Lower Back Injury in Stoop Type Lifting

THE RELATION BETWEEN TRUNK STRENGTH
MEASURES AND LUMBAR DISC
DEFORMATION DURING STOOP TYPE LIFTING

M. A. DeBeliso, J. P. O'Shea, C. Harris, K. J. Adams, FACSM.
Boise State University, Boise, ID., Oregon State University, Corvallis, OR., University of Louisville, Louisville, KY.

Low-back pain and injury are responsible for a major portion of lost workdays and injury compensation claims. Strong well-conditioned trunk musculature has been forwarded as a counter measure towards reducing low-back injuries in the industrial setting.

PURPOSE: The purpose of this study was to determine if strong well-conditioned trunk muscles relieve stresses encountered by the lumbar spine during stoop type lifting and thus reduce the risk of injury.

METHODS: Twelve male subjects (49.7+3.7 years) performed a session of stoop type lifting with a loaded milk crate (11.5 kg), at 4 repetitions per minute, for 15 minutes in accordance with the NIOSH lifting equation. Lateral fluoroscopic images of the lumbar spine were collected prior to and following the lifting session. Fluoroscopic images were collected with the subjects positioned at the initiation (flexed trunk), midrange, and completion of the lift (erect standing). The initial series of images were collected under a no-load condition, while the second series were collected with the subjects holding the 11.5 kg milk crate. Images were imported into AutoCAD where lumbar disc deformation and joint angles were measured by calculating changes in position of adjacent vertebra (L3-4 and L4-5). A reduction of disc deformation was deemed indicative of reduced stress. Trunk extension and flexion strength were measured with a Kin Com isokinetic dynamometer. Trunk flexion endurance was measured via a 60 second curl-up test. Trunk strength and endurance were compared to disc deformation and joint angles to determine if any meaningful relationships existed.

RESULTS: A significant inverse relationship was detected (p <. 05) between: abdominal strength and shear deformation (flexed trunk positions), abdominal endurance and shear deformation (erect trunk), and spinal erector strength and L4-L5 joint angle (erect trunk).

CONCLUSIONS: Strong well-conditioned trunk musculature is associated with reduced lumbar disc deformation and presumably less stress on the lumbar spine.

Contact: Mark DeBeliso, PhD mdebelis@boisestate.edu

Last Updated 03/24/2005