Iranian Journal of Ergonomics

Introduction: 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). 

Materials and Methods: 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.

Results: 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.

Conclusion: 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.

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.

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.

Introduction: Listening to music during physical activity reduces the perceived stress on body. Hence, this study aimed to evaluate the effects of music genre and sound pressure level on calorie consumption and physical performance of students during treadmill tests.

Methods: In this cross-sectional study, 27 students were randomly selected. A demographic questionnaire, Borg Rating of Perceived Exertion Scale (RPE 6-20), and the Physical Activity Readiness Questionnaire (PAR-Q) were used for data collection. During flat and sloped treadmill running (five minutes at 6 km/hour), two pieces of music with fast and slow tempo (200 and 70 beat per minute) were also played at two sound pressure levels (60 and 80 dB). During the exercise, the students’ heart rate and calorie consumption were measured by a calorimeter (Beurer PM100). At each stage, the physical performance of the participants was estimated using the relevant equation.

Results: The students had the lowest physical performance (61.48) when no music was played and the highest physical performance (92.48) with slow, loud music. The mean heart rate, calorie consumption, and perceived exertion were maximized without music and minimized when slow, loud music was played.

Conclusion: Playing soft music at high sound pressure levels can promote physical performance during exercise by decreasing heart rate, calorie consumption, and perceived exertion.

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.

Introduction: Understanding the physical capacity of people in different weather conditions can facilitate the assignment of right jobs to right individuals. People’s physical work capacity can change in response to weather conditions. Since military forces are usually obliged to work under different weather conditions, this study aimed to assess these individuals’ physical work capacity in desired, warm-humid, and very warm-humid weather conditions.

Materials and Methods: This cross-sectional study enrolled 36 military men (age: 20-29 years). Astrand treadmill tests were used to measure the participants’ physical work capacity, maximum aerobic capacity, and maximum oxygen uptake were measured under three weather conditions (desired, warm-humid, and very warm-humid).

Results: The mean physical work capacity of the participants in desired, warm-humid, and very warm-humid weather conditions was 3.69 ± 0.52, 3.69 ± 0.55, and 3.41 ± 0.50 Kcal/min, respectively. The participants’ maximum physical capacity under the mentioned conditions was 10.87 ± 1.54, 10.84 ± 1.63, and 10.02 ± 10.48 Kcal/min, respectively. Maximum aerobic capacity of the subjects was 29.52 ± 2.52, 29.76 ± 2.65, and 28.14 ± 2.76 ml/kg/min, respectively.

Conclusion: According to our findings, people have similar physical work capacity under desired and warm-humid weather conditions. However, physical work capacity reduced in very warm-humid weather. Moreover, the participants were allowed to perform light-moderate work during a work shift.

Introduction: Physical activity has been identified as a potential intervention to improve body composition in women with breast cancer. This research sought to investigate the effects of an eight-week aerobic training program on some anthropometric indices and cardiorespiratory fitness of middle-aged women with breast cancer.

Material and Methods: A total of 15 women with breast cancer (age: 40-60 years) were selected through convenience sampling. They attended an eight-week aerobic exercise program consisting of three 40-60-minute sessions per week. Exercise intensity was maintained at 30%-60% the subjects’ heart rate reserve (HRR). The participants’ weight, body mass index (BMI), waist circumference (WC), hip circumference (HC), waist to hip ratio, waist to height ratio (WHR), body fat percentage (BFP), and maximum oxygen consumption were measured at baseline and after eight weeks of exercise. Data were analyzed by paired samples t-tests at a significance level of 0.05.

Results: Significant reductions in the patients’ weight (P = 0.001), BMI (P = 0.001), WC (P = 0.006), HC (P = 0.001), WHR (P = 0.006), and PBF (P = 0.001) were observed after eight weeks of aerobic training. Moreover, exercise significantly increased the subjects’ maximum oxygen consumption (P = 0.008). However, changes in the participants’ waist to hip ratio were not significant (P = 0.235).

