THE INFLUENCE OF DIFFERENT SITTING POSITIONS ON CERVICAL AND LUMBAR POSTURE

Study Design. This study used a repeated measures design to assess the effects of multiple sitting postures on various spinal angles. All su bjects were tested in slouched, erect, forward inclined, and comfortab le postures. Objectives. The purposes of this study were to evaluate t he changes in head, cervical, lumbar, and pelvic postures in different sitting positions and also to determine if there is a relation betwee n lumbar posture and cervical posture during sitting. Summary of Backg round Data. Clinicians commonly assert that head and neck position is strongly influenced by lumbar and pelvic position. A biomechanical mod el was developed that allowed detailed, quantitative description of he ad, neck, lumbar, and pelvic postures. This model enabled a distinctio n to be made between upper and lower cervical motions. Methods. Variou s spinal angles were measured in 30 healthy subjects in four sitting p ositions using a three-dimensional digitizing system. Reliability of t he measurement procedure was determined using an intraclass correlatio n coefficient and the values for most angles was above 0.8. Results. W ith the exception of head orientation, analysis of variance revealed s ignificant differences in spinal angles between different sitting posi tions. Head orientation appeared to be maintained by compensatory adju stments in both the upper and lower cervical spine and changes in lumb ar posture were associated with compensatory changes in overall cervic al position. As the lumbar spine moved toward extension, the cervical spine flexed and as the lumbar spine flexed the cervical spine extende d. However, there was variation among subjects as to whether cervical spine adjustments occurred primarily in the upper or lower cervical re gion. Conclusions. Different sitting postures clearly resulted in chan ges in cervical spine position. Lumbar and pelvic position should be c onsidered when control of cervical posture is desired.