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Nutrient Administration and Resistance Training

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Nutrient Administration and Resistance Training

Journal of the International Society of Sports Nutrition. 2(1):50-67, 2005.


• Resistance training modestly stimulates protein synthesis and further stimulates protein breakdown resulting an overall negative protein balance after exercise.

• As the training status of an individual progresses, the magnitude of changes seen in protein synthesis and breakdown diminishes after each exercise bout as well as a diminished increase of protein synthesis after each subsequent exercise bout.

• Infusion or ingestion of amino acids is an effective way to increase amino acid concentrations at rest or after resistance exercise.

• Availability of amino acids after resistance exercise increases protein synthesis.

• Essential amino acids do appear to play a primary role in protein synthesis and adding carbohydrate to them may enhance this effect.

• Ingestion of carbohydrate alone after resistance exercise causes marginal improvements in overall protein synthesis while maintaining a negative net protein balance. No studies have found carbohydrate to be detrimental and it may be useful to enhance palatability; however the additional caloric burden may not be desired.

• A small dose of essential amino acids after resistance exercise has been found to stimulate protein synthesis to a similar degree when compared to studies that used much larger doses of both amino
acids (EAA, NEAA, or both) or that were combined with carbohydrate.

• Ingestion of amino acids after resistance exercise has been shown at many different time points in several studies to stimulate increases in muscle protein synthesis, cause minimal changes in protein
breakdown and increase overall protein balance. It has not been conclusively determined what time point is optimal.
Similar changes have been found for studies that have administered amino acids alone or with carbohydrate immediately upon completion of an acute exercise bout, 1 h after completion, 2 h after completion and 3 h after completion. Interestingly, ingesting nutrients before the exercise bout may have the most benefit of all the time points.

• It is possible for the mechanisms involving amino acid transport and protein synthesis to be overwhelmed with extremely high, continuous levels of amino acids. The likelihood of this
occurring is rare even upon considering the highest of protein intakes among individuals.

• An optimal dosage in which to ingest amino acids at this time does not exist.
Studies using similar techniques while resistance training have used 6 g EAA only, 6 g EAA + 6 g NEAA, 12 g EAA only, 17.5 g whey protein, 20 g casein protein, 20 g whey protein, 40 g mixed
amino acid, 40 g EAA only all with similar increases in protein synthesis and protein balance. Athletes who desire to increase muscle mass or are involved in power sports should consider consuming protein supplements that will provide amino acids in similar amounts used in these studies.

• Intact proteins or combinations of them that are commonly used in popular protein supplements appear to elicit similar increases in protein balance after resistance training as compared to other
studies using free amino acids.
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