Supramaximal exercise after training-induced hypervolemia. II. Blood/muscle substrates and metabolites

Blood and muscle substrates and metabolites were investigated in six healthy males (ranging in age from 19 to 23 yr) during three consecutive days of supramaximal exercise training. Muscle biopsies from the vastus lateralis and arterialized blood samples from a hand vein were extracted before the exercise and at selected times during the intermittent (1 min work to 4 min rest) cycling. The results indicated that blood glucose concentration was significantly depressed (P less than 0.05) on both days 2 and 3 of the training, whereas plasma free fatty acids and blood glycerol, pyruvate, alanine, and lactate were unaffected. At the muscle level, glucose and lactate concentrations were depressed on days 2 and 3, whereas ATP and glycogen were reduced only on the final day of training. No training-induced alterations were noted for muscle glucose 6-phosphate or muscle ADP. These results indicate that the approximate 10-11% reduction in O2-carrying capacity accompanying the short-term training does not directly and negatively influence muscle energy metabolism during the exercise. Rather, the explanation for the altered muscle and blood constituents must be sought from other effects of the training such as impaired carbohydrate repletion.