Iranian Journal of Ergonomics

---

Match between school furniture dimensions and children’s anthropometric dimentions in male elementary schools. Rashid Heidari Moghaddam1, Rasoul Ahmadi2 , Majid Motamedzade3, Ghodratollah Roshanaie4 stract: Introduction: Given the important role of appropriate furniture in the posture of the students and that non ergonomic furniture can produce uncomfortable posture, low ‌‌‌back pain, neck pain, lack of concentration and discomfort, therefore, this study examine match between school furniture dimensions and children’s anthropometric dimensions in male elementary schools in Hamadan city. Materials and Methods: In this study 600 children have been studied. Their weight and height and their anthropometric dimensions included shoulder height, elbow height, knee height, popliteal height, popliteal-bottock length and hip breadth have been measured. Then, the fitness between current furniture's dimensions and calculated ergonomic dimensions have compared. Results: : Findings showed that dimensions of available furniture included seat height, seat depth, seat width, back rest height, desk height, underneath desk height and anthropometric dimensions of students was not matched. This study has shown that by increasing the seat depth and decreasing the seat height in new designs, they have relatively improved in compare with the old designs. Conclusion: Available school furniture dimensions in Hamadan elementary schools are not appropriate for most students and induce postural discomfort and musculoskeletal disorders. Key words: Ergonomics, Anthropometrics, Design, Furniture 1- Department of Ergonomics, Faculty of Health and Medical Sciences Research Center, School of Public Health. Hamadan University of Medical Science, Hamedan, Iran. 2- Corresponding author, Ergonomics graduate student, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran. 3- Professor, Department of Occupational Hygiene, School of Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran. 4- Roshanaei, Ghodratollah, Department of Biostatistics and Epidemiology. Modeling of Noncommunicable diseases Research center, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.

---

Background: Safety signs are considered as visual intermediates for message transmission and play a crucial role in reducing accidents particularly in petrochemical industries. These signs are effective as long as they are designed in compliance with ergonomic principles, human factors, and cognitive features. Therefore, the present study aimed to investigate the psychological effects of safety signs in transmitting message given their designing features in the petrochemical industry. Materials and methods: This descriptive-cross-sectional study was carried out on 100 employees in Mahshahr Petrochemical Complex. A 2 partite questionnaire was used to collect data the first part for demographic information and the second part included designing features of signs (familiarity, objectivity, simplicity, meaningfulness, semantic proximity). The Pearson correlation test was used to identify the correlation coefficients between signs features and scores given by the participants. Findings: Mean and standard deviation of the scores of the signs’ message perception were 60.73 and 4.36, respectively. Cognitive features of the signs included familiarity and semantic proximity with a mean of 49.15 and 66.78, respectively. The factors of work experience, age, and academic level had no significant effect on guessing the meaning of signs (p>0.05). Conclusion: The results of this study showed that no significant relationship existed between cognitive features of the signs and transmission of the message and message transmission of safety signs is affected by other features than their design. Therefore, in order to improve individuals’ awareness about familiarity of employees with particular meaning of signs, ergonomic design of safety signs and proper training for perceiving their meaning are proposed.

---

Introduction: Manual handling of loads and carrying tasks widely exists in many occupations. Hospital staff because of Manual carrying of loads, are at increased risk of musculoskeletal disorders. Incorrect lifting methods, is an important risk factor for low back pain. The aim of this study was to analyze the biomechanical loads on the lumbar of nurses-aid in manual handling activities of serum cartons 12.5 kg in hospital and provide ergonomic solutions is the prevention of back pain. Methods: This study was conducted one of the hospitals in Ahvaz city in year 1392. evaluated Postures were sampled through observation and photography. Then load lifting of complex index, was calculated by NIOSH equation and estimate the compressive forces on vertebras L5/ S1 as a quantitative index using software 3 D SSPP, during 2 stages before and after the intervention. The results of tests using Correlation, Regression and T-test were analyzed Results: The results showed that the highest RWL in the top row 89/9 kg and minimum on the bottom row was 44/5 kg. The highest and lowest compressive force was estimated in the bottom and top rows, respectively, 6727 and 3707 Newton. Results of statistical tests showed significant reduction between the load lifting of complex index(CLI), and the compressive force average before and after the reform is the work station. Conclusion:Throgh biomechanical analysis of work stations with two methods quantitatively and qualitatively can be made more accurate assessment and ergonomic conditions at work stations can be modified more accurately.

