A comparison of peak vs cumulative physical work exposure risk
factors for the reporting of low back pain in the automotive industry
Abstract
Objective. To determine the relative importance of modelled peak spine loads, hand loads, trunk kinematics and cumulative
spine loads as predictors of reported low back pain (LBP).
Background. The authors have recently shown that both biomechemical and psychosocial variables are important in the
reporting of LBP. In previous studies, peak spinal load risk factors have been identified and while there is in vitro evidence for
adverse effects of excessive cumulative load on tissue, there is little epidemiological evidence.
Methods. Physical exposures to peak and cumulative lumbar spine moment, compression and shear forces, trunk kinematics,
and forces on hands were analyzed on 130 randomly selected controls and 104 cases. Univariable and multivariable odds ratios
of the risk of reporting were calculated from a backwards logistic regression analysis. Interrelationships among variables were
examined by factor analysis.
Results. Cases showed significantly higher loading on all biomechanical variables. Four independent risk factors were identified:
integrated lumbar moment (over a shift), ‘usual’ hand force, peak shear force at the level of L& and peak trunk velocity.
5. There is more than sixfold increase in the risk for reporting LBP for workers with high levels of exposure to all four major risk factors indentified: peak shear; integrated lumbar moment over the duration of the shift; peak torso flexion velocity; and usual hand force over the course of the shift.
6. Although the best statistical model included the combinations of variables listed in no. 5, above, very little predictive power was lost by substituting variables such as spinal compression or moment, which were eliminated from the ‘best’ multivariable model because of high correlation with spinal shear force. It would, therefore, be unwise to dismiss
compression or moment as risk factors only because they did not emerge in the best multivariable statistical
model.
 
A comparison of peak vs cumulative physical work exposure riskfactors for the reporting of low back pain in the automotive industryAbstractObjective. To determine the relative importance of modelled peak spine loads, hand loads, trunk kinematics and cumulativespine loads as predictors of reported low back pain (LBP).Background. The authors have recently shown that both biomechemical and psychosocial variables are important in thereporting of LBP. In previous studies, peak spinal load risk factors have been identified and while there is in vitro evidence foradverse effects of excessive cumulative load on tissue, there is little epidemiological evidence.Methods. Physical exposures to peak and cumulative lumbar spine moment, compression and shear forces, trunk kinematics,and forces on hands were analyzed on 130 randomly selected controls and 104 cases. Univariable and multivariable odds ratiosof the risk of reporting were calculated from a backwards logistic regression analysis. Interrelationships among variables wereexamined by factor analysis.Results. Cases showed significantly higher loading on all biomechanical variables. Four independent risk factors were identified:integrated lumbar moment (over a shift), ‘usual’ hand force, peak shear force at the level of L& and peak trunk velocity.5. There is more than sixfold increase in the risk for reporting LBP for workers with high levels of exposure to all four major risk factors indentified: peak shear; integrated lumbar moment over the duration of the shift; peak torso flexion velocity; and usual hand force over the course of the shift.6. Although the best statistical model included the combinations of variables listed in no. 5, above, very little predictive power was lost by substituting variables such as spinal compression or moment, which were eliminated from the ‘best’ multivariable model because of high correlation with spinal shear force. It would, therefore, be unwise to dismisscompression or moment as risk factors only because they did not emerge in the best multivariable statisticalmodel.
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