Effects of accelerometer orientation and sex on transmissibility during seated whole-body vibration exposure.

Abstract

Occupational whole-body vibration (WBV) exposure can result in back injuries, with females at greater risk. Transmissibility is one way to quantify injury risk; it is measured using accelerometers and defined in the basicentric coordinate system (BCS). The internal axes of accelerometers at the sacrum (S1) and thoracic spine (T6) have been shown to deviate from the BCS dependent on sex, however, the effects on transmissibility are unknown. This work aimed to compare original and corrected transmissibility, and to investigate sex differences at S1 and T6. 17 males and 22 females were exposed to vertical sinusoidal vibration while sitting on a rigid seat with no backrest. Four orthogonal motion capture markers were attached to accelerometers at S1 and T6 to correct acceleration data to the BCS. Transmissibility was calculated using original and corrected accelerations. Differences were examined using a mixed factorial ANOVA. At T6, females had larger (p = 0.031) vertical transmissibility, and sex differences were larger with corrected accelerations. At S1, female vertical transmissibility at resonance was 1.5 times larger (p = 0.007) than males. Cross-axis transmissibility at S1 was larger (p = 0.008) with corrected accelerations. Females experienced greater S1 cross-axis transmissibility at all frequencies, and sex differences were greater with corrected accelerations. Larger cross-axis transmissibility with corrected accelerations suggests that fore-aft spine motion is underestimated when acceleration data aren't corrected, highlighting the importance of accounting for accelerometer orientation. Moreover, despite exposure to the same input vibration, females experienced greater vibration transmission through the spine, which may be associated with higher compressive and shear forces.