Motor unit activity and preprogramming of movement in man.

The activity of single motor units (MUs) is studied during voluntary dynamic movements in man. It is shown that as soon as a MU is set into activity, i.e., at the beginning of the myoelectric burst which precedes the start of the limb movement, there exists a consistent relationship between the peak velocity (for a given inertia) had the interval between the first two consecutive discharges of this MU. Thus, it is likely that when the amplitude of the movement is voluntarily limited, the peak velocity of the movement is preprogrammed.