ESTIMATION OF MUSCULAR ENERGY METABOLISM DURING EXERCISE AND EFFECTS OF MUSCLE TRAINING STUDIED BY ^<31>P-NMR SPECTROSCOPY.

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We examined responses in muscular energy metabolism during exercise and effects of muscle training on muscular energy metabolism using ^<31>P-NMR spectroscopy. The results were summarized as follows :1. During a progressive exercise, intracellular pH decreased gradually with an increase of work load, and then a rapid acidification was observed at about 57% of the maximal work load (6.9 of pH value). This threshold in intracellular pH correlated significantly to thresholds detected from non-linear increases in integrated electromyogram and expired gas parameters.2. In a subnormal muscle temperature condition, intracellular pH during an anaerobic exercise showed the higher value than that at a control condition, and the anaerobic endurance performance decreased significantly. These results suggest that glycolytic energy pathway would be inhibited under the subnormal muscle temperature condition. On the contrary, intracellular pH during an aerobic exercise preceded by a warm-up exercise s … More howed the higher value than that of the control condition. This result means that the oxidative capacity in the muscle is improved by performing a warm-up exercise.3. As a result of an aerobic training (the exercise intensity of 30-40% MVC,the frequency of 4 days/week, and the 15 week training period), the oxidative capacity in muscle was significantly improved as shown by a decrease in Pi/PCr ratio and an increase in intracellular pH at the same sub-maximal work load. And also, the improvement of the endurance performance showed to paralleled to lesser degree of the acidification in the muscle.4. As a result of a power training (the exercise intensity of 10 repetition maximum, the frequency of 4 days/week, and the 5 week training period), muscular power output and anaerobic endurance time increased significantly. However, concerning phosphorus metabolic changes, it only occurred that %PCr during the anaerobic exercise increased due to the training. There was no difference in the intracellular pH between the pre- and the post-training. These results suggest that the increase in the anaerobic performance might be attributable to the increase of phosphagen, the improvement of glycolytic capacity, or the increase in creatine kinase activity in the muscle due to the training. Less