Studies have suggested that muscle-protein synthesis peaks 48 hours after an intense workout, implying that you have a large window of opportunity when it comes to consuming protein after a training session. In contrast, the carbohydrate scenario is quite different under the
same conditions: After a workout, the sooner you shovel in those carbs, the faster and more replete your muscle glycogen synthesis and consequent recovery. A soon-to-be-released study refutes the notion that you should take a laid-back attitude toward increased protein intake
after a hard workout. This study, scheduled to be published in a forthcoming issue of the American Journal of Physiology, looked at the effects of an intravenous infusion of selected amino acids in six untrained men at rest and after weight training their legs. The men were
given a mixture of amino acids amounting to 0.15 grams per kilogram (2.2 pounds) of bodyweight for three hours while at rest and after exercise A few of the amino acids were locked onto isotopes so that the researchers would be able to trace them in each subject's body.
In this way, the scientists could examine the ability of muscles to take up amino acids during different conditions. The results showed that, following exercise, the transport of amino acids into muscle was anywhere from 30 to 100% higher than the Level detected while the subjects were at rest. Also, muscle-protein synthesis rates increased with the combination of amino acids and exercise. Muscle-protein breakdown (catabolism) wasn't affected. The authors of this study suggest that the enhanced blood flow induced by exercise appears to increase both amino acid uptake and subsequent muscle-protein synthesis. This means it's a good idea to consume protein or amino acids as soon as possible after training to take advantage of the increased blood circulation and amino acid uptake in the muscle.
Combining protein with carbs will produce even better results, due to an upgraded insulin release.