Performance and muscle fiber adaptations to creatine supplementation and heavy resistance training

Purpose: The purpose of this study was to examine the effect of creatine su pplementation in conjunction with resistance training on physiological adap tations including muscle fiber hypertrophy and muscle creatine accumulation . Methods: Nineteen healthy resistance-trained men were matched and then ra ndomly assigned in a double-blind fashion to either a creatine (N = 10) or placebo (N = 9) group. Periodized heavy resistance training was performed f or 12 wk. Creatine or placebo capsules were consumed (25 g.d(-1)) for 1 wk followed by a maintenance dose (5 g.d(-1)) for the remainder of the trainin g. Results: After 12 wk, significant (P less than or equal to 0.05) increas es in body mass and fat-free mass were greater in creatine (6.3% and 6.3%, respectively) than placebo (3.6% and 3.1%, respectively) subjects. After 12 wk, increases in bench press and squat were greater in creatine (24% and 3 2%, respectively) than placebo (16% and 24%, respectively) subjects. Compar ed with placebo subjects, creatine subjects demonstrated significantly grea ter increases in Type I(35% vs 11%), IIA (36% vs 15%), and IIAB (35% vs 6%) muscle fiber cross-sectional areas. Muscle total creatine concentrations w ere unchanged in placebo subjects. Muscle creatine was significantly elevat ed after 1 wk in creatine subjects (22%), and values remained significantly greater than placebo subjects after 12 wk. Average volume lifted in the be nch press during training was significantly greater in creatine subjects du ring weeks 5-8. No negative side effects to the supplementation were report ed. Conclusion: Creatine supplementation enhanced fat-free mass, physical p erformance, and muscle morphology in response to heavy resistance training, presumably mediated via higher quality training sessions.