Paired comparison study to determine the impact of rotated neck/trunk posture combined with vibration exposure on seated comfort

Abstract

Literature shows that whole-body vibration (WBV) has been linked to low-back pain (LBP), but also that exposure to WBV while in non-neutral postures can further increase the risk of LBP (Bovenzi et al., 2002; T. Eger et al., 2008). Operating cranes, agricultural tractors, underground mining vehicles and some construction equipment can expose a worker to WBV and non-neutral postures (T. Eger et al., 2008; Kittusamy & Buchholz, 2004; Newell & Mansfield, 2008; Wikström, 1993). This study aims to determine if discomfort is greater due to WBV alone, axial rotation alone or WBV and axial rotation combined. It also aims to determine if the degree or type of rotation (neck vs trunk) causes more discomfort when WBV is present. Ten participants (5 male and 5 female, 21.1±0.57 years, 169.2±9.5 cm and 74.9±11.8 kg) participated in a single elimination tournament of 16 postures with varying axial rotations of the neck and trunk both with and without WBV, to identify the most uncomfortable condition. They also rated the discomfort of each condition on a scale of 1-9. Results of the head-to-head tournament indicated, six participants selected the max neck and max trunk rotation posture as most uncomfortable (4 with WBV and 2 without). While two participants selected the 15° neck and max trunk rotation without WBV, and two participants selected the max neck 0° trunk with WBV. Similarly, the average discomfort scores were highest for the max neck and max trunk rotations with WBV and slightly lower without WBV. These results indicate a trend of increased discomfort when axial rotation and WBV are both present. They also seem to indicate that discomfort continuously increases as the angle of rotation increases and that any maximum rotation leads to more discomfort than a combination of neck and trunk rotations. Future, machine designs should focus on eliminating both factors.