A recent study published in the British Journal of Nutrition sought to examine the impact of whey protein dosing, leucine content and essential amino acid content (Churchward-Venne, Burd et al. 2012). The authors divided 24 males into three different groups and determined changes in muscle protein synthesis after they ingested various combinations of nutrients without completing any resistance exercise and in the other condition they ingested their prescribed nutrients and complete a single bout of resistance exercise. This type of research study is extremely valuable because it provides information on muscle growth when someone ingests nutrients both with and without the influence of resistance exercise or in more practical terms on workout and non-workout days.
One group ingested a 25 gram dose of whey, the second group ingested just 6.25 grams of whey protein but it was specially formulated to contain the same amount of leucine as the 25 gram dose of whey. The final group ingested 6.25 grams of whey protein but it was also specially formulated to contain the same amounts of the essential amino acids as the first group (25 grams of whey) except leucine. In essence, the authors developed a study to examine the total impact of recommended amounts of leucine and essential amino acids with and without the support of other potentially important nutrients. When muscle biopsies were taken to determine muscle protein synthesis, the authors first reported that leucine content in the blood increased and were similar between the groups that contained leucine (group 1 and group 2) and as expected these levels of leucine were greater than group 3 (which contained the EAAs but no leucine). In an immediate fashion (1 - 3 hours after feeding), muscle protein synthesis values were similarly increased in all groups when resistance exercise was included and when it wasn't. In other words, on both workout days and non-workout days, adequate delivery of leucine and the essential amino acids effectively stimulates muscle protein synthesis for a period of 1 - 3 hours. Regular readers here know that ProSource's NytroWhey Ultra Elite is an unrivaled source of leucine, due to its inclusion of Leuvon, a leucine-bound leucine peptide that works to "switch on" anabolism in muscle tissue. NytroWhey Ultra Elite contains as much as four times the leucine available in other premium proteins. In closing, a high-quality whey protein isolate in combination with resistance training provides the longest stimulation of muscle protein synthesis when compared to other combinations of amino acids and exercise.
Churchward-Venne, T. A., N. A. Burd, et al. (2012). "Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men." Journal of Physiology 590(Pt 11): 2751-2765.
Norton, L. E. and D. K. Layman (2006). "Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise." J Nutr 136(2): 533S-537S.