Discharge properties of motoneurones: How are they matched to the properties and use of their muscle units?

A general survey is given of old as well as more recent findings concerning matches between electrophysiological properties of motoneurones and contractile properties of their muscle fibres. Mechanisms for creating and maintaining such matches are discussed. It is pointed out that it is not sufficient to describe the variation of functional motoneurone characteristics simply in terms of ‘fast’ or ‘slow’: all properties seem continuously graded and there is cytochemical evidence for several, seemingly independent parameters of functional specialisation.