By Robert R. Wolfe, University of Texas Medical Branch and Shriners Burns Hospital, Departments of Surgery and Metabolism Unit, Galveston, TX 77550
Excerpt with link to full study beneath:
Resistance exercise and amino acid intake
The response of muscle protein metabolism varies in magnitude according to the exact nature of intensity of exercise and the method used to quantify the response. Studies determining the fractional synthetic rate have consistently shown a stimulation after exercise (e.g., Ref. 21Citation ), and although results from the A-V balance method have been less consistent, a stimulation of synthesis has been observed with this method as well when the exercise involved several muscle groups of the leg (22Citation ). However, breakdown is also elevated, so that the balance between synthesis and breakdown does not become positive (22Citation ). Thus, nutritional intake is required for resistance exercise to be anabolic.
The response to amino acid intake after exercise is dependent on the composition and amount, as well as the pattern and timing of ingestion in relation to the performance of exercise. We assessed the effect of composition and amount of amino acids by comparing the response to two doses, given 1 h apart, of 6 g each of a mixture of EAA only versus 6 g of a balanced mixture (EAA + NEAA) (Borsheim, E., Tipton, K. D., Wolf, S. E. and Wolfe, R. R., unpublished results). The balanced mixture contained ~3 g of EAA per dose. The total response to the two doses of 6 g of EAA was double the response to the balanced mixture. In addition, in each case the response to the second dose was the same as to the first. This was true even though when the second dose was given the response of net MPS to the fist dose had returned to the basal rate, despite the persistent elevation in concentration after the first dose. Thus, it appears that an increasing concentration activates the synthetic process and the decline in concentration decreases synthesis, irrespective of the absolute value of the concentration. We also assessed the effect of the addition of 35 g of glucose to either the balanced or EAA mixtures (Borsheim, E., Tipton, K. D., Wolf, S. E. and Wolfe, R. R., unpublished results; Miller, S. L., Tipton, K. D., Chinkes, D. L., Wolf, S. E. and Wolfe, R. R., unpublished results). In contrast to the situation at rest, no interactive or even additive glucose effect was observed. This absence of anabolic effect of carbohydrate is consistent with the absence of action of local hyperinsulinemia on muscle protein metabolism after exercise (23Citation ). In contrast, local hyperinsulinemia stimulates MPS in resting individuals (20Citation ).
Timing of intake in relation to exercise
In the experiments described above the amino acids ± glucose were given after exercise. No difference in response was observed when EAA + glucose were given at 1 versus 3 h after exercise (24Citation ). Similarly, when the same mixture was given immediately after exercise the response of MPS was the same as when given 1 h after exercise (25Citation ). However, when the EAA/glucose mixture was given immediately before exercise the response was greatly amplified. Not only was the increase during exercise approximately fourfold above the basal value, the response in the first hour after exercise was just as large as the response over the same time interval when the supplement was given immediately after exercise (Fig. 5Citation ). When total area under the curve was calculated, the response was approximately threefold greater when the drink was given after exercise than at rest, and approximately double the response as when ingested after exercise (25Citation ).
http://jn.nutrition.org/cgi/content/full/132/10/3219S
