Impact of Nutritional Supplements and Resistance Training on Body Composition, Strength and Insulin-like Growth Factor -1

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The purpose of this study was to evaluate and compare the effect of nutritional supplementation (arginine/lysine [AL], versus Exceed® [EX], versus placebo [P]) and resistance-training (RT) on changes in body composition, strength and insulin-like growth factor -1 (IGF-1) levels. The study involved 37 physically active college men, ages 20 to 30, randomly assigned to one of five groups: placebo/control (P/C, n = 7); P/RT (n = 8); AL/C (n = 7); AL/RT (n = 8); or EX/RT (n = 7). An AL supplement at a dosage of 132 mg • kg–1 fat-free body (FFB) or placebo was administered to controls and training groups, whereas the EX/RT group received one to 1 1/2 cans of Exceed® daily, adjusted to ensure a one-pound gain in body weight each week. During the 10-week program, exercise subjects participated in a progressive resistance-training program stressing all major muscle groups. Significant increases in total strength (bench press + squat + deadlift 1 RMs) after the 10-week intervention were seen in all resistance-trained groups compared to controls, with no apparent advantage provided by nutritional supplementation. Further, while all RT groups significantly increased FFB mass more than non-exercising controls, the EX/RT group significantly increased FFB mass to a greater extent than did the other resistance trained groups. Finally, resting levels of plasma IGF-1 were found unchanged in all groups following the 10-week intervention, suggesting no effect of AL supplementation on human growth hormone levels. It was concluded that while nutritional supplements may have some effects on changes in body composition, resistance-training alone significantly influences strength, regardless of nutritional supplement status.

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