Iranian Journal of Ergonomics

Comparison of the Effect of Different Backpack Hip Belt Styles on Postural Control Indices and Center of Pressure Changes during Standing and Walking

Saeed Ilbeigi

Objectives: Backpacks equipped with hip belts are among the most common and essential tools for carrying loads during long treks and mountaineering. The use of a hip belt facilitates appropriate load distribution between the upper and lower body and minimizes muscular energy expenditure. However, it may also restrict movement. This study aimed to examine the effect of three different hip belt designs in backpacks, namely 1) movable hip belt, 2) cross-frame structure, and 3) conventional design, on postural alignment control indices and center of pressure (COP) changes during standing and walking.
Methods: This semi-experimental study was conducted on 20 male physical education students aged 19 to 25 years. Three types of backpacks were used to measure postural control indices and COP changes: (1) backpack with a movable hip belt, (2) backpack with a cross-frame in the back panel, and (3) conventional backpack. Participants carried the backpacks on a level, flat surface with a standard load of 13 kg. A control walking test was also performed without any backpack under similar conditions. COP data in the anteroposterior (AP) and mediolateral (ML) directions were recorded at a sampling rate of 1000 Hz. The device was fully calibrated before the test. Data were processed using MATLAB software, and a Butterworth filter with a cutoff frequency of 10 Hz. Output variables, including COP path, COP area, velocity of COP (VCOP), and sway, were calculated using standard formulas and analyzed in SPSS software. The Shapiro-Wilk test was used to assess data normality. Repeated measures ANOVA was employed to compare the three backpack types, and Bonferroni post-hoc tests were used for pairwise comparisons.
Results: The results showed no statistically significant differences in terms of COP area during standing and walking among the different backpack conditions. In terms of COP displacement (P=0.009) and COP velocity (P=0.009), significant differences were found only during eyes-closed standing in the AP direction. Pairwise comparisons revealed a significant difference between the conventional backpack and the one with a movable hip belt. Regarding COP sway (P=0.030), a significant difference was observed among the three backpacks only during eyes-closed standing in the ML direction. However, no statistically significant differences were found between any two backpacks in post-hoc comparisons.
Conclusion: Based on the findings, the backpack with a movable hip belt was the most effective among the three designs, as it resulted in the lowest COP sway, COP velocity, and COP displacement. Furthermore, the impact of hip belt design becomes more apparent in tests with higher complexity. However, it is important to note that reduced COP sway does not necessarily indicate improved postural control or motor performance, and it may reflect a restriction in the responsiveness of the neuromuscular system.

The Effectiveness of a Combined Ergonomic and Exercise Intervention in Optimizing Motor Performance among the Employees of Ilam Petrochemical Company

Nabi Omidi

Objectives: Musculoskeletal disorders (MSDs) are among the main occupational health challenges in industries with demanding working conditions, such as petrochemical plants. This study aimed to investigate the effect of a combined ergonomic and exercise intervention on pain reduction and motor performance improvement among the employees of Ilam Petrochemical Company.
Methods: This quasi-experimental study utilized a pre/posttest design with 40 male workers. Participants were randomly assigned to either an intervention group (receiving ergonomic training combined with exercise) or a control group. Data were collected using the Nordic Musculoskeletal Questionnaire and Motor Performance Questionnaire. Following that, the obtained data were analyzed using independent t-tests and repeated measures ANOVA.
Results: The combined intervention significantly reduced pain in the lower back (55%), shoulders (56%), and knees (57%), while improving the total motor performance score (43%; P<0.001). Cohen’s d effect sizes ranged from 1.8 to 2.5, indicating high effectiveness.
Conclusion: The integration of ergonomic and exercise interventions led to a significant reduction in musculoskeletal pain and improvement in motor performance among petrochemical workers. These findings demonstrate the positive impact of the intervention on workers' motor performance indicators.

