Abstract des Autors

Considerable progress has been made in describing the effects of training on substrate metabolism during exercise and in determining the mechanisms by which these effects are mediated. lt is now quite clear that endurance-trained humans rely less on muscle glycogen and plasma glucose and more on fatty acids for energy during exercise at any given absolute intensity, and that this carbohydrate-sparing effect of training plays a major role in the training-induced improvement in exercise performance. However, the specific tissue source of the additional fatty acids remains uncertain, and the effects of endurance training on amino acid metabolism during exercise are unknown. Likewise, although it is evident that the metabolic adaptations to training are largely mediated by an increase in muscle respiratory capacity, the specific biochemical mechanisms involved have been only partially elucidated. The importance of changes in hormone concentrations and/or action during exercise and of other training-induced adaptations in muscle (e.g., increased glucose transporter number) also remain to be determined. Finally, the possibility that training increases the maximal amplitude of various physiological responses during prolonged or intense exercise requires further evaluation. Thus, although much is known, much also remains to be learned about the effects of endurance training on substrate metabolism during exercise. Verf.-Referat