Evaluation of vertical and multi-axial suspension seats for reducing vertical-dominant and multi-axial whole body vibration and associated neck and low back joint torque and muscle activity.

ABSTRACT

The primary aim of this laboratory-based human subject study was to evaluate the biomechanical loading associated with mining vehicles' multi-axial whole body vibration (WBV) by comparing joint torque and muscle activity in the neck and low back during three vibration conditions mining vehicles' multi-axial, on-road vehicles' vertical-dominant, and no vibration. Moreover, the secondary aim was to determine the efficacy of a vertical passive air suspension and a prototype multi-axial active suspension seat in reducing WBV exposures and associated biomechanical loading measures. The peak joint torque and muscle activity in the neck and low back were higher when exposed to multi-axial vibration compared to the vertical-dominant or no vibration condition. When comparing the two suspension seats, there were limited differences in WBV, joint torque, and muscle activity. These results indicate that there is a need to develop more effective engineering controls to lower exposures to multi-axial WBV and related biomechanical loading. Practitioner Summary: This study found that mining vehicles' multi-axial WBV can increase biomechanical loading in the neck and back more so than on-road vehicles' vertical-dominant WBV. While a newly-developed multi-axial active suspension seat slightly reduced the overall WBV exposures, the results indicate that more effective engineering controls should be developed. Abbreviation APDF amplitude probability density function; Aw weighted average vibration; BMI body mass index; C7 The 7th cervical vertebra; EMG electromyography; ES erector spinae; IRB institutional review board; ISO International Organization for Standardization; L5/S1 the fifth lumbar vertebra (L5)/the first sacral vertebra(S1); MSDs musculoskeletal disorders; MVC maximum voluntary contraction; PSD power spectral density; RVC reference voluntary contraction; SCM sternocleidomastoid; SD standard deviation; SPL splenius capitis; TRAP trapezius; VDV vibration dose value; WBV whole body vibration.