Effect of exogenous creatine supplementation on muscle PCr metabolism.
31P NMR was used to assess the influence of two weeks creatine supplementation (21g x d(-1)) on resting muscle PCr concentration, on the rate of PCr repletion (R(depl)), and on the half-time of PCr repletion (t 1/2). Body mass (BM) and volume of body water compartments were also estimated by impedance spectroscopy. Fourteen healthy male subjects (20.8+/-1.9 y) participated in this double-blind study. PCr was measured using a surface coil placed under the calf muscle, at rest and during two exercise bout the duration of which was 1 min. They were interspaced by a recovery of 10 min. The exercises comprised of 50 plantar flexions-extensions against weights corresponding to 40% and 70% of maximal voluntary contraction (MVC), respectively. Creatine supplementation increased resting muscle PCr content by approximately 20% (P= 0.002). R(depl) was also increased by approximately 15% (P< 0.001) and approximately 10% (P = 0.026) during 40% and 70% MVC exercises, respectively. No change was observed in R(repl) and t1/2. BM and body water compartments were not influenced. These results indicate that during a standardized exercise more ATP is synthesized by the CK reaction when the pre-exercise level in PCr is higher, giving some support to the positive effects recorded on muscle performance.
Francaux
M
M
Institut d'Education Physique et de Réadaptation, Université Catholique de Louvain, Louvain-la-Neuve, Belgium. marc.francaux@edph.ucl.ac.be
Demeure
R
R
Goudemant
J F
JF
Poortmans
J R
JR
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000328:Adult; D001823:Body Composition; D003401:Creatine / Q000494:pharmacology*; D019587:Dietary Supplements; D015444:Exercise / Q000502:physiology*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*; D013647:Task Performance and Analysis
D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D003401:Creatine