Iranian Journal of Ergonomics

Ergonomic Redesign of Industrial Chair

Reza Osqueizadeh

Introduction: Job satisfaction and productivity among industrial workforce depend on multiple factors. Among these factors, designing the workstation based on bodily characteristics and dimensions of the workers is of critical significance. Since industrial chairs have direct impacts on biomechanical and anthropometric compatibility, they play a major role in enhancing workers’ interaction with their workplace. The current study approached the redesign of such a product with a focus on ergonomics. Materials and Methods: The present research was a typical combined design project. In the quantitative phase, 90 participants underwent 12 anthropometric measurements (which were important in designing industrial chairs). The underlying cognitive aspects of the question were evaluated via qualitative methodologies. Results: Since normal distribution of the data was confirmed, raw anthropometric data were descriptively processed and reported. Cognitive assessments revealed correlations between correct form and softness of the backrest, and appropriate slope of the seat-pan, being a main factor determining the level of comfort while interacting with industrial chairs. Conclusion: Diverse physical constraints and conditions caused by the variety of duties and workstations have made it somehow difficult for specialists to design a universal industrial chair functioning in all different contexts. Nevertheless, the current study confirmed the effectiveness of involving personnel in redesigning the workplace and easing the challenges.

The relationship between anterior knee pain and dysfunction of the sacroiliac joint

Gholamreza Haj-valie

Introduction: Concurrent pain in the knee joint and its-related muscles is expectable in patients with sacroiliac dysfunction. However, the association between the severity of knee pain and the level of sacroiliac dysfunction is still unclear. The present study aimed to determine the association between the severity of sacroiliac dysfunction and the severity of pain due to involvement of knee compartment.

Materials and Methods: One hundred consecutive patients who visited an orthopedic clinic with the primary complaint of knee pain were recruited. According to specific diagnostic tests, 50 had sacroiliac dysfunction and 50 had no history of sacroiliac dysfunction. The severity of knee pain was determined using the Anterior Knee Pain Scale (AKPS). T-tests were then performed to compare the two groups in terms of AKPS scores.

Results: The mean AKPS score was 33.2 ± 12.1 in patients with sacroiliac dysfunction and 62.6 ± 18.6 in those without sacroiliac dysfunction (p < 0.001). Moreover, anterior knee pain was more frequent in the first group (56% vs. 10% p < 0.001).

Conclusion: There is a significant association between the severity of anterior knee pain and severity of sacroiliac dysfunction. This association may be due to involvement of knee extensor muscles following the progression of sacroiliac dysfunction.

Biomechanical analysis of manual lifting of loads and ergonomics solutions for nursing assistants

Davood Afshari

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.

Effectiveness of ergonomics training in decreasing the risk of musculoskeletal disorders based on rapid upper limb assessment among computer operators

Marzieh Sadeghian

Introduction: Musculoskeletal disorders are one of the leading problems among computer users. They have attracted increasing attention over years and different solutions have been proposed for their resolution. This study evaluated the effects of ergonomic training on reducing the risk of musculoskeletal disorders in computer users.

Materials and Methods: This study was conducted among the office workers of a university. A total of 110 computer operators were randomly selected and allocated to intervention and control groups. The intervention group was trained about the ergonomic principles of working with computers. Nordic Musculoskeletal Questionnaire (NMQ) was used to investigate the prevalence of musculoskeletal disorders. Moreover, rapid upper limb assessment (RULA) was applied to determine the risk of musculoskeletal disorders before and six months after training. Data was analyzed using independent and paired t-test.

Results: The highest frequency of musculoskeletal disorders was seen in the back (55.4%) and neck (54.5%). In addition, risk assessment before the intervention suggested 31% of the participants to be high-risk. After the training program, significantly lower risk was detected in the intervention group. No such a significant difference was present in the control group.

Conclusion: The results of this study showed that corrective actions can reduce the risk of work-related musculoskeletal disorders (WMSDs). They can thus be implemented to enhance the effectiveness of ergonomic measures.

Effects of elbow and forearm support on upper trapezius muscle fatigue while typing

Mehrdad Anbarian

Introduction: Today, computers are widely used in many homes and workplaces. The relationship between computer use and musculoskeletal disorders in the neck and upper extremities has been well documented. Muscle fatigue in the shoulder and arm regions is one of the most frequently reported problems in computer users. Supporting the upper extremities has been suggested as a way to reduce the static load on upper body muscles while using a keyboard. The purpose of this study was to determine the effect of elbow and forearm support on upper trapezius muscle fatigue while typing.

Materials and Methods: Eight students of Bu-Ali Sina University (Hamadan, Iran) participated in this quasi-experimental study. The surface electromyography activity of the upper trapezius muscle of the dominant side was recorded in three positions, namely without elbow support, elbow support with the table, and elbow support with a pad while typing. The muscle fatigue index for the three typing positions was calculated based on the median frequency slope of the raw electromyography signals. Repeated measures analysis of variance (ANOVA) was employed for statistical analyses.

