Hierarchical clustering methodology and examples for two subjects.

<p>(A) Geometric illustration of heterogenous variance explained (HVE). HVE distance is determined by the correlations of musculotendon length between muscle pairs determined by the equation in (B). (B) The equation for calculating HVE distance. The negative regressions (r^-) indicate opposite or antagonistic actions of muscle pairs, when the positive ones (r⁺) correspond to the synergistic or agonistic actions. Insert shows a histogram of HVE values for one subject across all muscle pairs. (C) Examples of hierarchical clustering for individual subjects. Clustering across all muscles is shown in the top two polar dendrograms. The bottom plot shows clustering across only the distal muscles for one of the subjects. Lines emanating from the center indicate the distance between muscle clusters calculated from HVE. The main agonist-antagonist division can be established using a high clustering threshold (2 clusters with dark red and dark blue lines), and further subdivisions are revealed by the progressive lowering of the threshold. Example matching clusters are marked by outside brackets with * or ^.