Whole-body vibration exposure in unfavourable seated postures: apparent mass and seat-to-head transmissibility measurements in the fore-and-aft, lateral, and vertical directions

Abstract

Mobile machinery operators are exposed to whole-body vibrations (WBV) and unfavourable postures which may lead to adverse effects on the spine. 14 subjects were exposed to WBV on a rigid seat without a backrest. They adopted nine different postures. Apparent mass $MA\left(f\right)$ and seat-to-head transmissibility $T\left(f\right)$ were measured in the horizontal (X), lateral (Y) and vertical (Z) directions. They were compared to the reference posture from the ISO 2631-1 standard. Head and thorax inclinations in the sagittal plane had significant effects. An increase in the main resonant frequency $f_r,$ together with a decrease in ${\left|MA\left(f\right)\right|}_{\mathit{max}}$ were observed in the Z direction. A second lower frequency peak also appeared ($f_r\approx 1\mathrm{ }Hz$ for X, $f_r\approx 2.5\mathrm{ }Hz$ for Z). $f_r$ increased in the X and Z directions for $\left|T\left(f\right)\right|.$ ${\left|T\left(f\right)\right|}_{\mathit{max}}$ increased in the X direction. Head and thorax inclinations in the frontal and the horizontal planes had weak or non-significant effects.

Practitioner summary: Mobile machinery operators are exposed to whole-body vibration and unfavourable body posture. Laboratory measurements of the apparent mass $MA\left(f\right)$ and the seat-to-head transmissibility $T\left(f\right)$ in the horizontal (X), lateral (Y) and vertical (Z) directions are presented for 9 postures relevant to the exposure at the driving position and to the effects of vibration on the spine.

Keywords:

• Drivers
• whole-body vibration
• posture
• apparent mass
• seat-to-head transmissibility

Acknowledgements

This study was funded by INRS. The authors would like to thank Dr. Christine Bourniquel for conducting the inclusion medical visits. Their acknowledgements also go to the pedagogical team and the students of the Institut de Formation en Masso Kinésithérapie (IFMK) of Nancy for their essential contributions to the trials.

Disclosure statement

The authors declare no conflicts of interest relating to the material presented in this manuscript.

Notes

1 CUELA: ‘Computer-Unterstützte Erfassung und Langzeit-Analyse von Belastungen des Muskel-Skelett-Systems’ (computer-based measurement and long-term analysis of stresses upon the musculoskeletal system).