This study evaluated the influence of psychosocial stress upon the biomechanical system and the subsequent spine loading during a lifting task. Twenty-five subjects (15 males and 10 females) performed several sagittally symmetric lifts under psychosocially stressful and non-stressful conditions. Trunk muscle activity, trunk kinematics, and trunk kinetics were used to evaluate three-dimensional spine loading using an EMG-assisted model. The lifts performed under psychosocial stress resulted in a statistically significant increase in spine compression and lateral shear, but not in all subjects. Differences in muscle coactivation accounted for these increases in loading due to the stress manipulation. A pathway between psychosocial stress and spine loading has been identified, which may explain how psychosocial stress at the workplace increases the risk of low back disorders.
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