Protein and carbohydrate boost protein synthesis after exercise...

A mixture of whey protein, amino acids, and carbohydrates stimulates net muscle protein synthesis to a greater extent than carbohydrate alone after resistance exercise.

A group of eight subjects took part in two trials. In one, they ingested 77.4 grams of carbohydrate, 17.5 grams of whey protein, and 4.9 grams of amino acids one hour after resistance exercise. In the other, 100 grams of carbohydrate was ingested instead.

The researchers used a technique called metabolic tracing to estimate changes in protein synthesis for three hours after subjects received each drink.

Metabolic tracing involves tracking the movement of amino acids in and out of muscle cells. Amino acids are the building blocks of protein. Foods that contain protein, such as meat, chicken, or fish, consist of amino acids in varying amounts.

Net uptake of the amino acid phenylalanine was roughly four times greater following the protein-carbohydrate supplement.

The net protein balance response to the mixture consisted of two components, one rapid immediate response, and a smaller delayed response about 90 minutes after the drink.

The bottom line is that a mixture of whey protein, amino acids, and carbohydrates stimulate muscle protein synthesis to a greater extent than carbohydrate alone.

Reference
Borsheim, E., Aarsland, A., & Wolfe, R.R. (2004). Effect of an amino acid, protein, and carbohydrate mixture on net muscle protein balance after resistance exercise. International Journal of Sport Nutrition and Exercise Metabolism, 14, 255-271