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

Citation

Cribb, PJ and Williams, AD and Carey, MF and Hayes, A and Stathis, CG, 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 (2007) [Refereed Article]

DOI: doi:10.1249/01.mss.0000247002.32589.ef

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 g·kg 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. ©2007The American College of Sports Medicine.

Item Details

Item Type:Refereed Article
Research Division:Medical and Health Sciences
Research Group:Human Movement and Sports Science
Research Field:Exercise Physiology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Environmental Sciences
Author:Williams, AD (Associate Professor Andrew Williams)
ID Code:41202
Year Published:2007
Web of Science® Times Cited:70
Deposited By:Health Sciences A
Deposited On:2007-08-01
Last Modified:2009-08-25
Downloads:0

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