Whole-body vibration alters proprioception in the trunk

Occupational whole-body vibration has long been associated with low back injuries. However, the mechanism of these injuries is not well understood. In this paper, the effect of whole-body vibration on proprioception and dynamic stability was examined. Subjects exposed to 20 min of vertical, seated, whole-body vibration were found to have a 1.58-fold increase in position-sense errors after vibration relative to controls exposed to 20 min of the same seated posture without vibration exposure. To understand the potential effect of a sensory loss on dynamic low back stability, a lumped parameter model of the trunk and neuromotor response was created. Using this model, an increase in the threshold of the sensory system was predicted to increase trunk flexion and delay neuromotor response with a sudden, unexpected perturbation. These predictions were demonstrated in a second experiment where subjects exhibited both an 11.9% increase in trunk flexion and an 11.2% increase in time to peak paraspinal muscle response (measured using integrated electromyographic activity) after exposure to 20 min of vertical, seated, whole-body vibration. Relevance to industry For workers exposed to whole-body vibration (WBV), this research suggests that a loss in the ability to sense and control lumbar posture may occur. After exposure, unexpected perturbations during manual materials handling could lead to injury. Reducing vibration exposure or a break between exposure and manual materials handling could be used to reduce this risk. (c) 2007 Elsevier B.V. All rights reserved.