Conclusion: According to the obtained results, an eight-week aerobic training program could significantly improve some anthropometric indices and cardiorespiratory fitness in women with breast cancer.

Introduction: Improving the quality of work life requires a certain organizational culture that supports creativity, autonomy, accountability, and employee participation. The present study investigated the relationship between organizational culture and employees’ quality of work life.

Materials and Methods: This cross-sectional and correlational study was conducted in 2015. A total of 145 staff members of all deputies of Hamadan University of Medical Sciences were selected. Organizational culture and quality of work life were measured using previously designed self-administered questionnaires. Items of the questionnaires were scared on a Likert scale. Pearson correlation coefficients were calculated to analyze the data. All analyses were performed by SPSS.

Results: A moderate level of organizational culture was detected in this study (mean score = 3.04). Organizational culture and its components had significant positive correlations with quality of work life (r = 0.64; P = 0.001). Linear regression analysis confirmed the significant positive effects of organizational culture on quality of work life.

Conclusion: Based on the findings of the present study, modification of organizational culture and its components is necessary for improving personnel’s quality of work life, job satisfaction, and participation. Development of appropriate organizational culture can ensure higher quality of work life among university staff and enhance the quality and productivity of academic services.

Introduction: Work-related musculoskeletal disorders (WMSDs) are the most common occupational health problems, reported with high costs and loss of productivity in nurses. On one hand, the quality of life is a multidimensional concept that affects factors such as physical and psychological ones. This study aimed to evaluate the relationship between WMSDs and quality of life in nurses.

Methods: This descriptive-analytical study was performed on 940 nursing staff in Hospitals of Sari, Iran. The samples were selected by census sampling method. Data were gathered using particular questionnaires of musculoskeletal disorders (Nordic) and quality of life (SF-36). Collected data were analyzed by analysis of variance (ANOVA), t-test and Pearson's correlation using SPSS software (version 18).

Results: The results showed that low back disorder with prevalence of 60.9% was the most prevalent disorder among nurses. All aspects of quality of life, except for social functioning, were significantly correlated with WMSDs (P<0.05). In addition, there was a statistically significant relationship in age, gender and education level with WMSDs as well as in gender and work with quality of life (P<0.05).

Conclusions: According to this study, the prevalence of WMSDs was relatively high in nurses. In the majority of nurses, moderate quality of life was observed. Therefore, any intervention to improve quality of life and prevent WMSDs should be focused on, to reduce the physical needs and psychological pressures.

Introduction: Foot anthropometric dimensions could be useful in designing comfortable footwear. The objective of this study was the measurement of foot anthropometric dimensions in a group of students.

Methods: This was a descriptive study in which 21 dimensions of foot for 580 males and females were measured manually. To measure the foot dimensions, a digital caliper and a tape were used. The measured dimensions included the important lengths, widths, heights and girths of foot. Descriptive statistics such as percentiles, mean and standard deviation were calculated for the collected data. To test and survey of the mean of foot dimensions between males and females, statistics such as independent t-test and effect size (Cohen’s d) were used.

Results: The values of mean, standard deviation, the 5th, 50th, and 95th percentiles were calculate and tabulated for the total studied population and for gender. In all measured foot dimensions, males had bigger dimensions than females. Gender had different impacts on the measured foot dimensions. The mean of all foot dimensions was significantly different between males and females (P value = 0.001). Digital pattering of I and II were observed in 78% and 22% of the studied population, respectively.

Conclusions: In the present study, important anthropometric data of foot were collected for a group of students. The presented percentiles could be used in design of male and female shoes. Conducting similar studies in children with different age categories could help completion of the anthropometric database.

Introduction: Introduction: Inappropriate sizes of school furniture and the deformation of children’s bodies is one of the issues of concern in the world. The aim of this study was the evaluation of anthropometry of primary students aged 6-12 years in Mazandaran, Iran and the design of school furniture based on the anthropometric criteria of the students.

