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

摘要

Purpose: Studies that have attributed\udgains in lean body mass to dietary supplementation during resistance exercise (RE) training have not reported these changes alongside\udadaptations at the cellular and subcellular levels. Therefore, the purpose of this study was to examine the effects of two popular\udsupplements—whey protein (WP) and creatine monohydrate (CrM) (both separately and in combination)—on body composition, muscle\udstrength, fiber-specific hypertrophy (i.e., type I, IIa, IIx), and contractile protein accrual during RE training. Methods: In a double-blind\udrandomized protocol, resistance-trained males were matched for strength and placed into one of four groups: creatine/carbohydrate\ud(CrCHO), creatine/whey protein (CrWP), WP only, or carbohydrate only (CHO) (1.5 gIkgj1 body weight per day). All assessments were\udcompleted the week before and after an 11-wk structured, supervised RE program. Assessments included strength (1RM, three exercises),\udbody composition (DEXA), and vastus lateralis muscle biopsies for determination of muscle fiber type (I, IIa, IIx), cross-sectional area\ud(CSA), contractile protein, and creatine (Cr) content. Results: Supplementation with CrCHO, WP, and CrWP resulted in significantly\udgreater (P G 0.05) 1RM strength improvements (three of three assessments) and muscle hypertrophy compared with CHO. Up to 76% of\udthe strength improvements in the squat could be attributed to hypertrophy of muscle involved in this exercise. However, the hypertrophy\udresponses within these groups varied at the three levels assessed (i.e., changes in lean mass, fiber-specific hypertrophy, and contractile\udprotein content). Conclusions: Although WP and/or CrM seem to promote greater strength gains and muscle morphology during RE\udtraining, the hypertrophy responses within the groups varied. These differences in skeletal muscle morphology may have important\udimplications for various populations and, therefore, warrant further investigation.