Evaluation of the properties of postural displacement optimization in people with post-stroke motor impairment: a cross-sectional observational study

Abstract

Introduction: Postural control impairments, usually assessed through posturography, is a common feature of poststroke persons, being associated with standing problems and increased risk of fall. Recently, a new method for the identification of optimization
features of postural sway was developed for the investigation of postural control processes in health, young people. Objective: The main goal of our study is to investigate whether and how the optimization properties of postural sway during upright stance is affected in poststroke persons. Methods: Twenty-nine poststroke people (ranged 34-86 years old), along with 15 healthy controls (48-70 years-old) participate in this study. Based on their body weight distribution (BWD), poststroke persons were allocated in an
asymmetric (BWD≥10%, N=13) or symmetric (BWD<10%, N=16) group. Additionally, poststroke persons were assigned to a high- (N=10) or low-risk-of-fall (N=19) groups, based on their scores in Berg Balance Scale (BBS, scores ≤45 as criteria for high-riskof-
falls). Participants were asked to stand over a force platform in a comfortable position. Center-of-pressure coordinates were acquired in a single 60s trial and converted to radial distances (RD). An index of postural sway variability along with optimization features were computed; briefly, assuming RD minimal values as the optimized parameter, measures related to general, local, and global performance were computed to describe how optimization processes unfold during the standing task. One-way ANOVA was applied for comparison among control and poststroke groups, while Welch t-test was used for comparison between high- and low-risk-of-falls groups. Associations among BBS and optimization variables were estimated through Pearson correlation coefficient analysis. A statistical threshold was set at 5%. Results: As main results, a significant between-group effect was found for the rate of convergence to postural sway minimum (gamma-value; P=0.030, h2=0.157); posttest reveals a significant difference between control and poststroke asymmetric group (P=0.042). Significant, moderate positive associations were found between BBS and the minimal
expected value of postural sway (local minima; r=0.424, P=0.022) and the postural sway lowest value (global minima, r=0.378, P=0.043). Statistical differences between high- and low-risk-of-falls group were found for these same variables (P<0.043).
Conclusion: Optimization parameters reflecting postural sway control during standing were altered in poststroke persons with asymmetric BWD, being inversely proportional to the risk of fall in stroke persons.