Excitability and firing behavior of single slow motor axons transmitting natural repetitive firing of human motoneurons

Excitability of single slow axons was estimated by motor unit firing index in response to motor nerve stimulation, and its changes throughout a target interspike interval were explored during transmitting human motoneuron natural firing. It was found that axons exhibited early irresponsive, responsive, and later irresponsive periods. Findings question whether the traditionally described axonal excitability recovery cycle is realistic in natural motor control.