Differences in metabolic potential of skeletal muscle fibres and their significance for metabolic control

Abstract

When exposed to chronic overloads skeletal muscle is remodelled, thereby equipping it to better meet the stresses it is encountering. Examples abound in nature of the adaptive response of muscle exposed to different tasks (i.e. Armstrong, lanuzzo & Kutz, 1977; Newsholme & Start, 1973). The principles that are outlined in this paper for the relationship between metabolic potential and control of metabolism apply to all situations where differences in metabolic potential exist. The basic model discussed is that of physical training, particularly endurance training, on skeletal muscle and metabolic control. Training was selected as the model as it is a convenient method for inducing changes in skeletal muscle and for illustrating the consequences of these adaptations on the local and total body metabolism. Thus, heavy resistance exercise taxes the tension development capacity but not prolonged energy production so the fibres enlarge without a significant modification in the metabolic systems (Gollnick et al. 1972). In contrast, endurance training stresses energy production, particularly aerobic energy production, but not the tension developing capacity, with the end result being augmentation of the aerobic energy-producing systems. Corollaries of these exist throughout the animal kingdom.