It has been reported that various types of mammalian muscle fibers differ regarding the content of several metabolites at rest. However, to our knowledge no data have been reported in the literature, concerning the muscle energetic status at rest in high class athletes when considering the dominant and non-dominant leg separately. We have hypothesised that due to higher mechanical loads on the dominant leg in athletes, the metabolic profile in the dominant leg at rest in the calf muscles, characterized by [PCr], [ADPfree], [AMPfree] and GATP, will significantly differ among endurance athletes, sprinters and untrained individuals. In this study we determined the GATP and adenine phosphates concentrations in the dominant and non-dominant legs in untrained subjects (n = 6), sprinters (n = 10) and endurance athletes (n = 7) at rest. The (mean ± SD) age of the subjects was 23.4 ± 4.3 years. Muscle metabolites were measured in the calf muscles at rest, by means of 31P-MRS, using a 4.7 T superconducting magnet (Bruker). When taking into account mean values in the left and right leg, phosphocreatine concentration ([PCr]) and GATP were significantly lower (p<0.05, Wilcoxon-Mann-Whitney test), and [ADPfree] was significantly higher (p = 0.04) in endurance athletes than in untrained subjects. When considering the differences between the left and right leg, [PCr] in the dominant leg was significantly lower in endurance athletes than in sprinters (p = 0.01) and untrained subjects (p = 0.02) (25.91 ± 2.87 mM; 30.02 ± 3.12 mM and 30.71 ± 2.88 mM, respectively). The [ADPfree] was significantly higher (p = 0.02) in endurance athletes than in sprinters and untrained subjects (p = 0.02) (42.19 ± 13.44 µM; 27.86 ± 10.19 µM; 25.35 ± 10.97 µM, respectively). The GATP in the dominant leg was significantly lower (p = 0.02) in endurance athletes than in sprinters and untrained subjects (p = 0.01) (-60.53 ± 2.03 kJ·M-1; -61.82 ± 1.05 kJ·M-1, -62.29 ± 0.73 kJ·M-1, respectively). No significant differences were found when comparing [PCr], [ADPfree], [AMPfree], [Mg2+free], GATP in the dominant leg and the mean values for both legs in sprinters and untrained subjects. Moreover, no significant differences were found when comparing the metabolites in non-dominant legs in all groups of subjects. We postulate that higher [ADPfree] and lowerGATP at rest is a feature of endurance-trained muscle. Moreover, when studying the metabolic profile of the locomotor muscles in athletes one has to consider the metabolic differences between the dominant and non-dominant leg.
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