Most, but not all studies have shown that supplementation of whey alone or with carbohydrates immediately after and possibly before and during resistance exercise can enhance the muscle hypertrophy response to resistance training in healthy adults. Such a response seems to at least be the case when comparing the effects of whey versus a non-energetic, or carbohydrate or soy protein alternative. Some studies also suggest that whey may enhance recovery from heavy exercise and possibly decrease muscle damage and soreness. This could, over time, enhance training adaptations by way of increasing training volume or reducing the potential for over-reaching/over-training. (Hulmi. 2010)In that, it is of particular interest that the fundamental reasons for the superiority of whey supplementation (short-term effect), even over the provision of isolated free-form amino acids, have not yet been finally established:
[...] something other than EAAs within whey are important for muscle hypertrophy. For example, it is possible that via the PEPT-1 cotransporters' high capacity, low specificity rate of transport, and an apparent increased transport affinity for L-valine bound peptides, that the bound form of an EAA may be more efficiently utilized than when delivered in its free-form . Similarly, new discoveries continue to surface regarding bioactive peptides present within dairy, and specifically in whey that may facilitate improved recovery and antioxidative capacity to support physiological adaptations to exercise . However, possible long term superiority of whey compared to its constituent amino acids (all, or just its EAAs) is not known. (Hulmi. 2010)Yet, whatever it might be that renders whey proteins so effective, it is reason enough, not fall for the advertisements of the supplement industry and keep using your favorite, tried and proven whey protein be it a concentrate, an isolate (preferable immediately after workout) or a hydrosolate (perf. improvements over isolate, is at least in view of costs vs. effects debatable).