Notions of "optimal" posture are widespread in modern society and strongly interconnected with preconceived beliefs.
To quantitatively evaluate spinal posture among members of the community during habitual sitting, and when asked to assume an "optimal" posture.
Marker-based kinematic analyses of the head, spine, and pelvis were conducted on 100 individuals. Habitual sitting posture and self-perceived "optimal" posture, and whether participants believed that their habitual sitting reflected an "optimal" posture, were evaluated. The Wilcoxon signed-rank test assessed angular differences between the two postures adopted. Exploratory post-hoc analyses were conducted by using the Mann-Whitney U test to assess differences between genders.
None of the participants stated that their habitual sitting was "optimal". Statistically significant differences were observed in most of the measured angles (p < 0.001) between habitual and self-perceived "optimal" posture. In habitual sitting posture, a significant interaction with gender was found only in the thoracolumbar (p < 0.05) and pelvic (p < 0.001) angles, with small effect sizes. In self-perceived "optimal" posture females were more extended in the head, upper thoracic, lower thoracic, lumbar and pelvic (p < 0.01) regions, than the males.
A group of young, asymptomatic participants, consistently changed their habitual sitting posture to a more upright posture when asked to assume an "optimal" sitting posture, although the amount of change observed varied between spinal regions. These findings also highlight gender differences in not just habitual sitting posture, but also the degree to which habitual sitting posture is modified when trying to assume an "optimal" sitting posture.