Assessment of biomechanical loads in asymmetric manual lifting - a pilot study.
From Experience to Innovation. IEA'97, Vol. 3, Complex Systems, Cognitive Ergonomics, Occupational Safety, Materials Handling, Proceedings of the 13th Triennial Congress of the International Ergonomics Association, Tampere, Finland, June 29-July 4, 1997. Seppala P, Luopajarvi T, Nygard H, Mattila M, eds. Helsinki, Finland: Finnish Institute of Occupational Health, 1997 Jun; 3:549-551
The results of a pilot study assessing biomechanical loads on the lumbar spine during asymmetric lifting were summarized. Four male volunteers performed a series of one and two handed asymmetric lifts while standing on a force plate. Body movements were measured with a Peak 5 movement monitoring system that was based on following the motions of reflective markers placed on the body using recordings made with two video cameras. Lumbar motions were recorded using the Lumbar Motion Monitor, a commercial goniometer system that was fixed to the subject's back. Electromyographic activity (EMG) was recorded from the right and left erector spinae, latissimus dorsi, internal oblique, external oblique, and rectus abdominis muscles. The forces exerted by the subjects during the lifts were recorded off the force plate. The video, EMG, and force plate data were incorporated into a three dimensional biodynamic model to predict compressive and shear forces acting on the lumbar spine. Torques associated with sagittal and lateral flexions or extensions ranged up to 120 Newton meters (Nm). The peak torques in the sagittal and lateral planes averaged across all lifts were of comparable magnitude although they varied between different lifts. The peak axial torques, however, were much smaller, averaging less than 20Nm. Predicted compressive forces acting at the L5/S1 level ranged up to 2 to 3 kilonewtons (kN). The peak predicted shear forces acting at the L5/S1 level were around 500 Newtons (N). Peak shear forces of 200 to 300N, however, were typical of many lifts. The authors conclude that the biodynamic model predicts that asymmetric lifts produce high shearing forces on the lumbar spine. These forces appear to be associated with lateral and sagittal flexions and extensions rather than axial torques. These results support previous findings that considerable cocontraction of trunk muscles occurs during asymmetric lifting and that this should be taken into account when evaluating spinal forces produced by the lifts.
Manual-lifting; Biomechanics; Men; Laboratory-testing; Electrophysiological-measurements; Muscle-function; Mathematical-models; Back-injuries; Injury-prevention; Safety-research;
Seppala-P; Luopajarvi-T; Nygard-C-H; Mattila-M
From Experience to Innovation. IEA'97, Vol. 3, Complex Systems, Cognitive Ergonomics, Occupational Safety, Materials Handling, Proceedings of the 13th Triennial Congress of the International Ergonomics Association, Tampere, Finland, June 29-July 4, 1997