核磁気共鳴装置による運動中の筋代謝の非観血的及び連続測定

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It has been well documented that ^<31>phosphorus-nuclear magnetic resonance spectroscopy (^<31>P-MRS) has been used as a non invasive measurement of changes in concentrations of adenosine 5ユ^<**> triphosphate (ATP), phosphocreatine (PCr) and inorganic phosphate (Pi), as well as the intramuscular pH both during and after exercise. Splitting of the Pi peak into two peaks has been observed during exercise and is attributed to two different pH distributions in exercising muscle (high pH and low pH). Previously, we reported that the two split Pi peaks showed different time courses at the onset of exercise and during recovery, the high-pH Pi increased promptly at the onset of exercise and disappeared rapidly after exercise, while the low pH Pi peak increased gardually with after a delay of about 60 sec at the onset of exercise and decreased over a longer period after exercise. To assess the physiological mechanism for Pi spiltting, we have studied the effect of exercise intensity, inspired oxygen concentration and/or cooling down on Pi peak splitting.Pi peak splitting is observed dependent on the exercise intensity. In other words, the splitting was observed when the exercise energy metabolism can not solely derive from aerobic metabolism, above 1.0 value of Pi/PCr ratio, suggesting anaerobic glycolysis recruitment. Furthemore, low-pH Pi peak much more documented when hypoxic gas inhalation, suggesting anaerobic glycolysis documented. When active recovery was performed after the exercise, the low-pH value returned more quickly to the pre-exercise level than during passive recovery. The quick disappearance of the low-pH Pi peak can be explained by differences in removal of lactate by blood flow rate maintained during active recovery, and the subsequent acceleration of glycolysis in the FT fibers.