand grip strength in the left and right hands (r=0.94 and P<0.001) and a significant difference then between the power hand grip strength in the dominant and non-dominant hands. The findings of the present study and similar studies about power hand grip strength in the Iranian population can be used by ergonomists and manufacturers to improve the design of hand tools and the performance of tasks requiring hand muscle power.

As workplaces, hospitals are filled with stressors, including environmental and physical stressors (such as noise pollution and poor lighting), human stressors (such as conflicts with colleagues) and organizational stressors (such as heavy workloads and unsuitable work shifts). The inability to cope with these stressors entails physical, psychological and behavioral outcomes for the employees. The present study was conducted to evaluate job stress in nursing personnel and to design a model for assessing the severity of musculoskeletal disorders caused by job stress among nurses. The present cross-sectional analytical study was conducted on 500 nurses working in various teaching hospitals of Hamadan. Data were collected through four questionnaires, including the Job Content Questionnaire, Maslach’s Burnout Inventory, the Visual Analogue Scale and a Demographic Questionnaire. Data were then analyzed in SPSS-16 and LISREL-8.3 using descriptive statistics. The results of the structural equation modeling showed that job burnout has a mediating effect between the severity of musculoskeletal disorders and job stress. In other words, if factors contributing to job burnout are present, the psychosocial risk factors yielded by the Job Content Questionnaire then contribute to the severity of musculoskeletal disorders. Given the negative effects of job stress among nurses, health decision-makers are recommended to take measures to reduce stressors such as the physical and psychological demands of the workplace, the lack of support and the lack of job security.

Despite the introduction and development of agricultural mechanization in the dairy farm sector of Iran, many tasks are still performed by manual labor in the country’ dairy farms, including milking, and necessitate poor body postures and movements that help increase the risk of musculoskeletal disorders among hand milking workers. The present study was conducted to assess the postural workload of workers during hand milking in the dairy farms of Ramin Agriculture and Natural Resources University and Ramhormoz county. Three milking techniques were assessed, including traditional hand milking, milking stanchion (mobile milking unit) and tandem parlor milking (the double-3 tandem). The postural workloads of 34 male milking workers were evaluated through mixed-methods. The results obtained showed that hand and stanchion milking require major parts of the body to be in a bent position over 70% of the time due to the operations taking place at a low height from the ground. In contrast, tandem milking required the body to be in a straight position over 90% of the time due to the operations taking place at a substantial height from the ground. Moreover, in terms of finger posture, all three techniques required the workers’ five fingers to be wrapped around different milking tools and parts of the cattle throughout the processes. Being bent for long periods of time during the process of hand and stanchion milking and standing upright for long periods during tandem milking both caused musculoskeletal disorders of the back and backache for workers of both traditional and mechanized milking. In the case of the finger posture, prolonged repetitive finger postures decrease for milking workers with the increased mechanization of milking.