Comparison of spinal profiles while standing, supine, prone, and seated in four chair types. A pilot study

A 3-dimensional digitizer was used to evaluate the spinal profiles of 16 subjects. These subjects (8 female, 8 male) are from 4 age ranges: 12-14, 20-22, 40-42, and 60-62 years of age. Each subject was measured in 7 different body positions to include: standing, supine, prone, and seated on one of 4 different chair styles. The 4 chairs were a metal folding chair, a stackable plastic molded chair, a 5-caster padded 'secretarial' chair, and an ergonomic kneeling 'posture' chair similar to a Balans chair. The measured spinal profiles were separated into 4 spinal angles (measured with respect to a vertically projected line), the cervical, thoracic, lumbar, and sacral angles. Each spinal angle was the dependent variable for an ANOVA analysis. The independent variables were posture, age, gender, and subject. The ANOVA analysis showed that the main effect of posture was significant for the thoracic, lumbar, and sacral angles. Post hoc testing demonstrated that the supine thoracic angle differed significantly from the other 6 body postures, which were grouped together. The mean lumbar angle had two groupings. One group included the standing, prone, and supine postures, while the other group was comprised of the seated postures. The sacral angle for the standing, prone, and supine postures did not differ significantly, but were different from the seated postures. The sacral angle for the ergonomic posture chair was significantly different from the other chairs, with the magnitude of its mean angle between the standing, prone, and supine group, and the group of other seated postures.