Methods: In this cross-sectional study, 18 anthropometric dimensions of 2336 boys and girls aged 6-12 years in 2014-2015 were measured. To collect data, anthropometric chair, camera and camera stand, and Anthropometric photo graphical software were used. After determining the anthropometric dimensions, ergonomic school furniture was designed.

Results: Average, minimum, maximum, standard deviation, median and percentile value of 2.5 to 97.5 of the anthropometric dimensions of students were calculated. The results showed that gender had no effect on the popliteal height in the age groups of 6 to 7 and 7 to 8, but age had effects on popliteal height (P < 0.001). In the age groups of 8 to 9 and 9 to 10 years and also the age groups of 10 to 11 and 11 to 12 years both gender and age had effects on popliteal height (P < 0.001).

Conclusions: The results showed that by eliminating the effects of gender, 16.2 mm popliteal height increased per year. It was also found that after eliminating the effects of age, popliteal height increased 20.39 mm more in girls than in boys. Until the age of puberty, the anthropometric dimensions in girls increased more than in boys. The dimensions of ergonomics tables and chairs for students were designed in three sizes.

Introduction: Many employees in different professions including nurses work with shifts. On the other hand, different and long shift work  can endanger physical and mental health of nurses. This study, according to ergonomic standards, aimed to design a model for shift working in order to minimize the problems caused by shift work.

Methods: In this study, all 35 nurses working in the emergency ward of Imam Sajjad (AS) Hospital of Ramsar city, Iran, were considered. Then, the information gathered from answering the Morningness-Eveningness questionnaire (MEQ) (Circadian rhythm) and Survey Sampling International (SSI) (personal and social charactristics) questionnaire were changed to a model and then reconstruct after comparing it again with circadian rhythm principals. The final model was implemented with GAMS (gamma-glutamylaminomethylsulfonic acid) and at the end, shift working with ergonomic criteria were proposed.

Results: Shift working were designed for each nurse. Also, the obtained objective function value (Z=1.110223e-16) showed that the designed model was really close to ideal model. According to hospital rules and policies, if five more nurses get added to the currently employed ones, the proposed working program on one hand will improve satisfaction and efficiency of nurses and on the other hand it can decrease the effects of disorders on shift work.

Conclusions: Hospitals can have healthy and motivated workforce by applying the scientific approach to adjust a suitable working plan for their nurses and decrease the number of disabilities and also the rate of early retirement.

Abstract                                                                

Introduction: Job stress such as role ambiguity, a situation that arises from the interaction between people and jobs, reduces the performance and job satisfaction. Proactive people eliminate ambiguity in their jobs by behaviors such as innovation. The present study aimed at investigating the impact of proactive personality on job satisfaction and performance mediated by information seeking.

Methods: The statistical population of this survey consisted of the official staff and contractual personnel of Bid Boland gas refinery, from whom 260 were selected using the hierarchical random sampling method. The research design of this study was correlation, through structural equation modeling. The data collection tools were Role Ambiguity Scale, Proactive Behavior Questionnaire (Ashford and Black), Job Satisfaction Questionnaire (Brayfield & Rothe), and Job Performance Questionnaire (Paterson). The assessment of the proposed pattern was conducted through path analysis.

Results: The results supported the suitability of the relationship between the patterns and the collected data. The results revealed that proactive behavior mediated the effect of role ambiguity in job satisfaction and performance. All the routes in the research model were meaningful (P < 0.001) and the overall fit index [root mean square error of approximation (RMSEA)] was 0.04, which represents an excellent fit pattern.

Conclusions: Proactive behavior eliminates uncertainty for employees and finally eliminates the negative effects of role ambiguity on job performance and satisfaction and leads to increased performance and satisfaction of employees.

Introduction: The importance of product design has been dramatically increased in recent years due to economic considerations as well as changes in user preferences, policy making and legal needs. In response to this, and as one of the most influential branches in the field of product design (in terms of the fit between product and user), ergonomics has also been developed proportionally. The aim of this study was to review the most important considerations and different traditional and new approaches in product design as well as challenges and limitations in this regard.

