Effects of smartphone use in various floor sitting positions on spinal and pelvic alignment and gluteal pressure in healthy adults

[Purpose] This study investigated the effects of prolonged sitting and smartphone use on the craniocervical angle (CCA), trunk flexion angle (TFA), pelvic obliquity, and gluteal pressure asymmetry in healthy adults. [Participants and Methods] Thirty healthy participants used smartphones for 30 min in three sitting positions: cross-legged, side sitting, and long sitting. Cervical and lumbar angles, pelvic obliquity, and gluteal pressure asymmetry were measured at the start of upright sitting, 30 s, 10 min, 20 min, and 30 min. Visual 3D software was used for data collection and analysis. [Results] CCA and TFA progressively decreased in all three positions. Significant CCA reductions were observed at 30 min in both cross-legged and side sitting positions, and as early as 30 s in long sitting. TFA decreased significantly at all measured times in side sitting, and at most intervals in cross-legged sitting, but not in long sitting. Pelvic obliquity increased significantly in both cross-legged and side sitting, while remaining unchanged in long sitting. Gluteal pressure asymmetry significantly increased at 30 s in cross-legged sitting and at all intervals in side sitting, with no significant changes in long sitting. [Conclusion] If prolonged floor sitting is unavoidable, adopting a symmetrical long sitting posture is preferable.