A Sloped Seat Wedge Can Change the Kinematics of the Lumbar Spine of Seated Workers with Limited Hip Flexion

[Purpose] The purpose of this study was to determine whether a wedge type seat decreases the lumbar flexion angle of seated workers with limited hip flexion. [Subjects] Twelve sedentary workers with limited hip flexion were recruited. [Methods] Three seat surfaces were used: a level surface, a forward-inclining wedge, and a backward-reclining wedge. The angles of lumbar flexion and pelvic tilt were measured using a three-dimensional motion analysis system. Differences in kinematic data of the subjects seated on the three seat surfaces were analyzed using repeated one-way analysis of variance. [Results] The degree of lumbar flexion decreased significantly when using the forward-inclining wedge compared with the level surface and backward-reclining wedge. [Conclusion] These findings suggest that sitting on a forward-inclining wedge may be useful for minimizing the compensatory lumbar flexion of individuals with limited hip flexion who work in a seated position.