Methods: A review was made of the relevant electronic databases including Ergonomics Abstracts, PubMed/Medline, Web of Science, Science Direct, Scopus and Google Scholar using the following keywords: product, design, ergonomic, design procedures and design approach. The search was limited to full text articles in the English language, published in peer reviewed journals between 1990 and 2015.

Results: Comparison of the traditional and new approaches in product design indicated that the new approaches helped designers to choose the best product model based on various aspects and a more detailed interaction between user and product. Ergonomic considerations in product design also include engineering and psychological aspects as well as taking into account abilities and limitations of both products and users, to find a good fit between user and product.

Conclusions: The findings suggest that the traditional approaches in product design alone may not anymore guarantee the success of a product in the market, particularly in universal scale and for a wide range of users. In other words, consideration of various technical (in terms of user-product interaction) and legal (environment, sustainability, cost benefit, etc.) aspects in new ergonomic approaches may be taken into account to improve the quality and success of the products in the global market. Ergonomists may encounter with some challenges to achieve this goal, but high-quality ergonomics services can be considered as an effective solution in this regard.

Introduction: In the recent decades, owing to the advancement of technology, most jobs and occupations require the use of computers. Lack of information about ergonomic conditions has resulted in various occupational injuries. Break time between work and doing exercise, help in reduction of musculoskeletal symptoms. The present study aimed to use a new ergo-feedback software and to assess its usability in office staff.

Methods: Thirty office staff participated in this study. In the first step, muscle-skeletal symptoms were checked by a body map checklist. Then, the Borg score was determined by the participants, initially and after one work day. The software was then run in their systems and they worked with it for about two weeks. After two weeks, the Borg scale was completed again and efficacy of the software was evaluated by the system usability scale (SUS). Data analysis was performed using descriptive statistics (mean and standard deviation) and Wilcoxon test. Statistical analysis was done by the SPSS software version 19.

Results: The results showed that there was a significant difference between the Borg score pre and post intervention (P > .05). The majority of the users were satisfied with the software with the SUS score showing about 82.25% satisfaction.

Conclusions: According to this study, office workers were satisfied with using this software and it can help reduce musculoskeletal symptoms during a prolonged time period.

Introduction: Nominal noise reduction rate of the earmuff manufacturers can be different compared with the actual attenuation rate. The present study aimed to determine the actual noise reduction rate of common hearing protection devices using microphone in real ear method.

Materials and Methods: In this study, five brands of common earmuffs used in Iranian industries were investigated on 30 subjects under laboratory conditions. Noise reduction rates of earmuffs were measured based on the ISO 11904 standard, microphone in real ear method, using noise dosimeter (SVANTEK, SV 102 model) equipped with a microphone SV 25 model. The earmuffs comfort was also assessed by the developed questionnaire.

Results: The results showed that the real noise reduction rates of the earmuffs were between 49% to 86% of nominal reduction rates. Moreover, the actual insertion losses were much negligible at low noise frequencies. The performances of earmuffs based on manufacturers were not statistically different (Pv> 0.05). Based on subjects’ comfort scores, comfort of ear muffs were within the acceptable range. The noise reduction rates of the different earmuffs of each model were not statistically different as well (Pv > 0.05).

Conclusions: Irregular use of earmuff can reduce the real attenuation of earmuff to lower than the minimum rate acquired in this study. Proper training and adequate supervision on proper use of earmuff can affect earmuff fitting along with increasing of real noise attenuation.

Introduction: Nursing in hospitals, because of the nature of the work, is a job in which work-related musculoskeletal disorders are highly prevalent. The main cause of musculoskeletal disorder amongst nursing staff is the movement of patients. The aim of this study was to evaluate the risk of musculoskeletal disorders caused by movement of patients in nursing staff of a hospital affiliated with the Allah University of Medical Sciences.

Methods: This cross-sectional study was conducted on 325 nurses from 30 wards of Baqiyatallah hospital during summer 2015. Data were collected using demographic and Body map Musculoskeletal Disorders Questionnaires and PTAI index checklist. Statistical analysis was performed using the SPSS software version 16.

