Whole body vibration alters proprioception in the trunk

Abstract

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 minutes 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 minutes 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 minutes of vertical, seated, whole body vibration.