---

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.

---

---

Background and Objectives: Accurate measurement of the employees’ satisfaction with their office chairs can provide valid feedback on the chair design quality for the manufacturers and researchers. This study aims to design a valid and psychometrically evaluated questionnaire for measuring satisfaction with office chairs.
Methods: Through studying the two main documents about chair ergonomics including Iranian office chair standard No. 11388-1 and a valid Persian questionnaire on satisfaction with educational chairs (Mirmohammadi et al.), the initial 39-item office chair satisfaction questionnaire has been developed. Then face and content validity of the questionnaire have been checked out using qualitative and quantitative approach. Quantitative face validity was analyzed using impact score method. Content Validity Index (CVI) and Content Validity Ratio (CVR) have been used for quantitative content validity analysis. In order to analyze the questionnaire’s reliability, two methods including the internal consistency and constancy have been applied. To measure the internal consistency, α-Cronbach (alpha coefficient) and to evaluate constancy (test-retest) have been employed. Also, the receiver operating characteristic (ROC) curve was utilized for specifying its sensitivity, specificity, and cut-off point. The data was analyzed by SPSS 21 and Stata V.14
Results: Mean (CVR) and (CVI) of final questionnaire have been calculated as 0.93 and 0.95, respectively. Questionnaire’s α-Cronbach coefficient has been gained 0.8. Kappa coefficient (for inter-rater agreement) has showed high score (0.91) in the test-retest results, indicating high correlation and good constancy of the questionnaire. In the ROC, the cut-off point was reported as 75.5 with the sensitivity and specificity of 86.2 and 100, respectively, and area under the ROC curve at this cut-off point was 0.96.
Conclusion: The final 34-item questionnaire has exhibited acceptable reliability and validity for measuring satisfaction level of office chairs.
 

---

Introduction: The aim of this study was to evaluate the effect of unstable shoes on lower limb kinetic parameters of walking in healthy male students with different geometric shapes. Today, various shoes have been developed to reduce the effects of injury parameters and improve performance parameters for walking.
 
Methods: 20 of the healthy male lambs were selected 178.96 ± 3.92 cm, 27 ± 3 years old, 73.99 ± 6.6 kg and 42 (EU) number, in four position, domestic production unstable shoes , foreign Similar unstable shoes, regular control shoes, and barefoot, The Kinetic parameters associated with Lower limbs was evaluated by force plate while walking. To examine the significant statistical differences between dependent variables between the four conditions of foot cover, the general linear model and the analysis of variance with repeated data and / or Friedman in the case of normalization of data in the alpha level of 5% using software version 23 SPSS was used.
 
Results: In relation to the kenetic parameters of the lower extremity, there was no change in the peak Postereior Force and the peak active force in the case when there was a significant change in the peak passive force and  peak anterior Force and and the free movment and loading rate.
 
Conculosion: The results indicate to the domestic production unstable shoes inefficiency  in reducing the damage and increasing the comfort of the lower limbs.

---

Background and Objectives: The progress and rebound of organizations depends on their productivity. Many factors affect the organization’s productivity; identifying these factors the organization’s deterrence can be prevented. In this study, the relationship between job burnout and employee productivity has been investigated.  
Methods: This research is applied and its statistical population is 1265 people in Shariati and Kharazi hospitals. 294 of these employees were selected by Convenience sampling method considering the Cochran formula. Data was collected using the Maslach Burnout Standard Questionnaire and Hersey and Goldsmith Human Resources productivity Standard Questionnaire. Pearson correlation test and SPSS18 was used to analyze the data.
Results: The results of data analysis showed that burnout, emotional exhaustion, depersonalization and reduced personal accomplishment with -0.82, -0.86, -0.83 and -0.85 correlation values, respectively, have a reverse and meaningful relationship with employee productivity of Shariati and kharazmi Hospitals employees.
Conclusion: Since the results showed that burnout and its dimensions have a significant relationship with productivity of Shariati and Kharazmi Hospitals in Isfahan, it is necessary for organizations to apply measures to reduce the feeling of burnout in the staff. The results of this study are consistent with the results of other studies. At the end of the study, were presented several research proposals based on the results of the study.

