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Pivoting with the Load: An Alternative for Protecting the Back in Asymmetrical Lifting

Gagnon, M., PhD*; Plamondon, A., PhD*; Gravel, D., PhD*†

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The purpose of this study was to examine different lifting conditions with combined flexion and twisting of the trunk relative to the pelvis (full twist and half-twist techniques) and to compare them to a situation using feet pivoting with minimization of trunk motions relative to the pelvis. Nine subjects with limited experience were tested with two force platforms and two 16-mm cameras coupled with two mirrors; dynamic three-dimensional multisegment models were constructed and the net muscular moments as well as the angular velocities of the trunk relative to pelvis were determined about the three orthogonal orthopaedic axes of the trunk at L5-S1 in flexion-extension, lateral bending, and twisting. The results showed that pivoting required larger extension moments but considerably smaller twisting moments and that these moments were exerted from a safer trunk posture. Pivoting appears to be a good compromise to avoid or minimize complex trunk postures and loadings.

*From the Biomechanics Laboratory, Départment d'éducation physique, and École de Réadaptation, Université de Montréal, Montréal, Québec, Canada. Dr. Plamondon is currently at École de l'Activité Physique, Université laurentienne, Sudbury, Ontario, Canada.

Supported by the Institut de Recherche en Santé et en Sécurité du Travail du Québec (IRSST) and the Natural Sciences and Engineering Research Council of Canada (NSERC grant OGP0020812).

Accepted for publication March 29, 1993.

© Lippincott-Raven Publishers.