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Effect of Load Asymmetry on Internal Loading of the Trunk (1991-1997)
Ali Sheikhzadeh, PhD, CIE (PhD Research)
This study is designed to provide a better understanding of the effect of asymmetrical
lifting on mechanical and neuromuscular performance and on the risk of injury to the back.
The aim of the study is to quantify the activities of ten trunk muscles by using surface
electromyography (EMG) during maximal and submaximal isometric exertion under pure and
combined loading conditions of the trunk. Combined loading is defined as the vectorial
sum of moments in the sagittal and transverse planes. These planes are selected based
on their prevalence in industrial tasks and low back injuries.
To determine the effect of internal loading (compression and shear forces), the muscle parameters
are calculated from the CT-scan images and muscle forces are estimated using an EMG-driven model.
The effects of planar exertion (pure exertion) and combined exertion on the trunk muscle
recruitment patterns and compression and shear forces are compared.
The primary hypotheses that are tested in this study are:
- The peak EMG activity of trunk muscles will be higher during the maximal combined exertion than
during pure maximal exertion.
- The mean of RMS-EMG of the ten selected trunk muscles will change significantly with the orientation
of the net resultant moments of the trunk.
- The compression and shear forces will be changed significantly by the orientation of the resultant moment.
This is a Ph.D. thesis project. Data collection on 10 male and 5 female subjects was completed
in 1995. Currently, the data is being analyzed. Some of the results obtained have been submitted
to scientific journals for review and publication.
This project has been supported by the National Institute for Occupational Safety and Health
through grant R03-OH03087-01 and received one of six John J. O'Toole Safety Memorial Scholarship
Awards given in 1996 by New York University. |
