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J Appl Physiol 88: 1181-1191, 2000;
8750-7587/00 $5.00
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Vol. 88, Issue 4, 1181-1191, April 2000

Creatine reduces human muscle PCr and pH decrements and Pi accumulation during low-intensity exercise

Jesús Rico-Sanz

Nuclear Magnetic Resonance Center, Department of Medical Biochemistry and Genetics, Panum Institute, University of Copenhagen, and Copenhagen Muscle Research Center, DK-2100 Copenhagen, Denmark; and Group of Biomedical Applications of Magnetic Resonance, Department of Biochemistry and Molecular Biology, University Autonoma of Barcelona, 08193 Bellaterra, Spain

The purpose of this study was to examine with 31P-magnetic resonance spectroscopy energy metabolism during repeated plantar flexion isometric exercise (Ex-1-Ex-4) at 32 ± 1 and 79 ± 4% of maximal voluntary contraction (MVC) before and during a creatine (Cr) feeding period of 5 g/day for 11 days. Eight trained male subjects participated in the study. ATP was unchanged with Cr supplementation at rest and during exercise at both intensities. Resting muscle phosphocreatine (PCr) increased (P < 0.05) from 18.3 ± 0.9 (before) to 19.6 ± 1.0 mmol/kg wet wt after 9 days. At 79% MVC, PCr used, Pi accumulated, and pH at the end of Ex-1-Ex-4 were similar after 4 and 11 days of Cr supplementation. In contrast, PCr utilization and Pi accumulation were lower and pH was higher for exercise at 32% MVC with Cr supplementation, suggesting aerobic resynthesis of PCr was more rapid during exercise. These results suggest that elevating muscle Cr enhances oxidative phosphorylation during mild isometric exercise, where it is expected that oxygen delivery matches demands and predominantly slow-twitch motor units are recruited.

nuclear magnetic resonance; oxidative phosphorylation; skeletal muscle; phosphocreatine; inorganic phosphate


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