The theory of “Muscle Synergies” has been formulated in the last few decades to have a better understanding of the optimization strategies applied by the Central Nervous System (CNS) in the control of the activation and coordination of the many muscles involved in any voluntary movement. The synergies can be considered as patterns of co-activation corresponding to the activity of few muscles: having to control a number of these modules lower than the actual number of muscles involved, the computational cost of every task is significantly reduced. The synergies are modeled as a time-invariant profile of activation across muscles, activated by a time-varying coefficient.