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Spine loading as a function of lift frequency, exposure duration, and work experience.

Authors
Marras-WS; Parakkat-J; Chany-AM; Yang-G; Burr-D; Lavender-SA
Source
Clin Biomech 2006 May; 21(4):345-352
NIOSHTIC No.
20030677
Abstract
Physiological and psychophysical studies of the effects of lifting frequency have focused on whole-body measurements of fatigue or subjective acceptance of the task and have not considered how spine loads may change as a function of lift frequency or lift time exposure. Our understanding of biomechanical spine loading has been extrapolated from short lifting bouts to the entire work day and may have led us to incorrect assumptions. The objective of this project was to document how spine loading changes as a function of experience, lift frequency, and lift duration while repetitively lifting over the course of an 8-h workday. Twelve novice and twelve experienced manual materials handlers performed repetitive, asymmetric lifts at different load and lift frequency levels throughout an 8-h exposure period. Compression, anterior-posterior shear, and lateral shear were evaluated over the lifting period using an EMG-assisted biomechanical model. Spinal loads increased after the first 2 h of lifting exposure regardless of the lift frequency. Loading was also greater for the inexperienced subjects compared to experienced lifters. The greatest spine loads occurred at those lift frequencies and weights to which the workers were unaccustomed. Increases in spine loading were tracked back to the changes in muscle recruitment patterns that typically involved increased muscle coactivation. The results emphasize the importance of previous motor programming in defining spine loads during repetitive lifting. These results indicate a very different influence of frequency and lift time exposure compared to physiologic and psychophysical assessments. This study has shown that it is not sufficient to extrapolate from short lift periods to extended exposure periods if the biomechanical loading implications of the task are of interest.
Keywords
Biomechanics; Workers; Shift-work; Shift-workers; Manual-lifting; Manual-materials-handling; Materials-handling; Models; Biomechanical-modeling; Exposure-levels; Exposure-assessment; Ergonomics; Back-injuries
Contact
Biodynamics Laboratory, The Ohio State University, 1971 Neil Ave., Rm 210, Columbus, OH 43210, USA
CODEN
CLBIEW
Publication Date
20060501
Document Type
Journal Article
Email Address
marras.1@osu.edu
Funding Type
Grant
Fiscal Year
2006
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-003913
Issue of Publication
4
ISSN
0268-0033
Source Name
Clinical Biomechanics
State
OH
Performing Organization
Ohio State University, Columbus, Ohio
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