Figure 4

Muscle synergies: comparison between the retaining criteria. Panel A. On the top left, the percentage of subjects presenting different number of synergies, according to the criteria of the eigenvalue > 1 and the eigenvalue > 0.5, is reported. For each limb (healthy in black, unaffected in dark gray, affected in light gray), bars represent the result achieved for all ordered walking speeds (i.e., 0.5, 0.7, 0.9, and 1.1 km/h). On the top right, the explained cumulative variance (mean ± standard deviation errorbar) of five retained synergies is reported. The explained cumulative variance refers to the fastest walking speed. The Panel B shows primitive signals (on the left) and weight coefficients for homologous muscle synergies retained according to both criteria (the dark gray is for the eigenvalue > 1 and the light gray is for the eigenvalue > 0.5), and related to the fastest pace. Mean (standard deviation) of the Pearson correlation coefficients between homologous temporal components and mean (standard deviation) of the normalized scalar products between weight coefficients are reported on both features of muscle synergies.