Muscle phosphorus magnetic resonance spectroscopy oxidative indices correlate with physical activity

The purpose of this study was to assess the effect of physical deconditioni ng on skeletal muscle's oxidative metabolism as evaluated by phosphorus-31 magnetic resonance spectroscopy (P-31 MRS). Twenty-seven subjects without m uscle disease, representing a wide range of fitness levels, were evaluated with P-31 MRS. Spectra were obtained at rest and during recovery from in-ma gnet exercise. The data show a significant correlation between maximum rest ing metabolic equivalent (MET) score and the following P-31 MRS recovery in dices: adenosine diphosphate and phosphocreatine recovery half-time; initia l phosphocreatine resynthesis rate; calculated estimation of mitochondrial capacity; pH at end of exercise; and phosphocreatine depletion. In addition , significant differences between the deconditioned and conditioned group w ere found for all of the aforementioned recovery indices. At rest, only the inorganic phosphate concentration was significantly different between the two groups. These data indicate that physical activity level should be take n into account when assessing patients' oxidative metabolism with P-31 MRS. (C) 2000 John Wiley & Sons, Inc.