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Networks of Internal Trunk-Loading Activities under Controlled Trunk-Motion Conditions

MARRAS, W. S., PhD; REILLY, C. H., PhD

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Many attempts have been made to describe the activity of the internal trunk-loading components (muscles and intra-abdominal pressure) in response to external forces acting on the trunk, as is often the case in the workplace. Most models that describe the activity of these internal components are static and do not consider the time series of events that occurs during performance of a task under dynamic conditions. This research has investigated the time sequence activity of ten trunk muscles and intra-abdominal pressure in ten males as they produced sagittally symmetric maximum trunk extension motions (lifting motions) at different velocities. These exertions include an isometric exertion and isokinetic exertions equal to 25, 50, 75 and 100% of a subject's maximum extension velocity. Several event times were noted for each internal trunk-loading component, and hypothesis tests were performed to determine which of these event times were statistically different from each other under the various motion conditions. This information was used to construct networks of internal trunk-loading activities under the various motion conditions. Time-series events that occur under all conditions, as well as those that changed as a function of velocity, have been identified. This information will be useful for the construction of dynamic internal trunk models, and will facilitate the assessment of dynamic loading of the lumbar spine in the workplace.

From the Department of Industrial and Systems Engineering, The Ohio State University, Columbus, Ohio.

Partial funding for this research was provided by The Ohio State University Seed Grant Program.

Submitted for publication December 23, 1986, and revised May 3, 1987.

We wish to express our gratitude to Ms. Delia Treaster and to Mr. Anthony R. DeGennaro for their assistance in performance of this project.

© Lippincott-Raven Publishers.