Mj. Mckenna et al., Creatine supplementation increases muscle total creatine but not maximal intermittent exercise performance, J APP PHYSL, 87(6), 1999, pp. 2244-2252
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.