Data Analysis and Statistical Analysis
Time series COP data of the pre-test and post-test were collected with a 100 Hz sampling frequency. Zero-phase, low-pass Butterworth filter with a 10 Hz cut-off frequency was used for the COP data. The timing of the electrical trigger to open the solenoid valve for the air cylinders and the time until the air cylinder contacted the pelvis of the participants were used to identify the timing of the perturbations (time = 0) in the pre-test and post-test. The baseline of mediolateral and anteroposterior COP (COPTo compare these COP parameters, the main effects of group (WBED/Sham) and time factors (pre-test/post-test) were investigated by analyzing the variance for split-plot factorial design. Post-hoc tests with Shaffer’s modified sequentially rejective Bonferroni procedure were performed to determine between the group and time factors. These statistical analyses were performed using R (version 4.2.1; CRAN, freeware). The partial eta-squared 