The effect of three different angles of the working seat on lumbar spine curvatures and comfort: An observational study

Objective: The purpose of this study was to verify the influence of three different seat inclinations for work as measured by comfort and changes in vertebral curvatures for the position of work. Methods: The kinematic analysis was recorded at the vertebral levels of T5, T10, L3 and S2 to measure the lumbar and thoracic-lumbar angles. The seat allowed adjustments of the angles (0o, 15o and 30o) and the Likert scale was used to assess the subjects' level of comfort. Each data collection session was performed in a 60-min period. The statistical analysis compared groups through multivariate analysis of variance considering the factors: gender, seat angles and instant. As dependent variable, the comfort level, spine angles were considered. Results: We included 32 healthy subjects with aged 18-25 years. Male present bigger thoracic-lumbar angles and smaller lumbar angles. Male present more comfort levels. The seat inclination at 30 degrees causes less thoracic-lumbar angle and less comfort, whereas the seat angle at 0o causes less lumbar angle. There are several and frequent variations in the spine curvatures along a 60-min period and, after 27 min in sitting posture there was a gradual decrease in the comfort level, independent on the angle of seat inclination. Conclusions: The best inclination of the seat was that maybe it is between 0 degrees and 15 degrees, since the results show that in both analysis, the thoracic-lumbar and lumbar angles, and, comfort level, the inclination of 30 degrees seems to be inadequate.