Abstract des Autors

To investigate the splitting of the inorganic phosphate (Pi) peak during exercise and recovery, a time-resolved 31-phosphorus nuclear magnetic resonance-spectroscopy (31-P-MRS) technique was used. Seven healthy young sedentary male subjects performed knee flexion exercise in the prone position inside a 2.1-T magnet, with the surface coil for 31P-MRS being placed on the biceps femoris muscle. After a 1-min warm-up without loading, the exercise intensity was increased by 0.41 W at 15-s intervals until exhaustion, followed by a 5-min recovery period. The 31-P-MRS were recovered every 5 s during the rest-exercise-recovery sequence. Computer aided contour analysis and pixel imaging of the Pi and phosphocreatine peaks were performed. Five of the seven subjects showed two distinct Pi peaks during exercise, suggesting two different pH distributions in exercising muscle (high pH and low pH region). In these five subjects, the high-pH increased rapidly just after the onset of exercise, while the low-pH peak increased gradually approximately 60 s after the onset of exercise. During recovery, the disappearance of the high-pH peak was more rapid than that of the low-pH peak. These findings suggest that our method 31-P-MRS provides a simple approach four studying the kinetics of the Pi peak and intramuscular pH during exercise and recovery.