Long-term plasticity

Abstract

This chapter deals with long-term (weeks, months) changes in the properties of motoneurones and muscle fibres after disuse or after various patterns of enhanced activity. In voluntary motor activity the optimal parameters differ between endurance training and force training. Chronic electrical stimulation of whole muscles during long times per day causes muscles to become more fatigue resistant; muscle contractions may also become slower and there are corresponding alterations in myosin composition and muscle histochemistry. Long-term effects of pulse rate on muscle speed are inconsistent and muscles may become slowed down also by physiologically fast rates. Many of the denervation-elicited changes of membrane and other muscle properties may become counteracted and reversed by chronic muscle stimulation. Also properties of motoneurones are influenced by training and by chronic stimulation of motor nerves, but less dramatically so than their muscle fibres. Changes in motoneurones include alterations of their afterhyperpolarization and other membrane properties.