Spinal kyphotic alignment changes spinal movement strategy during lateral reaching motion while in a sitting position

[Purpose] This study investigated spine kinematics during normal sitting and flexion sitting with lateral reaching using a three-dimensional motion analysis system. [Participants and Methods] Nineteen healthy young adult males participated in this study. While seated, each participant was asked to reach toward the right using his right hand. Spine angles were defined as T1, T4, T8, L1, and L5 segments. Kinematic data were calculated using the Euler angle and compared to normal sitting and flexion sitting. During flexion sitting, each participant wore a trunk flexion brace. [Results] In the frontal plane, the angle of the T8 segment during flexion sitting was significantly less than during normal sitting. In the axial plane, there were significant differences among the T4, L1, and L5 segments. [Conclusion] Changes in spinal alignment decrease spinal movement and change the movement strategy during lateral reaching while seated.