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Although many studies have assessed the acute effects of protein and carbohydrate after resistance exercise on measures of protein balance, few studies have actually determined how this affects long-term changes in muscle strength and size to training. In a study published in the August issue of the Journal of the American College Nutrition, 19 untrained men engaged in a 10 week resistance training program (workouts 3x/week) and were randomized to receive either a carbohydrate beverage or a carbohydrate + protein beverage immediately after their workouts. Muscle strength and body composition using dual-energy X-ray absorptiometry were determined before and after training. Both groups benefited from the training program. After 10 weeks, there were trends for the protein-carbohydrate group to increase body weight more than the carbohydrate group (+0.9 vs -0.8 kg). Lean body mass was also greater in the protein-carbohydrate group (+1.6 kg) than the carbohydrate group (+0.8 kg) but this was only a trend. There were no differences in strength gains between groups. The study reveals potential for protein-carbohydrate supplementation after exercise to benefit gains in muscle size after only 10 weeks compared to carbohydrate only. The small sample and the fact that subjects were untrained may have resulted in the findings not being statistically significant. Untrained subjects respond well to just about any intervention because they have such a large window to improve and this makes it difficult to distinguish between subtle interventions. Nevertheless, the study provides evidence to support the notion that protein-carbohydrate mixtures after exercise are superior to carbohydrate only beverages.

Rankin JW, Goldman LP, Puglisi MJ, Nickols-Richardson SM, Earthman CP, Gwazdauskas FC. Effect of post-exercise supplement consumption on adaptations to resistance training. J Am Coll Nutr. 2004 Aug;23(4):322-30.