title: 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.
abstract: BACKGROUND
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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.
authors.forename: Ali Salehi Sahl
authors.initials: AS
authors.lastname: Abadi
authors.affiliation: Ph.D. of Occupational Health Engineering, Assistant Professor, Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Adel
authors.initials: A
authors.lastname: Mazlomi
authors.affiliation: Ph.D. of Occupational Health Engineering, Professor, Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Gebraeil Nasl
authors.initials: GN
authors.lastname: Saraji
authors.affiliation: Ph.D. of Biostatistics, Professor, Department of Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hojjat
authors.initials: H
authors.lastname: Zeraati
authors.affiliation: Ph.D. of Physiotherapy, Professor, Department of Physical Therapy, School of Rehabilitation Sciences, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Hadian
authors.affiliation: Ph.D. of Biomedical Engineering, Assistant Professor, Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Amir Homayoun
authors.initials: AH
authors.lastname: Jafari
keywords: MAWL; MMH; heart rate; psychophysical methodology