Malleability of the motor system: training for maximizing power output

The training programmes used to improve the strength and/or endurance capacities of athletes are described. Specific stimuli are either high tension in contracting myofibrils or high turnover rates in the oxidative metabolism of the muscle cell. Structural adaptations consist of the synthesis of additional myofibrillar material or increased volume density of both interfibrillar and subsarcolemmal mitochondria. Transformation of fibre types at the level of the molecular structure of myosin seems possible with high-intensity training of long duration. Functional adaptations consist of higher activities of important enzymes in either anaerobic or aerobic energy metabolism and of larger intracellular stores of the respective substrates. All adaptations are highly specific and reversible through detraining or immobilization of the muscle.