Iranian Journal of Ergonomics

Comparison of Strain Index (SI) and ACGIH-HAL in Assessing the Risk of Upper Extremities Disorders and Prediction of Carpal Tunnel Syndrome in Butchers

Kamran Gholamizadeh

Background and Objectives: Upper extremities are very vulnerable to work-related musculoskeletal disorders and selecting the best technique for assessing their exposure to ergonomic risk factors is of pivotal importance. This study aimed to compare two techniques of SI and ACGIH-HAL and assess their relationship with carpal tunnel syndrome (CTS) among butchers.
Methods: The study population was all butchers in Hamadan, Iran. After observing the activities, the assessments were conducted using both techniques. The severity of CTS syndromes was assessed using Boston questionnaire. The agreement between the techniques was investigated using Kappa coefficient. The association between the risk levels obtained from the techniques with the severity of CTS syndromes were assessed by regression analysis and fixing the effect of personal factors such as age, body mass index, and wrist ratio index.
Results: a total number of 152 butchers were evaluated. SI and ACGIH-HAL techniques respectively recognized 76 and 102 cases as low risk (agreement in 69 cases), 40 and 27 cases as moderate risk (agreement in 8 cases), and 36 and 23 cases as high risk (agreement in 18 cases). The Kappa coefficient between two techniques was 0.36 (P<0.001). By fixing the effects of age, body mass index, and wrist ratio index, both techniques had significant association with the severity of CTS syndromes. However, the association between SI and severity of CTS syndrome was higher than that of ACGIH-HAL.
Conclusion: SI had a higher estimate of risk than ACGIH-HAL. It seems that the predictive ability of SI for the severity of CTS syndrome is better than that of ACGIH-HAL.

Investigating the Effect of Package Parameters on Driver Comfort Using the DOE Method and the DHM Ergonomics Analysis Tool

Milad Karimi

Background and Objectives: Due to the necessity of the proper driver packaging, setting parameters for the driver to achieve the highest ergonomics of the driver has a great importance. The range of variations in some parameters of the package is wide, and the correct selection of the packaging parameters until to achieve driver’s ergonomics position, requires some tests.
Methods: In this study, using the MINITAB16 software and using these parameters, several driving simulation were performed using the DHM (Digital human modeling) and DOE (Design of experiment) tools. Hence, for the C segment vehicles, the range of all driver’s package parameters, such as seat height, steering angle etc., was extracted using the A2MAC1 site, and was considered as the basis for the input parameter. According to the proposed tests by MINITAB16 software, the driver’s comfort level was evaluated based on the PORTER (1998) criteria.
Results: The seat height and also vertical and horizontal distances of the steering wheel to the accelerator heel point have the greatest impact on the driver’s ergonomics. Also, due to the high correlation between some of the parameters of the package and the ergonomics outputs of the body while driving, predictive equations were presented in this regard.
Conclusion: The results are the optimal model for ergonomic driving position. The most influential parameters of the driver’s package are ergonomically known and using the ANOVA (Analysis of variance), mathematical predictor models were presented.

Design and Development of a Persian Office Chair Satisfaction Questionnaire

Elham Ahmadi Kivanani

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.

Relationship Between Musculoskeletal Disorders and Quality of Life in Employees of Selected Hospitals in Golestan Province

Shahnaz Tabatabaei

Background and Objectives: Musculoskeletal disorders is a working environmental damage that affects staff’s quality of life; in addition to high costs, it reduces physical, mental and social heath, and thus reduces the efficiency of staff. This study aimed to investigate the relation between musculoskeletal disorders and quality of life in selected hospital’s staff.
Methods: In this descriptive-analytical study, the study population included all the employees (n=770) of Kordkuy Heart Hospital and Khatam al-Anbia Hospital of Gonbad Kavus, Golestan Province, Iran. The standard sample size of 300 employees (150 Kurdkuy and 150 Gonbad Kavus) from different occupational groups were randomly selected by stratified sampling. To collect the data, a demographic information form, the Nordic Musculoskeletal Questionnaire, and the Lancashire quality of life profile were used. Independent t-test and Backward stepwise were run in SPSS 22.
Results: A significant relationship was observed between musculoskeletal disorders and musculoskeletal disorders (general) in staff. A significant relationship was observed between gender and musculoskeletal disorders. Between quality of life at different levels and demographic variables, a significant difference was observed between the average quality of life with emphasis on gender and body mass index.
Conclusion: According to the results, gender and working shifts were effective in risk of musculoskeletal pains and can have a negative effect on staff’s quality of life. Thereby optimizing work conditions has a considerable effect on quality of life.