Analysis of the Impact of Hidden Withdrawal Profile on Key Indicators of Organizational Performance

Mohammadreza Omidi

Objectives: Hidden withdrawal profiles, as subtle behavioral patterns in the workplace, can significantly influence key indicators of human resource performance. This study aimed to analyze the impact of these profiles on "turnover intention", "career intentions", and "job performance" among employees of Bustan Hospital in Ahvaz, Iran.
Methods: This applied, descriptive-survey research included 240 hospital staff members. Using Cochran's formula, 146 completed questionnaires were analyzed. Data were collected using standardized and validated instruments in the field of organizational behavior. Statistical analyses were conducted using SPSS and SmartPLS software; moreover, measurement validity and reliability were confirmed through KMO, Bartlett, AVE, CR, and Rho-A indices.
Results: Path analysis results indicated a significant positive relationship between hidden withdrawal profiles and turnover intention (β=0.636, t=13.297); however, there were significant negative effects on career intentions (β=-0.482, t=9.519) and job performance (β=-0.803, t=21.079). All t-values exceeded 1.96, and P-values were below 0.001.
Conclusion: Hidden withdrawal behaviors play a critical role in reducing performance and increasing turnover tendencies. The findings highlight the need for early identification of such behavioral patterns and the implementation of psychological and managerial interventions to enhance motivation and employee retention.

Investigating the Relationship of Work-Related Rumination with Work-Family Conflict and Work-Family Enrichment

simindokht kalani

Objectives: The interaction between work and family roles can result in various outcomes, including work-family conflict or enrichment. The way individuals manage the boundaries between these two domains plays an essential role in shaping the quality of this interaction, with work-related rumination being a common manifestation of role integration. The present study aimed to assess the relationship of work-related rumination with work-family conflict and enrichment.
Methods: This cross-sectional study included 330 employees from an industrial organization in Isfahan, selected via convenience sampling. Participants completed questionnaires measuring work-family conflict, work-family enrichment, work-related rumination, positive and negative work reflection, the Irritation scale, as well as the subscales of excessive commitment and Wok Obsession/Inability to Recover. Data were analyzed using stepwise regression analysis.
Results: Among the nine types of work-related rumination, cognitive Irritation (P<0.001), affective rumination (P<0.001), and negative reflection (P<0.001) predicted work-family conflict and together explained 56% of its variance. Problem-solving pondering (P<0.001), positive reflection (P<0.001), and negative reflection (P=0.003) predicted work-family enrichment and explained 12% of its variance.
Conclusion: Work-related rumination does not necessarily have a negative impact on work–family relations and may lead to different outcomes depending on its nature. Certain types of rumination may facilitate the transfer of beneficial work experiences to the family domain. These results highlight the importance of examining the consequences of specific forms of work-home integration rather than broadly rejecting any integration.

Effect of Upper Material in Military Boots on Lower Limb Loading during Walking

Abbas Farjad Pezeshk

Objectives: The role of shaft stiffness in military boots is widely recognized, yet the majority of studies focus on quantifying stiffness rather than examining how the material composition of the boot shaft influences performance. The present study aimed to assess the effect of different boot materials on kinetic parameters, comparing conventional leather boots to a hybrid leather-synthetic design to assess their impact on mobility and biomechanical efficiency.
Methods: A repeated-measures experimental design was employed, assessing 20 healthy male participants under four conditions: walking with a formal shoe and three military boot types, each featuring distinct shaft materials (two leather and one a hybrid leather-synthetic design). Ground reaction forces, rate of force development, and impulse were recorded using a force plate. Statistical analysis involved repeated-measures ANOVA with Bonferroni correction.
Results: Featuring synthetic materials in the shaft, boot 3 displayed reduced negative impulse and elevated positive impulse relative to traditional leather boots during gait.
Conclusion: These findings highlighted the biomechanical advantages of hybrid boot designs, suggesting that reduced shaft stiffness improves mobility and motion efficiency. The study underscores the need for optimized traditional boot materials to enhance gait performance while minimizing injury risks, particularly for military personnel.

Investigating Occupational Exposure Levels and Health Effects Associated with Hand-Arm Vibration during Work with Vibrating Equipment in Furniture Carpentry Workshops

