Iranian Journal of Ergonomics

Introduction: Driver fatigue is one of the major causes of accidents in roads. It is suggested that driver fatigue and drowsiness accounted for more than 30% of road accidents. Therefore, it is important to use features for real-time detection of driver mental fatigue to minimize transportation fatalities. The purpose of this study was to explore the EEG alpha power variations in sleep deprived drivers on a car driving simulator.

Materials and Methods: The present descriptive-analytical study was achieved on nineteen healthy male car drivers. After taking informed written consent, the subjects were requested to stay awake 18 hrs before the experiments and refrain from caffeinated drinks or any other stimulant as well as cigarette smoking for 12 hrs prior to the experiments. The drivers sleep patterns were studied through sleep diary for one week before the experiment. The participants performed a simulated driving task in a 110 Km monotonous route at the fixed speed of 90 km/hr. The subjective self-assessment of fatigue was performed in every 10 minute interval during the driving using Karolinska Sleepiness Scale (KSS). At the same time, video recordings from the drivers face and their behaviors were achieved in lateral and front views and rated by two trained observers. Continuous EEG and EOG records were taken with 16 channels during driving. After filtering and artifact removal, power spectrum density and fast Fourier transform (FFT) were used to determine the absolute and relative alpha powers in the initial and final 10 minutes of driving. To analyze the data, descriptive statistics, Pearson and Spearman coefficients and paired-sample T test were employed to describe and compare the variables.

Results: The findings showed a significant increase in KSS scores in the final 10 minutes of driving (p<0.001). Similar results were obtained concerning video rating scores. Meanwhile, there was a significant increase in the absolute alpha power during the final section of driving (p=0.006).

Conclusion: Driver mental fatigue is considered as one of the major implications for road safety. This study suggests that alpha brain wave rhythm can be a good indicator for early prediction of driver fatigue.

Introduction: Mental fatigue is defined as body or soul tiredness which can be caused by stress, overwork, excessive use of drugs or physical or mental illnesses. Fatigue is one of the reasons of productivity loss as well as occurring accidents. Therefore, mental fatigue measurement is of great importance. This study was aimed to determine the consistency of mental fatigue measurement by self-reported VAS and the flicker fusion apparatus.

Material and Methods: A descriptive study was conducted on 30 students. After they had accomplished mental tasks (i.e. mathematical problem solving and responding to MMPI questionnaire), mental fatigued was measured by self-reported VAS and flicker fusion apparatus. To analyze the results, paired sample T-test and Spearman correlation test were applied in SPSS software version 11.5 (P<0.05).

Findings: The results of mental fatigue measurements by both methods of self-reported VAS and the flicker fusion apparatus showed significant increase in mental fatigue after finishing each of the mental tasks. But the findings revealed no consistency between the two methods. 

Background: Driver’s fatigue is a major factor contributing to the prevalence of road accidents. A vast number of city dwellers in most countries use public transport bus services to move around the city. Driver’s fatigue causes job burnout and affects the risk of a traffic accident injuring the public. Several methods have been used to date for evaluating mental fatigue however, using questionnaires tends to be a less time-consuming and more accessible technique. The present study was therefore conducted to develop a mental fatigue questionnaire for public transport bus drivers.

Materials and Methods: The study was conducted based on the criteria used for qualitative research. Semi-structured interviews were held with public transport bus drivers using probing questions and data were collected until their saturation so as to enable access to a direct description of mental fatigue by the bus drivers. Data saturation occurred with 30 interviews and sampling was then discontinued. The analysis of the interviews led to the extraction of the themes and an initial list of questionnaire items was then developed. The psychometric properties of the questionnaire were then evaluated through examining the content validity and internal consistency of the items. The content validity of the items was calculated using Lawshe’s table. A minimum CVR of 0.99 and a minimum CVI of 0.75 denoted an acceptable content validity for the items. To determine the internal consistency of the items, 200 bus drivers completed the final version of the questionnaire. The data obtained were then analyzed in SPSS-16 using Cronbach's alpha to measure the reliability of the questionnaire and considering an acceptance level of 0.7.

Results: The interviews conducted at the beginning of the study with 30 drivers led to the emergence of an initial list with 26 items. A total of 9 items with a CVR less than 0.99 were omitted from the list and 17 items with adequate simplicity, clarity and correlation between them and which had a minimum CVI of 0.75 were kept. The questionnaire had a Cronbach's alpha value of 0.87 and was therefore considered a reliable tool.

Conclusion: The questionnaire developed in this study has a good validity and reliability and can therefore be used to assess mental fatigue in public transport bus drivers.

Introduction: Advances in technology and the use of complex systems at work have imposed high mental workloads to operators; so, continuous monitoring of mental workload can help to prevent mental problems and maintain mental health. Therefore, this study aimed to investigate the impact of mental workload on physiological and subjective responses.

Methods: This cross-sectional descriptive-analytical study was performed on 16 healthy university students in 2014 at a laboratory setting. Physiological parameters of surface electromyography and electrocardiography in six blocks (resting, high mental work, moderate, low, very low and recovery) were measured using NeXus-4. After performing each block, the NASA-TLX questionnaire was completed. Statistical analysis was conducted using SPSS software version 21.0. A 5% significance level was adopted in all the tests.

