Inter-individual postural variability of off-road machine drivers exposed to WBV

Seated mobile machinery operators are exposed to whole-body vibration (WBV) that may lead to low back pain (LBP). The procedure defined by ISO 2631-1:1997 for the evaluation of vibration does not take into account the physical stress caused by maintained seated positions and body movements. Their effects have to be investigated in order to protect workers from physical injuries. A field experiment has been conducted to estimate both inter and intra-individual variability in the vibration exposure and body postures of 20 drivers. WBV and body postures were measured at the driving position of 3 vehicles (loader, dumper and excavator). These recordings were performed during real working tasks. Each task was representative of the typical use of each machine. WBV measurements were performed according to the ISO 2631-1 standard. Body postures were measured with the C.U.E.L.A. system (Computer assisted registration and long-term analysis of muskulo-skeletal workloads) developed by the I.F.A. (German institute for occupational safety and health). This paper describes the experimental setup and presents a detailed analysis of each descriptive quantity. Finally, the inter-individual variability was calculated for both vibration and body postures.