Postural control investigation in postmenopausal women with and without osteoporosis: The relationship between the center of pressure variability and weight bearing asymmetry index in quiet standing.

INTRODUCTION: Postural instability is a key predictor of falls. This study explored center of pressure (CoP) variability using linear and nonlinear parameters. It examined how Weight-Bearing Asymmetry (WBA) relates to postural stability, offering insights into fall mechanisms in postmenopausal osteoporotic women.

METHODS: Thirty-four postmenopausal women, aged 57.10 ± 4.49, BMI 29.11 ± 4.76 Kg/m2, non-exercising, participated in the study and were divided into two groups based on their lumbar T-score: the osteoporotic (n = 17, T-score ≤ -2.5) and the non-osteoporotic (n = 17, T-score > -1). The fall efficacy scale International (FES_I) was administered through an interview. Isometric strength of the lower extremity muscles was measured through digital hand-held dynamometer, and CoP trajectories were recorded to extract linear and non-linear parameters. Simultaneously, the subjects' base of support (BoS) was tracked using a motion capture system.

RESULTS: No significant differences were found in age and BMI between groups. The osteoporotic group demonstrated significantly higher FES_I scores, reduced hip abductor strength, increased standard deviation (SD) of CoP sway velocity and displacement, and decreased CoP entropy in the frontal plane compared to the non-osteoporotic group. Additionally, osteoporotic women exhibited a pronounced WBA, favoring the non-dominant side, whereas non-osteoporotic women showed a less marked degree of WBA.

SIGNIFICANCE: It is concluded that the reduced CoP entropy and increased WBA in the frontal plane may represent central nervous system strategies aimed at minimizing unpredictability in postural control during quiet standing. These adjustments may also provide the necessary stability for dynamic tasks in osteoporotic women, warranting further investigation.