Analysis of sliding and pressure distribution during a repositioning of persons in a simulator chair

This study was undertaken to investigate the effect of system tilt and back recline angles on sliding and pressure distribution of seated subjects. Ten able-bodied subjects adopted successively 12 postures on a multiadjustable simulator chair. The system tilt angle was varied from 0° to 45° posterior tilt, while the seat to back angle varied from 90° to 120°. A maximum of 40.2% of weight shift was found when combining a system tilt angle of 45° to a seat to back angle of 120°. Maximum value of 74 mm of sliding was observed for the acromion marker during repositioning. Significant weight shift at the level of the seat is obtained only when the system tilt angle exceeds 15° in a posterior direction. We can put forward here that a small tilt ≤15° can be used to adjust back pressure distribution, whereas large posterior tilts are used for an effective weight shift at the seat level. The peak pressure gradient remains in general in the interval of ±30% from the neutral posture for the able-bodied subjects and is fairly constant at 15° of tilt. A significant amount of displacement along the back and seat reference plane were found for the shoulder and hip markers, but this displacement does not necessarily correspond to a pure translation motion of the pelvic segment.