Activity of Motoneurons in Man under Stationary Conditions

The activity of motoneurons can be assessed electromyographically by recording the action potentials of the muscle fibers they supply (motor unit potentials). Under stationary conditions, e.g., stable isometric contractions, motor units (MUs) fire tonically if they have once been recruited [2, 7, 10, 12, 14]. The major advantage of stationary conditions is that they are appropriate for a more detailed analysis of the discharge sequence of MUs, with particular respect to their regularity. If several MUs can be recorded simultaneously, their interaction can be studied by correlating the times of their discharges. The following contribution, which deals with the discharges of single MUs, will refer to both their regularity and their temporal relations.