Availability of MRI and MRS for talent identification in terms of muscle properties.

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It is necessary to identify effectually and properly individuals who are endowed with outstanding sports capabilities in order to improve Japan's international competitiveness in sports. Talent identification in terms of skeletal muscle is especially important because the muscle performance affects sports performance. This study investigated the availability of magnetic resonance imaging(MRI) and magnetic resonance spectroscopy(MRS) for evaluation of muscle properties in order to identify individuals with a talent for sports.We performed MRI, phosphorus (^<31>P)- and carbon (^<13>C)-MRS, and biochemical assay of the skeletal muscle in volunteers. There were significant correlations between phosphocreatine (PC) / adenosine triphosphate (ATP), (PCr + inorganic phosphate (Pi) ) /ATP, transverse relaxation time (T2) and muscle fiber type composition. In the experiment comparing MRI and ^<31>P-MRS data between sprinters and endurance runners, the former showed significantly higher PCr/ATP, (PCr+Pi)/ATP, intracellular pH and lower T2 than the latter. We demonstrated that ^<13>C-MRS using normal 1.5-tesla clinical scanner enables noninvasive measurement of the muscle glycogen concentration. Moreover, we found an optimal condition for evaluating the diffusion capacity of skeletal muscle, which distinguished muscles that have a distinct diffusion property.To investigate muscle energetics during exercise, we performed ^<31>P-MRS and near infrared spectroscopy simultaneously and demonstrated that muscles possessing higher oxidative capacity show superior oxygen availability.These findings suggest that MRI and MRS can noninvasively evaluate the fiber type composition, concentration of energy substrates, microcirculation and oxidative capacity in human skeletal muscle.