Whole-body-vibration: Investigation of health risks associated with vibration exposure, vibration transmissibility and posture during operation of mining vehicles

Operators of load-haul-dump (LHD) vehicles are exposed to whole-body vibration (WBV) while sitting sideways to the direction of travel as they remove rock from underground mines. Health risks associated with WBV exposure under asymmetric trunk/neck positions have not been explored extensively. Therefore, the overall objective of this research was to investigate health risks associated with WBV exposure, under asymmetric trunk/neck postures, during the operation of LHD vehicles.;WBV exposure levels and driving postures were simulated to determine if vibration transmissibility (seat-head; seat-L1; seat-T1) and trunk/neck muscle activity (electromyography was measured at six locations) were affected by vibration magnitude and asymmetric sitting postures. Vibration transmissibility and muscle activity were both significantly affected by posture and vibration acceleration magnitude. Higher vibration acceleration levels and rotated postures resulted in changes to resonance and attenuation frequencies, magnitude of vibration transmitted to the spine and head, and neck/trunk muscle activity.;In conclusion, LHD operators are exposed to WBV levels above ISO 2631-1 HGCZ limits and LHD operators use driving postures that increase their risk of musculoskeletal injury (above Swedish National Work Injury Criteria for neck rotation). The transmission of WBV from the seat to the spine/head was influenced by vibration acceleration magnitude and asymmetric postures. Therefore, current ISO standards (ISO-2631-1; ISO 2631-5) should be modified to consider the influence of posture when determining "safe" vibration exposure guidelines since asymmetric postures increased the risk of operator injury.;Field measurements of WBV were conducted in accordance with the ISO 2631-1 standard and health risks were determined with ISO 2631-1 and ISO 2631-5 standards. Operators of small (n= 4) and large (n= 6) LHDs were exposed to WBV levels above ISO 2631-1 health guidance caution zone (HGCZ) limits. Health risks predicted by ISO 2631-5 were always lower than the risks predicted by ISO 2631-1. LHD operator driving postures were recorded with video cameras and postures were evaluated with a 3D video matching program. LHD operators spent 89%, 3%, and 24% of their driving time with the neck rotated >40°, trunk rotated >30°, and trunk flexed between 20-45°, respectively. Overall injury risk, as measured by WBV exposure, driving posture, and postural loading, was correlated with operator-reported musculoskeletal injuries.