Abstract
Quantitative data of spine alignment is required during positioning of human body model, analysis of spine-related injury mechanism and ergonomic study of vehicle seat. Although spine alignment varies depending on individuals and body postures, only few studies regarding the variation of spine alignment can be found. In this study, by fitting Bezier curve on the lateral X-ray images of spine in standing and sitting posture, variations in spine alignments were quantified. Furthermore, relationships between the spine alignment and body pressure during sitting or EMG of abdominal muscle were also clarified. As a result, large variation in spine alignment could be found in cervical and lumbar spine. Cervical spine showed an increased tendency of S-shaped curvature during sitting posture compared to standing posture. Lumbar spine indicated a strong trend of lordotic and kyphotic curvature during standing and sitting posture respectively. Moreover, the maximum value of normalized iEMG in sitting posture was found to be higher than in standing posture. Comparisons of normalized maximum body surface pressure and contact area between two typical cervical and lumbar spine curvatures showed that the differences were not significant.
