Phosphorus-31 nuclear magnetic resonance study on the effects of endurance training in rat skeletal muscle

Summary

To evaluate changes in muscle energetics following endurance training, we measured phosphorus-31 nuclear magnetic resonance (³¹P NMR) spectra on rat muscle in vivo before and after training in the same animals. The endurance training lasted for 3 months. The³¹P NMR spectra were obtained serially at rest, during exercise by electrical stimulation, and during recovery. Intramuscular phosphocreatine (PCr), inorganic phosphate (P_i, adenosine 5′-triphosphate (ATP) and pH were determined from the NMR spectra. The ratio of PCr : (PCr + P_i) at rest showed no difference between the trained and control groups even after 3 months of training. During exercise, however, this ratio was significantly higher in the trained group than in the control group. The ratio also recovered more rapidly after exercise in the trained group. The intramuscular pH decreased slightly by approximately 0.1 pH unit during exercise but did not show a significant difference between the groups. These results indicated that endurance training of 3 months duration improved the ATP supply system in the muscle. They also demonstrated that³¹P NMR is a potent method for evaluating the effects of training in the same individuals.