What happens in the vertebral body during lifting?
The exact biomechanics of the lumbar spine during loading remain unclear. Up until today, it is the complexity and invasiveness of such a measurement making it impossible to perform a detailed biomechanical study regarding the spinal loading. Squat loading and stoop loading have been frequently investigated and controversially discussed. Studies have led to various results and opinions as to which movement creates the most load on the lower back.
The aim of this study was to compare stoop loading with squat loading.
The patients were asked to lift a bottle crate in front of their body and were asked to perform the squat lifting and the stoop lifting. The loads in the lumbar spine were modified by inserting strain gauges. During all measurements sessions, the patients were videotaped and the digital telemetry signals and the video data were synchronously stored together.
This study shows that patients bend their upper body more during stoop lifting than during squat lifting. However, maximal resultant forces were not observed at maximal inclination during stoop lifting. Maximal forces were typically observed shortly after the crate lift-off, when the upper body was slightly more straightened.
Even though the lifting techniques were performed differently, they caused almost similar maximal implant forces with 4% higher resultant forces on average during the squat than in stoop lifting. In two patients, the resultant forces during squat lifting were slightly smaller on average.
When interpreting these results, the differences in the achieved median trunk inclinations and knee-bending angles are not only among but also within patients, which can partly explain the inter-individual as well as the intra-individual load variations.
> From: Dreischarf, J Biomech (2016) (Epub ahead of print). All rights reserved to Elsevier Ltd. Click here for the Pubmed summary.