[Role of aerobic metabolism in prolonged intensive exercise]

The purpose of this review is to analyze the different factors which intervene with respect to the ability to perform intense exercises of long duration. This ability implies : (a) a high level of maximal oxygen uptake (Vo 2 max) and (b) a great endurance, i.e. the capacity of maintaining for a long time a high percentage of this Vo2 max. First of all, the values Vo2 max usually recorded on normal subjects are given, as well as those of subjects specially trained for endurance events ; then the factors which condition a high level of Vo2 max are described. These factors consist on great capacity in all of the links of the oxygen transport system. These capacities appear to be essentially dependant on the genetic endowment, but their maximal size can only by attained through intensive training. Endurance can be defined as the maximal period of time during which a given percentage of the Vo2 max can be sustained. The values recorded on normal subjects and on those specially trained for endurance events are given, and then the factors conditioning a high level of endurance are studied. Endurance appears to depend on the feeding of muscular fibers with energentic substrates. Training permits the muscles to store large quantities of glycogen. It also seems to enable the organism to increase the percentage of energetic substrates made up by lipids. This latter ability in associated with an alteration of the endocrine reactions induced by exercise. Finally, endurance is accompanied by an ability of the body to store and to eliminate the heat produced during exercise.