TEST-RETEST RELIABILITY OF POSTURAL STABILITY MEASURES DURING QUIET STANDING IN PATIENTS WITH A HISTORY OF NONSPECIFIC LOW BACK PAIN

Abstract

As balance is the foundation for all voluntary motor skills, considerable research has been conducted to evaluate postural control in patients with low back pain (LBP). Although reliability is a population-specific property, to the authors' knowledge, there has been no study to determine the test-retest reliability of the center of pressure (COP) measures in the general population of LBP patients. As many as 11 patients with a history of nonspecific LBP randomly completed postural measurements with three levels of difficulty (rigid surface-eyes open, rigid surface-eyes closed, and foam surface-eyes closed) in two sessions. The COP data were used to calculate standard deviation of amplitude, phase plane portrait, standard deviation of velocity, mean total velocity, and area (95% confidence ellipse). Relative reliability of these measures was assessed using intraclass correlation coefficient (ICC) and absolute reliability using standard error of measurement (SEM), and coefficient of variation (CV). Among different COP parameters, the mean total velocity in all conditions of postural difficulty showed the highest reliability, with the ICC range of 0.73–0.80, SEM range of 0.09–0.32 cm/s, and CV range of 5.7–8.2%. Therefore, the mean total velocity may be an optimal COP parameter to be used for quantification and assessment of balance performance in LBP patients.