Abstract
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.
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