Combined Effect of Whole-Body Vibration and Posture on Vibration Discomfort Assessment: A Posture-Corrected Framework

This study introduces a framework to incorporate a posture-related correction into discomfort evaluation during seated whole-body vibration. In total, 24 participants (12 male and 12 female) were exposed to simulated three-dimensional random vibration representative of an agricultural machine, with an unweighted root mean square (RMS) acceleration of 1.08 m/s2 and frequency content up to 30 Hz, while adopting four seated configurations: the Forward, Recline, Forward/Recline Oscillation, and Left/Right Twist Oscillation postures. Weighted vibration magnitudes were evaluated at the seat surface per ISO 2631-1 point vibration total value (pVTV) and adjusted using Rindex to produce a posture-corrected point vibration total value, pVTV(p). Rindex represents the unweighted deviation of the neck and trunk posture from neutral. In an exploratory comparison with Borg CR-10 subjective discomfort ratings, pVTV(p) showed a descriptive alignment across the four posture means (R2 = 0.682; Spearman ρ = 0.949) with the observed posture rank order. These findings support pVTV(p) as a preliminary posture-adjusted exposure descriptor for seated WBV conditions, while further validation is needed. The preliminary Rindex formulation can be expanded through adequately powered studies to include joint-specific contributions to discomfort in a weighted form.