Ramin Rahmani

Objectives: In the furniture industry, workers operating woodworking machinery are exposed to hand-arm vibration. The present study aims to assess the occupational exposure levels and associated health effects of vibration transmitted to the hand during the operation of vibrating equipment in furniture carpentry workshops.
Methods: This case-control study was conducted on 59 carpenters (case group) and 39 painters (control group) in Malayer city, Iran. Hand-arm vibration exposure was measured in accordance with ISO 5349. Symptoms related to hand-arm vibration were assessed via questionnaire. Vascular disorders were evaluated through the hand temperature recovery test, according to ISO 14835. Sensory function was examined using the monofilament test kit, and grip strength of the hand and fingers, as well as hand dexterity, were measured for both groups. The collected data were analyzed using SPSS (version 26).
Results: Based on the findings of the present research, the 8-hour equivalent acceleration of hand-arm vibration among carpentry workers was 2.74 ± 0.85 m/s². The most frequently reported symptoms among carpenters were hand pain, tingling, and finger pruritus, while Raynaud’s phenomenon (finger blanching) was the least frequently reported. Grip strength, finger strength, hand dexterity, and motor skills were significantly lower in the exposed group compared to the controls (P<0.05). Around 10 percent of carpenters exhibited reduced superficial tactile sensitivity. However, no significant difference was observed between the exposed and control groups in terms of vascular impairments.
Conclusion: Chronic exposure to hand-arm vibration in furniture carpentry workshops, even at levels below the permissible limit, can lead to a range of sensory-neurological, vascular, and musculoskeletal symptoms in the hand and arm region, and can adversely affect motor function in these workers.

Design and Psychometric Evaluation of the “Kids Spine Ergonomics Awareness” (KidSEA) Questionnaire

mahnaz Saremi

Objectives: Musculoskeletal disorders, including back pain, are increasingly prevalent among school-aged children. Poor postural habits and improper backpack carriage are significant contributing factors. However, there is currently no comprehensive, standardized tool available to assess children’s knowledge of ergonomics related to spinal health.
Methods: This methodological study involved the development of a questionnaire through a seven-step process. Following the creation of the preliminary version and assessment of face validity, content validity was evaluated using the Content Validity Index (CVI) and Content Validity Ratio (CVR) by ten experts. The reliability of the instrument was assessed using a test-retest procedure with 15 students and internal consistency was evaluated using Cronbach’s alpha coefficient with a sample of 180 students.
Results: The final version of the questionnaire, entitled Kids’ Spine Ergonomics Awareness (KidSEA), comprised 13 items across three domains: "Spinal Anatomy," "Correct Posture," and "Ergonomics of Carrying School Supplies." The CVI and CVR for each item exceeded 0.79 and 0.62, respectively, indicating that all items were validated. Cohen’s kappa coefficient for individual items was above 0.41, and the overall Cronbach’s alpha was 0.74, demonstrating acceptable levels of reliability and internal consistency.
Conclusion: The KidSEA questionnaire is a valid and reliable instrument for assessing knowledge of ergonomic principles related to spinal health in children. It can be utilized to evaluate health literacy concerning spinal care, design targeted interventions, and inform educational programs for children in the studied age group. Further studies are recommended to establish the validity of the instrument across different age groups.

The Relationship between Ergonomic Workplace Climate and Employee Resilience: A Study in a Gas Company

Teimour Allahyari

Objectives: In modern demanding work environments, workforce resilience and ergonomic climate are recognized as critical factors for maintaining employee well-being and enhancing organizational productivity.
Methods: This cross-sectional, descriptive-analytical study investigated the relationship between ergonomic climate and employee resilience in a gas company. A total of 170 employees were selected through cluster random sampling. Data were collected using two validated instruments, namely the Ergonomic Climate Questionnaire and the Connor-Davidson Resilience Scale. Statistical analyses were conducted in SPSS software (version 26), using descriptive statistics, Pearson correlation, one-sample t-tests, and regression analysis.
Results: Mean scores of gas company ergonomic climate and employee resilience were obtained at 135.03±29.96 and 96.5±16.44, respectively. The correlation coefficient between ergonomic climate and employee resilience for 171 samples was calculated at +0.22. The findings indicated that the mean scores for ergonomic climate, operational performance, employee well-being, and individual resilience were significantly higher than the midpoint of the Likert scale. Moreover, individual resilience was found to have a positive and significant correlation with all dimensions of ergonomic climate, namely management commitment, employee involvement, hazard identification and control, and training and knowledge. However, no significant relationships were observed between demographic variables (age, gender, education, work experience) and resilience.
Conclusion: An appropriate ergonomic climate plays a significant role in reducing stress and improving the psychological conditions of the workplace. Employees' resilience can be positively affected by physical and mental health enhancements, stress reduction, job satisfaction increases, and improvements in work-life quality. Therefore, organizational attention to ergonomic issues and the implementation of supportive strategies can improve workplace ergonomics, thereby enhancing individual resilience among employees.