Results: Median frequency slope decreased significantly in elbow support with the table in comparison with non-support position (p = 0.04). There were no significant differences between elbow support with a pad and other two positions.

Conclusion: These results suggested elbow support as a mechanism to delay trapezius muscle fatigue and thus increase task efficiency. More research is required to determine the advantages or disadvantages of using different pads.

Confirmatory and exploratory factor analyses of adaptive performance scale: a study among hospital nurses

Teimour Allahyari

Introduction: Adaptive performance is defined as an employee’s ability to deal with changes and new and unusual situations in the workplace. The present study mainly focused on factor analysis of the Adaptive Performance Scale (APS) and determining its validity and reliability. Adaptive performance is a multi-dimensional structure with five latent factors.

Materials and Methods: This method validation study was conducted in Ahvaz, Iran. 210 randomly selected public hospital nurses completed the Persian version of the APS. Exploratory factor analysis (varimax rotation) was used to explore the factor structure of the scale. Confirmatory factor analysis and structural equation modeling were applied to fit the model.

Results: The overall reliability of the APS was confirmed (Cronbach’s alpha = 0.89). Factor analysis was used to evaluate the factor structure of the scale. Kaiser-Meyer-Olkin index (0.88) and Bartlett's sphericity test result (1639.093) were both significant. Finally, varimax rotation showed all items to have significant factor loadings.

Conclusion: Our findings confirmed the acceptable psychometric properties (reliability and validity) of the APS for administration among nurses. Therefore, the adaptive performance construct contains five distinct dimensions, namely dealing with emergency and unexpected situations, work stress management, creative problem solving, learning, and interpersonal adaptability. These results are consistent with previous studies.

Validity and reliability of the Swedish Occupational Fatigue Inventory (SOFI-20) among Iranian working population

Sareh Keshavarzi

Introduction: Perceived work-related fatigue is an important issue since it may adversely impact workers’ performance. Additionally, workers’ fatigue is known as a main cause of occupational accidents in workplaces. Considering the consequences of perceived work-related fatigue, assessing fatigue at workplace is critical to work-related fatigue risk management. Therefore, this study assessed the validity and reliability of the Persian version of the Swedish Occupational Fatigue Inventory (SOFI-20) among Iranian employees.

Materials and Methods: In this cross-sectional study, 501 employees of two petrochemical companies were selected by simple sampling method. The Persian version of SOFI-20 was developed using forward and backward translation processes and used to collect the required data. The validity and reliability of the translated inventory were examined by confirmatory factor analysis (CFA) and Cronbach’s alpha coefficient, respectively.

Results: Assuming that some items of the Persian version of the SOFI-20 were correlated, the confirmatory factor analysis was repeated to achieve better fitness. The results of CFA revealed an acceptable fit for the Persian version of SOFI-20. The total Cronbach’s Alpha coefficient for the SOFI-20 was 0.95. Cronbach’s alpha coefficients for different dimensions of the SOFI-20 were found to range from 0.690 to 0.887.

Conclusion: The validity and reliability of the Persian version of the SOFI-20 was acceptable for assessing the dimensions of work-related fatigue among Iranian employees.

The relationship between teachers’ job involvement and demographic characteristics in Dalahou (Kermanshah) secondary schools in 2013

Faramarz Gharagozlou

Introduction: Job involvement is defined as one’s psychological dependence on his/her job. Employees with high job involvement pay more attention to their job. The present study aimed to determine the relationship between teachers’ job involvement and demographic characteristics in Kermanshah (Iran) secondary schools during 2013.

Materials and Methods: This cross-sectional study was performed on 211 teachers (161 male and 50 female). Data were collected using the Job Involvement Scale. The collected data were analyzed using Spearman’s correlation coefficient, independent t-test, and analysis of variance (ANOVA). P values less than 0.05 were considered significant.

Results: The teachers’ mean age and work experience were 32.21 and 8.49 years, respectively. Low, moderate, and high levels of job involvement were detected in 22.3%, 54.5%, and 23.2% of the teachers, respectively. Job involvement was significantly higher in married teachers than single subjects (p = 0.027). Moreover, teachers without a second job had higher job involvement than those with a second job (p = 0.006). There were no statistical correlations between job involvement and age, sex, work experience, or level of education.

Conclusion: The participating teachers generally had low-moderate levels of job involvement. Low salary, working multiple jobs, and low social prestige were mostly responsible for such low levels of job involvement. Therefore, increasing teachers’ salary, providing teachers with special facilities (e.g. low-interest loans), and developing a system for teachers’ promotion (similar to that existing for faculty members) can be effective in increasing job involvement among teachers