The purpose of this study was to examine the effects of oral creatine supplementation on muscle energy metabolism during high-intensity dynamic exercise. Twelve healthy male subjects [age=23.2±0.6 yrs ; height=173.9±1.0 cm ; weight=69.5±1.5 kg (Mean±SE)] performed high-intensity dynamic handgrip exercise inside a ³¹P magnetic resonance system with near infrared spectroscopy before and after supplementation with 30 g of creatine monohydrate (Cr) or placebo per day for 14 days. Exercise protocol used was 40% of maximum voluntary contraction, 10-second maximal dynamic handgrip effort. Cr supplementation produced a 11.9±2.8% increase in the resting muscle phosphocreatine (PCr)／β-ATP ratio and a 15.3±4.8% increase in mean power during a 10-s maximal effort dynamic handgrip exercise, while the placebo did not change significantly. Following Cr supplementation, PCr degradation during a 10-s maximal effort exercise tends to be greater. There were no significant differences for both the change in muscle pH and the rate of deoxygenation during exercise between pre- and post-Cr supplementation and between pre- and post-placebo treatment. The results suggest that Cr supplementation enhanced performance of a 10-s maximal effort exercise and, furthermore, improved PCr degradation during high-intensity exercise, possibly because of the muscle PCr increase at rest.

DESCENTE SPORTS SCIENCE Vol.21/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE