Iranian Journal of Ergonomics

Developing a Mixed-Integer Quadratic Programming Model for Equitable Construction Task Allocation to Mitigate Cumulative Low-Back Load Based on the MDD Model

Hamed Salmanzadeh

Background and Objectives: Low back musculoskeletal disorders are among the major concerns in the construction industry and are primarily caused by biomechanical loads imposed on the lower back. Previous studies on task allocation and job rotation have mainly focused on reducing maximum physical risk and, in some cases, psychological risk, while ergonomic indices have predominantly been assessed using qualitative or semi-quantitative methods. However, fairness in the distribution of risk and working time among workers has received less attention. Therefore, this study was conducted to develop a model for reducing risk and ensuring its equitable distribution, as well as the equitable distribution of working time. From a macro ergonomic perspective, such a model can enhance personnel motivation and prevent tensions arising from perceived inequality in the workplace.
Methods: Posture and applied force data were collected from four construction workers performing nine tasks, and the forces exerted on the lumbar region were determined using 3DSSPP software. Subsequently, using the Mainz-Dortmunder Dosis model (MDD), the quantitative risk associated with force intensity and exposure duration was calculated, and a mathematical model for equitable task allocation was developed.
Results: Implementation of the mixed-integer quadratic programming model showed that, with divisible task allocation, the cumulative low back risk and working time for each worker were 5,176 units (below the allowable limit of 5,500) and 1.575 hours, respectively. The objective function value approaching zero also indicated equality in the distribution of risk and working time.
Conclusion: While maintaining operational constraints, the proposed model improves ergonomic equity and can be used as a decision-making tool for project managers to protect workers’ spinal health while maintaining operational efficiency.

The Impact of Transformational Leadership on Psychological Well-Being: The Mediating Roles of Job Satisfaction and Employees’ Work Engagement

Hamideh abbasi

Background and Objectives : The present study aimed to investigate the impact of transformational leadership on psychological well-being, with a focus on the mediating roles of job satisfaction and employees’ work engagement.
Methods : This study was applied in terms of purpose and employed a descriptive-survey research design. The statistical population consisted of 200 employees of the Central Organization of the Technical and Vocational University in Tehran. Based on Cochran’s formula, 131 employees were selected using simple random sampling. Data were collected using the questionnaire developed by Abolnaser et al. (2023). The validity of the research instrument was established through face and content validity, while its reliability was confirmed using Cronbach’s alpha coefficient. Data were analyzed using Structural Equation Modeling (SEM) through SmartPLS software.
Results : The findings indicated that transformational leadership had positive and significant effects on job satisfaction, employees’ work engagement, and psychological well-being. Moreover, job satisfaction and employees’ work engagement had positive and significant effects on psychological well-being. The results also demonstrated that both job satisfaction and employees’ work engagement significantly mediated the relationship between transformational leadership and psychological well-being.
Conclusion : Overall, the findings suggest that educational organizations can enhance employees’ psychological well-being by adopting a transformational leadership style and strengthening job satisfaction and work engagement, thereby contributing to sustainable productivity.

Examining the Relationships Between Interior Architectural Elements and Productivity Indicators in Architecture Design Studios

Reza Naghdbishi

Background and Objectives: This study examined how interior architectural elements affect employee productivity in architectural design studios. As offices adapt their physical environments to support creativity and performance, understanding users' actual needs has become essential. The research assumed that interior environment quality can influence multiple productivity dimensions.
Methods: A mixed-methods approach was used within a pragmatic paradigm. In the qualitative phase, variables were identified through content analysis using MAXQDA software, leading to a researcher-developed questionnaire. Quantitative data were collected from 97 participants in architectural offices.
Results: Spearman’s correlation test revealed a positive but weak relationship between interior architecture and productivity (r = 0.208, p < 0.05). Among the variables, materials showed the strongest link with the workplace’s physical dimension (r = 0.275), while ventilation correlated most with employee motivation (r = 0.248). Overall, correlations between environmental components and productivity dimensions were weak, suggesting that individual and organizational factors may also contribute to employee productivity.
Conclusion: Overall, productivity in architectural workplaces results from interactions among interior environmental quality, individual characteristics, and organizational structures. A balanced attention to these dimensions can enhance work experience and support sustainable employee performance

The Impact of Biophilic Components on Happiness in Residential Complex Residents: The Mediating Role of Stress Reduction

