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 subjects were tested in slouched, erect, forward inclined, and comfortable postures. Objectives. The purposes of this study were to evaluate the changes in head, cervical, lumbar, and pelvic postures in different sitting positions and also to determine if there is a relation between lumbar posture and cervical posture during sitting. Summary of Background Data. Clinicians commonly assert that head and neck position is strongly influenced by lumbar and pelvic position. A biomechanical model was developed that allowed detailed, quantitative description of head, neck, lumbar, and pelvic postures. This model enabled a distinction to be made between upper and lower cervical motions. Methods. Various spinal angles were measured in 30 healthy subjects in four sitting positions using a three-dimensional digitizing system. Reliability of the measurement procedure was determined using an intraclass correlation coefficient and the values for most angles was above 0.8. Results. With the exception of head orientation, analysis of variance revealed significant differences in spinal angles between different sitting positions. Head orientation appeared to be maintained by compensatory adjustments in both the upper and lower cervical spine and changes in lumbar posture were associated with compensatory changes in overall cervical position. As the lumbar spine moved toward extension, the cervical spine flexed and as the lumbar spine flexed the cervical spine extended. However, there was variation among subjects as to whether cervical spine adjustments occurred primarily in the upper or lower cervical region. Conclusions. Different sitting postures clearly resulted in changes in cervical spine position. Lumbar and pelvic position should be considered when control of cervical posture is desired.