Fig. 3

Illustration of some selected parameters computed during the data feature extraction process. A: Data features extracted from the Standing COP analysis. The black line illustrates the COP excursion trajectory. The light blue area illustrates the surface covered by the COP excursion trajectory. B: Variables used in 1-foot COP trajectory analysis. The black line illustrates the COP trajectory. The red line segment illustrates the 1-foot COP excursion. The numbered black squares indicate the virtual locations of the 7 sensors. The green triangle marks are the starting point and the endpoint of the COP trajectory. C: Example of plantar pressure time series for one isolated step obtained during the walking test. Plantar pressures treated for each isolated step are the raw material for the extraction of all time domain features in the following categories: “peak analysis and area under the curves”, “1-foot COP trajectory analysis”, “gait phase analysis” and “Wavelet analysis”. Blue: heel, orange: lateral midfoot, green: center of the midfoot, red: lateral forefoot, purple: center of the forefoot, brown: medial forefoot, pink: big toe. D: Variables used in the wavelet analysis (extracted from C). The black line corresponds to the envelope of the 7 sensors. The blue triangle illustrates the first and the second peaks typically observed during the stance phase. The red diamond illustrates the valley between the two peaks. The orange lines describe the peak widths, calculated at 30% of their magnitude. The green break lines correspond to the slopes on each side of the peaks. x: medial-lateral axis. y: anterior-posterior axis. In panel A, COP excursion distances were doubled on the x and y axes to increase readability