Test-retest reliability of static postural balance variables in natural and feet-together stance conditions

초록

Background and aims The aim of this study was to investigate the test-retest reliability of postural balance variables during the natural and feet-together stance conditions. It is important to confirm the reliability of postural balance variables because the results of balance tests would be different with different balance test protocols, i.e., stance conditions such as natural and feet-together stances. Methods Sixteen young healthy adults were instructed to sustain their center of body mass as stably as possible on the force plate. As balance standing conditions, natural (a comfortable self-selected stance width) and feet-together stances (placing the feet 0˚ apart) were selected. The mean distance, mean velocity, mean frequency, and 95% confidence ellipse area were derived from the center of pressure (COP) time series in the overall, anteroposterior (AP), and mediolateral (ML) directions. To evaluate the test-retest reliability of the postural balance variables, Cronbach's alpha coefficient was calculated in each stance condition. Results Mean velocity was the most reliable variable particularly in three times balance test with in both the natural and feet together stances (α = 0.805–0.921). The reliability of all variables of three times balance test was greater than that of twice balance test, mainly in the natural stance. In contrast, the mean ML distance of the feet-together stance had poor reliability despite three balance tests (α = 0.243). Conclusions These results suggest that the balance test protocol should consider the appropriate stance conditions as well as the number of balance trials to select the reliable postural balance variables.