The Effect of Whole Body Horizontal Vibration in Position Sense and Dynamic Stability of the Spine

Abstract

In many workplaces, workers are exposed to whole body vibration which involves multi-axis motion in fore-aft (x axis), lateral (y axis) and vertical (z axis) directions. In previous studies, our laboratory has found changes in biomechanical responses such as response time and position sense with exposure to vibration in single vertical direction. The objective of the current study was to investigate the effect of whole body, horizontal vibration on proprioception and sudden loading dynamics and to compare these results with the previously studied whole body vertical vibration experiment. Both position sense test and sudden loading test were performed in three conditions: a pre-exposure condition (pre), a post-washout condition (postw) and a post-vibration condition (postv). Subjects were exposed to the whole body horizontal vibration frequency of 5 Hz and constant acceleration of 0.284 RMS (m/s-2) for 30 minutes. Absolute reposition sense error increased slightly after vibration exposure (relative to after quiet sitting (postw)), although the results were not significant. Times to peak muscle response and flexion magnitude were also increased after horizontal vibration exposure, suggesting a decreased stability of the spine, but again these results were not significant. Compared to the previous study of vertical whole body vibration, the effects of horizontal vibration in this study were small and not significant. This may be due to differences in the transmissibility of vertical and horizontal vibrations at the 5 Hz frequency. These results would suggest that horizontal vibration may be less of a factor in whole-body vibration induced injuries. This work was supported by University of Kansas Transportation Research Institute Grant Program.