Forward sloping chair effects on spinal shape in the Hong Kong Chinese andIndian populations

Forward sloping seats are universally accepted based on their increased tru nk-thigh angle during sitting. However, these seats are not preferred by so me individuals due to reasons such as excessive pressure on knees, difficul ties during ingress and egress, and postural fixity during sitting. Some re searchers have claimed that forward sloped sitting preserves the lumbar lor dosis, thereby making it more comfortable for the sitter. This claim has no t been validated across all populations and, therefore, appears to have som e disagreement among researchers. In this study, spinal shape during standi ng and sitting in forward sloping chairs is measured and quantified using a three-dimensional sonic digitizer. Twenty subjects (ten Hong Kong Chinese and ten Indian) have participated in the experiment. Fifteen points on the spine are digitized during standing and sitting in a forward-sloping seat w ith trunk-thigh angles of 70 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, and 120 degrees. Different measures are used to analyze and di fferentiate the spinal shape. The correlation between the length of spine d uring standing and a subject's height is low, but significant. The behavior of the spinal shape change during sitting differs between the populations as shown by the maximum lumbar and maximum thoracic deviations. The Indian subjects seem to approach the standing curvatures in the thoracic region du ring 30 degrees forward sloping sitting. The Hong Kong Chinese subjects, on the other hand, do not show any resemblance to the standing curvatures dur ing forward sloping sitting. One possible reason could be the differences i n arch angle between the two populations. The variations in spinal shape am ong subjects appear to be similar within a population.