Iranian Journal of Ergonomics

Review the Effectiveness of Ergonomic Interventions in Reducing the Incidence of Musculoskeletal Problems of Workers in Fatal Truck Assembly Hall

Farhad Tabatabai Ghomsheh

Introduction: Different studies around the world have shown that Work-Related Musculoskeletal Disorders (WMSDs) are the causes of lost time, absenteeism, and disability. The purpose of this study was to investigate the prevalence rate of musculoskeletal disorders (WMSDs) and to evaluate their ergonomic risk factors and determine the effect of ergonomic intervention on awkward postures among workers of Saipa Diesel Truck manufacturing plants.
Methods: This interventional study (Before-after) was conducted on 130 workers of 2 largest truck-manufacturing plants in Iran. The prevalence rate of MSDs and ergonomic risk factors was assessed by valid and reliable translated Body Map Questionnaire (BM) and Quick Exposure Check (QEC) method, respectively.
Results: According to Body Map results, 87.5% of participants had MSDs at least in one of their eleven body regions during the previous year, before study. The highest prevalence rate of MSDs was observed in lower back (51.5%) and foot area (18.5%). Chi square test revealed that the prevalence rate of MSDs was higher among those with higher QEC risk level (P < 0.001). Results also indicated the significant effect of ergonomic interventions on reducing the prevalence rate of MSDs and QEC risk level (P < 0.001).
Conclusions: This study showed that the prevalence rate of MSDs and QEC risk levels among workers was significantly high. Therefore, it can be mentioned that the need for early ergonomic interventions is felt in all industrial units of these truck-manufacturing plants.

An Investigation of the Relationship between Psychosocial Work Factors and Fatigue among Nurses

Teimour Allahyari

Introduction: Psychosocial factors and fatigue are significant factors in nurses’ performance. Since the relationship between psychosocial factors and fatigue has been rarely studied, the aim of this study was investigating the relationship between psychosocial work factors and fatigue among nurses.
Method: In this cross-sectional study, 270 nurses from hospitals of Urmia University of Medical Sciences randomly participated. The Job Content Questionnaire and Swedish Occupational Fatigue Inventory were used for data collection. Pearson’s correlation coefficient and Structural Equation Modeling were used for data analysis.
Results: The mean (SD) of control was 66.32 (7.36), psychological job demand 35.47 (3.68), social support 22.31 (2.64), physical job demand 15.22 (2.18), and job insecurity 8.72 (4.06). Control and social support dimensions had low levels. Moreover, psychological and physical job demand had high levels, which indicates a high stress level. According to the results, psychological and physical job demand had a significant relationship with all dimensions of fatigue (P < 0.001).
Conclusions: The majority of nurses were exposed to high levels of job stress. Among psychosocial factors, physical demand was identified as the most effective factor on fatigue. Any comprehensive interventional program regarding psychosocial work factor in order to reduce job stress and fatigue can improve health care quality and also prevent medical errors.

Design and Cross-Validation of Six-Minute Walk Test (6MWT) Prediction Equation in Iranian healthy Males Aged 7 to 16 Years

Farzad Nazem

Introduction: Application and correct interpretation of the 6-minute walk test (6MWT) in medical, therapeutic, and exercise settings requires normal values of the 6MWT. The aim of this study was to develop and cross-validate the 6MWT prediction equation in Iranian healthy children and adolescent males.
Methods: The 6MWT and anthropometric variables were measured in 391 males (8 to 17 years old) with standard methods. Pearson correlation was used to assess the relationship between distances walked in the 6MWT and independent variables. Multiple regression analysis was used to design 6MWT prediction equation from dependent variables. Furthermore, accuracy of the present 6MWT prediction equation was cross-validated.
Results: Significant correlation was found between distances walked in the 6MWT and anthropometric characteristics (P < 0.001). Multiple stepwise regression reviled that age and Body Mass Index (BMI) could explain 63% of the variability of 6MWT in children and adolescent males (r²= 0.627, SEE= 36 m, P < 0.001). Accuracy of native 6MWT prediction equation was approved by good correlation between measured and predicted distance walked in the 6MWT (r² = 0.79, P < 0.001).
Conclusions: This is the first study on the development of native 6MWD reference values. With application of this 6MWD prediction equation, physicians, physical therapists, and fitness coaches could receive correct feedback of pharmacological, rehabilitation, and exercise interventions.

Identifying Dimensions of Organizational Culture Affecting Job Motivations in Public Libraries in Iran: A Qualitative Research

Mohammad Reza Amiri

Introduction: Job motivation as one of the factors that affect the behavior of librarians can improve their performance. Considering that organizational culture is one of the factors influencing job motivation, the aim of this study was to identify dimensions of organizational culture that can affect job motivation of librarians in public libraries of Iran.
Methods: This qualitative study was conducted using content analysis. Using the purposive sampling, 19 people of librarians of public libraries in 10 provinces were interviewed using depth and semi-structured interviews. After extracting the primary codes, they classifyied into three dimmensions and eight components.
Results: Based on the results of this study, dimmensions of organizational culture, which can affect job motivation included knowledge-oriented and capability-oriented culture (professionalism and meritocracy, professional capability, use of technology, and organizational learning), independency culture (non-politicization in the library, and decentralization), and participatory and motivational leadership culture (participatory management, and motivational management).
In view of nature and social roles of public libraries and broad impressive factors on them, these models have limitations to assess status of organizational culture in public libraries. So, it is necessary to identify dimensions and components of effective organizational culture in public libraries of Iran and then manage the organizational culture on the basis of this effective culture.
Conclusions: Dimensions and components of effective organizational culture resulted from this study can be used as an ideal model for managing organizational culture or efforts to rule these cultural components in the public library of Iran.

