Biomechanics of forward-reaching movements while sitting on fixed forward- or backward-inclining or tiltable seats.

Possible differences in spinal stress were evaluated during forward-reaching movements from chairs with, respectively, fixed backward-inclining, forward-inclining, and tiltable seat. Twenty-four healthy subjects, 12 female and 12 male, performed rhythmical sagittal movements with pins over a 40-cm distance. The posture in an upright and in a forward position was described by means of seven variables, measured by an inclinometer. Posture changes between these positions were then compared for the three types of chairs. No significant influence from the chairs on posture changes was observed. Thus, no variation in spinal stress can be anticipated during forward-reaching movements in any of the three types of chair. The discussion also presents a current status regarding tiltable and fixed forward-inclining seats.