Table 2 Partial correlations between simulated center of pressure (COP) fluctuations and mechanical stiffness controller gains. Shown are the coefficients of correlation between each COP measurement and the mechanical stiffness gain which was varied as 0 < K < 300 Nm/rad, while controlling for the effect of proportional gain (K _P ) and derivative gain (K _D ). Included are the mean distance (MD), mean velocity (MV), range (RANGE), mean frequency (MFREQ), centroidal frequency (CFREQ), frequency dispersion (FREQD) and 50 % power (P50) frequency, obtained in the simulation study

From: Trunk muscle co-activation using functional electrical stimulation modifies center of pressure fluctuations during quiet sitting by increasing trunk stiffness