Measuring Loads in the Spine While Lifting Off CenterA previous history of low back pain (LBP) increases a worker's chances of having another episode. How can we change this? Studying the forces through the spine during lifting might offer us some helpful clues when retraining a worker after the first injury.
The object of this study was to show how spine loading compares between workers with and without low back pain. Everyone lifted four different weights in five positions. Electrical activity of 10 muscles was recorded. The muscles included trunk and abdominal muscles. A computer monitored the speed, direction, and force of trunk and back motions.
Signals were collected using special software developed by the Biodynamics Laboratory at the University of Ohio. The program made it possible for patients with LBP to lift without using maximum exertion. The researchers could still get the needed readings for the study.
In this study they measured downward pressure and sideways (shear) forces when lifting in patients with LBP compared to subjects who've never had back pain. In some positions there was more than twice as much pressure through the spine for the back pain group. Shear forces were much higher for LBP patients when lifts weren't in the center or midline. These lifts required combinations of movements like bending and twisting. They are called asymmetric movements. The greatest differences in force between the two groups occurred when lower weights were lifted.
The authors of this study have spent the last 20 years developing a three-dimensional model that shows how much the spine is loaded during motion. Movements tested so far include forward bending, side bending, and twisting. This study is a first step toward matching a patient's ability to lift with the amount of load that goes through the spine during asymmetric lifting.
This information will help workers prepare to return to work safely. The results of this study will help find ways to train muscles to contract with the right amount of force and with the right timing. Workers need to be able to lift weights from the center and from off center.
William S. Marras, PhD, et al. Spine Loading in Patients with Low Back Pain during Asymmetric Lifting Exertions. In The Spine Journal. January/February 2004. Vol. 4. No. 1. pp. 64-75.
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