The Comparisons of Whole Body Vibration Exposures and Supporting Musculature Loading between Single- and Multi-axial Suspension Seats during Agricultural Tractor Operation

Abstract

Due to rough terrain, agricultural tractor drivers are likely exposed to a high level of whole body vibration, especially impulsive shocks. These WBV exposures are often predominant in the fore-aft (x) or lateral (y) axis. However, the current industry standard seats are designed to reduce mainly vertical (z) axis WBV exposures, and therefore, may be less effective in reducing tractor drivers’ exposure to WBV. Therefore, in a repeated-measures design with 11 subjects, this study evaluated efficacy of a multi-axial (vertical + lateral) suspension seat in reducing WBV exposure and low back (erector spinae) muscle activity relative to an industry standard single-axial suspension seat. The results showed that while there was no difference in fore-aft (x) and vertical (z) axis WBV exposures between the seats, the multi-axial suspension seat had lower A(8) lateral (y) WBV exposures [median (interquartile range): 0.7 (0.41, 0.83) m/s2] and VDV(8) [13.5 (7.4, 16.4) m/s1.75] WBV exposures than the single-axial suspension seats [ A(8): 0.81 (0.48 0.93) m/s2; VDV(8): 13.5 (8.7, 18.5) m/s1.75] (p = 0.02 and 0.04, respectively). Low back muscle activity was also lower on the multi-axial suspension seats, however this difference was not significantly significant. These results indicate that mu the multi-axial suspension may have potential to reduce the WBV exposures and muscular loading on low back among agricultural vehicle operators.