Creatine supplementation affects muscle creatine during energy restriction

Anaerobic performance and body protein may decrease with energy restriction practiced by some athletes for weight loss. This investigation examined the effects of creatine (Cr) supplementation during energy restriction on muscle Cr, exercise performance (10 sprints of 6 s, with 30-s rest), nitrogen balance, and body composition in male resistance trainers. Creatine supplemented (CrS, 20 g x d(-1) of Cr) and those given a placebo (P1) consumed a formula diet of 75.3 kJ (18 kcal) x kg(-1) x d(-1) (54.7% C, 21.3% P, 24% F) for 4 d. A control group was unsupplemented and continued their normal diet. There were no changes in body composition or performance of the control group. CrS and P1 demonstrated similar decreases in body weight and percent body fat. The percent change in fat-free mass was more for P1 (2.4+/-0.3% reduction) than CrS (1.4+/-0.4%), but urinary nitrogen losses were similar. Significant increases in muscle total Cr and CrP of 15-16% were demonstrated by CrS over the energy restriction period, whereas P1 had no changes in muscle Cr. Total work done during the sprints expressed per body weight tended to be 3.8% higher in CrS and 0.5% less in P1 after the energy restriction (P = 0.058). It was concluded that Cr supplementation increased muscle Cr during short-term energy restriction but did not affect body fat or protein loss. The change in muscle creatine was reflected in a tendency for higher total sprint work for the Cr group.