Results: Some musculoskeletal symptoms had been experienced during the last 12 months by 78.3% of the nursing personnel. The results indicated that PTAI index score was significantly associated with musculoskeletal disorders occurrence (P < 0.05)

Conclusions: According to the findings, PTAI is an appropriate tool for musculoskeletal disorders risk identification and assessment due to patient handling in nursing personnel.

Introduction: Sleep disorder is very common among employees and is considered as one of the crucial health problems. Sleep disorders have a negative impact on job performance. The present study was regarding the relationship of sleep quality, sleepiness and sickness absence.

Methods: This cross-sectional study was conducted on 400 employees of a gas company through random sampling. The study data were collected using the Pittsburg Sleep Quality Index (PSQI) and the Karolinska Sleepiness Scale (KSS). Mann-Whitney U test and Spearman’s correlation coefficient were applied for data analysis.

Results: While 43.2% of the participants enjoyed satisfactory sleep quality, 56.8% had unsatisfactory sleep quality. Statistical tests indicated a significant difference in sickness absence of the personnel with good and poor sleep qualities (P = 0.0001). Spearman’s correlation coefficient (ρ = 0.777) indicated a statistically significant correlation between sleepiness index and sickness absence (P = 0.0001).

Conclusions: The results showed a strong positive correlation in sleep quality, sleepiness index of the personnel and sickness absence; i.e. along with decline in sleep quality and incline in sleepiness, the personnel’s sickness absence increased.

Introduction: Firefighting is amongst jobs that require high physical strength and high aerobic capacity. These are required because of the nature and the physical demands of the job. The maximum aerobic capacities of firefighters were investigated using the step test.

Methods: This cross-sectional descriptive-analytical study was conducted on 73 firefighters. At first, demographic information was collected by a questionnaire. Then, the step was built with adjustable height, for step testing, and using the Francis method, maximum aerobic capacity of the participants, was studied. The results of the questionnaire and step test were analyzed by the SPSS 16 software.

Results: maximum aerobic capacity of firefighters was calculated as 3.65 L/min and 47.4 mL/kgmin. Moreover, the results of statistical analysis revealed a significant relationship between body mass index and exercise, and maximum aerobic capacity (P ˂ 0.05). Also no significant relationship was found between maximum aerobic capacity, age, smoking and work-related fatigue (P > 0.05).

Conclusions: Studying the firefighters cardiorespiratory capacity, to reduce the probability of firefighters injuries is very important due to occupational sensitivity and having to perform difficult tasks under demanding circumstances. The results of this study showed that maximal oxygen uptake (vo2 max) and cardiopulmonary capacity of examined firefighters are greater than the minimum amount recommended by the international association of firefighters, which can be due to regular physical fitness programs conducted by the organization.

Introduction: According to the effectiveness and low cost of prevention, ergonomic assessment methods as a means to predict the potential occurrence of injury are being used. The aim of the present research was the assessment of validity and reliability of researcher-made ergonomic assessment test for freestyle wrestling skills.

Methods: In this research, according to the jobs ergonomic evaluation tests and wrestling pathology research, an ergonomic evaluation test for wrestling skills (WSEAtest) was designed. Content and face validity were proved by using the opinions of sports biomechanics and pathology experts, as well as physicians, physiotherapists, trainers and wrestlers of Freestyle national team. Furthermore, the test was performed on three skills in two different days by five examiners, using Kinovea software 0.8.15; also, intra- and inter-tester reliability were calculated. After the reliability and validity approval, WSEAtest was performed on video records of four selected skills of Iranian freestyle wrestlers in London 2012 Olympic games.

Results: The injury exposure in various parts of body, traumatic factors related to collisions and loads, and athlete and environment conditions were consistent with wrestling pathological research and confirmed the validity of the test results.

Conclusions: WSEAtest has acceptable validity and reliability; trainers, specialists, and sports therapists can use this test to assess traumatic factors and identify priorities for training and corrective exercises in different wrestling levels, and in various ages.