The effect of unstable Shoe on Kinetic parameters associated with Lower limbs during walking among healthy male students.

Saed Ahmadi Ganjeh

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.

A Survey lifting the cylindrical things and comparing them with the NIOSH lifting index

Emad Mirsalimi

Background and Objectives: This study focused on lifting drill rods. Drilling is a repetitive and heavy mining operation with a high incidence and severity of musculoskeletal injuries. The purpose of this study was to examine how to lift a vertical drill bit (1.61m and 35kg in height) using two types of rod height and four feet positions, and finally compare them with the Lifting Index (LI).
Methods: Seven workers participated in this study. Each person raised a rod and held it vertically. Reflective markers were installed on each person, and from three cameras and an Ergo-meter plate for record forces and Movement of the limbs. In this case, four positions of the foot and pressures on the lower back were Investigated (position0=to the rod, position45=diagonally to the rod, position90=right side of the bar and free posture). In addition, two positions of the height of the rod were Investigated, at the first, the end of rod was on the ground (height of the rod was 83 m), and in the following the end of rod was on the Basket with height 20cm (rod height of 1.03 m).
Results: The Lifting Index (LI) for each person was equal to 1.4 in the NIOSH lifting equation. It was found that the vertical height of the rod had the greatest effect at the load on the lower back. Some workers use techniques that endure less pressure on their waist.
Conclusion: Finally, it was found that the asymmetric loading Condition (90 ° angle) was the worst case compared to the Lifting index and NIOSH standard.

Examining the Effect of Smartphone on Musculoskeletal Disorders and Neck Kinematic Among Smartphone Users in Different Postures and Tasks

Adel Mazlomi

Background and Objectives: In the last decade, the smartphones have become one of the most popular technologies around the world. Due to the multi-functional use of smartphones, the technology users spend long hours using it.
Methods: This was a semi-experimental and experimental study. In the first section, 98 students entered the semi-experimental part and completed demographic and body map questionnaires before starting the study. They were asked to perform their duties with their phone for 20 minutes and then complete the body map questionnaire again. In the second part of this study, 12 women from the first group participated in the experimental study to assess the neck flexion using the motion capture. SPSS 24 was used for statistical analysis.
Results: Searching the Internet and sending texts were the most common tasks among the participants in this study. The use of cell phone caused an increase in pain and discomfort in the neck, shoulder, thumb, thenar. The results of the study showed that there is a significant association between sitting posture and high level of neck forward flexion. Furthermore, neck flexion increased during typing while both hands holding the handset.
Conclusion: Smartphone users have had repetitive motions in fixed postures for a long time, and these factors are thought to increase the likelihood of musculoskeletal disorders.

Introducing a New Model for Individual Cognitive Factors Influencing Human Error Based on DEMATEL Approach

Alireza Choobineh

Background and Objectives: The recognition of a system failure causes and their related factors are considered as the most important factor in preventing accident occurrence in different organizations including industries. Human error is a known important factor in unpredictable events of which cognitive factors are the most influential ones. The purpose of this study was to introduce a new model for individual cognitive factors influencing human error as well as determining the interactions between the factors and their intensity using DEMATEL approach.
Methods: First a qualitative study was performed in order to identify and elicit the individual cognitive factors influencing human error among the workers of different industries. To ensure the adequacy and comprehensiveness of the elicited factors, then, the experts’ opinion was applied. DEMATEL method was used for understanding the interactions among the individual cognitive factors influencing human error. Finally, using these relationships, a new model of the study was proposed.
Results: Calculating D-R and D+R relating to the factors in terms of being cause or effect factor, D-R was -1.213 for C5 as the highest negative value, and D+R was 2.294 for the same factor (C5). Also, threshold level was calculated as 0.087 in the current study
Conclusion: In this study, the factors of failure in problem solving and decision making (C5) and difficulty in predicting possible hazards in the workplace are effects and the other factors were the cause factors. The factor of C5 was the highest interactive factor.