The generally accepted model of energy systems has been used for many years. When exercise intensity rises and glucose uptake by working muscles is increased, a drop in circulating glucose is observed while in higher intensity exercise, muscle glucose uptake can increase by as much as 30 -50 times, compared to the resting rate. Changes is glucose metabolism have been described by numerous authors and forms an integral part of the modification of energy systems to training stimulus. This is

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... ral to understanding the changes that may occur in the use of blood borne glucose and intra muscular glycogen that may be a marker of exercise intensity. Further Increased cytosolic and more effectively mitochondrial calcium during high ATP turnover in exercise increases glucose phosphorylation while in some cells MAS converted lactate to pyruvate whereas glucose oxidation and lactate production are influenced by the activity of MAS when the intensity of exercise rises, it can lead to down-regulation of MAS activity, which leads to an increase in lactate production Where MAS is inhibited, there is a 50% decrease in lactate oxidation. Likely sites for the adaptation of MAS are highlighted and the effect that this can have on our view of how the energy systems function during high intensity exercise are also suggested. Through consideration of these metabolic events a new vision of energy system function is proposed. from aerobic glycogenolysis. The recruitment of the relative muscle fibers will then give a mixture of these two pathways. This would be why, with relative improvements in efficiency, the energy cost of an exercise can be reduced (Figure 3) (Table 2) .