Effects of whey isolate, creatine, and resistance training on muscle hypertrophy.
OBJECTIVE
Studies that have attributed gains in lean body mass to dietary supplementation during resistance exercise (RE) training have not reported these changes alongside adaptations at the cellular and subcellular levels. Therefore, the purpose of this study was to examine the effects of two popular supplements--whey protein (WP) and creatine monohydrate (CrM) (both separately and in combination)--on body composition, muscle strength, fiber-specific hypertrophy (i.e., type I, IIa, IIx), and contractile protein accrual during RE training.


METHODS
In a double-blind randomized protocol, resistance-trained males were matched for strength and placed into one of four groups: creatine/carbohydrate (CrCHO), creatine/whey protein (CrWP), WP only, or carbohydrate only (CHO) (1.5 g x kg(-1) body weight per day). All assessments were completed the week before and after an 11-wk structured, supervised RE program. Assessments included strength (1RM, three exercises), body composition (DEXA), and vastus lateralis muscle biopsies for determination of muscle fiber type (I, IIa, IIx), cross-sectional area (CSA), contractile protein, and creatine (Cr) content.


RESULTS
Supplementation with CrCHO, WP, and CrWP resulted in significantly greater (P < 0.05) 1RM strength improvements (three of three assessments) and muscle hypertrophy compared with CHO. Up to 76% of the strength improvements in the squat could be attributed to hypertrophy of muscle involved in this exercise. However, the hypertrophy responses within these groups varied at the three levels assessed (i.e., changes in lean mass, fiber-specific hypertrophy, and contractile protein content).


CONCLUSIONS
Although WP and/or CrM seem to promote greater strength gains and muscle morphology during RE training, the hypertrophy responses within the groups varied. These differences in skeletal muscle morphology may have important implications for various populations and, therefore, warrant further investigation.
Cribb
Paul J
PJ
Exercise Metabolism Unit, Center for Ageing, Rehabilitation, Exercise and Sport and the School of Biomedical Sciences, Victoria University, Victoria, Australia.
Williams
Andrew D
AD
Stathis
Chris G
CG
Carey
Michael F
MF
Hayes
Alan
A
D000328:Adult; D003285:Contractile Proteins / Q000187:drug effects*; D003401:Creatine / Q000494:pharmacology*; D019587:Dietary Supplements; D006801:Humans; D008297:Male; D008894:Milk Proteins / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D014891:Weight Lifting / Q000502:physiology*; D000067816:Whey Proteins
D003285:Contractile Proteins; D008894:Milk Proteins; D000067816:Whey Proteins; D003401:Creatine