The intra-rater reliability of the measurement of the center of pressure sway in young women with dorsal hyper kyphosis and young healthy women in standing position: a pilot study

Background: Posturography is a method in which the postural stability of adults is evaluated by measuring the center of pressure sway. This study aims to evaluate the reproducibility of measuring the center of pressure oscillation in standing position with internal perturbation in healthy young women with and without hyperkyphosis. Methods: Ten women with dorsal hyperkyphosis with the mean age of 23.5±2.65 years and 10 healthy women with the mean age of 21.9±1.3 years (October 2018 to February 2019) were recruited for the study. Subjects were asked to perform rapid bilateral arm elevation while standing on a force plate. Standard deviation of the amplitude and The standard deviation of the velocity of the center of pressure sway in anterior-posterior, Medio-lateral directions and the area of sway were used for statistical analysis. Measurements were carried out by one examiner with a 1-day interval in The Biomechanics laboratory of The School of Rehabilitation Sciences, Shahid Beheshti University of Medical Sciences. The relative reproducibility of the measurements was calculated by Intra-class Correlation Coefficient (ICC), standard error of measurement (SEM) and minimal detectable changes (MDC). Results: The intra-rater reliability of standard deviation of the center of pressure sway velocity and amplitude of both directions in both groups were more than 0.75. The intra-rater reliability of the area of the center of pressure sway in the healthy and hyperkyphosis group were 0.42 and 0.38 respectively. Conclusion: Standard deviation of the amplitude and standard deviation of the velocity of the center of pressure sway can be considered as reliable variables for assessing static balance in young women with and without dorsal hyperkyphosis in future studies. However, the inconsistency of sway area especially in women with hyperkyphosis suggests that the use of it for differentiation between subjects and the assessment of the outcome of any interventions on the postural stability should be considered with caution.