The Mediating Role of Sleep Quality in Relationship between Workload and Physical and Mental Health among Nurses

Ali Mohamadzade Ebrahimi

Introduction: Nurses as the most important part of human resources in the health service system are often faced with problems associated with shift work. The present study aimed to examine a mediating role of sleep quality in the relationship between workload and physical and mental health among nurses.
Methods: This cross-sectional study was conducted on 236 nurses working in three educational hospitals in Bojnord city. To collect data, the survey of shiftworkers (SOS) questionnaire was used. Data were analyzed using the structural equation modeling by AMOS-21 and SPSS 19 software packages. In addition, the Preacher and Hayes’ SPSS Macro program was used for testing mediation.
Results: The results showed that the proposed model fitted the data properly. Also, workload directly affected only physical health, and the quality of sleep had a mediator role in the relationship between workload and physical and mental health.
Conclusions: Sleep quality as an important variable can mediate the relationship between workload and physical and mental health in nurses. So, it is suggested that interventional interventions to improve the health of the staff be focused on adjusting and shifting job shifts and teaching the principles of sleep hygiene to them.

The Effects of Lighting on Mental and Cognitive Performance: A Structured Systematic Review

Ebrahim Darvishi

Introduction: Lighting affects many non-visual functions such as Circadian rhythm, alertness, core body temperature, hormone secretion and sleep. The aim of this study was to investigate the effects of lighting on human cognitive and mental performance.
Methods: In this systematic review, databases including ISI Web of Knowledge, Scopus, PubMed and Science Direct were searched to access the relevant studies. The search was performed using the keywords "Lighting" and "Illumination" and "Cognitive Performance", "Mental Performance", "Memory ", "Attention", and "Concentration" by title, keyword and abstracts of articles published in mentioned databases from 2010 to 2016.
Results: Lighting affects human cognitive performance in three areas of psycho-cognitive (visual comfort, visual perception, color recognition, identification of symbols, attention, working memory, learning, reaction time and brain function), biocognitive area (alertness, mood, vitality, subjective feelings, motivation, well-being and quality of sleep) and mental workload (amount of workload, psychological stress, and mental fatigue). The best light to regulate cognitive, biological (circadian rhythm) and mental processes is bright daylight in the morning with a short wavelength (wavelength 420-480 nm) and high intensity (1000lx).
Conclusions: Lighting design in addition to providing comfort and visual needs should provide the non-visual and cognitive needs such as attention, alertness, mood, sleep quality and decrease mental fatigue and eventually well-bing.

Ergonomically Adjustable Laptop Desk Designed Based on Anthropometric Characteristics of 20-30 Year-Old Students of Mazandaran University of Medical Sciences

Ismail Shokrolahi

Introduction: In recent years, with the progressive development of various scientific, research and industrial fields, there are musculoskeletal disorders in computer and laptop users. Musculoskeletal disorders including pain and pressure in areas such as wrists, elbows, neck and shoulders, along with the fatigue of these areas, especially back and waist pain are common among many computer and laptop users. The aim of this study was to design a customizable ergonomic table for using laptops based on the anthropometric characteristics of students of Mazandaran University of Medical Sciences.
Methods: This study was conducted on 108 (61 males and 47 females) students of Mazandaran University of Medical Sciences. Ten parameters including knee height sitting on a chair, eyes- elbows height, cross-legged posture kneeling length, cross-legged posture kneeling height, thick thighs, elbow rest height-sitting, shoulder-fingertip length, abdominal depth, hip breath, and elbow-fingertip length were measured using the adjustable seating, caliper and meter. The SPSS software version 20 was used to analyze the data. Then, the percentiles 1 to 99 and the golden number 1.618 were used to design the table.
Results: The mean age of the subjects was 23 ± 3.14 years. Based on anthropometric characteristics, gold number, resulting percentiles and design equations, an adjustable ergonomic table was designed in three seated sitting, four-knee and Fowler’s positions.
Conclusions: It is expected that after putting this device on the laptop, the musculoskeletal disorders caused by its use will be reduced. Because of limited studies have been conducted in this area, it is suggested that further studies in this regard be undertaken in the future.

Ergonomic Design and Evaluation of Fabric Cutting Scissors with Regard to Pinch Force and Wrist Posture

Iman Dianat

Introduction: Scissors are essential tools in different occupations including sewing and clothes making. Improper design of fabric cutting scissors can lead to the development of musculoskeletal symptoms among users. The aim of this study was to evaluate pinch force and wrist posture while working with three designs of sewing scissors and a traditional sewing scissors.
Methods: The first model of the scissor had a bent-handle (to improve wrist posture), the second model had a thumb-ring that was located closer to the pivot (to reduce thumb’s abducted position and range of movement), and the original oval ring in the third model was changed to a hook-shaped handle (to reduce hand and finger discomfort). Pinch force was measured using a pinch gauge and wrist posture was measured in two anatomical planes including flexion/extension and ulnar/radial deviation using the observational method.
Results: The results showed significant effects of scissors' design on pinch force exertions (P < 0.01) and ulnar/radial deviation of the wrist (P < 0.001). The lowest level of pinch force decrement between pre- and post-pinch force measurements was recorded for the second model (2.4%), while the highest level was recorded for the traditional model (7%). More neutral wrist postures in ulnar/radial direction (83%) were recorded for the first model compared to the other designs.
Conclusions: The second scissors, which was designed to reduce thumb’s range of motion and abduction, showed some improvement in pinch force compared to the traditional model.