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 associ ations of these variables with low-back and lower-extremity pain in a working population. Design. Test-retest measurements of 18 healthy sub jects. Cross-sectional study of 165 working women and 343 men. Backgro und. Sudden loss of postural balance may result in microtraumas of bac k structures. Therefore workers with decreased postural control may ru n an increased risk of low-back pain. There are few reports describing the reproducibility of force-plate-based posturography. Methods. Ampl itude and velocity of postural sway were measured with a force-plate i n a two-feet stance with eyes open and closed, and in a one-foot stanc e with eyes open. A stepping response test was developed to measure th e dynamic components of balance. Results. The mean differences between the repeated measurements were generally 5-10% and the standard devia tions of these differences were up to a quarter or one third of the me an measurement values. Sway velocity showed the best overall reproduci bility. Men had a larger sway than women independent of age and anthro pometry. The group of non-symptomatic subjects showed wide variation a nd a slightly lower sway than the groups with low-back or lower-extrem ity pain. Conclusions. Postural sway has moderate stability, wide vari ation, and slight associations with low-back symptoms in a working pop ulation. Relevance The wide variation among non-symptomatic subjects i n the results of the tests of postural control and the only weak assoc iation between the values for postural sway and low-back disorders sug gest that poor postural control is at the most a weak determinant for low-back disorders in a working population. (C) 1997 Elsevier Science Ltd. All rights reserved.