Fig. 5

Representative cases. Left panel: The CoP Lissajous figure of CoP, the EMG activity in the gastrocnemius (blue) and tibialis anterior muscles (red), and the power spectral density (PSD) log plot in four representative cases are shown. The blue line in the CoP Lissajous figures shows the trajectory of the CoP, and the green line shows the 95% confidence ellipse. The PSD log plot showed a range from 0.15 to10 Hz. The blue line is the regression line for 0.15–1 Hz, and the red line is the regression line for 1–5 Hz. Right panel: Radar chart of key variables for each factor in four representative cases. The cases are shown as individual Z-scores and Young as mean Z-scores