ABSTRACT
<p><b>BACKGROUND</b>Low back pain (LBP) is a common clinical problem. Many researchers have demonstrated that LBP disorders have difference in sensory strategies for postural control. Optokinetic stimulation (OKS) of optic flow has been widely applied to study its effect on vision, but has not been applied to LBP. Here we used OKS on different surfaces to investigate the characteristics of chronic nonspecific LBP (CNLBP) posture control, so as to provide new theoretical and experimental data for further recognizing CNLBP and enriching its treatment.</p><p><b>METHODS</b>Fifteen individuals with CNLBP (age range 25-40 years) and 15 age and gender-matched control subjects were recruited. Each subject, while standing on a stable or soft surface, was exposed to random-dot patterns projected on a large screen, with the dots displaying expansion (+) and contraction (-) and velocities including 80°, 40°, and 20° per second. The visual stimulus used a "stimuli-interval" pattern. The peak velocity, different phases' standard deviation (SD) of the anterior-posterior centre of pressure (COP) displacements and the total length of the medial-lateral COP sway (LML) for stable surface and soft surface were recorded by force platform.</p><p><b>RESULTS</b>The main effect of surface on all parameters was significant, while the main effect of group and OKS showed no significance with the exception of peak velocity (F(3, 95) = 3.6, P = 0.01) and A2 (F(5, 140) = 9.34, P < 0.01) for which the effect of OKS was significant. The interactions of group by OKS of A2 (F(5, 140) = 3.65, P < 0.01) and group by surface by OKS (F(5,140) = 2.83, P = 0.02), and surface by OKS of A1 and A3 (P < 0.05) were significant. It was reported that significantly more SD in amplitude in the T2 phase was seen in persons with CNLBP when confronting the + 40 stimuli on the soft surface (P < 0.05) compared to healthy individuals.</p><p><b>CONCLUSIONS</b>There was no significance between persons with CNLBP and healthy people when using the stable surface. Subjects with LBP showed decreased efficiency of postural adjustment when exposed to more complicated tasks and environments, especially OKS in the expansion direction, and displayed a visual-dependent phenomenon. This result suggested that the treatment of abnormal motor patterns in people with LBP should take the properties of task and environment into account.</p>