Postural alignment in standing: A repeatability study.

Interpretation of any postural changes over time relies on the knowledge that the person's perception of comfortable erect posture remains sufficiently constant. This study measured the repeatability of sagittal spinal alignment during one day, and the degree of variability in that alignment measured subsequently four, eight and 12 days, and 16 and 24 months later. Normal women, pregnant women and women with low back pain, in the age range of 15 to 34 years, were included in the study. Spinal curvature was determined using a clinometer, while an electro-goniometer attached to callipers determined the degree of pelvic tilt. Results demonstrated that on any one day, a consistent postural alignment is assumed (in terms of spinal curvature and pelvic inclination) when an individual is asked to stand comfortably erect. In addition, in the normal, symptom-free, young adult subject, the perception of posture, and therefore postural alignment remains constant for at least two years.