Can non-linear muscle dynamics explain the smoothness of handwriting movements?

The paper addresses the issue of the role of non-linear muscle dynamics in determining the smoothness and invariance of handwriting trajectories. In particular, a specific neuromuscular control model is described that has recently been shown to explain the detailed time course of hand stiffness during arm reaching movements. In the paper the model is applied to more complex handwriting trajectories, with the purpose of verifying to which extent the load compensation capabilities of the periphery can subserve motor equivalence. Simulations show the power of the mechanism for movements of "normal" speed. For quicker movements periphery alone is not enough and a central load compensation action is clearly required.