Postural sway and stepping response among working population: reproducibility, long-term stability, and associations with symptoms of the low back

Objective. To investigate the day-to-day reproducibility and long-term (9 months) stability of variables of postural control, and the associations of these variables with low-back and lower-extremity pain in a working population. Design. Test-retest measurements of 18 healthy subjects. Cross-sectional study of 165 working women and 343 men. Background. Sudden loss of postural balance may result in microtraumas of back structures. Therefore workers with decreased postural control may run an increased risk of low-back pain. There are few reports describing the reproducibility of force-plate-based posturography. Methods. Amplitude and velocity of postural sway were measured with a force-plate in a two-feet stance with eyes open and closed, and in a one-foot stance with eyes open. A stepping response test was developed to measure the dynamic components of balance. Results. The mean differences between the repeated measurements were generally 5–10% and the standard deviations of these differences were up to a quarter or one third of the mean measurement values. Sway velocity showed the best overall reproducibility. Men had a larger sway than women independent of age and anthropometry. The group of non-symptomatic subjects showed wide variation and a slightly lower sway than the groups with low-back or lower-extremity pain. Conclusions. Postural sway has moderate stability, wide variation, and slight associations with low-back symptoms in a working population.