Characterization of bi-directional movement primitives and their agonist-antagonist synergy with the delta-lognormal model.

A general definition of a movement primitive and of the elements that have to be taken into account in attempts to its characterization is proposed. As an example, the delta-lognormal model is used to define the kinematic primitives associated with rapid, stroke-like movements. The quantitative characteristics of the agonist-antagonist synergy that underlie a specific primitive predicted by the model, the bidirectional stroke, are described. The results reveal the existence of a universal correlation between the agonist and the antagonist neuromuscular systems that produce this primitive.