Int J Sports Med 2000; 21: 139-145
NMR was used to assess the influence of two weeks creatine supplementation (21 g . d-1) on resting muscle PCr concentration, on the rate of PCr repletion (Rdepl), and on the half-time of PCr repletion (t1/2). 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 ~20% (P = 0.002). Rdepl was also increased by ~15% (p<0.001) and ~10% (P=0.026) during 40% and 70% MVC exercises, respectively. No change was observed in Rrepl 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.