Results: The results showed significant differences for the average score of NASA-TLX between the different levels of mental work load (P < 0.05). Also, the analysis of repeated measures variance showed significant differences for heart rate and heart rate variability parameters in the six blocks (P < 0.05), but no significant difference was observed for the shoulder muscles activity.

Conclusions: Different levels of mental work load can impact on people's subjective responses and some of their physiological responses. Thus, in such workplaces, it will be necessary to conduct an ergonomic program to manage mental health.

Introduction: The progress of technology and modern technology has changed today’s workplaces and imposed more mental and cognitive demands to workers. Control room is an example of these workplaces. Currently, assessment of mental workload is a key point in the research and development of human-machine relationships in workplaces. This study aimed to validate an analytical approach in evaluating demanded mental workloads for control room operators in Pars combined cycle power plant.

Methods: This was a fundamental-practical and cross-sectional study. First of all, a task analysis was used to understand the operation steps of control room operators. Then, the Visual, Auditory, Cognitive, Psychomotor (VACP) technique was applied to determine the mental workload demanded for performing each step of the works. Finally, the assigned ratings of the VACP method were validated by the analysis of Pearson’s correlation with the answers of the NASA-Task Load Index (NASA-TLX) questionnaire, collected from the control room operators.

Results: Based on the results, the correlation between the assigned ratings of VACP technique and the answers of the NASA-TLX questionnaire was positive and significant.

Conclusions: Due to the high correlation between the assigned ratings of VACP technique and the answers of the NASA-TLX questionnaire, the proposed VACP technique, which can be carried out in the early stage of the design, was suitable as an analysis tool for predicting metal workloads of control room operators.

Introduction: The working population spends an increasing amount of waking times at work that is full of social relationship and meaningful resource of social capital. With regard to relationship between workplace social capital and employee health, this systematic review was performed with aim to evaluate the effects of workplace social capital in health workforce.

Materials & Methods: This is a systematic review study. The articles were in full text and  in English language that were cited in Pubmed, Scopus, and Google scholar database with key words such as "workplace social capital" ,"health", "hypertension", "diabetes", "depression" without time limit were selected, at least 14 articles were eligible.

Results: Workplace social capital was related with cardio-vascular disease, hypertension, diabetes and depression among the employees.

Conclusions: Workplace social capital should be considered as one of the most important issue in health promotion.

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.

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.
 

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: Mental fatigue is a condition triggered by prolonged cognitive activity. Mental fatigue causes brain over-activity. This is a condition where the brain cells become exhausted, hampering person productivity, and overall cognitive function. The aim of this study was to assess students’ mental fatigue using brain indices.
Methods: The present descriptive - analytic study has been conducted on 20 students of the Faculty of Health mean age (SD) of 24.40 (3.73) years old in Ahwaz University of Medical Sciences (2019). To assess the performance of the participants, they were asked to study a text with spelling errors and correct those errors. This activity was performed in five stages, each lasting 15 min and EEG was recorded at all stages, and at each stage, the visual analog scale was completed by participants. Data analysis was done by SPSS 24.
Results: The results showed that the activity of alpha, beta, and theta signals in the first 15 minutes was 0.89±0.30, 0.70±0.33, and 1.19±0.36, and the last 15 minutes, 0.63±0.34, 0.55±0.26, and 1.03±0.34 respectively. Reducing the activity of the signals indicated there has been an increase in the amount of mental fatigue in individuals. Also, using visual analog scale, the individuals have acknowledged that they have experienced symptoms of mental fatigue. Finally, there was no significant relationship between students’ EEG and visual analog scale.
Conclusion: The results showed that alpha, beta and theta indices could be suitable indicators for evaluating mental fatigue. Also, mental fatigue can be one of the factors that affect the accuracy and performance of individuals, so that it can reduce their attention and efficiency.

Background and Aim: A good work environment is a place where one can feel relaxed and focused. In the field of environmental psychology, color is one of the environmental factors that greatly influence human perception and behavior. The purpose of this systematic review study was to investigate the effect of color on work environment.
Methods: This article is a systematic review study. Full-text and English-language articles published in PubMed, Scopus, Science Direct, Google Scholar were searched using the following keywords: Color perception, color ergonomics, color psychology, color effect, mental health and Workplace. The search was without time limit, and 45 eligible articles were reviewed.
Results: Initially, 262 articles were identified from different databases. Among them, 93 articles met the criteria for entering the study. After that, 48 articles were removed from the study due to lack of experimental studies and 45 articles were selected for final review. A total of 18 studies focused on color priority, 25 studies on mood and emotions, 6 studies on health outcomes, and 19 studies on the effect of workplace color on work-related outcomes. The results showed that color has a significant effect on emotions (eg mood), well-being (eg stress, comfort, well-being) and performance (eg productivity, creativity).
Conclusion: Workplace color should be considered as one of the main ways to promote the (mental and physical) health of individuals.