---

Background and Objectives: Studies have shown the effect of smoking on mental and cognitive performance of the individuals who need to concentrate on their work. The present study aimed to investigate the effect of smoking on cognitive performance of the automotive industry workers. 
Methods: In this case-control study conducted in 2018, 280 automotive industry workers were selected through the simple random sampling and then assigned to  two groups of smokers (100 cases) and non-smokers (180 controls). All the subjects were selected from the environments with the sound levels of 82 to 88 dB. The workers’ cognitive performance was also tested using the CPT, Stroop and Tower of London tests.
Results: The mean age of the case group was 36/02 (3/7) and that of the control group was 36/25 (3/65) years. The results showed that the scores of the TOL test in the case group (smokers) were lower than those of the non-smokers (OR=0/903, P<0.01), and other items of the TOL test had no significant relationship with the individuals’ smoking status (P>0/05). The Stroop and continuous performance tests also had a significant relationship with the individuals’ smoking status in terms of the number of correct responses and the response time as well as interference (P<0.01). Other items had no relationship with the individuals’ smoking status (P>0/05).
Conclusion: The results of this study showed that the use of cigarettes and nicotine substances significantly decreased the workers’ mental and intellectual performance, and smokers were more likely to suffer from concentration interference, low brain processing speed in decision-making, and low precision at work, compared to non-smokers.
 

---

Background and Objectives: Noise pollution is one of the most harmful physical factors in working environments in developed and developing countries, which has significant impacts on the workers’ quality of life. The aim of this study was to investigate mental and physiological effects of chronic exposure to noise.
Methods: This is a cross-sectional study carried out randomly in 2018 on 250 workers in the automotive Industry. To measure the subjects’ aggression and annoyance levels, the Buss and Perry’s Aggression Questionnaire was used as well as an annoyance questionnaire. In this study, blood pressure measurement was also done using ALPK2 mercuric pressure gauge.
Results: The results showed that there was a significant difference in the systolic and diastolic blood pressure and noise annoyance in the groups with a lower-than-85 and higher-than-85 dB sound pressure levels (P<0.001). Besides, the results of multivariate regression showed that the annoyance level and sound pressure level had a significant relationship with the workers’ blood pressure (P<0.01). Also, there was a significant correlation between aggression components and sound pressure level (P<0.01).
Conclusion: The results of this study clearly showed that chronic exposure to noise in work environments was associated with psychological and physiological changes, such as increased blood pressure and aggression levels. Hence, implementation of preventive programs can help reduce the incidence of the psychological and physiological disorders.
 

---

Background and Objectives: Sewing is one of the occupations where the prevalence of musculoskeletal disorders is high. Sewing conditions at the workstation have made tailors face musculoskeletal injuries in various areas of their body, particularly pain in the neck, shoulder, and upper back and even waist. The purpose of this study was to evaluate the effect of a workstation designed for tailoring considering the results of previous studies on the neck and shoulder muscles of users by electromyography.
Methods: In this interventional analytical study, the activity levels of four superficial neck and shoulder muscles (meridian, anterior deltoid, middle deltoid, posterior deltoid) were Electromyographed on 33 participants (male and female) at two new and custom designed workstations.
Results: There was a significant difference in the amount of muscle activity in the new and existing workstations (P<0.05). But there was no significant difference between the different modes of the new workstation.
Conclusion: All four muscles were less active at the new workstation than the conventional workstation, meaning that the designed workstation was able to reduce neck and shoulder muscle activity during work.

---

---

---