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The effects of whey isolate, creatine and resistance training on muscle fiber characteristics, strength and body composition

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Cribb, PJ and Williams, AD and Carey, MF and Hayes, A (2007) The effects of whey isolate, creatine and resistance training on muscle fiber characteristics, strength and body composition. Medicine and Science in Sports and Exercise, 39 (2). pp. 298-307. ISSN 0195-9131

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Abstract

Purpose: 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 gIkgj1 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 G 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.

Item Type: Article
Keywords: Protein Supplementation, Histochemistry, Skeletal Muscle Strength, Fiber Area, Contractile Protein
Journal or Publication Title: Medicine and Science in Sports and Exercise
Publisher: Lippincott, Williams and Wilkins
Page Range: pp. 298-307
ISSN: 0195-9131
Identification Number - DOI: 10.1249/01.mss.0000247002.32589.ef
Date Deposited: 07 Apr 2008 14:02
Last Modified: 18 Nov 2014 03:32
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