Iranian Journal of Ergonomics

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Abstract Background: Heat exposure is one of the harmful agents at work environments. Workers in high temperature environments are susceptible to heat strain. The purpose of this study was to evaluate the performance of Iranian cooling vests containing phase change material in hot and humid conditions in the Persian Gulf. Materials and Methods: This interventional study carried out on 6 subjects of oil tanker ship's engine room staff in summer in 2013. The Heat Strain Score Index (HSSI), oral temperature and blood pressure measured with and without the cooling vest wearing for two hours, and data were analyzed by paired t test. Results: The mean oral temperature were 36.98± 0.22 °C (without cooling vest) and were 36.68± 0.68°C (cooling vest) at 30th minutes in heat exposure. The mean oral temperature were 37.06± 0.25 °C (without cooling vest) and were 36.78± 0.16°C (cooling vest) at 60th minutes in heat exposure. (p <0.042) and also HSSI was 12.72 ±3.03 (without cooling vest) and 8.65 ±2.9 (with cooling vest) (p <0.039) but the mean systolic and diastolic blood pressure were not significant statistically with and without the use of cooling vests (p>0.05). Conclusion: Our findings showed that cooling vests with phase change material packs reducing heat strain (oral temperature and perceptual heat) in hot and humid climates in Persian Gulf

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Introduction: This study aimed to investigate the effects of cooling vests on heat strain and reaction time while wearing protective clothing against chemical, biological, and radioactive contamination.

Materials and Methods: Twelve male students with the mean age of 25 ± 2 years and mean body mass index (BMI) of 23.0 ± 1.5 kg/m2 were recruited in this experiment. Each student was asked to run on a treadmill at a speed of 2.4 km/h for 20 minutes. The experiments were performed at 35 °C and 30% relative humidity. Physiological strain index score, oral temperature, heart rate, reaction time, and number of errors were measured at the end of the two phases. The findings were analyzed by SPSS.

Results: According to Wilcoxon test, exercising with and without the cooling vest resulted in significantly different physiological strain index scores (P = 0.02), oral temperature (P = 0.02), reaction time (P = 0.02), heart rate (P = 0.02), and errors (P = 0.03). The mean physiological strain index score was 4.038 ± 0.882 without the cooling vest and 1.42 ± 0.435 with the cooling vest. The mean reaction times with and without the cooling vest were 0.539 ± 0.977 and 0.769 ± 0.0972, respectively.

Conclusion: The results of this study showed that using a cooling vest reduced the physiological strain, reaction time, and error rates in workers.

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Introduction: Understanding the physical capacity of people in different weather conditions can facilitate the assignment of right jobs to right individuals. People’s physical work capacity can change in response to weather conditions. Since military forces are usually obliged to work under different weather conditions, this study aimed to assess these individuals’ physical work capacity in desired, warm-humid, and very warm-humid weather conditions.

Materials and Methods: This cross-sectional study enrolled 36 military men (age: 20-29 years). Astrand treadmill tests were used to measure the participants’ physical work capacity, maximum aerobic capacity, and maximum oxygen uptake were measured under three weather conditions (desired, warm-humid, and very warm-humid).

Results: The mean physical work capacity of the participants in desired, warm-humid, and very warm-humid weather conditions was 3.69 ± 0.52, 3.69 ± 0.55, and 3.41 ± 0.50 Kcal/min, respectively. The participants’ maximum physical capacity under the mentioned conditions was 10.87 ± 1.54, 10.84 ± 1.63, and 10.02 ± 10.48 Kcal/min, respectively. Maximum aerobic capacity of the subjects was 29.52 ± 2.52, 29.76 ± 2.65, and 28.14 ± 2.76 ml/kg/min, respectively.

Conclusion: According to our findings, people have similar physical work capacity under desired and warm-humid weather conditions. However, physical work capacity reduced in very warm-humid weather. Moreover, the participants were allowed to perform light-moderate work during a work shift.

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Background and Objectives: Accurate measurement of the employees’ satisfaction with their office chairs can provide valid feedback on the chair design quality for the manufacturers and researchers. This study aims to design a valid and psychometrically evaluated questionnaire for measuring satisfaction with office chairs.
Methods: Through studying the two main documents about chair ergonomics including Iranian office chair standard No. 11388-1 and a valid Persian questionnaire on satisfaction with educational chairs (Mirmohammadi et al.), the initial 39-item office chair satisfaction questionnaire has been developed. Then face and content validity of the questionnaire have been checked out using qualitative and quantitative approach. Quantitative face validity was analyzed using impact score method. Content Validity Index (CVI) and Content Validity Ratio (CVR) have been used for quantitative content validity analysis. In order to analyze the questionnaire’s reliability, two methods including the internal consistency and constancy have been applied. To measure the internal consistency, α-Cronbach (alpha coefficient) and to evaluate constancy (test-retest) have been employed. Also, the receiver operating characteristic (ROC) curve was utilized for specifying its sensitivity, specificity, and cut-off point. The data was analyzed by SPSS 21 and Stata V.14
Results: Mean (CVR) and (CVI) of final questionnaire have been calculated as 0.93 and 0.95, respectively. Questionnaire’s α-Cronbach coefficient has been gained 0.8. Kappa coefficient (for inter-rater agreement) has showed high score (0.91) in the test-retest results, indicating high correlation and good constancy of the questionnaire. In the ROC, the cut-off point was reported as 75.5 with the sensitivity and specificity of 86.2 and 100, respectively, and area under the ROC curve at this cut-off point was 0.96.
Conclusion: The final 34-item questionnaire has exhibited acceptable reliability and validity for measuring satisfaction level of office chairs.
 

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