Creatine supplementation increases muscle total creatine but not maximal intermittent exercise performance

This study investigated creatine supplementation (CrS) effects on muscle to tal creatine (TCr), creatine phosphate (CrP), and intermittent sprinting pe rformance by using a design incorporating the time course of the initial in crease and subsequent washout period of muscle TCr. Two groups of seven vol unteers ingested either creatine [Cr; 6 x (5 g Cr-H2O + 5 g dextrose)/day)] or a placebo (6 x 5 g dextrose/day) over 5 days. Five 10-s maximal cycle e rgometer sprints with rest intervals of 180, 50, 20, and 20 s and a resting vastus lateralis biopsy were conducted before and 0, 2, and 4 wk after pla cebo or CrS. Resting muscle TCr, CrP, and Cr were unchanged. after the plac ebo but, were increased (P < 0.05) at 0 [by 22.9 +/- 4.2, 8.9 +/- 1.9, and 14.0 +/- 3.3 (SE) mmol/kg dry mass, respectively] and 2 but not 4 wk after CrS. An apparent placebo main effect of increased peak power and cumulative worts was found after placebo and CrS, but no treatment (CrS) main effect was found on either variable. Thus, despite the rise and washout of muscle TCr and CrP, maximal intermittent sprinting performance was unchanged by Cr S.