Effects of box size, frequency of lifting, and height of lift on maximum acceptable weight of lift and heart rate for male university students in Iran

Ali Salehi Sahl Abadi; Adel Mazlomi; Gebraeil Nasl Saraji; Hojjat Zeraati; Mohammad Reza Hadian; Amir Homayoun Jafari

doi:10.14661/2015.1365

Effects of box size, frequency of lifting, and height of lift on maximum acceptable weight of lift and heart rate for male university students in Iran

Electron Physician. 2015 Oct 19;7(6):1365-71. doi: 10.14661/2015.1365. eCollection 2015 Oct.

Authors

Ali Salehi Sahl Abadi¹, Adel Mazlomi², Gebraeil Nasl Saraji³, Hojjat Zeraati⁴, Mohammad Reza Hadian⁵, Amir Homayoun Jafari⁶

Affiliations

¹ M.Sc. of Occupational Health Engineering, Ph.D. Student, Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
² Ph.D. of Occupational Health Engineering, Assistant Professor, Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
³ Ph.D. of Occupational Health Engineering, Professor, Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
⁴ Ph.D. of Biostatistics, Professor, Department of Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
⁵ Ph.D. of Physiotherapy, Professor, Department of Physical Therapy, School of Rehabilitation Sciences, Tehran University of Medical Sciences, Tehran, Iran.
⁶ Ph.D. of Biomedical Engineering, Assistant Professor, Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

Abstract

Introduction: In spite of the widespread use of automation in industry, manual material handling (MMH) is still performed in many occupational settings. The emphasis on ergonomics in MMH tasks is due to the potential risks of workplace accidents and injuries. This study aimed to assess the effect of box size, frequency of lift, and height of lift on maximum acceptable weight of lift (MAWL) on the heart rates of male university students in Iran.

Methods: This experimental study was conducted in 2015 with 15 male students recruited from Tehran University of Medical Sciences. Each participant performed 18 different lifting tasks that involved three lifting frequencies (1lift/min, 4.3 lifts/min and 6.67 lifts/min), three lifting heights (floor to knuckle, knuckle to shoulder, and shoulder to arm reach), and two box sizes. Each set of experiments was conducted during the 20 min work period using the free-style lifting technique. The working heart rates (WHR) were recorded for the entire duration. In this study, we used SPSS version 18 software and descriptive statistical methods, analysis of variance (ANOVA), and the t-test for data analysis.

Results: The results of the ANOVA showed that there was a significant difference between the mean of MAWL in terms of frequencies of lifts (p = 0.02). Tukey's post hoc test indicated that there was a significant difference between the frequencies of 1 lift/minute and 6.67 lifts/minute (p = 0. 01). There was a significant difference between the mean heart rates in terms of frequencies of lifts (p = 0.006), and Tukey's post hoc test indicated a significant difference between the frequencies of 1 lift/minute and 6.67 lifts/minute (p = 0.004). But, there was no significant difference between the mean of MAWL and the mean heart rate in terms of lifting heights (p > 0.05). The results of the t-test showed that there was a significant difference between the mean of MAWL and the mean heart rate in terms of the sizes of the two boxes (p = 0.000).

Conclusion: Based on the results of this study, it was concluded that MAWL and heart rate are influenced by the variables of lifting frequency and the size of the boxes.

Keywords: MAWL; MMH; heart rate; psychophysical methodology.