Predictive discomfort of non-neutral head–neck postures in fore–aft whole-body vibration

Abstract

It seems obvious that human head–neck posture in whole-body vibration (WBV) contributes to discomfort and injury risk. While current mechanical measures such as transmissibility have shown good correlation with the subjective-reported discomfort, they showed difficulties in predicting discomfort for non-neutral postures. A new biomechanically based methodology is introduced in this work to predict discomfort due to non-neutral head–neck postures. Altogether, 10 seated subjects with four head–neck postures—neutral, head-up, head-down and head-to-side—were subjected to WBV in the fore–aft direction using discrete sinusoidal frequencies of 2, 3, 4, 5, 6, 7 and 8 Hz and their subjective responses were recorded using the Borg CR-10 scale. All vibrations were run at constant acceleration of 0.8 m/s² and 1.15 m/s². The results have shown that the subjective-reported discomfort increases with head-down and decreases with head-up and head-to-side postures. The proposed predictive discomfort has closely followed the reported discomfort measures for all postures and rides under investigation.

Statement of Relevance: Many occupational studies have shown strong relevance between non-neutral postures, discomfort and injury risk in WBV. With advances in computer human modelling, the proposed predictive discomfort may provide efficient ways for developing reliable biodynamic models. It may also be used to assess discomfort and modify designs inside moving vehicles.

Keywords:

• neck posture
• predictive discomfort
• reported discomfort
• transmissibility
• whole-body vibration

Acknowledgement

We would like to thank Dr Ting Xia from Palmer University in Davenport, Iowa and Rosalind Smith and John Meusch at the 3D Bio-Motion Research Lab at the University of Iowa for their help in the experiments.