Mahdi Zandieh

Background and Objective: Rapid urbanization in Iran has increasingly alienated residents from nature, raising concerns about declining mental health. The biophilia hypothesis suggests that exposure to natural elements can restore psychological well-being. This study aimed to investigate the impact of biophilic components on happiness in residential complex residents and identify the most effective natural elements.
Methods: This descriptive-survey study employed a quantitative approach with 120 residents of the Binalood residential complex in Mashhad, selected through cluster random sampling. Data were collected using a researcher-developed questionnaire (33 items) with good reliability (Cronbach's alpha = 0.88) and content validity (CVI = 0.87). Exploratory factor analysis confirmed construct validity (KMO = 0.85). Data were analyzed using Pearson correlation, regression, and path analysis.
Results: Natural light was identified as the most effective component (40%). The exterior space generated greater satisfaction (46.7% vs. 23.3%) and happiness (50.8% vs. 20.0%) than the interior courtyard. Biophilic components explained 56% of satisfaction variance (R² = 0.56), with plants (β = 0.42), natural light (β = 0.35), and natural views (β = 0.28) as significant predictors. A strong positive correlation was found between green space use and happiness (r = 0.58). Path analysis revealed that stress reduction mediated 52% of the biophilic effect on happiness.
Conclusion: Biophilic components, particularly natural light, plants, and natural views, significantly enhance happiness and vitality through stress reduction. Revising Iranian housing design with emphasis on optimal natural lighting and developing public green spaces is essential. These findings highlight the need to integrate biophilic design principles in contemporary Iranian residential complexes.

Investigation of the relationship between indoor illumination and luminance with sustained attention among administrative staff in selected healthcare centers of Ardabil Ardabil city in 2025

Rasoul Hemmatjo

Background and Objectives: Advances in technology have led to widespread use of visual display terminals across occupations, resulting in prolonged exposure. Scientific studies show lighting significantly influences human attention by affecting consciousness levels. This study aimed to investigate the relationship between indoor illuminance, luminance and sustained attention among administrative staff in healthcare centers in Ardabil.
Methods: This descriptive study was conducted among 98 administrative staff in healthcare centers. Illuminance levels (at the work surface and user’s eye level) and luminance (at the user’s eye level from the screen and light source) were measured at workstations using a Hagner Universal photometer model S4. Sustained attention was assessed using the Continuous Performance Test (CPT) under workplace lighting conditions. Data were analyzed with SPSS version 27 using non-parametric statistical tests and Dunn’s post-hoc test.
Results: Results revealed a positive but non-significant correlation between sustained attention and work surface illuminance (p=0.123), luminance at the user's eye level from lighting sources (p=0.335) and from the screen (p=0.7). A positive and statistically significant relationship was observed between illuminance at the user's eye level and sustained attention (p=0.029). Dunn’s post-hoc test indicated this relationship was significant between lighting levels below 100 lx and 300 to 500 lx (p<0.05). Higher levels of lighting parameters were associated with shorter reaction times in the sustained attention test, although these associations did not reach statistical significance (p>0.05).
Conclusion: According to the results, illuminance at the user's eye level has a positive and statistically significant relationship with sustained attention among administrative staff. Therefore, implementing lighting interventions in the design and arrangement of lighting sources, along with use of visual display terminals with appropriate luminance, can be considered an effective strategy to enhance sustained attention in administrative personnel.

Analysis of Teachers' Willingness to Pay for Ergonomic Interventions: A Cross-Sectional Study Among Education Staff

Vajihe Ramazani-Doroh

Background and objectives: Musculoskeletal disorders (MSDs) are among the most common occupational health problems among teachers. Ergonomic interventions can play an important role in preventing and reducing these disorders; however, successful implementation of such interventions requires understanding employees’ acceptance and willingness to contribute financially. This study aimed to assess teachers’ willingness to pay (WTP) for ergonomic interventions and identify factors associated with it.
Method: This cross-sectional study was conducted among 361 teachers. Data on demographic, socioeconomic, occupational, psychosocial, and musculoskeletal health characteristics were collected using a structured questionnaire. Willingness to pay for ergonomic interventions was assessed using the contingent valuation method (CVM). Multivariable logistic regression analysis was performed to identify factors associated with WTP.
Results: Overall, 186 participants (51.5%) reported willingness to pay for ergonomic interventions. The mean WTP was 193,490 Iranian Tomans, while the median WTP was 50,000 Tomans. Bivariate analyses showed significant associations between WTP and adequate rest, sleep disorders, workplace violence, overall support, and supervisor support (P < 0.05). In the multivariable logistic regression model, managerial support was associated with more than a twofold increase in the likelihood of WTP (OR = 2.32, 95% CI: 1.41–3.82). Poor working posture (OR = 1.81, P = 0.021) and employment status (OR = 2.17, P = 0.039) were also positively associated with WTP, whereas workplace violence was negatively associated with WTP (OR = 0.57, P = 0.028). Musculoskeletal pain and activity limitation during the previous 12 months were not significantly associated with WTP.
Conclusion: Teachers’ willingness to pay for ergonomic interventions was influenced more by organizational and workplace-related factors than by individual characteristics or musculoskeletal health conditions. Strengthening managerial support and improving workplace conditions may enhance employees’ acceptance of and participation in ergonomic intervention programs.