title: Performance and muscle fiber adaptations to creatine supplementation and heavy resistance training.
abstract: OBJECTIVE
  The purpose of this study was to examine the effect of creatine supplementation in conjunction with resistance training on physiological adaptations including muscle fiber hypertrophy and muscle creatine accumulation.
  
  
  METHODS
  Nineteen healthy resistance-trained men were matched and then randomly assigned in a double-blind fashion to either a creatine (N = 10) or placebo (N = 9) group. Periodized heavy resistance training was performed for 12 wk. Creatine or placebo capsules were consumed (25 g x d(-1)) for 1 wk followed by a maintenance dose (5 g x d(-1)) for the remainder of the training.
  
  
  RESULTS
  After 12 wk, significant (P < or = 0.05) increases 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 32%, respectively) than placebo (16% and 24%, respectively) subjects. Compared with placebo subjects, creatine subjects demonstrated significantly greater 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 were unchanged in placebo subjects. Muscle creatine was significantly elevated after 1 wk in creatine subjects (22%), and values remained significantly greater than placebo subjects after 12 wk. Average volume lifted in the bench press during training was significantly greater in creatine subjects during weeks 5-8. No negative side effects to the supplementation were reported.
  
  
  CONCLUSIONS
  Creatine supplementation enhanced fat-free mass, physical performance, and muscle morphology in response to heavy resistance training, presumably mediated via higher quality training sessions.
authors.affiliation: Department of Kinesiology/Center for Sports Medicine, The Pennsylvania State University, University Park 16802, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Volek
authors.forename: N D
authors.initials: ND
authors.lastname: Duncan
authors.forename: S A
authors.initials: SA
authors.lastname: Mazzetti
authors.forename: R S
authors.initials: RS
authors.lastname: Staron
authors.forename: M
authors.initials: M
authors.lastname: Putukian
authors.forename: A L
authors.initials: AL
authors.lastname: Gómez
authors.forename: D R
authors.initials: DR
authors.lastname: Pearson
authors.forename: W J
authors.initials: WJ
authors.lastname: Fink
authors.forename: W J
authors.initials: WJ
authors.lastname: Kraemer
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001823:Body Composition; D003401:Creatine; D019587:Dietary Supplements; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology; D006801:Humans; D006984:Hypertrophy; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000473:pathology
chemical_list: D003401:Creatine