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A study of lifting tasks performed on laterally slanted ground surfaces.

Jiang Z; Shin G; Freeman J; Reid S; Mirka GA
Ergonomics 2005 Jun; 48(7):782-795
Lifting in most industrial environments is performed on a smooth, level ground surface. There are, however, many outdoor work environments (e.g. agriculture and construction) that require manual material handling activities on variable grade ground surfaces. Quantifying the biomechanical response while lifting under these conditions may provide insight into the aetiology of lifting-related injury. The aim of the current study was to quantify the effect of laterally slanted ground surfaces on the biomechanical response. Ten subjects performed both isometric weight-holding tasks and dynamic lifting exertions (both using a 40% of max load) while standing on a platform that was laterally tilted at 0, 10, 20 and 30 degrees from horizontal. As the subject performed the isometric exertions, the electromyographic (EMG) activity of trunk extensors and knee extensors were collected and during the dynamic lifting tasks the whole body kinematics were collected. The whole body kinematics data were used in a dynamic biomechanical model to calculate the time-dependent moment about L5/S1 and the time-dependent lateral forces acting on the body segments. The results of the isometric weight-holding task show a significant (p < 0.05) effect of slant angle on the normalized integrated EMG values in both the left (increase by 26%) and right (increase by 70%) trunk extensors, indicating a significant increase in the protective co-contraction response. The results of the dynamic lifting tasks revealed a consistent reduction in the peak dynamic L5/S1 moment (decreased by 9%) and an increase in the instability producing lateral forces (increased by 111%) with increasing slant angle. These results provide quantitative insight into the response of the human lifter under these adverse lifting conditions.
Surface-properties; Ground-stability; Work-environment; Biomechanics; Injuries; Models; Materials-handling; Manual-lifting; Manual-materials-handling; Humans; Author Keywords: Asymmetric lifting; Surface angle; Biomechanical model; Slant; Slope; Slip
The Ergonomics Laboratory, Department of Industrial Engineering, North Carolina State University, Box 7906, Raleigh, North Carolina, NC, 27695-7906, USA
Publication Date
Document Type
Journal Article
Email Address
Funding Type
Cooperative Agreement; Grant
Fiscal Year
Identifying No.
Cooperative-Agreement-Number-U50-OH-007551; Grant-Number-T42-OH-008673
Issue of Publication
Source Name
Performing Organization
East Carolina University
Page last reviewed: March 3, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division