Pre-Exercise Amino Acid Levels in Conjunction with Resistance Exercise
By Chad Kerksick, PhD
Nov 6, 2012
A recent study from a productive group of exercise and nutrition researchers provides us with additional nuggets of information regarding how resistance exercise and nutrition interact to stimulate changes in
muscle protein synthesis
This study was unique because it manipulated how protein was given to the research participants in an effort to alter the pattern at which the amino acids contained within the protein appeared in the bloodstream. It has become more and more clear that protein quality and nutrient timing are two extremely important nutrition-related factors which predicate the extent to which changes in muscle protein synthesis occur. In addition, a host of factors directly related to the exercise bout being completed are also important and must appropriately interact with nutrition factors to effectively stimulate positive changes such as an increase in strength and power as well as hypertrophy. Briefly, these factors include the intensity of your workout, the order of exercises performed, the frequency of workouts completed each week, the amount of rest taken between sets of exercises as well as how much muscle is activated by the completed exercises.
In this study published in the October 2012 issue of Medicine and Science in Sports and Exercise, twelve resistance-trained men with an average of 27 years completed three testing sessions (Burke, Hawley et al. 2012). The testing sessions were identical and involved a 45 minute lower body resistance training workout along with a series of muscle biopsies and blood samples. The biggest difference was the nutrition which was provided. In the placebo condition, the participants consumed artificially flavored water. The bolus condition had the participants ingest a 500mL solution which contained 25 grams of whey protein and 5 grams of leucine. The pulse condition had the participants ingest the exact same drink as what was ingested in the bolus condition except they consumed the drink in 15 separate 33mL servings. As mentioned previously, the purpose of this approach was to determine if the pattern of ingesting the exact same nutrients favorably (or unfavorably) impacted changes in several markers associated with muscle protein synthesis.
The results revealed that pre-exercise amino acid levels after pulse ingestion of the protein and amino acids was less than the bolus pattern, but after the exercise bout this response was actually reversed which resulted in the pulse ingestion having higher amino acid levels. Analysis of key proteins found in muscle which are known to impact muscle growth were similar between the two patterns of ingestion, but most importantly, both patterns showed greater levels than when flavored water was ingested. Finally, an analysis of muscle protein synthesis was performed over a five hour period after the exercise bout and again both patterns of protein and amino acid ingestion were greater than the placebo ingestion, but no differences were found between either pattern of ingestion. The authors of this study concluded that protein sources producing a slow release of amino acids (pulse ingestion) were equally as effective as those proteins or ingestions patterns that produce or simulate rapid digestion.
Burke, L. M., J. A. Hawley, et al. (2012). "Preexercise aminoacidemia and muscle protein synthesis after resistance exercise." Med Sci Sports Exerc 44(10): 1968-1977.
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